[cda 455]

I know forks like Niner CF forks, say right on the forks, "Max. rotor size 185mm", is one example.

But what else dictates the rotor size? I like the idea of using as big a rotor as possible up front and would like to know what limitations (Besides the one given) to look for when researching.

I'm currently researching cycle frame geometry, carbon forks, etc. I'm looking to build a touring-type geometry set up with mechanical disc brakes, front and rear. MTB frame and touring bike frame geometry is what I've narrowed down in what I'm looking for because I want a high/tall stack dimension.

 

[Squash]

There isn't anything else to look for. The manufacturer of the fork is certifying that the fork will handle X size rotor. That's all there is to it. They are certifying that the fork has been tested with and will stand up to the torque, flex, etc. placed on it by the size rotor that they specify without cracking, breaking or the wheel pulling out of the dropouts. And stating by implication that they do not recommend using a rotor of a larger size. Doing so is at your own risk, most likely will void any warranty, and may well damage the fork or you. Any fork that is disc brake compatible that does not give a maximum rotor size spec, for reasons of safety, should be assumed to have a maximum of 160mm. I would also find that fork manufacturer rather suspect, as they are not concerned enough about either/or product liability or consumer safety to test their forks and publish a spec for it.

The bottom line is, you have nothing else to go on. The fork manufacturer is putting the companies collective butt on the line when giving a max rotor spec. So unless they are complete idiots, you can be pretty sure that they've done their home work and taken things into consideration that you or I wouldn't even think of in coming up with that spec.

I would also suggest contacting manufacturers and asking about the use of their fork with disc brakes and your intended use. If you are looking at loaded touring, a fork that was not designed specifically for loaded touring, was not likely tested with more load than the bike and rider would put on it. Fully loaded, self supported touring can add quite a bit of weight over and above what the bike and rider weigh. If you are just looking at day trips or commuting you'd most likely be fine with any fork you choose.

Good Dirt