Originally Posted by
mtseymour
Beautiful ride!
My impression is that Shimano R785 uses 140 or 160mm rotors. Did you use adapters for the 180mm rotors? What's your hub, lacing pattern and rim width?
Although the product description indicates rotor sizes of 140 and 160mm, like most disc calipers the Shimano R785 will work with much larger rotors such as a typical 203mm for the rear. Caveat with this caliper is that they are very strong brakes and so 203mm may develop too much force for a frame to handle. The downside of going with a smaller rotor is reduced heat capacity (larger rotors handle heat dissipation better). You will need to decide which size will work for your setup and usage.
The appropriate adapter size required is not unique to this caliper, it just depends on the frame or fork mount provided. For example, the Whisky No.9 disc fork post mounts need a 203mm Post/Post adapter to work with a 180mm rotor, but the rear ISO mount on our Calfee uses a typical 203mm ISO/Post adapter for a 203mm rotor.