Specialized bicycles represent an excellent donor pool for Toseven DM01 and DM02 mid-drive conversions. The frames offer proven geometries, robust proprietary aluminum alloys designated A1, E5, and M5, and high-grade FACT (Functional Advanced Composite Technology) Carbon constructions, and predominantly spacious front triangles that readily accommodate large battery packs. However, Specialized’s engineering history is characterized by an exceptionally wide variety of bottom bracket standards — from traditional threaded BSA shells on aluminum hardtails and carbon road bikes, to the brand’s proprietary OSBB press-fit standard on select carbon mountain bike frames, to the BB386 EVO press-fit standard used on earlier carbon gravel frames. Successful and safe electrification requires a precise understanding of these mechanical interfaces before any hardware is ordered.
The bottom bracket (BB) shell is the transverse cylindrical housing at the lowest point of the bicycle frame, connecting the downtube, seat tube, and chainstays. In a standard bicycle, this shell houses the bearings that allow the crankset to rotate. In a mid-drive conversion, the Toseven motor axle must pass completely through this shell. The Toseven hardware is natively designed for a shell width of 68 millimeters to 73 millimeters and requires an internal shell diameter large enough to clear a 33.5 millimeter motor axle.
01 Compatibility Overview (All Major Specialized Platforms)
- BSA (British Standard Cycle) A traditional, threaded bottom bracket shell. It features a 1.37-inch diameter with 24 threads per inch, yielding an inner diameter of 33.6 millimeters to 33.9 millimeters. This is the optimal standard for Toseven motors.
- Press-Fit (PF) A threadless shell design where bearings or bearing cups are pressed directly into a smooth frame bore using mechanical force.
- OSBB MTB (Open Standard Bottom Bracket — Mountain) Specialized’s proprietary press-fit standard used on select FACT Carbon mountain bike frames. Features a 73 millimeter shell width and a 46 millimeter internal diameter. Within this guide’s scope, found only on the carbon Epic Hardtail (2018–2019) and the early 2018 symmetrical-generation carbon Stumpjumper.
- OSBB Road / BB30 A separate OSBB variant used on the pre-2022 cyclocross Crux. Features a 68 millimeter shell width and a 42 millimeter internal diameter. Mechanically distinct from OSBB MTB — requires different bushing specifications.
- BB386 EVO A press-fit standard used on the 2018–2020 carbon Diverge. Features an 86.5 millimeter shell width and a 46 millimeter internal diameter. Wider than OSBB MTB but shares the same bore diameter.
- Boost Spacing A modern hub standard that widens the rear wheel axle spacing to 148 millimeters (up from the older 135 millimeter or 142 millimeter standards). This pushes the rear cassette outward, requiring specific chainring offsets at the motor to prevent severe chainline misalignment.
- FSR (Horst Link / Four-Bar Suspension) Specialized’s proprietary four-bar linkage rear suspension system used on all Specialized full-suspension platforms in this guide. As the rear suspension compresses, the physical distance between the bottom bracket and the rear axle changes, creating chain growth that must be accounted for before finalizing chain length.
Mandatory Toseven Hardware Directives
Before assessing individual Specialized frame platforms, you must strictly adhere to three universal engineering constraints regarding the Toseven hardware:
- First, Carbon Frame Torque Limits Specialized FACT Carbon frames are highly susceptible to crushing failures under torsional motor loads. The Toseven DM01 motor produces 160Nm of torque and is strictly prohibited from being installed on any carbon Specialized frame. Carbon conversions are limited entirely to the DM02 motor. When installing the DM02 on a FACT Carbon frame, you must use protective interface pads between the motor housing and the frame to distribute the load, and the primary bottom bracket lockring torque must be strictly limited to 35 to 40Nm.
- Second, The DM02 Shift Sensor Exclusion The Toseven DM02 kit does not include a shift sensor. Riders utilizing the DM02 must shift gears manually. You must intentionally pause pedal input during derailleur actuation to unload the motor torque from the chain. Failure to do so will result in accelerated drivetrain wear or immediate chain failure under load.
- Third, Motor Sizing Must Match Your Frame’s BB Shell Width The Toseven DM01 is available in 68mm, 73mm, 100mm, 110mm, and 120mm variants. The Toseven DM02 is available in 68mm, 73mm, 100mm, and 110mm variants. For standard Specialized production frames in this guide, only the 68mm, 73mm, and 100mm variants are relevant. The 110mm and 120mm variants fall outside the scope of this guide as no Specialized frame within the 2018 to present production window uses a shell width in that range.
Compatibility is determined strictly by the frame’s bottom bracket standard and metallurgical composition.
| Model Name | Frame Material | Bottom Bracket Type | Compatibility Status | Notes |
|---|---|---|---|---|
|
Works Perfectly
Fully drop-in compatible. No special adapter hardware required.
|
||||
| Rockhopper (All Gen) | A1 Aluminum | BSA Threaded (73mm) | 🟢 Works Perfectly | Use 73mm motor and 9mm offset chainring for 52.5mm chainline. Verify Boost vs. non-Boost rear spacing on pre-2020 models. |
| Chisel (All Gen) | M5 Aluminum | BSA Threaded (73mm) | 🟢 Works Perfectly | Boost 148 throughout production run. Use 73mm motor and 9mm offset chainring. |
| Fuse (Aluminum, Boost 148) | M5 Aluminum | BSA Threaded (73mm) | 🟢 Works Perfectly | Verify rear spacing — Super Boost 157mm variants require chainline verification. |
| Epic Hardtail (Aluminum) | A1 / M5 Aluminum | BSA Threaded (73mm) | 🟢 Works Perfectly | Boost 148. Use 73mm motor and 9mm offset chainring. |
| Stumpjumper (Aluminum) | M5 Aluminum | BSA Threaded (73mm) | 🟢 Works Perfectly | FSR compression check mandatory before finalizing chain length. |
| Stumpjumper EVO (Aluminum) | M5 Aluminum | BSA Threaded (73mm) | 🟢 Works Perfectly | 160mm travel increases FSR chain growth magnitude. Compression test is critical. |
| Enduro (Aluminum) | M5 Aluminum | BSA Threaded (73mm) | 🟢 Works Perfectly | Longest-travel FSR platform in this guide. Motor housing clearance check at full compression is mandatory. |
| Sirrus 1.0 / 2.0 / 3.0 / 4.0 | E5 Aluminum | BSA Threaded (68mm) | 🟢 Works Perfectly | Use 68mm motor variant. Achieves perfect 50mm chainline with 9mm offset ring. |
| Sirrus X | E5 Aluminum | BSA Threaded (68mm) | 🟢 Works Perfectly | Use 68mm motor variant. Verify QR vs. thru-axle on specific model year. |
| Roll | A1 Aluminum | BSA Threaded (68mm) | 🟢 Works Perfectly | Installation difficulty is extremely low. DM02 recommended. |
| Allez / Allez Sprint | E5 Aluminum | BSA Threaded (68mm) | 🟢 Works Perfectly | Use 68mm motor variant. Chainline sits ~6.5mm outboard of road target — best suited as commuter build. |
| Diverge (Aluminum) | E5 Aluminum | BSA Threaded (68mm) | 🟢 Works Perfectly | Use 68mm motor variant and 9mm offset chainring for 50mm chainline. |
|
Works Well
Compatible, but requires specific Toseven adapter hardware or a non-standard motor variant.
