Greiselman

Is it possible to add a spacer to widen the distance between my left crankarm and the bottom bracket/frame?

For some reason, my Pioneer power meter (built into my left crank arm) has started rubbing my downtube very slightly - I'd imagine just 0.5mm would give it enough clearance but I'm not remotely familiar with using spacers in the bottom bracket / crankarm spindle.

2018 Trek Domane SL6, Ultegra R8000.

blamester

So it wasn't rubbing but now it is?
Figure out what changed?
And then come up with a solution.

cpach

.5mm out of spec for axle engagement isn't a big deal, so I'd go ahead and try a very thin spacer. You'd either need a 24mm ID spacer to go on the axle between the BB and crankarm .https://www.amazon.com/Wheels-Manufa...8-1&th=1&psc=1 . Normally I'd say go to your LBS, as they normally have them lying around, but given the circumstances online may make sense. You'll just need a 5mm wrench (preferably with a torque wrench, but otherwise, this pinch bolt isn't too sensitive) and a Shimano preload cap tool.

August West

The only problem I see with using a .5mm spacer it might be tough to get the pin on the "stopper plate" (as Shimano calls it) to align with the hole machined in the axle. I had a Domane SL 6 that to get the stopper plate to sit down I had to snug up the preload cap pretty tightly to get the arm on far enough for pin to drop in the hole. Moving the crank arm out .5mm I don't think it would have worked. If it ends up not being able to seat the plate you could enlarge the hole 𝜙1mm but that is not something I would try at home on a hardened steel axle.

Greiselman

Thanks - I just had a tuneup so I thought perhaps the mechanic might tweaked something (exchanging emails with him now) but it also seems like the plastic power meter unit might have separated the tiniest bit from the crank arm.

Thanks - I'm going to see if adding the 0.5mm spacer works and if I encounter this problem, I'll probably take it into the shop.

The responses are much appreciated!

cpach

I'll bet it works--my guess is that Shimano built around a BB width tolerance of at least +/-1mm.

Greiselman

Wanted to close this out... I was actually able to add 2x 0.5mm spacers, which gave me more than enough clearance and didn't cause any issues with the stopper plate.

Thanks to everyone who weighed in!