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...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
[img] 
[/img]
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.
[img] 
[/img]
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
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[url= https://www.flickr.com/photos/39062108@N03/15718526187/ ]image[/url] by [url= https://www.flickr.com/people/39062108@N03/ ]thegreatape[/url], on Flickr
[url= https://farm8.staticflickr.com/7562/15718240109_073e717d6c_b.jp g" target="_blank">
[url= https://www.flickr.com/photos/39062108@N03/15718240109/ ]image[/url] by [url= https://www.flickr.com/people/39062108@N03/ ]thegreatape[/url], 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.
Front pads
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[url= https://www.flickr.com/photos/39062108@N03/15878654866/ ]image[/url] by [url= https://www.flickr.com/people/39062108@N03/ ]thegreatape[/url], on Flickr
Rear pads
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[url= https://www.flickr.com/photos/39062108@N03/15718691097/ ]image[/url] by [url= https://www.flickr.com/people/39062108@N03/ ]thegreatape[/url], on Flickr
Original Shimano resin ones. It's water you can see on the backing plates.
They don't look bad, the rear seem to be pitted though and have different colours.
Are the fronts the same to the naked eye?
Is the friction material an equal thickness all over?
I don't think the issue is with the XT, but it does look like a mismatch with the rotors. I think there is not enough contact between the face of the pad and the rotor. Pads in Hayes brakes may sit a bit lower in the caliper than Shimano, but I'm not sure.
FWIW I have SLX on two bikes with Shimano floating rotors, 180/160 on the more XC one, 203/180 on the more "Gnar" and no complaints at all, riding weight 80kg.
I've emailed the pictures of the rotors to the company to see what they say. I can't see an obvious reason for speccing these and not Shimano rotors, other than a cost saving, but a quick look at CRC suggests not much at all in it, although different for OEM perhaps.
I don't think it's a good comparison to check RRP. Obviously they need to correct this if it is a component mismatch.
I do think you need to change the rotors and a 203/180 combo would be best for you.
Ok, thanks for taking the trouble to look/post. That leaves me needing a 23mm adapter for the front and 20mm for the back, both post to post. Struggling to find Shimano ones that spec, but there are Hope ones that should.
Superstar have a good range of adapters. They were doing 25% off as well although that might have run out. I have used Superstar adapters with Shimano calipers a few times and never had any issues.
Strange that people are suggesting smaller rear rotors. Makes zero sense.
Ok, thanks for taking the trouble to look/post. That leaves me needing a 23mm adapter for the front and 20mm for the back, both post to post. Struggling to find Shimano ones that spec, but there are Hope ones that should.
No problem.
I could be wrong, but I think you can use a Shimano 180 post mount adaptor on the forks to fit the 203 rotor. I can double check later today if you're willing to wait? If you need a little more clearance between edge of rotor and caliper body you can fit a washer as a spacer.
Will that fit, with a 3mm difference? It would be much easier if they labelled the adapters as 20, 23, 40, 43 etc. rather than by rotor size, because that assumes a default of 160/140 on forks/frames. And no one should have to do sums on a Saturday 🙂
But yeah, if you're able to find out later that would be great. So it's what I would need to fit a 203 rotor where a 180 currently fits with no adapter, and to fit a 180 rotor where a 160 currently sits with no adapter. Cheers.
You only need to gain 1.5mm on the radius of the disc.
I'm sure that for 203 front disc a 160 to 180mm PM adaptor will fit, might need a washer as above.
For the rear a standard 160 to 180 PM adaptor.
Will double check later.
hang on. the rear rotor looks fine. the front isn't using the whole of the braking surface, for sure, but may just be that the braking surface area on these discs is bigger than what shimano use ( ie the OD may be the same but the ID of the braking surface may be smaller ).
you don't need new rotors! there's a lot of magic in this thread...
certainly shimano ice tech rotors are a bit different, but generally speaking they're all a plain bit of metal for the pad to clamp on. so long as you're using the whole pad, it doesn't really matter if you're missing off a bit of braking surface on the rotor [b]at all[/b].
clean the rotors with some IPA or meths. clean/sand/file the pads a bit, then go get the buggers good and hot!
As above, give them a clean first.
Not sure where the magic is but if you are cooking the front disc you need to change something.
Quick response from the bike company, they have found that the Hayes rotors fit better with some Shimano calipers, such as Deore, than others, eg. XT, so they use Shimano rotors now. They're sending me two Shimano rotors FOC, so you can't say fairer than that.
Bed those pads in, don't just go for a ride with new pads. Find a nice steep hill and be them in properly. It makes a massive difference to both braking performance and pad life.
There's an eejit's guide on the uberbikes website, I'll follow that 🙂
Sorted then, nice.
Yep, happy again!
What fixed it, OP? Was it properly bedding in the pads?
Nothing yet, happy that they are sending some Shimano rotors to put on instead of the Hayes. But that will be done with the new ones.