|
||||
| Fatboy (Aluminum) | A1 Aluminum | BSA Threaded (100mm) | 🟡 Works Well | Must use 100mm motor variant for both DM01 and DM02. Standard 73mm motor is physically too short for this shell. DM01 prohibited on carbon Fatboy variants. |
|
DM02 Only — Carbon Caution
DM01 is strictly prohibited. DM02 requires professional installation.
|
||||
| Epic Hardtail (Carbon, 2018–2019) | FACT Carbon | OSBB MTB (PF46) | 🟠 DM02 Only | PF46-to-BSA reducer bushings required. Universal carbon rules apply. |
| Epic Hardtail (Carbon, 2020–present) | FACT Carbon | BSA Threaded (73mm) | 🟠 DM02 Only | No reducer bushings required. Universal carbon rules apply. |
| Stumpjumper (Carbon, early 2018) | FACT Carbon | OSBB MTB (PF46) | 🟠 DM02 Only | PF46-to-BSA reducer bushings required. Visual ID: symmetrical rear shock cradle. |
| Stumpjumper (Carbon, late 2018+) | FACT Carbon | BSA Threaded (73mm) | 🟠 DM02 Only | No reducer bushings required. Visual ID: asymmetrical Sidearm design. |
| Stumpjumper EVO (Carbon, 2020+) | FACT Carbon | BSA Threaded (73mm) | 🟠 DM02 Only | No reducer bushings required. 160mm travel — measure chain growth empirically. |
| Epic FS / Epic EVO (Carbon, 2018+) | FACT Carbon | BSA Threaded (73mm) | 🟠 DM02 Only | No reducer bushings required. Universal carbon rules apply. FSR chain growth check mandatory. |
| Enduro (Carbon, 2018–present) | FACT Carbon | BSA Threaded (73mm) | 🟠 DM02 Only | No reducer bushings required. Universal carbon rules apply. FSR chain growth check mandatory. |
| Roubaix (Carbon, 2018–present) | FACT Carbon | BSA Threaded (68mm) | 🟠 DM02 Only | No reducer bushings required. Universal carbon rules apply. |
| Diverge (Carbon, 2018–2020) | FACT Carbon | BB386 EVO (PF46) | 🟠 DM02 Only | Use 68mm motor. PF46-to-BSA reducer bushings required. Extensive spacer management mandatory. |
| Diverge (Carbon, 2021–present) | FACT Carbon | BSA Threaded (68mm) | 🟠 DM02 Only | No reducer bushings required. Universal carbon rules apply. |
| Crux (Carbon, 2018–2021) | FACT Carbon | OSBB Road (PF42) | 🟠 DM02 Only | PF42-to-BSA reducer bushings required. Distinct standard from both OSBB MTB and BB386 EVO. |
| Crux (Carbon, 2022–present) | FACT Carbon | BSA Threaded (68mm) | 🟠 DM02 Only | No reducer bushings required. Universal carbon rules apply. |
| Aethos (2021–present) | FACT 12r Carbon | BSA Threaded (68mm) | 🟠 DM02 Only | No reducer bushings required. 35Nm absolute limit — never higher. See Aethos entry for full caution. |
|
Not Compatible
Cannot be safely converted with standard hardware.
|
||||
| Turbo Levo / Turbo Kenevo | Alu / FACT Carbon | Proprietary Brose Cavity | 🔴 Not Compatible | Factory e-bikes with integrated Brose motor cavity. No standard BB shell present. |
| Turbo Creo | FACT Carbon | Proprietary Brose Cavity | 🔴 Not Compatible | Factory e-bike. Motor cavity geometry is not a standard BB interface of any known type. |
These three rules apply to every 🟠 DM02 Only entry in the table above without exception. They are not repeated in each platform entry below — read them once and apply them universally.
- Rule 1 — DM01 Strictly Prohibited The Toseven DM01 is strictly prohibited on every FACT Carbon Specialized frame regardless of BB standard, model year, trim level, or torque setting. There are no exceptions. DM02 only.
- Rule 2 — Primary Lockring Torque Strictly Limited When installing the DM02 on any FACT Carbon frame, the primary bottom bracket lockring torque must be strictly limited to 35 to 40Nm. Do not exceed this under any circumstances. On the Aethos specifically, the limit is 35Nm exactly — never higher.
- Rule 3 — Protective Interface Pads Mandatory Protective interface pads must be installed between the motor housing and the carbon frame surface on every FACT Carbon conversion without exception. These pads distribute the motor clamping load across the carbon shell face. Installing the DM02 directly against bare carbon without interface pads risks progressive shell crushing and frame destruction.
14+ Specialized MTB Platforms:
Specialized’s hardtail platforms are the most mechanically straightforward candidates for mid-drive electrification due to their rigid rear triangles and lack of suspension linkage interference.
Rockhopper (All Generations, 2018–Present)
- Frame Material: A1 Premium Aluminum
- Bottom Bracket: BSA Threaded (73mm)
- Rear Spacing: Non-Boost 135mm QR (pre-2020) or Boost 148mm Thru-Axle (2020–present)
- Motor Required: 73mm Variant
- Chainring Offset: 9mm (Achieves a 52.5mm chainline)
No bottom bracket adapters are required. Installation difficulty is low. Both DM01 and DM02 are highly recommended. The 9mm offset chainring achieves a 52.5mm chainline, which is within accepted tolerance for both non-Boost and Boost 148 rear spacing standards.
Verify rear axle spacing on your specific Rockhopper model year before ordering. The transition from non-Boost to Boost spacing occurred across the 2019–2020 production window and was not uniform across all trim levels simultaneously.
Chisel (All Generations, 2018–Present)
- Frame Material: M5 Aluminum
- Bottom Bracket: BSA Threaded (73mm)
- Rear Spacing: Boost 148mm Thru-Axle
- Motor Required: 73mm Variant
- Chainring Offset: 9mm (Achieves a 52.5mm chainline)
No bottom bracket adapters are required. Installation difficulty is low. Boost 148 spacing is standard throughout the entire Chisel production run. Both DM01 and DM02 are highly recommended.
