With all the different types of bottom brackets and adapters available, I can’t seem to find a straight answer on this.
Will a frame which has a BB86 bottom bracket already installed straight up accept a SRAM GXP crank or is additional hardware required? My research leads me to believe SRAM’s GXP cranks are made for the “normal” Shimano designed bottom brackets, however I’ve seen enough confusing forum posts out there to leave me with some doubt.
Any clarification is greatly appreciated.
To add extra confusion there are also two GXP configurations. GXP and GXP-PF, which is for the new Trek/Giant standard. Not to be confused with the differences between BB30 and PF30.
However, any standard crank designed for the modern threaded standard should fit into a BB86/BB90 BB shell. Including any Hollowtech II, MegaExo, X-Type or GXP crank.
You should still measure the spindle and BB size to make sure the tolerances are all fine to be sure. I can well imagine different companies might have different specs despite theoretical compatibility.
Most GXP cranks will fit into any kind of bottom bracket. Some will require the use of adapter cups or some variation of sorts but will usually work. The only problem with using adapters is that you need to use the proper type and amount of spacers. If you don’t get it right, you’ll either end up with off-center cranks, crank play, or too many spacers and your crank won’t stay on. For example, using gxp on a BB30 frame, you’re still supposed to use the wavy washer for preload however, it’s designed to fit on a BB30 spindle. So when you try to use it with GXP crank, it’s too big to properly brace against the crank arm, so you’re stuck trying to find another one.
In my own personal experience, I’ve been using GXP on BB30 with adapters and it’s tricky to say the least. I’ve gone through a non-drive side crank arm trying to get the right balance between proper torque and seizing crankarm movement.
From working on various bikes from different shops, i’ve noticed a lot of variation in hardware used and improper installations even bikes with multiple conversion kits, i’ve come to the conclusion that most places have no idea what works. Too many industry standards and too much variation in the hardware used to make them work. Like adapter cups for example, some are designed to replace dust caps on bearings, and others are not and meant to work with PF30 shells, and you basically have to figure out how much play you end up with, how many spacers you need, and once you torque it down does your crank actually turn. If not, you’d better start over and switch everything to find out what works.
That being said, it’s not always a pain in the ass and you can usually getting it working pretty well. The only issue otherwise that might drive you crazy is BB creaking. Most adapters leave a small space in-between the cup and the frame so there’s a nice little gap for dirt to get in there. So whenever you get caught out in the rain, you can expect to have to take apart everything and clean it or people will get annoyed with you pretty quickly.
Dennis knows what I’m talking about
Overall compatibility for BB30 is rather different (and much worse) than for BB86/90 which is what the question is about.
BB30 is, IMO, fucking stupid. BB30 makes sense in one application: when used with an integrated Cannondale crank designed specifically for BB30.
Having to use large sets of spacers and the like automatically sets you up for torque/preload issues with basically guarantees you performance issues (mostly in largely cosmetic but utterly infuriating creaking). But since nothing pisses me off more than random and annoying sounds from my bike, I’ve been staying away from BB30.
And perhaps more importantly, all of these new BB standards are mostly stupid marketing smoke and mirrors. Show me some FEM and test data or GTFO.
At any rate, GXP cranks should be totally fine in BB86/90. They are fiddly as hell in BB30.
Don’t even get my started on the moronic issues with bearing environmental exposure on BB30 either. The external cup mouted Hollowtech stuff was bad enough, but BB30 brings it to a whole new level of stupid.
Thanks guys, that clears things up. I should be good to go once the parts arrive.
Justin’s cranks went squeak squeak squeak
the only sensible solution to this, is to get a bb30 to gap converter sleeve and epoxy it to the inside of the frame. goodbye bearing cartridges. No more BB30 issues