Rockshox Yari – Rotor Adapter sizing

Hello good people; wonder if one of you can help me please because I’m not the best with these things and it’s a hard thing to google:

I am in the process of swapping my SLX brakes onto my 2021 Slash, replacing the Guide T brakes on there.

The front rotor is 203mm – and I have a 203mm adapter for it as well (all taken from my old bike). My old bike had a Fox 34 fork on it.

so I take the rotor, caliper, and adapter off the old fork, bung it onto the new one in the correct configuration, and my caliper is sitting too high, meaning the rotor is only caught by the lower half of the pads – I can already feel the brake isn’t braking properly just pushing it around in the shed. But without the adapter the caliper is too far away from the posts before the top of the slot fouls the rotor.

Would I be right in thinking that the standard for the old Fox fork would be 160mm…and the Yari has a 180?

if so, do you know what caliper I need to ask the bloke in the bike shop for tomorrow please?

Would I be right in thinking that the standard for the old Fox fork would be 160mm…and the Yari has a 180?

Yes

https://bike.shimano.com/en-EU/product/service-upgradeparts/shimano/ESMMAF203PPM.html

I’d hazard a guess that your assumption is correct. Post Mount or PM adaptors are sized by how much they add on to the diameter. So you probably have a PM40 adaptor to take you from 160 to 200. It should/may have some writing on it telling you this. But it sounds like you need a PM20 adaptor. That’s what I run on my Rockshox Revelation with a 200mm rotor.

Cheers folks. I’ve gone through life thinking all forms have a standard offset, despite constantly faffing around with brake setups etc. must have always got it right by sheer luck.

Merlin are doing 180mm to 203mm adapters for £3.99 + p&p

https://www.merlincycles.com/shimano-disc-brake-brackets-46083.html

Wouldn’t it have been easier just to have taken the adapter out and looked if your caliper fitted over the rotor without it before posting?

Did you get out of the wrong side of bed @dave_h? Sounds like they did that already but still were not sure.

@dave_h – I did that…What’s the point in forums if you cant post there asking for help with something you didn’t know before? Not exactly ruining these guys days by forcing them to reply.

@cerrado-tu-ruido – brilliant thanks for that!

It even varies within fork models, I’ve 4 sets of Yari’, three are 180mm mount and one is 160mm. Be aware +20 and +23mm mounts are slightly different, but it’s easy to make a +20 into a +23 using 2×1.5mm washers.