Hi all, I'm a bit perplexed and hoping for some insight. My bike is a 2021 Specialized Diverge and it is running Sram Force flat mount calipers and a 160 mm rotor. Currently, have about 2000 miles on this set up and it works well, but I'm always trying to pimp out the brakes. Looking to step up to a 4 piston caliper, I ordered the Hope RX4 Sram Front Flat Mount Caliper a few months ago. These calipers specify that they ONLY work with 160mm rotors. Well, it finally came in today and it doesn't seem to fit. When mounted to the fork, the caliper sits way to high. The 160 mm rotor only goes about half way up the pads. I couldn't get a great pic, but essentially, if I were to squeeze the brakes, only the bottom half of the pads would contact the top half of the rotor. The caliper just rides too high and since it is a direct mount, there doesn't look like a thing I can do about it. I guess, I 'm curious about what is going on here. Why would they be so far off? Is the fork optimized for a 140mm direct mount? Is there an adapter? Or am I just SOL?
I answered this over on mtbr, but I'll answer here so everyone else can see. Maybe I can clarify it a little also. Force calipers are designed for use with 140mm rotors. To use them with 160mm rotors you place an adapter under them. If your stock Force calipers had adapters, you should not use these adapters with the Hope caliper as it will space it out 20mm too far (The Hope caliper has this spacer built in to its body essentially) In this case you simply need to remove the adapter.
If your Force caliper did not use an adapter, then it means the fork was designed to already space them out for 160mm rotors. If you place the Hope caliper on a fork that is already spaced for 160mm use without an adapter, it will place them 20mm too far out. In this case your only option is to get a new fork, or use a 180mm rotor (if your fork allows this, most do not).
If you place the Hope caliper on a fork that is already spaced for 160mm use without an adapter, it will place them 20mm too far out.
Thanks, this is what I was worried about. Bummer, I really wanted to try these after waiting 2 and a half months. I'm pretty sure the fork doesn't allow for a 180mm rotor.
A larger rotor can produce more torque, maybe more than the fork is designed for. My 3T Luteus II is specified for rotors to 180 mm, I believe that's a bit out of the ordinary.
A person on another site sent me a link to a review that mentions that the fork for the 2021s can run a 180mm rotor, so I ordered one and will see if it all works together. I can't find any official word from Specialized, surprise, surprise, but I'm cautiously optimistic.
We could use better pics, but you should be able to flip or remove the thing between the caliper and the fork. It may still be on the SRAM caliper if you didn't remove it.
So, here are some pics of the caliper. As you can see, this flat mount design does not use any mounting plates. It is designed to bolt directly to the fork using the existing holes.
Ok, so after a little confusion and some help from the community, my problem is solved. My 2021 Diverge was designed around 160/180 mm rotors, but I couldn't find that info anywhere. My confusion was exacerbated because Specialized shipped the bike with a flat mount adapter marked 140mm/160mm; AND, because Hope advertises the RX4 Direct Flat Mount caliper as compatible with ONLY 160mm rotors. So, since I was already running 160mm rotors, I figured I was good. When the calipers didn't fit, I was confused. Thanks to @Joe Nation on MTBR for linking a great source; it really helped a lot. I managed to corroborate that source with another, and another. Based on this evidence, I ordered the 180 mm center lock rotor, mounted everything up, and installed/bled the caliper.
So after going through all of that, I am happy to report back on my initial impressions. First of all, the caliper works and works very well. Once I got it bedded in pretty well, I have to say that RX4 quite powerful with predictable modulation. I felt the Force caliper while possessing decent power, really felt vague at the lever, and did tend to lack top-end stopping power, especially on long steep down hills and fast approaches to downhill singletrack switchbacks. I can't wait until, the rear caliper finally ships.
![[bmc-scheibenbremsadapter-front-flatmount-300710-820728]](https://cdn.bike24.net/i/mb/27/e4/01/bmc-scheibenbremsadapter-front-flatmount-300710-820728.jpg)
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