Disc Rotor Size and Caliper / Frame Compatibility

[andybones78]

Looking for people on the forum who might have either; exact experience with the combinations of parts below, or just at least a really good knowledge of disc brake calipers and changing rotors / using adapters etc. Any help well received!

I have a couple of very recently released bikes (both carbon, one Road, one Gravel) from the same brand, and a desire to use the new Yokozuna Ultimo closed hydraulic cable actuated 4 piston disc brake calipers, on my builds.

The bikes currently run with full Sram Force HRD on one, and Sram Red eTap 11 speed mech levers paired with TRP HY RD's on the other. Both of these current builds perform really well, stop great despite me being 220lbs, and use 160mm rotors all round without any adapters whatsoever (the frames are designed specifically in order to achieve this no adapter setup).

The Yokozuna Ultimo calipers ship with their own brand 160mm rotors (so one could assume or guess that they are designed to work with 160mm!?), and only include an adapter for the front fork caliper which in this case should not be needed, and in reality actually pushes the caliper the wrong way (on these frames).

The calipers attach to the frame flat mounts with the supplied bolts perfectly, but at both front and rear on both frames, the correct spacing / distance to the pads comes out to be perfect for a 180mm rotor, and doesn't work with the 160mm rotors attached to all 3 of my interchangeable wheel sets.

So the dilemma is now - do I run the new setup with 180mm rotors on the Gravel bike and try to find an adapter solution for the Road bike so I can still use the current 160mm rotors, or do I scrap the whole change / upgrade because it's not straightforward or ends up being a bit odd / ugly with adapters etc!?

Any helpful / interesting thoughts, questions or comments well received!
Thanks

[joevers]

Normally, for the rear flat mount, it's native for a 140mm rotor without adapters. You can add a spacer/mount to use a 160. Yokozuna builds that "spacer" (for lack of a better word) into their caliper.

So for a frame that takes a 140mm rotor without an adapter (which is almost all of them), you mount the Yokozuna brake and run a 160mm rotor. It sounds like your frame is designed for 160mm native, and the caliper offset is making it fit a 180mm rotor.

The front is a little more confusing, but I think the same thing is happening. You can take the plate off the front caliper and flip it around, but it sounds like you know that and it would only make the caliper further away.

[Dave]

I agree that is sounds like 180mm rotors would be needed. The bigger question is why spend all that money if both bikes are working well? The Yokozuna calipers cost a lot more than the Juin-Tech version and you'd have to change the hydraulic levers over to mechanical brake models. Force AXS levers are about $460 per pair.

I have the Juin-Tech calipers on two bikes, with 160mm Campy rotors and they work great, but I already had Force AXS rim brake levers to move over from previous rim brake frames. At the time, Force HRD levers and brakes were $700 per pair. Prices have come down, but now there are availability problems.

I spent a lot less on the Juin-Tech calipers and Campy rotors.

[FriarQuade]

At 220# you will not regret switching to 180mm rotors.

[RobJ]

I would check as others said because usually the frame is designed adapterless for 160/160 or 160/140. Then use the adapter for the latter with a 160mm rotor. For standard road/gravel this is the usual max setup. I haven’t seen 180’s.

Juin is great and use them a lot but also have mechanical levers already.


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[andybones78]

Thanks for the input so far guys, very helpful to have your incite & experience.

I'm pretty set on just running the 180mm rotors with the Ultimo calipers on the gravel bike as it seems to be a simple swap, and looks to work "perfectly" as a 160mm "native" setup but with the rotor size increase to compensate the weird sizing on the calipers.

The road bike seems to be a lot trickier - I'm trying out different adapters to try to find a workaround, but as most of you agree and rightly so; definitely not much sense in running the Ultimo's if they only work on that frame with 180mm rotors - it'll look silly and is total overkill...