Fuse (All Generations, 2018–Present)
- Frame Material: M5 Aluminum
- Bottom Bracket: BSA Threaded (73mm)
- Rear Spacing: Boost 148mm Thru-Axle (standard) — verify Super Boost 157mm on specific trim levels
- Motor Required: 73mm Variant
- Chainring Offset: 9mm (Achieves a 52.5mm chainline on Boost 148 models)
No bottom bracket adapters are required on standard Boost 148 Fuse models. Installation difficulty is low. Both DM01 and DM02 are highly recommended on standard Boost 148 variants.
Certain higher-specification Fuse trim levels may utilize a 157mm Super Boost rear axle spacing. This wider spacing shifts the cassette outboard, pushing the chainline target closer to 55mm. The 9mm offset chainring still achieves 52.5mm — approximately 2.5mm inboard of the Super Boost ideal — which is the less harmful compromise. Verify that the chainring teeth do not contact the chainstay, and expect marginally degraded shifting in the outermost cogs compared to a correctly specced drivetrain.
Epic Hardtail (Aluminum, All Trim Levels, 2018–Present)
- Frame Material: A1 / M5 Aluminum (varies by trim)
- Bottom Bracket: BSA Threaded (73mm)
- Rear Spacing: Boost 148mm Thru-Axle
- Motor Required: 73mm Variant
- Chainring Offset: 9mm (Achieves a 52.5mm chainline)
No bottom bracket adapters are required. Installation difficulty is low. Both DM01 and DM02 are compatible and recommended.
Epic Hardtail (Carbon, 2018–2019)
- Frame Material: FACT 9m Carbon
- Bottom Bracket: OSBB MTB Press-Fit (73mm width, 46mm inner diameter)
- Rear Spacing: Boost 148mm Thru-Axle
- Motor Required: 73mm Variant
- Hardware Required: CNC-machined PF46-to-BSA reducer bushings
Universal carbon frame rules apply — see Section 01.
The 2018 and 2019 Epic Hardtail Carbon used the OSBB MTB press-fit shell with a 46mm internal bore. You must use PF46-to-BSA CNC-machined reducer bushings specifically. Do not use PF41 bushings — they will not correctly fill the 46mm bore and will produce a dangerously loose fit. Do not use PF42 bushings — they will also produce a loose fit in a 46mm bore. Installation difficulty is moderate.
Epic Hardtail (Carbon, 2020–Present)
- Frame Material: FACT 11m Carbon
- Bottom Bracket: BSA Threaded (73mm)
- Rear Spacing: Boost 148mm Thru-Axle
- Motor Required: 73mm Variant
- Hardware Required: None
Universal carbon frame rules apply — see Section 01.
Specialized redesigned the Epic Hardtail Carbon for the 2020 model year, switching to a BSA threaded 73mm shell. No reducer bushings are required. Installation difficulty is moderate.
23+ Specialized Full Suspension MTB Platforms:
Specialized’s full-suspension models introduce significant engineering complexity. All platforms in this section utilize Specialized’s FSR (Horst Link) four-bar linkage rear suspension kinematics. In the FSR system, a dedicated chainstay pivot positioned just forward of the rear dropout decouples braking forces from suspension movement. As the rear suspension compresses, the physical distance between the bottom bracket and the rear axle changes, producing chain growth. Before finalizing chain length on any full-suspension Specialized frame, you must remove the rear shock, cycle the suspension through its full travel, and verify that the chain tension can accommodate maximum chain growth without tearing the derailleur from the frame. Additionally, you must verify that the motor housing does not contact the lower suspension linkage at full compression.
Stumpjumper Generation Reference
| Generation | Years | Material | BB Standard | Motor Variant | DM01 |
|---|---|---|---|---|---|
| Symmetrical / X-Wing (early) | Pre-April 2018 | FACT Carbon only | OSBB MTB PF46 (46mm ID) | 73mm | ❌ |
| Sidearm (Asymmetrical) | April 2018–2020 | Aluminum or FACT Carbon | BSA Threaded (73mm) | 73mm | Aluminum ✅ / Carbon ❌ |
| Current Generation | 2021–2024 | Aluminum or FACT Carbon | BSA Threaded (73mm) | 73mm | Aluminum ✅ / Carbon ❌ |
| Stumpjumper 15 | 2025–present | Aluminum or FACT Carbon | BSA Threaded (73mm) | 73mm | Aluminum ✅ / Carbon ❌ |
| EVO (Aluminum) | 2020–present | M5 Aluminum | BSA Threaded (73mm) | 73mm | ✅ |
| EVO (Carbon) | 2020–present | FACT Carbon | BSA Threaded (73mm) | 73mm | ❌ |
⚠️ The early 2018 symmetrical carbon Stumpjumper is the only full-suspension carbon Stumpjumper within this guide’s scope that requires reducer bushings. Every other carbon Stumpjumper variant — including all Sidearm-generation 2018 models sold from April 2018 onward — uses BSA threaded and requires no bushings. If you do not know whether your 2018 Stumpjumper is early or late production, see the visual identification instructions in Entry 2 below.
Stumpjumper (Aluminum, 2018–Present)
- Frame Material: M5 Aluminum
- Bottom Bracket: BSA Threaded (73mm)
- Rear Spacing: Boost 148mm Thru-Axle
- Motor Required: 73mm Variant
- Chainring Offset: 9mm (Achieves a 52.5mm chainline)
No bottom bracket adapters are required. Installation difficulty is high. FSR suspension kinematics apply — full compression test and chain growth verification are mandatory before finalizing chain length. Confirm motor housing clearance against the lower swingarm and linkage hardware at full compression. Both DM01 and DM02 are compatible on the aluminum variant.
Stumpjumper (Carbon, 2018–Present)
The 2018 model year is a transition year. Two entirely different carbon Stumpjumper frames were sold under the 2018 model designation. You must identify which frame you have before ordering any hardware.
Stumpjumper Carbon — Early 2018 (Symmetrical / “X-Wing” Frame, sold before April 2018)
- Frame Material: FACT Carbon
- Bottom Bracket: OSBB MTB Press-Fit (73mm width, 46mm inner diameter)
- Motor Required: 73mm Variant
- Hardware Required: CNC-machined PF46-to-BSA reducer bushings
Universal carbon frame rules apply — see Section 01.
The original Stumpjumper Carbon sold before approximately April 2018 used the symmetrical FSR frame design with an OSBB MTB press-fit shell and a 46mm internal bore. PF46-to-BSA reducer bushings are mandatory. FSR chain growth protocol applies — full compression test is mandatory before finalizing chain length.
Visual Identification — Symmetrical Frame: The rear shock sits centrally between carbon stays that cradle it symmetrically on both sides. Both the left and right side of the frame support the shock equally. If you see this design, you have a 46mm press-fit bore and bushings are mandatory.
