Iv set up my new Formula Rx front brake using a Shimano 180mm center lock rotor and shimano 180mm IS to post front brake adapter as these are bits I had lying around.

All is well and the brake works fine but I as surprised to find that in order to line the calliper up I had to use quite a lot of thick washers and shims between the fork and the brake mount.

I was surprised since I assumed everything (forks, hub, rotor, adapter, caliper) would be built to standard sizes.

Am I risking problems using the washers – there is probably about 2-3mm worth and the threads of the bolts do not completely engage the threads of the adapter (probably about 3/4 engaged).

Better shimmed to fit, than just left as bought, IMHO.

Should be fine.

Speaking of mix and match, I’ve often wondered if I could mix lever and calliper of different manufacturers. E.g. a Hope lever and an Avid calliper. I guess it would depend on displacement of the lever piston being about the same. Anyone done this?

Piston displacement and reservoir volume are the only variables I can think of in terms of comparability.

wouldn’t have thought reservoir volume mattered much, its all about fluid displacement volume.

oh, and fluid used – don’t mix mineral oil (e.g. shimano) with dot 4 (e.g. avid)

I’d definitely fit longer bolts!

Also- I’ve made a couple of pairs of frankenbrakes in the past. You may also need to consider hose diameter and end fittings. Lots of kits available for this though.

wouldn’t have thought reservoir volume mattered much

My thinking was….
If you increase the size of your slave piston which could be the case if you fit a different caliper, the difference in volume in the system between new pads and dead pads will be greater – meaning a larger volume reservoir is required.