DScience
New Member
- Jul 19, 2026
- 3
- 0
Hi there,
First post here.
I had an Ibis Oso V1 with the Bosch Gen 4 motor, and I recently picked up a new Santa Cruz Bullit with the Bosch Gen 5. My plan was to swap most of the components from the Oso onto the Bullit, and everything went smoothly until I got to the chainring.
I bought the Park Tool BBT-18 for the lockring, thinking it worked with a standard 36 mm socket so I could torque it properly. When it arrived, I realized it's an 8-point interface, so I had no way to use a torque wrench.
Unfortunately, I also made another mistake. I installed my SRAM XO Transmission chainring from the Oso, not realizing that the Gen 4 and Gen 5 Bosch motors use different chainrings. I finger-tightened the lockring first to make sure the threads started correctly, then used the BBT-18 with a chain whip and adjustable wrench to tighten it by hand.
After tightening it, I noticed the slightest amount of lateral play in the chainring. It wasn't visible, but I could barely feel it if I grabbed the chainring and tried to move it side to side. I tightened it a bit more until it felt secure, being careful not to overdo it.
I ended up riding the bike for about three rides (roughly 60 miles total).
Last night I did some more research and realized the Gen 5 motor requires the newer DU38 chainring, which unfortunately isn't very common yet. I immediately pulled the crank and removed the chainring. The lockring came off without any issues, and after inspecting both the lockring and the motor threads, I don't see any signs of damage or cross-threading.
For those of you with Bosch or shop experience, do you think riding about 60 miles with the incorrect Gen 4 chainring could have caused any damage to the Gen 5 motor or the drive interface? Everything looked normal when I took it apart, but I'm hoping I didn't unknowingly hurt anything.
First post here.
I had an Ibis Oso V1 with the Bosch Gen 4 motor, and I recently picked up a new Santa Cruz Bullit with the Bosch Gen 5. My plan was to swap most of the components from the Oso onto the Bullit, and everything went smoothly until I got to the chainring.
I bought the Park Tool BBT-18 for the lockring, thinking it worked with a standard 36 mm socket so I could torque it properly. When it arrived, I realized it's an 8-point interface, so I had no way to use a torque wrench.
Unfortunately, I also made another mistake. I installed my SRAM XO Transmission chainring from the Oso, not realizing that the Gen 4 and Gen 5 Bosch motors use different chainrings. I finger-tightened the lockring first to make sure the threads started correctly, then used the BBT-18 with a chain whip and adjustable wrench to tighten it by hand.
After tightening it, I noticed the slightest amount of lateral play in the chainring. It wasn't visible, but I could barely feel it if I grabbed the chainring and tried to move it side to side. I tightened it a bit more until it felt secure, being careful not to overdo it.
I ended up riding the bike for about three rides (roughly 60 miles total).
Last night I did some more research and realized the Gen 5 motor requires the newer DU38 chainring, which unfortunately isn't very common yet. I immediately pulled the crank and removed the chainring. The lockring came off without any issues, and after inspecting both the lockring and the motor threads, I don't see any signs of damage or cross-threading.
For those of you with Bosch or shop experience, do you think riding about 60 miles with the incorrect Gen 4 chainring could have caused any damage to the Gen 5 motor or the drive interface? Everything looked normal when I took it apart, but I'm hoping I didn't unknowingly hurt anything.