Stumpjumper Carbon — Late 2018 (Sidearm / Asymmetrical Frame) Through Present
- Frame Material: FACT 11m Carbon
- Bottom Bracket: BSA Threaded (73mm)
- Rear Spacing: Boost 148mm Thru-Axle
- Motor Required: 73mm Variant
- Hardware Required: None
Universal carbon frame rules apply — see Section 01.
The Sidearm asymmetrical frame launched in April 2018 and introduced the BSA threaded 73mm shell. This standard has been maintained across every subsequent Stumpjumper Carbon generation — the 2021 redesign and the 2025 Stumpjumper 15 all use BSA threaded 73mm. No reducer bushings are required on any Sidearm-generation carbon Stumpjumper. FSR chain growth protocol applies — full compression test is mandatory.
Visual Identification — Sidearm Frame: The right side of the rear shock has a single visible carbon support arm extending from the frame. The left side is open — there is no corresponding carbon stay supporting the shock from that side. If you see this asymmetrical design, you have a BSA threaded shell and no bushings are required.
⚠️ If you cannot determine your production date visually, remove the bottom bracket and inspect the inside of the shell. A smooth bore with no internal threads = 46mm press-fit = bushings mandatory. Visible internal threads = BSA threaded = no bushings required.
Stumpjumper EVO (Aluminum, 2020–Present)
- Frame Material: M5 Aluminum
- Bottom Bracket: BSA Threaded (73mm)
- Rear Spacing: Boost 148mm Thru-Axle
- Motor Required: 73mm Variant
- Chainring Offset: 9mm (Achieves a 52.5mm chainline)
No bottom bracket adapters are required. Installation difficulty is high. The Stumpjumper EVO runs 160mm of rear travel compared to the standard Stumpjumper’s 130 to 140mm. The additional travel increases FSR chain growth magnitude, making the full compression test even more critical — do not estimate chain growth from standard Stumpjumper figures. Measure empirically with the shock removed. Both DM01 and DM02 are compatible on the aluminum variant.
Stumpjumper EVO (Carbon, 2020–Present)
- Frame Material: FACT 11m Carbon
- Bottom Bracket: BSA Threaded (73mm)
- Rear Spacing: Boost 148mm Thru-Axle
- Motor Required: 73mm Variant
- Hardware Required: None
Universal carbon frame rules apply — see Section 01.
No reducer bushings are required. The 160mm travel makes FSR chain growth verification especially critical — measure empirically, do not carry figures from the standard Stumpjumper. Installation difficulty is high.
Epic (Full Suspension, Carbon, All Trim Levels, 2018–Present)
- Frame Material: FACT 12m Carbon
- Bottom Bracket: BSA Threaded (73mm)
- Rear Spacing: Boost 148mm Thru-Axle
- Motor Required: 73mm Variant
- Hardware Required: None
Universal carbon frame rules apply — see Section 01. The Epic FACT 12m Carbon is among the thinnest-walled MTB carbon in the Specialized lineup — apply the 35 to 40Nm torque limit with particular strictness.
The carbon Epic full-suspension uses a BSA threaded 73mm shell throughout the entire 2018 to present production window, consistent across all trim levels from Comp to S-Works. No reducer bushings are required. Specialized has never offered an aluminum full-suspension Epic. The Epic’s XC-focused FSR platform has shorter travel (100 to 120mm) than the Stumpjumper, which reduces but does not eliminate chain growth. The full compression test is still mandatory. Installation difficulty is high.
Epic EVO (Carbon, 2020–Present)
- Frame Material: FACT 12m Carbon
- Bottom Bracket: BSA Threaded (73mm)
- Rear Spacing: Boost 148mm Thru-Axle
- Motor Required: 73mm Variant
- Hardware Required: None
Universal carbon frame rules apply — see Section 01.
No reducer bushings are required. The Epic EVO runs 120mm of rear travel. FSR chain growth protocol applies. Installation difficulty is high.
Enduro (Aluminum, 2018–Present)
- Frame Material: M5 Aluminum
- Bottom Bracket: BSA Threaded (73mm)
- Rear Spacing: Boost 148mm Thru-Axle
- Motor Required: 73mm Variant
- Chainring Offset: 9mm (Achieves a 52.5mm chainline)
No bottom bracket adapters are required. Installation difficulty is high. The Enduro is Specialized’s long-travel all-mountain platform, running 160 to 170mm of rear travel — the longest-travel FSR platform in this guide. This produces the most significant chain growth of any Specialized frame listed here. The full compression test is especially critical on the Enduro; the extended travel and aggressive linkage geometry create greater motor housing clearance risk than on shorter-travel platforms. You must cycle the full suspension travel with the motor in its installed position before tightening any hardware. Both DM01 and DM02 are compatible on the aluminum variant.
Enduro (Carbon, 2018–Present)
- Frame Material: FACT Carbon
- Bottom Bracket: BSA Threaded (73mm)
- Rear Spacing: Boost 148mm Thru-Axle
- Motor Required: 73mm Variant
- Hardware Required: None
Universal carbon frame rules apply — see Section 01.
All carbon Enduro models from 2018 onward use a BSA threaded 73mm shell. No reducer bushings are required. Note: if your carbon Enduro is a pre-2017 model, it falls outside this guide’s scope and uses a PF30/OSBB shell with a 46mm bore — consult the OSBB bushing protocol in Section 2 before proceeding. The Enduro’s 160 to 170mm of rear travel produces the greatest FSR chain growth magnitude of any platform in this guide — do not estimate chain growth from other Specialized FSR platforms. Measure empirically with the shock removed. Installation difficulty is high.
3 2+ Specialized Hybrid and Fitness Platforms:
Specialized’s hybrid platforms are outstanding candidates for urban commuting conversions, offering flat-bar control geometries, upright riding positions, and spacious main triangles.
Sirrus 1.0, 2.0, 3.0, and 4.0 (2018–Present)
- Frame Material: E5 Premium Aluminum
- Bottom Bracket: BSA Threaded (68mm)
- Rear Spacing: 135mm Quick-Release
- Motor Required: 68mm Variant
- Chainring Offset: 9mm (Achieves a perfect 50mm chainline)
No bottom bracket adapters are required. Installation difficulty is low. The 68mm shell width is the absolute optimal baseline for the Toseven system. It allows for perfect centering using standard spacer kits and guarantees maximum thread engagement for the locknuts. The DM02 is the definitive recommendation for these commuter and fitness frames.
