Ok, BB30 to GXP adapters are available from Wheels Manufacturing for £ 28 so why make one? The bike, specialized epic, has PF30 which seems to be slightly different; with this adapter, the bearing won't rotate freely even with the crank bolt being done up a fraction of the recommended torque. (I was using thread lock to stop it undoing but that is far from ideal)
Removing the crank and doing up the bolt to 30 lb ft, it can be seen that the adapters are about 1.5 mm too long. I cannot turn down the Delrin adapters because I do not have a lathe so the alternative was to make my own from aluminium tubing. As luck would have it, 30mm tube with 3 mm wall thickness and 32 mm with 1 mm wall thickness are available and these were cut to length, as per photo.
The 30 mm tube takes up the space between the crank spindle and BB30 bearing race whereas the 32 mm tube, which is pressed over the 30 mm tube, sets the distance of the crank from the BB. (It took a few hours to sand down the 30 mm tube since it is close to 30.1 mm and wouldn't fit in the BB30 race).
Notice there is a insert inside one of the adapters since GXP is 24 mm on the non drive side - this was made from the 32 mm tube with a slice out of it to reduce its diameter.
Now the crank spins freely at the recommended torque as well as being 15 g lighter
Cost for 300 mm of each tube was about £ 9.
Removing the crank and doing up the bolt to 30 lb ft, it can be seen that the adapters are about 1.5 mm too long. I cannot turn down the Delrin adapters because I do not have a lathe so the alternative was to make my own from aluminium tubing. As luck would have it, 30mm tube with 3 mm wall thickness and 32 mm with 1 mm wall thickness are available and these were cut to length, as per photo.
The 30 mm tube takes up the space between the crank spindle and BB30 bearing race whereas the 32 mm tube, which is pressed over the 30 mm tube, sets the distance of the crank from the BB. (It took a few hours to sand down the 30 mm tube since it is close to 30.1 mm and wouldn't fit in the BB30 race).
Notice there is a insert inside one of the adapters since GXP is 24 mm on the non drive side - this was made from the 32 mm tube with a slice out of it to reduce its diameter.
Now the crank spins freely at the recommended torque as well as being 15 g lighter
Cost for 300 mm of each tube was about £ 9.
