Chainring Spider Mount Types I have been wondering about the different types of spider (or direct mount chainrings) to crank arms and was surprised that I could not find anything spot-on about it.
I kind of know that BMX direct mount chainrings attach to crank arms differently but I am curious about the &quot;other&quot; types.
There is a profusion of information on the spider to chainring mounts - the outer mount (e.g BCD 110) - but not much on the inner mount - the spider to crank arm mount.
What are the different standards in place when it comes to how the spider mounts to the crank arm ?
If someone wants to write an answer that really runs everything down, I would applaud that. But it would probably be out of date the following week.
What I will say is this: for the most part, every current big crank manufacturer has their own direct mount standard, for which one can buy either a direct mount chainring or a spider adapter. Shimano, SRAM, Race Face, FSA, and Cannondale are all examples I can think of off the top, and there's more. You can get in the weeds quickly these days if you get a direct mount ring or spider that's made for anything else but the specific crank and specific rear end spacing you're working with.
For the most part, there is no cross-compatibility. There are a couple cases where two different manufacturers use the same physical interface. Cannondale and FSA are like that. The spline pattern and the lockrings are the same. But what's important to understand is that even if the interface is the same, chainring offset considerations will sometimes dash any hope of cross-compatibility with using a ring or spider intended for one crank on a different one. Whether that's true and why gets into a larger discussion of the decisions manufacturers now make in making their cranks and attempting, or not, to create arm compatibility among the different rear end spacings and drivetrain types.
Wolf Tooth and OneUp both make third party rings for these sorts of cranks, and you can often figure out what you need to know from studying their sites.