Sirrus X (2018–Present)
- Frame Material: E5 Aluminum
- Bottom Bracket: BSA Threaded (68mm)
- Rear Spacing: 135mm QR on most models
- Motor Required: 68mm Variant
- Chainring Offset: 9mm (Achieves a 50mm chainline)
No bottom bracket adapters are required. Installation difficulty is low. Certain higher-specification Sirrus X models may use a 142mm thru-axle rear spacing — verify your specific frame before selecting chainring offset. Both DM01 and DM02 are compatible.
Roll (2018–Present)
- Frame Material: A1 Aluminum
- Bottom Bracket: BSA Threaded (68mm)
- Rear Spacing: 135mm Quick-Release
- Motor Required: 68mm Variant
No bottom bracket adapters are required. Installation difficulty is extremely low. The DM02 is the optimal choice for this entry-level comfort platform.
4 5+ Specialized Road and Gravel Platforms:
Converting Specialized road and gravel bicycles requires rigorous mechanical vetting. These platforms span a variety of bottom bracket standards and the majority of high-performance variants are FACT Carbon, triggering the universal carbon rules throughout the lineup.
Allez and Allez Sprint (2018–Present)
- Frame Material: E5 Premium Aluminum
- Bottom Bracket: BSA Threaded (68mm)
- Rear Spacing: 130mm Quick-Release
- Motor Required: 68mm Variant
- Chainring Offset: 9mm (Achieves a 50mm chainline)
No bottom bracket adapters are required. Installation difficulty is low. The standard road drivetrain chainline target for Shimano 11-speed road is approximately 43.5mm, which means the 50mm Toseven chainline sits approximately 6.5mm outboard of the road-optimized target. This produces a noticeable diagonal chain angle in the small cogs — not enough to cause chain drops, but enough to produce audible friction and accelerated wear at the extremes of the cassette. This platform performs best as a commuter or light fitness e-bike. Both DM01 and DM02 are compatible on the aluminum Allez.
Roubaix (Carbon, 2018–Present)
- Frame Material: FACT Carbon
- Bottom Bracket: BSA Threaded (68mm)
- Rear Spacing: 130mm Quick-Release
- Motor Required: 68mm Variant
- Chainring Offset: 9mm (Achieves a 50mm chainline)
- Hardware Required: None
Universal carbon frame rules apply — see Section 01.
All carbon Roubaix models from 2018 onward — Sport, Comp, Expert, Pro, and S-Works, spanning the Future Shock 1.0/1.5, SL7, and SL8 generations — use a standard BSA threaded 68mm shell. No reducer bushings are required. Installation difficulty is moderate. Note: pre-2017 carbon Roubaix models used OSBB press-fit and fall outside this guide’s scope.
Diverge (Aluminum, 2018–Present)
- Frame Material: E5 Aluminum
- Bottom Bracket: BSA Threaded (68mm)
- Rear Spacing: 135mm QR or thru-axle depending on model year
- Motor Required: 68mm Variant
- Chainring Offset: 9mm (Achieves a 50mm chainline)
No bottom bracket adapters are required. Installation difficulty is low. Verify rear axle spacing on your specific Diverge aluminum model year before selecting chainring offset. Both DM01 and DM02 are compatible.
Diverge (Carbon, 2018–Present)
The carbon Diverge underwent a significant bottom bracket standard change with the 2021 model year redesign. The two generations use entirely different BB standards and require different hardware. Identify your model year before ordering anything.
Diverge Carbon 2018–2020 (BB386 EVO)
- Frame Material: FACT Carbon
- Bottom Bracket: BB386 EVO Press-Fit (86.5mm width, 46mm inner diameter)
- Rear Spacing: Thru-Axle
- Motor Required: 68mm Variant
- Hardware Required: CNC-machined PF46-to-BSA reducer bushings
Universal carbon frame rules apply — see Section 01.
The BB386 EVO shell is 86.5mm wide with a 46mm internal diameter. You must use PF46-to-BSA reducer bushings specifically. Do not use PF41 bushings — they will not fill the 46mm bore and will produce a dangerously loose fit. Do not use PF42 bushings — they are sized for the Crux BB30 shell and will not fill this bore correctly. The 86.5mm shell width far exceeds what the 68mm motor variant is designed for — extensive spacer management using the factory 1mm and 2mm precision spacer kits is mandatory to prevent axle bottoming. Installation difficulty is high.
Diverge Carbon 2021–Present (BSA Threaded)
- Frame Material: FACT Carbon
- Bottom Bracket: BSA Threaded (68mm)
- Rear Spacing: Thru-Axle
- Motor Required: 68mm Variant
- Chainring Offset: 9mm (Achieves a 50mm chainline)
- Hardware Required: None
Universal carbon frame rules apply — see Section 01.
Specialized redesigned the Diverge for the 2021 model year, switching to a standard 68mm BSA threaded shell across all carbon trim levels — FACT 8r, 9r, and S-Works 11r. No reducer bushings are required. Installation difficulty is moderate.
Crux (Carbon, 2018–Present)
The Crux underwent a complete platform transformation for the 2022 model year, transitioning from a dedicated cyclocross racing frame to a lightweight gravel racing frame. The two generations use entirely different BB standards. Identify your model year before ordering.
Crux Carbon 2018–2021 (Cyclocross Generation, OSBB Road / BB30)
- Frame Material: FACT Carbon
- Bottom Bracket: OSBB Road / BB30 Press-Fit (68mm width, 42mm inner diameter)
- Motor Required: 68mm Variant
- Hardware Required: CNC-machined PF42-to-BSA reducer bushings
Universal carbon frame rules apply — see Section 01.
The pre-2022 cyclocross Crux uses a BB30-style shell with a 68mm width and a 42mm internal diameter. This is a distinct standard — different from both OSBB MTB (73mm wide, 46mm ID) and BB386 EVO (86.5mm wide, 46mm ID). You must use PF42-to-BSA CNC-machined reducer bushings specifically. Do not use PF46 bushings — too large to enter the bore. Do not use PF41 bushings — will produce a loose, rocking fit in the 42mm bore. Installation difficulty is moderate.
Crux Carbon 2022–Present (Gravel Generation, BSA Threaded)
- Frame Material: FACT Carbon
- Bottom Bracket: BSA Threaded (68mm)
- Motor Required: 68mm Variant
- Chainring Offset: 9mm (Achieves a 50mm chainline)
- Hardware Required: None
Universal carbon frame rules apply — see Section 01.
No reducer bushings are required. Installation difficulty is moderate.
Aethos (2021–Present)
- Frame Material: FACT 12r Carbon
- Bottom Bracket: BSA Threaded (68mm)
- Motor Required: 68mm Variant
- Chainring Offset: 9mm (Achieves a 50mm chainline)
- Hardware Required: None
⚠️ Extreme Caution: Aethos — Modified Carbon Rules
The universal carbon rules apply — but with one critical modification. The Aethos is constructed from FACT 12r Carbon — Specialized’s lightest and most advanced carbon construction, featuring extremely thin tube walls engineered for minimum weight. This is the most structurally delicate carbon interface in the entire Specialized lineup. The lockring torque limit is 35Nm exactly — not 40Nm, not 37Nm, 35Nm. The DM01 is strictly prohibited. Protective interface pads are mandatory and must cover the maximum possible surface area of the motor-to-frame contact zone. Installation difficulty is extreme. This platform should only be approached by experienced fabricators with prior carbon conversion experience.
