Flat mount to flat mount 160mm adapter confusion

I’ve been gathering together components for a Ragley Trig build and bought a couple of 160mm rotors. It turns out that the default rotor size for flat mount is 140mm so I’ll need adapters.

I have a couple of these on order – Shimano SM-MA-R160D/D Mount Adapter | Wiggle which, supposedly, can be used front or rear to take a 160mm rotor.

The image on the Wiggle page shows the adapter screwed in from the rear and Shimano’s instructions (SI-8NU0A-001-00-ENG.pdf (shimano.com)  confirm this.

What do I do at the fork? Do I just screw them in from the front like post mount adapters or do I need a different one?

Sorry, I’m completely new to flat mount.

Sorry, I’ve also noticed that the rear flat mount on the Trig doesn’t run through the frame (as shown in the Shimano instructions), but is offset to the side. I assume the adapters still screw in from the rear of the mount?

Yes, the rear caliper screws from underneath. I think forks usually come with a front adapter, you mount the caliper to the adapter and then the adapter to the fork

Thanks, I haven’t opened the groupset fully yet so I’m not sure if the front brake (GRX400) has an adapter included (perhaps I only need one SM-MA-R160D/D.

The Wiggle listing does say that they can be used front or rear, frame or fork, so are they not useable as fork adapters.

Sorry, I’m probably being thick.

If you Google flat mount caliper images, then you’ll see how the caliper is mounted on the fork. There is a long adapter piece that fits between the caliper and fork, even with a 140mm rotor. The fork needs this different mount as it can’t have a bolt from the front of the fork right through to the back and into the caliper (as per how the rear caliper mounts)

Cheers, I’ll have a hunt around.

So if the front caliper needs the mount to fit a 140mm rotor, do I then need to add the additional 160mm adapter on top? The post mount approach seems a tad simpler.

No, you just unbolt the 140mm adapter, turn it upside down and bolt it back together again. Job jobbed.

Thanks. I’m a bit green when it comes to newer stuff, my Swift is IS at both ends. There’s bound to be something on YouTube too.

Going back to the SM-MA-R160D/D adapters I have on order, is the Wiggle listing wrong then? Can they only be used on the rear?

What fork have you got and does it have an adapter attached to it already?

It’s a Ragley Trig fork with no adapter attached.

I have a boxed GRX 400/600 groupset which I haven’t really delved into, but I suspect that there’s the mounting piece in with the brakes.

When I contacted Ragley about using 160mm rotors on the Trig (their pre-built Trigs are 160mm each end) they said that I’d need adapters, hence the Shimano ones.

I guess that this is what you’re referring to for the front brake:-

You could save yourself all of this angst by a) opening the box you already **** have and b) looking at the Shimano tech docs.

Anyway, as you’re too lazy to do either, front and rear flat mount adaptors are different. Your front brake caliper will have an adaptor. On a 140mm native fork it will work with a 140 or 160mm rotor depending on which way up you attach the mount. With a 160mm native fork it will work with 160 or 180mm rotors depending on which way up you attach the mount.

(Sorry, been drinking)

I went through a similar confusion recently after buying a road bike that came with 140s and I wanted to run 160s so tried to sort the adapter in advance with nothing to look at.

Rear flat mount standard is 140 native so for 160 the adapter is as your link above is what you need.

Front uses a plate that is 140 one way or 160 if flipped. Hopefully that’s included with the front caliper and you can set it up at 160 before bolting to the fork. Assuming fork is flat mount…

Great, I think I know what I’m doing now. I’ll check the front brake but I assume the mounting piece will be supplied. I was a bit thrown by the SM-MA-R160D/D listing saying front or rear and assuming that I’d need one at each end; they would seem to be rear only.

Again, check the rotor size the fork supports natively. My Revolt came from the factory as 160 front / 140 rear, and the fork’s default position fits a 160 rotor. I only needed a rear adaptor to bring the frame up to 160 at the back.