In this edition of Ask a Wrench, pulled from the members-only segment of the Geek Warning podcast (June 5, 2025 episode), tech editor Dave Rome and pro mechanic Zach Edwards (Boulder Groupetto) tackle five listener submissions. They dive into whether crank preload needs loosening when adjusting an eccentric bottom bracket, share pro tips for finding tiny parts lost on the shop floor, debate the best hand cleaners and glove choices for grimy wrench work, and outline multiple strategies, including a proven manual method, for removing a stubborn SRAM DUB crankset.
Geek Warning is tailored for riders who love to tweak, tune, and push their setups. Questions and answers have been edited for length and clarity, so if you want the full nuance and discussion, you can listen to the complete members-only episode embedded down at the bottom of this post.
Q1: Adjusting an eccentric bottom bracket – should you loosen the crank?
Peter from San Francisco asks:
I have a steel Squid bike with a Oner PF30 (designed by Beer Components, made by White Industries) eccentric bottom bracket. When I adjust chain tension after a cog swap, do I need to loosen the crank preload (like on a Shimano or SRAM crank)? I know you shouldn’t preload bearings too much on systems like PF30, BB30, etc., so I wonder if rotating the eccentric without loosening things could damage the bearings?
Zach Edwards: I’ve worked on eccentric bottom brackets like this one, even if not the exact unit. The mechanism usually consists of two cups that sandwich the frame. In theory, rotating the assembly to tension the chain should move both cups together, thanks to the crank spindle holding everything in place.
However, if there’s any looseness or misalignment, one cup might move while the other lags. That’s when you might need to use a bottom bracket tool or lockring wrench to rotate both evenly. But even in that case, I don’t think you’re risking any real bearing damage. The rotation you’re doing to tension the chain is quite minimal – not enough to load up or wear out the bearings.
Dave Rome: I’ve used similar setups too. I actually have a PF30 bike in the garage with a Wheels Manufacturing eccentric BB. In my experience, you can sometimes move the BB without loosening the crank, but it depends on how much friction is involved. In some cases it'll be just right and move freely. But if things are tight, the preload might prevent the BB from spreading open slightly – and that can make it hard to tension the chain.
So I’d say: try adjusting it without loosening the crank preload. If the eccentric bottom bracket moves, then all good. If it doesn’t budge or tension is felt in undoing the eccentric bolts, then back off the crank preload slightly. For a SRAM crank, that’s as easy as undoing the preload collar. Shimano is a bit more involved – you need to loosen the pinch bolts and adjust the plastic cap.
Q2: How to find dropped small parts on the workshop floor
Nicholas from Austria shares this workshop trick:
“When I drop a small part, like a bearing or screw, I use a flashlight flat against the floor to sweep the area. It casts a shadow behind the object, helping it stand out. I got the tip from a goldsmith who used a laser pointer for this purpose where dropped items are highly valuable, but a torch still works well in messier bike workshops.”
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