🚲 Frame ​
I'm using a custom XL version without the battery holder. North Bay Bikes will take care of that for you.
| Model | ST | HT | BB Drop | RC | ST Angle | HT Angle | FL | Offset | Wheelbase | TT | Reach | Stack |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| CM-Alpha1 | 432 | 130 | 60 | 468 | 73.5° | 68° | 528 | 51 | 1170.1 | 605 | 412.2 | 651 |
Specifications ​
- Materials: Aluminum alloy 6061, T4/T6 heat treatment. Front Triangle TIG
- Motor: Lightning Rods-Small Block Ultra Drive System
- Frame size: 432mm (Med) Lg & Med frames are standard stock. Sm & XL - on request
- Dropout: 148x12mm
- Rear axle: 173Lx12mm OD/P1.5
- Max. Tire: 29x2.60, 27.5x3.00
- Headtube: 44/56mm Tapered headset
- Seatpost: 30.9 ID
- Max. Chainring: 36T for LR-SB Ultra Drive unit / 44T for Bafang Ultra M620
- Drive type: Belt / Chain Drive
- Brake: Disc Post Mount 160mm Rotor (CM versions sold with 203 front/220 rear)
- Routing: Internal front triangle, external RC
- RC: 468mm (15mm extendable)
Guide to Fixing and Adjusting the Bottom Bracket (BB) and Pulley System
Issue Overview ​
During shipping or handling, the bottom bracket (BB) and large belt pulley may shift, leading to difficulties in crank installation, misalignment, and unusual noises when turning the motor by hand. This guide provides a step-by-step approach to diagnosing and fixing these issues.
Diagnosing the Problem ​
Signs of a Misaligned BB or Pulley ​
- Cranks barely fit or have restricted movement.
- The BB is difficult to turn by hand at certain angles.
- Scratching or creaking noises when turning the motor by hand.
- The large belt pulley has shifted and is not flush against the BB lockring.
Fixing the Issues ​
1. Realigning the Bottom Bracket (BB) ​
If the BB appears misaligned or hard to turn at certain angles:
- Loosen the two small set screws under the BB.
- Use a mallet and a soft piece of wood to gently tap the BB back into place.
- Confirm smooth rotation by turning it by hand.
- Retighten the set screws once aligned.
2. Adjusting the Large Belt Pulley ​
If the pulley has shifted out of place:
- Apply even pressure with your hands to push the large pulley back into place.
- The pulley should rest against the BB lockring (red arrow in provided image indicates correct positioning).
- If necessary, use a flat piece of wood and a mallet to gently tap the pulley back.
- Check behind the pulley to ensure it is fully seated.
Note: The pulley is made from a non-metal material with an aluminum outer ring. Handle it carefully to avoid damage.
3. Ensuring Pulley Stability ​
- If the pulley moves too easily, ensure the crank is properly installed.
- The white PVC piece, when installed with the crank, keeps the pulley from shifting.
- If using a non-standard crank (not supplied by the manufacturer), spacers, shims, or washers may be needed to fill any gaps.
- Do not over-torque the crank, as excessive tightening can cause binding.
Checking Belt Alignment and Tension ​
1. Checking Belt Alignment ​
- After repositioning the pulley, rotate the motor by hand to let the belt re-align naturally.
- If the belt produces excessive noise or appears misaligned, remove the top and side bolts of the small pulley cover (keeping the bottom bolt loose) and rotate the cover down.
- Turn the motor by hand a few times and inspect the smaller pulley and belt alignment.
2. Adjusting the Belt Tensioner ​
- No immediate adjustments to the belt tensioner should be necessary if the system is aligned correctly.
- The belt tensioner location is provided for reference but should not need modification at this stage.
Final Checks ​
- Reinstall all bolts and covers securely but without over-tightening.
- Perform a final hand rotation test of the crank and motor.
- Expect minor creaking from the belt; this is normal.
- If the BB remains rough in some angles, it could be normal resistance or slight belt vibration, no immediate action is required.
Conclusion ​
Following these steps should resolve issues with crank fitting, BB alignment, and pulley positioning. If problems persist, further consultation may be needed, especially when using non-standard components. Enjoy the build process, and ensure everything is securely in place before your first ride!