Cyclocross Frames and Disc Brake Compatibility?

Question

I'm looking for some guidance on how to determine if a certain disc brake is compatible with a certain cyclocross frame.

Specifically, here is my particular situation. I have an extra set of Spyre TRP brakes (and wheel set with matching rotors). I'm looking to get a carbon frame direct from a Chinese manufacturer and build a bike, preferably from Dengfu since they seem to have a very good reputation and have been around for quite a while now.

Originally I was interested in the FM286:

http://dengfubikes.com/Cyclo_Cross/112.html

But that frame is not available in the size I would need until another production run can be produced, which will be about a 3 month wait. Dengfu does have their older cyclocross frame available in the size I'm looking for, the FM059:

http://dengfubikes.com/Cyclo_Cross/110.html

I'm really not concerned with the 50 gram weight difference, but I would prefer the FM286 due to the newer style front derailleur mount.

Anyhow, my question is how universal is the compatibility of disc brakes to frames? Would the Spyre TRP Cs fit both frames in the front and the rear? I notice with the older style frame (the FM059) the rear caliper mount is on the bottom of the seat stay, but on the newer frame (the FM286) the rear caliper mounts are towards the rear of the chain stay. Does this matter as far as rear caliper compatibility? Please advise, thanks!

Answer 1

There are two (ignoring flat mount for the moment...) main standards in use for disk brake mounting systems, IS 51mm and 74mm Post Mount (Disk Brake Mounting Standards - Bikeman). Both of the linked frames appear to be using 74mm Post Mount on both the frame and fork since the brake mounting lugs are parallel with the plane of the wheel. TRP Spyre calipers default to post mount, so your calipers would bolt up fine on those mounts (on either frame) barring any manufacturing defects.

The main disadvantage of having a brake mount on the seat stay (outside the rear triangle) is that the caliper will interfere with standard racks, necessitating the purchase of disk brake compatible racks that are usually slightly more expensive. Moving the mounts to the chainstay (bringing the caliper inside the rear triangle) makes the frame compatible with a wider variety of racks if that is something you're interested in.