Rotor size for Flat Mount Road Discs.

tim_wand

I ve currently got 160 mm rotors fitted with my TRP Spyre cable actuated discs. On my Kinesis Grand Fondo Ti frameset build.

This frameset and tracer fork is designed for flat mount style brake calipers. I m using post mount adapters at the moment to fit the 160 rotors and the TRP Spyre calipers.

I ve now got the budget to get some Hydraulic Shimano ST-RS685 with RS 805 Flat mount calipers.

I take it straight out the box flat mounted this will only fit 140 mm calipers. If I want to stick to the 160 rotors for now then I d still need the post mount adapters I ve got , which would slightly ruin the aesthetic and design ideal of having a flat mount frame?

So to cut a long story short , I m asking can I get away with the using the post mounts and 160 rotors with the RS805 flat mount calipers , until I ve saved up again for some 140mm Ice tech rotors.

meanredspider

So are the forks designed to be used with 140mm rotors? Personally (and I think the majority of bike designers agree) I think a 160mm rotor is the smallest that makes sense at the front. If you're particularly light, 140mm might do the trick. Otherwise, not only will the heat issue (that I'm guessing you're hoping the ice tech disc will deal with) be an issue but you won't get all of the braking force and modulation benefit from disc brakes. That said, if the fork is only designed for 140mm, you might have warrantee issues if you run 160mm.

Forget the aesthetics - it's brakes.

tim_wand

meanredspider wrote:

So are the forks designed to be used with 140mm rotors? Personally (and I think the majority of bike designers agree) I think a 160mm rotor is the smallest that makes sense at the front. If you're particularly light, 140mm might do the trick. Otherwise, not only will the heat issue (that I'm guessing you're hoping the ice tech disc will deal with) be an issue but you won't get all of the braking force and modulation benefit from disc brakes. That said, if the fork is only designed for 140mm, you might have warrantee issues if you run 160mm.

Forget the aesthetics - it's brakes.

I m 90kg , so will probably stick with the 160 rotor on the front. Just wanted to know if the flat mount calipers will fit a 160 rotor with post mount adapters. Pretty sure they will, Definitley try and get the rear to run on flat mount only, it looks a lot neater on this frame as the calipers are fitted in board. I know the benefits to braking should come before the aesthetics . but either way they are an improvement over the current set up.

kajjal

I am 100kg and have r785 brakes with 160mm front and rear rotors. They work very well for me in general with no problems on long steep hills with plenty of power and control. I accidentally got over 50mph on a steep downhill and they stopped me fine.

The Rookie

You need to sort out your terminology, you've used disc for calliper and calliper for disc in that description, (noting that rotor and disc mean the same thing) or you'll confuse people!

Shimano say you can use 140 at the front as long as it's an icetech, power really won't be an issue, I use a 160 front on mine but with a shitty Clarke cable calliper and can still lift the rear wheel.

tim_wand

Calipers to me are the piston housing that contracts or expands to activate the pads against the disc.

The whole query is fundamentally about what size rotors work with flat mount calipers straight out the box ( I.e with no post mount adapters) . I geuss the answer is 140mm.

Don't know if I ve used either term incorrectly. knew what I meant in my own head.

The Rookie

Read your first post and you'll see where it's wrong, for example 140mm calipers, there is no such things, there are callipers you fit to lots of disc sizes, so it is reads like you meant 140mm discs.

You also mention cable actuated discs, only calipers are cable actuated the disc doesn't know or care!

tim_wand

The Rookie wrote:

Read your first post and you'll see where it's wrong, for example 140mm calipers, there is no such things, there are callipers you fit to lots of disc sizes, so it is reads like you meant 140mm discs.

You also mention cable actuated discs, only calipers are cable actuated the disc doesn't know or care!

Fair point! at least I didn't call them Breaks

The Rookie

No worries....Shimano breaks are what you get when your Shimano brakes fail right?