…with 180/160 Hayes rotors. They just don’t feel that strong. There is also a few mm of the braking surface that appears not to be getting grabbed by the pads, which are the original Shimano ones. Wondering whether to try 200/180 rotors and see if it improves? Pretty confident it’s not a bleeding issue. 120kg rider. Worth a try or waste of money?

I’ve used them since the newer ones came out. No problems with power at all for
downhill and trail UK or abroad where longer descents are usual.

I used to have 203 rotors front and rear, but just front now with a 160 rear.

Make sure you’ve not contaminated your pads or owt. I use superstar organic and find them great.

Not sure about pad contact area. I’ve never noticed an issue personally.

Yeah, guess I can give everything a clean up and see. Got some uberbikes race matrix pads coming too.

115kg here, 203 and 180mm do the trick with XTs, but 180/160 would do.

Did you clean the rotors then bed in the pads properly?

120kg!

I’d go 203mm front/rear for sure.

I was 98kg now 95kg and ALWAYS use 203/180. Otherwise Im a very nervous rider.

90kg here and I have 203 front and back. Why have anything smaller?

I would say get the proper sized shimano rotors because if there is some of the pad not hitting the disc it won’t be working as it should.

Just get Saints.

84kg and use Deores with 160 Hayes rotors, more powerful than I could ever need

65kg, XTs with 203mm front and rear!

When you say its got a few mm of not touching the rotor, do you have the correct adaptor on? (Some adaptors can be different even between brands),

I have 180/180 and I seriously think its crazy good power, i’m 100kg all kitted up. Stops me instantly. However I have also had the saints (M820) and they just have too much power for my type of riding, DH ONLY for saints, believe me.

Use Shimano Rotors.

ditto above- rotors.

Saints

It’s got what it came with, so M785 brakes, whatever adapters they saw fit to fit, and 180/160 Hayes lightweight rotors. When I say a few mm not touching the rotor, it’s like this

but just on the inner (closer to the hub, not round the outside) edge of the braking surface, although it’s more of a brown colour. Both rotors.

I had wondered about the SRAM Centreline rotors that come with the new Guide brakes, they seem to have received good press?

My forks are specified for up to 203mm rotors. Do frames have a maximum, can’t find anything on their website? I had assumed one always went bigger on the front.

65kg, XTs with 203mm front and rear!

400mm rotors then!

Did you clean the rotors then bed in the pads properly?

No, just went riding

I Really rate the new shimano rotors ove the older Plain style ones (like the Hayes in the pic) Seem to give much better grab ime

Rotors seem to make a huge difference. When I first got mine I used them on my old 26 HT with well worn shimano 180, avid 160 discs and found the power and modulation fantastic. When I built the new 29ht and swapped the brakes over (only 2 months old at that point) I used very lightweight 180/160 XC discs with lots of openings/holes. The braking does not even come close to how it was before. Works, but not with the same WOW factor.

Just been out to look at the bike, and neither brake has an adapter, so the frame is 160mm post mount and the fork 180mm post mount. So that’s a 20/23mm and a 40/43mm adapter depending on whether I get 200 or 203mm rotors.

So is that these rotors?

http://www.chainreactioncycles.com/shimano-xt-rt76-6-bolt-disc-rotor/rp-prod39007

or do I want Ice Tech ones?

That style braking surface, needn’t be the aluCentre one, All steel slx are great too.

So now struggling to find a 23mm Shimano adapter. 43, for the rear, is easy enough, as is a 20 for the front, but no 23?

Found Hope ones.

So if I order two 203mm Shimano rotors, a 43mm adapter for the back, and a 23mm adapter for the front, I should be all set. Got some of Uberbikes race matrix pads coming too, but the new finned/Ice Tech copies.

Why not wait and see what the new pads do before splashing out on new rotors and adapters?

FWIW I’m upwards of 90kg and use 180/160 with older XT765s with no problems, they’ve been fine for UK and longer continental descents. I don’t think 203 F&R would get properly warm very often.

Aye maybe you’re right.

just give them a good clean, rough up your existing pads, bed them in. they’ll be fine. lot cheaper and easier than throwing money at rotors which i suspect you have no need for.

Here’s what I mean about the rotors

image by thegreatape, on Flickr

image by thegreatape, on Flickr

Just makes me question if these rotors are a good fit? At their thinnest points there is about 6mm in contact with the pads. As you can see, there are no adapters, so it’s not like there is an incorrect adapter on there!

Those rotors look terrible!

Get some shimano ones and your brakes will improve massively!

And stick with 180/160?

Your original setup should be more than okay, as above, could be contaminated pads so try fixing that first.

The contact area will be fine as long as the pad is not hanging over the edge of the disc.

At 120kg I would definitely consider a 203/180 combination.

EDIT – After seeing your photos, that’s not good and would question that choice of components with the manufacturer.

Have you pulled the pads at all?

I’m running slx brakes on my cannondale sl.. I left the cheapo rotors that came on bike and no problems at all …

I’d defo look at cleaning/bedding in etc as its cheapest option 🙂

Used loads of different types of rotors over many years and can’t say I’ve noticed a blind bit of difference imho..

Never used new shimano ones though …

First step for me would be a pair of 203mm shimano discs, these ones are good: http://www.chainreactioncycles.com/shimano-xt-rt76-6-bolt-disc-rotor/rp-prod39007
and a pair of Shimano brake adapters. That should get the pads lined up with the discs. Drop the pads you’ve got out, give them a wee sand on some fine, clean abrasive paper and pop them back in. Bed the brakes in and try it like that. It should be fine, if not you’ve maybe contaminated the pads in which case, new pads and clean the discs and that should definitely be it. Id spring for the Shimano pads myself for the first set, to get a datum of how well they can work before you try a cheaper replacement and decide the brakes are no good when it could just be cheap pads.
At 75 kg my SLXs with the discs above are borderline too powerful, they grab like crazy.

Pulled the pads?

Pulled the pads?

Have you taken them out for an inspection?

The discolouration on the discs is probably due to overheating.

No, I’ll do that.

Looking at the photos, clearly something isn’t right there. Unfortunately I can’t tell what it is. You need to work out what the issue is before wasting money on new components which may not all fit together properly.
180/160 should be fine for general xc riding. If you ride steeper stuff then go bigger. If you don’t mind a slight increase in weight then go bigger. If you ride in the Alps once a year go as big as you can.
What sort of riding do you do?

It mostly comprises a long, arduous and miserable slog uphill followed by a fast, partially in control descent on rocky or muddy paths through the forests, repeated until it’s time to go home. And Nevis Range, Laggan Wolftrax type trails.

Bigger discs will give more modulation as well as more power on these brakes in my experience.

Id get superstar ones myself though, maybe 203 front 180 rear.