5 Specialized Fat Bike Platform:
Fatboy (2018–Present)
- Frame Material: A1 Aluminum (Fatboy 5 / Fatboy 7) — FACT Carbon on higher trim levels
- Bottom Bracket: BSA Threaded (100mm)
- Rear Spacing: 190mm (2018–present)
- Motor Required: 100mm Variant — standard 73mm motor is physically incompatible
- Hardware Constraint: DM01 Prohibited on any carbon Fatboy variant
The Fatboy’s threaded 100mm shell uses the standard BSA thread pitch (1.37-inch, 24 TPI) and does not require press-fit reducer bushings. However, the 100mm shell width far exceeds the 68 to 73mm range the standard Toseven axle was designed for. You must order the 100mm motor variant. Attempting to span the extra width with spacers and a standard 73mm motor is not safe — the axle thread length will be insufficient for lockring clamping pressure against the frame faces.
On aluminum Fatboy variants, both DM01 and DM02 are compatible using the 100mm motor variant. Both motors are available in the 100mm width. On any FACT Carbon Fatboy variant, the universal carbon rules apply — DM02 only at 35 to 40Nm with interface pads mandatory. Chainline on the Fatboy represents a significant engineering compromise due to the 190mm rear spacing; consult Toseven directly for the raw chainline figure produced by the 100mm motor variant before ordering. Installation difficulty is high.
6 Specialized Factory E-Bike Platforms — A Note on Scope
The Turbo Levo, Turbo Kenevo, and Turbo Creo are factory-built e-bikes with Specialized’s proprietary motor system (developed in partnership with Brose) integrated directly into the frame architecture. The bottom bracket area on these frames is not a standard BB shell — it is a dedicated motor housing cavity with proprietary dimensions specific to the Specialized motor system.
Converting these platforms to Toseven would require removing the factory Specialized motor, and the remaining cavity geometry is not a standard BB interface of any known type. Until direct measurement of a stripped Turbo frame confirms whether the cavity dimensions align with any known BB standard, these models should be considered out of scope for this guide.
02 Bottom Bracket Deep Dive
The bottom bracket shell is the cylindrical housing at the lowest junction of a bicycle frame. In a conventional bicycle, it houses the bearings that support the pedal crank spindle. In a mid-drive e-bike conversion, this shell becomes the primary structural anchor for the motor. The Toseven motor axle must pass entirely through this hollow cylinder, and the motor housing is then clamped against the outer faces of the shell to resist the rotational force generated by the electric drive.
To ensure a safe and mechanically sound installation, you must understand the interface between the frame and the motor. Bottom brackets generally fall into two categories: threaded and press-fit.
- Threaded Shell Features internal spiral grooves machined directly into the frame. Installing a threaded bottom bracket is analogous to driving a precisely machined bolt into a tapped nut. The threads provide a massive surface area for load distribution and lock the hardware firmly in place.
- Press-Fit Shell Is entirely smooth inside. Installing a press-fit bottom bracket is analogous to forcing a slightly oversized metal or composite sleeve into a smooth bore using heavy mechanical pressure. The system relies entirely on friction and tight manufacturing tolerances to remain secure.
The Toseven DM01 and DM02 motors are natively engineered for a traditional threaded standard. Adapting them to varying Specialized frames requires specific hardware, precise alignment, and a strict adherence to torque ratings.
1BSA Threaded (68 To 73 Millimeters)
The British Standard Cycle (BSA) threaded bottom bracket is the most proven and universally accepted standard in bicycle mechanics. It features a 1.37-inch shell diameter with 24 threads per inch, resulting in an internal diameter of approximately 33.6 to 33.9 millimeters. The shell width will measure either 68 millimeters (road, hybrid, and fitness platforms) or 73 millimeters (mountain bike platforms).
Specialized utilizes the BSA standard extensively — across its aluminum hardtail mountain bikes; across its full-suspension platforms including every Stumpjumper generation (Sidearm onward), the carbon Enduro, the carbon Epic FS, the carbon Epic EVO, and the carbon Epic Hardtail (2020–present); across its hybrid and road platforms; and across modern gravel platforms including the Diverge carbon (2021–present), Crux (2022–present), and Aethos.
For Toseven conversions, the BSA standard is the absolute ideal scenario. The Toseven motor axle measures approximately 33.5 millimeters in diameter. Because the internal diameter of a BSA shell is just slightly larger, the axle slides through the frame with minimal radial play. No internal adapters or reducer bushings are required.
2OSBB MTB Press-Fit (73mm Wide, 46mm Inner Diameter)
The OSBB MTB standard is found within this guide’s confirmed scope on two platforms only: the carbon Epic Hardtail (2018–2019 only) and the early 2018 symmetrical-generation carbon Stumpjumper. The shell is 73 millimeters wide with a smooth, threadless bore and a 46 millimeter internal diameter.
You must use CNC-machined PF46-to-BSA reducer bushings. Do not use PF41 or PF42 bushings — neither will correctly fill the 46mm bore. Do not use 3D-printed or low-grade plastic adapters. Strict spacer management using the factory 1mm and 2mm precision spacer kits is required to prevent axle bottoming.
3OSBB Road / BB30 Press-Fit (68mm Wide, 42mm Inner Diameter)
Found exclusively on the pre-2022 cyclocross-generation Crux carbon within this guide’s scope. The shell is 68 millimeters wide with a 42 millimeter internal diameter — a unique bore diameter among Specialized platforms in this guide.
Requires CNC-machined PF42-to-BSA reducer bushings exclusively. PF46 bushings are too large to enter the bore. PF41 bushings are too small and will produce a loose fit.
4BB386 EVO Press-Fit (86.5mm Wide, 46mm Inner Diameter)
Found exclusively on the 2018–2020 carbon Diverge within this guide’s scope. The shell is 86.5 millimeters wide with a 46 millimeter internal diameter — shares its bore diameter with OSBB MTB but is substantially wider.
Requires CNC-machined PF46-to-BSA reducer bushings. The 86.5mm shell width is significantly wider than the 68mm motor variant is designed for. Extensive spacer management using the factory 1mm and 2mm precision spacer kits is mandatory to prevent axle bottoming.
