Shimano Hollowtech-II Crank Spacer by 4Crawler

Last crawled date: 3 years, 1 month ago

This is a spacer for the spindle on a HollowTech-II MTB bottom bracket that allows narrowing the crank (Q-factor) by 2.5mm - 7.5mm by eliminating one or more of the outboard bearing spacers. This spacer fits over the end of the crank spindle and allows the "fixing bolt" to press against the crank arm, via the spacer, and properly pre-load the bearings.
Above 2.5mm narrower, you'll need to remove some of the inner splines inside the crank arm. I went 0.2" (5mm) deep with a 15/16" drill bit then cleaned up the rest of the splines with a Dremel bit. This allows the crank to press farther down on the spindle splines. However, this prevents the "fixing bolt" from contacting the outside of the crank. Thus this crank spacer that fits over the spindle and pushes against the crank.
I now run with no spacers on my MTB bottom bracket and get approx. a 170mm Q-factor between the outer faces of the cranks. This also gives me a 45mm chain-line on the front triple crank, reducing chain angle in the small/front - large/rear combination.
The spacer and fixing bolt can be removed once you torque the crank clamp bolts down. This can help reduce the chance your of shoe rubbing on the fixing bolt sticking out of the crank spindle.