I have a CX bike with PM fork and FM frame, and am looking at getting hydraulic brakes. Are there any performance reasons for getting the flat mount brake caliper for the frame, over a post mount with an adapter?

Looking at RS785 PM and RS805 FM calipers which I think take slightly different pads – would prefer to run the same pads all things being equal.

Not sure there’s much in it apart from aesthetics but a flat mount caliper ought to be less prone to vibration or movement since it’s  more directly attached… Doubt there’s a significant difference though.

on frame? so rear brake? I can only think flat mount looks neater as it’s a smaller package overall, I would say performance difference would be zero

be warned rear flat mount calipers only come with one set of bolts, though there are 3 lengths to choose from – and they aren’t cheap buying them on their own, I found this out the hard way

No performance difference, pure aesthetics.  I read it was initially to make it look less mountain bikey.

be warned rear flat mount calipers only come with one set of bolts, though there are 3 lengths to choose from – and they aren’t cheap buying them on their own, I found this out the hard way

And, if you do need to order some, the length that they are labelled with is the thickness of the frame, where they pass through – NOT the length of the bolt itself.

This matters little, though, as you can’t fit a flat mount caliper to a post mount fork (even with an adaptor), so you will have to buy post mount. (Unless you want to buy a pair of post mount calipers and a pair of flat mount calipers, use one of each and keep the others for spares)

I do wish that, when designing frames with flat mounts, they would design a fork to go with it, instead of just using an existing post mount fork. There is at least one company that made it to my shopping list, only to be removed again, purely because of this crazy design ‘decision’.

P.S. it’s purely a cosmetic choice, but the flat mount calipers look far nicer (IMO)

Dunno, I’m not a fan of the flat mount look, they look like 1970’s motorcycle callipers, too big and square.  MTB callipers look like brake callipers, which look like modern car and motorbike callipers, making them look different really means either coming up with a really good idea that improves things (hopes radial mount for example) or being different for the sake of it.

If flat mounts so good, why hasn’t a single mountain bike had them fitted?

Cannondale use flat mount on MTBs as do Genesis and Saracen on their newest Carbon hardtails.

Cannondale use flat mount on MTBs as do Genesis and Saracen on their newest Carbon hardtails.

Can anyone else here confirm this?

If flat mounts so good, why hasn’t a single mountain bike had them fitted?

FM caliper limits you to 160mm front brake. Some bikes use FM to PM adapters, works OK for the rear but the front adapter looks a bit ‘out there’.

If you are using road hydro STI then your PM caliper ideally needs to be one of the newer versions, which uses the 2.3mm bore hose. Most are this type nowadays.

be warned rear flat mount calipers only come with one set of bolts, though there are 3 lengths to choose from – and they aren’t cheap buying them on their own, I found this out the hard way

Hacksaw?

Can anyone confirm this?

I can post a pic of mine if someone tells me how?

Fresh Goods Friday 368

Pic of rear FM on Mantle in the above link.

Check out the revamped 2017 Cannondale Scalpel

Scroll down for brake mount pic and chat.