5T47 Threaded — Contextual Reference
T47 is a threaded bottom bracket system featuring an M47x1.0 thread pitch with an internal diameter of approximately 46 millimeters. T47 does not appear on any Specialized production frame within this guide’s 2018 to present confirmed scope. It is documented here for completeness and to prevent misidentification. If you measure your shell bore at approximately 46 millimeters and find threads rather than a smooth bore, you have a T47 shell — contact Toseven directly before proceeding.
6Fatboy 100mm Threaded Shell
Threaded at the standard BSA pitch. No reducer bushings required. However, the 100mm shell width substantially exceeds the standard Toseven axle design range. The 100mm motor variant is mandatory. Refer to Section 1.5 for full detail.
7Bushing Specification Summary
Always confirm your BB standard with a caliper before purchasing bushings. This table is a cross-check, not a substitute for physical measurement.
| BB Standard | Shell Width | Internal Diameter | Found On | Bushing Required |
|---|---|---|---|---|
| BSA Threaded | 68mm or 73mm | ~34mm | Most Specialized platforms | None |
| OSBB MTB (PF46) | 73mm | 46mm | Carbon Epic HT 2018–2019, Carbon Stumpjumper early 2018 only | PF46-to-BSA |
| OSBB Road / BB30 (PF42) | 68mm | 42mm | Crux Carbon 2018–2021 | PF42-to-BSA |
| BB386 EVO (PF46) | 86.5mm | 46mm | Diverge Carbon 2018–2020 | PF46-to-BSA |
| Fatboy 100mm Threaded | 100mm | ~34mm | Fatboy | None (requires 100mm motor variant) |
03 Chainline & Chainring Offset Engineering
1 What Is a Chainline?
The chainline is the distance measured in millimeters from the exact longitudinal centerline of the bicycle frame to the centerline of the front chainring teeth. For a drivetrain to function properly, the front chainring must align with the center of the rear cassette. Mid-drive motors push the chainring mounting point significantly outward — the raw, uncorrected chainline of a Toseven motor sits at approximately 59 millimeters on the 68mm variant and 61.5 millimeters on the 73mm variant. Left uncorrected, this causes harsh grinding, poor shifting, and immediate chain drops.
The raw chainline figures stated throughout this section assume the motor has been ordered in the size that precisely matches your frame’s BB shell width. If you install a 68mm motor in a 73mm shell, or a 73mm motor in a 68mm shell, the raw chainline figures will be incorrect and no off-the-shelf chainring offset will fully correct the resulting misalignment. Always order the motor to match your shell width, confirmed by caliper measurement.
2 Boost Versus Non-Boost Spacing
- Non-Boost Spacing Features a rear axle width of either 135mm (QR) or 142mm (Thru-axle). Found on older Specialized hardtails, most Sirrus and Roll hybrid models, and Allez road platforms. Target front chainline is 49 to 50mm for 68mm shells and approximately 52mm for 73mm shells.
- Boost Spacing Widens the rear axle to 148mm. Found on all modern Specialized mountain bikes. The target front chainline must move outward to approximately 52 to 55mm to maintain a straight chain path.
3 The Offset Chainring Solution
Toseven offset chainring options:
- 3mm Offset Least inboard correction
- 6mm Offset Moderate inboard correction
- 9mm Offset Maximum inboard correction; correct for the vast majority of Specialized conversions in this guide
The 9mm offset chainring paired with the 68mm motor variant achieves a corrected chainline of approximately 50mm. Paired with the 73mm motor variant it achieves approximately 52.5mm.
4 Chainline by Platform
| Platform | BB Shell | Motor Variant | Offset Required | Corrected Chainline | Rear Spacing |
|---|---|---|---|---|---|
| Rockhopper (Boost 148, 2020+) | 73mm BSA | 73mm | 9mm | 52.5mm | Boost 148 ✅ |
| Rockhopper (non-Boost, pre-2020) | 73mm BSA | 73mm | 9mm | 52.5mm | Non-Boost ⚠️ marginally long |
| Chisel | 73mm BSA | 73mm | 9mm | 52.5mm | Boost 148 ✅ |
| Fuse (Boost 148) | 73mm BSA | 73mm | 9mm | 52.5mm | Boost 148 ✅ |
| Fuse (Super Boost 157) | 73mm BSA | 73mm | 9mm | 52.5mm | Super Boost ⚠️ ~2.5mm short |
| Epic Hardtail (Aluminum) | 73mm BSA | 73mm | 9mm | 52.5mm | Boost 148 ✅ |
| Epic Hardtail (Carbon, 2018–2019) | 73mm OSBB MTB | 73mm | 9mm | 52.5mm | Boost 148 ✅ |
| Epic Hardtail (Carbon, 2020–present) | 73mm BSA | 73mm | 9mm | 52.5mm | Boost 148 ✅ |
| Stumpjumper (Aluminum & Carbon, Sidearm onward) | 73mm BSA | 73mm | 9mm | 52.5mm | Boost 148 ✅ |
| Stumpjumper EVO (Aluminum & Carbon) | 73mm BSA | 73mm | 9mm | 52.5mm | Boost 148 ✅ |
| Epic FS / Epic EVO (Carbon) | 73mm BSA | 73mm | 9mm | 52.5mm | Boost 148 ✅ |
| Enduro (Aluminum & Carbon) | 73mm BSA | 73mm | 9mm | 52.5mm | Boost 148 ✅ |
| Sirrus 1.0–4.0 | 68mm BSA | 68mm | 9mm | 50mm | Non-Boost 135 ✅ |
| Sirrus X | 68mm BSA | 68mm | 9mm | 50mm | Non-Boost 135 ✅ |
| Roll | 68mm BSA | 68mm | 9mm | 50mm | Non-Boost 135 ✅ |
| Allez / Allez Sprint | 68mm BSA | 68mm | 9mm | 50mm | Non-Boost 130 ⚠️ ~6.5mm outboard of road target |
| Diverge (Aluminum) | 68mm BSA | 68mm | 9mm | 50mm | Verify QR or TA |
| Roubaix (Carbon, 2018–present) | 68mm BSA | 68mm | 9mm | 50mm | Non-Boost 130 ⚠️ ~6.5mm outboard of road target |
| Diverge (Carbon, 2018–2020) | 86.5mm BB386 EVO | 68mm | 9mm | 50mm | Thru-Axle ✅ |
| Diverge (Carbon, 2021–present) | 68mm BSA | 68mm | 9mm | 50mm | Thru-Axle ✅ |
| Crux (Carbon, 2018–2021) | 68mm OSBB Road / BB30 | 68mm | 9mm | 50mm | Thru-Axle ✅ |
| Crux (Carbon, 2022–present) | 68mm BSA | 68mm | 9mm | 50mm | Thru-Axle ✅ |
| Aethos (2021–present) | 68mm BSA | 68mm | 9mm | 50mm | Non-Boost 130 ⚠️ ~6.5mm outboard of road target |
5 Road Platform Chainline Note
The Allez, Roubaix, and Aethos are all road platforms designed around a chainline target of approximately 43.5mm (11-speed) or 44.5mm (12-speed). The Toseven 68mm motor with a 9mm offset ring produces a 50mm chainline — approximately 6 to 6.5mm outboard of this target. This produces diagonal chain angles in the smaller cogs, increased cassette wear, and degraded shifting at the extremes of the gear range. These platforms are best treated as commuter or distance e-bikes rather than performance road machines.
