Скачать или смотреть Shimano HollowTech-II Bottom Bracket Narrowing, Part 2

Finishing touches on narrowed bottom bracket with fixing bolt spacer and shorter inner shield.

To cover the exposed splines on the spindle and allow the fixing bolt to press the crank arm against the bearing housing, I designed a printed a spacer, 24mm to fit the over the splines, 28mm ID to fit the recess in the crank arm and 5mm tall. It was printed in ABS plastic on my Type A Machines Series 1 Pro 3D printer, 100% infill

This leaves a gap of 23mm between the spacer and the bearing and the crank itself is 24mm thick. Thus there is 1mm of clamping pressure available for setting the bearing pre-load, which seems to be sufficient. Once the pre-load is set, you use the pair of pinch bolts to clamp the crank onto the end of the spindle.

The original Shimano inner shield tube was shortened about 7.5mm by cutting the end portion free of the thinner center section. There's a ridge on the inner section at just the right spacing for the narrowed width, which makes me think this was intended. I glued the outer ring to the inner section and set that to ~50mm width before installing between the bearing cups. This shield is only there to keep water and dirt that might fall down the seat tube from getting into the bearings.

Results:
Before: 175mm Q-Factor, 5mm pedal offset
After: 170mm Q-Factor, pedals centered
With a stock HollowTech-II MTB crank set, your Q-Factor would be 177.5mm, I had already removed one 2.5mm spacer on mine. First test ride was nice, having the narrowed Q-factor and centered pedals just felt right.

And 8+ years later, still loving the narrowed and centered crankset. I had been having an on-again, off-again pain in my left knee (the side that was offset by 2.5mm before) and that has now gone. I've subsequently removed the spacer ring and just leave the end of the crank spindle exposed. Gives move room for my heel to move in and out while riding technical single track trails. And no issues at all with the modified crank loosening up.

Bottom bracket from Acer Racing:
https://www.acerracing.com/Bottom_Bra...

3D model of spacer available on Thingiverse:
https://www.thingiverse.com/thing:235...

And TinkerCad:
https://www.tinkercad.com/things/bvXi...
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And as always, thanks for watching

Intro:
Louisiana Fairytale by Austin Rogers
https://web.archive.org/web/201704022...