04 FSR Suspension Chain Growth Protocol
All Specialized full-suspension platforms in this guide use the FSR (Horst Link) four-bar linkage suspension design. Chain growth is not eliminated by the FSR design and must be measured empirically before any chain is cut.
Remove Shock
Remove the rear shock completely from both mounting points and allow the rear triangle to hang freely under gravity.
Compress Suspension
With the motor installed and the chain routed, slowly compress the rear suspension by hand through its complete travel until the rear axle is at its highest point.
Observe Tension
Observe chain tension throughout the full travel range. The chain must never go slack enough to risk derailleur contact with the swingarm, and must never pull so tight that it risks pulling the derailleur cage forward under full extension.
Observe Clearance
Observe motor housing clearance throughout the full travel range. The motor casing must not contact the lower swingarm, linkage pivot hardware, or frame tubes at any point in the travel. This is especially critical on the Enduro.
Adjust if Necessary
If chain tension or motor clearance is insufficient at any point, do not cut the chain or finalize the installation. Adjust chain length, motor position, or derailleur type before proceeding.
Chain Growth by Platform
| Platform | Rear Travel | FSR Chain Growth Severity | Notes |
|---|---|---|---|
| Epic FS / Epic EVO (Carbon) | 100–120mm | Low | Shortest-travel FSR platform — chain growth is minimal but not zero |
| Stumpjumper (Aluminum & Carbon) | 130–140mm | Moderate | Standard FSR reference platform — use empirical measurement |
| Stumpjumper EVO (Aluminum & Carbon) | 160mm | High | Do not carry figures from standard Stumpjumper — measure independently |
| Enduro (Aluminum & Carbon) | 160–170mm | Very High | Longest-travel FSR in guide — motor clearance check especially critical |
05 Frequently Asked Questions
1Can I use the DM01 on a carbon Specialized frame if I keep the torque low?
No. See Universal Rules in Section 01. The prohibition is structural, not torque-based.
2My carbon Stumpjumper is from 2018. Do I need reducer bushings?
It depends on which 2018 frame you have. If it has a symmetrical rear shock cradle (X-Wing design), it is press-fit 46mm — PF46-to-BSA bushings are mandatory. If it has the asymmetrical Sidearm design (single right-side shock arm, open left side), it is BSA threaded — no bushings required. If you cannot determine this visually, remove the BB and inspect the bore. Smooth = press-fit = bushings required. Threaded = no bushings.
3My carbon Stumpjumper is from 2019 or later. Does it need reducer bushings?
No. Every carbon Stumpjumper from 2019 onward uses BSA threaded 73mm. No bushings required on any trim level through the current 2025 Stumpjumper 15.
4My carbon Epic Hardtail is from 2018 or 2019. What bushings do I need?
PF46-to-BSA CNC-machined reducer bushings. Do not use PF41 or PF42 bushings.
5My carbon Epic Hardtail is from 2020 or later. What bushings do I need?
None. BSA threaded 73mm from 2020 onward.
6My carbon Epic full-suspension is from 2018. Does it need reducer bushings?
No. The carbon Epic full-suspension uses BSA threaded 73mm throughout the entire 2018 to present window. Note: this is different from the carbon Epic Hardtail, which used OSBB MTB press-fit through 2019.
7Does the Roubaix need reducer bushings?
No. All carbon Roubaix models from 2018 onward use BSA threaded 68mm throughout all generations. Pre-2017 models fall outside this guide’s scope.
8My Diverge Carbon is a 2019. What bushings do I need?
PF46-to-BSA CNC-machined reducer bushings. The 2018–2020 carbon Diverge uses BB386 EVO — 86.5mm wide, 46mm bore. Extensive spacer management is also mandatory.
9My Diverge Carbon is a 2022. What bushings do I need?
None. The 2021–present carbon Diverge uses BSA threaded 68mm. Order the 68mm motor and a 9mm offset chainring.
10What bushings does the Crux need?
Pre-2022 cyclocross Crux: PF42-to-BSA bushings (68mm wide, 42mm bore). 2022–present gravel Crux: no bushings, BSA threaded 68mm.
11Does the Aethos need reducer bushings?
No. BSA threaded 68mm throughout. The critical concern is structural — 35Nm lockring limit exactly. See the Aethos entry in Section 1.4 for full caution.
12How do I identify my BB standard if I don’t know my model year?
| Shell Width | Internal Bore | Bore Type | Standard | Found On |
|---|---|---|---|---|
| 73mm | ~34mm | Threaded | BSA MTB | Stumpjumper (Sidearm+), Epic FS/EVO, Epic HT (2020+), Enduro, etc. |
| 68mm | ~34mm | Threaded | BSA Road | Roubaix, Diverge (2021+), Crux (2022+), Aethos, etc. |
| 73mm | 46mm | Smooth | OSBB MTB | Carbon Epic HT (2018–2019), Carbon Stumpjumper early 2018 only |
| 68mm | 42mm | Smooth | OSBB Road / BB30 | Crux Carbon 2018–2021 |
| 86.5mm | 46mm | Smooth | BB386 EVO | Diverge Carbon 2018–2020 |
| 100mm | ~34mm | Threaded | BSA Fatboy | Fatboy |
If in doubt, photograph the inside and outside of your shell with the existing BB removed and contact Toseven support before ordering.
13Why is the Allez chainline not ideal for road riding?
The Toseven 68mm motor with a 9mm offset ring produces a 50mm chainline. Road drivetrains target 43.5 to 44.5mm. The 6 to 6.5mm outboard offset produces diagonal chain angles in the small cogs and accelerated wear at the cassette extremes. Use this platform as a commuter, not a road race machine. The same applies to the Roubaix and Aethos.
14I have a pre-2017 carbon Specialized frame. Can I use this guide?
No. This guide covers 2018 to present only. Pre-2017 carbon frames used various OSBB press-fit standards with different shell dimensions. Hardware specifications must be confirmed with Toseven directly.
15My Fatboy is a carbon variant. Can I still use the DM02?
Yes. Universal carbon rules apply — DM02 only at 35 to 40Nm with interface pads mandatory, using the 100mm motor variant. Consult Toseven directly regarding chainline figures for the 100mm motor before ordering.
