203 rotor fitment

w6llace

Hi, I’ve got a 2016 GT force x expert with slx brakes and I want to put a 203 rotor on the rear , however having trouble getting the caliper to fit as the disc that was at the rear was 180 I’ve purchased the 203 post to post mount but the caliper still doesn’t fit flush to the frame and the caliper has bottomed out on the disc so won’t fit , was looking for a fix to this issue if anyone has any ideas that would be great many thanks in advance.

cobba

More info or some photos would be useful.

Is the adapter on the correct way?

Does the frame have 160mm post mounts?

What adapter was used with a 180mm rotor?

What do you mean by 'the caliper still doesn’t fit flush to the frame'?

cooldad

Why would you want or need that on the back?

If it doesn't fit you've bought the wrong adaptor.

Post a link to what you actually bought.

cycleclinic

You should not need a 203mm rotor at the back. If you do your front rotor is undersized.

robertpb

Makes no sense at all putting a 203mm on the back, unless you have very low grip in your left hand.

Most of the braking is done by the front brake where you would normally put a 203mm with a 180mm on the back.

swod1

Also have you thought that the frame won’t have been designed for those size discs on the rear.

Unless your riding extreme places you won’t need more than 180 even that is too much for a lot of riding style unless your riding downhill.

You’ve got slx brakes these are good however I bet your using the shimano resin pads, I didn’t like them and found aftermarket pads to be better.

w6llace

Hi all , thanks for the reply’s the bike came with a 203 up front and and a 180 at the rear they are the slx m675 with the ice Tec disc . I purchased this bike from new and from the off was not impressed with the brakes I’ve bleed them the correct way and cleaned the disc and deglaze the pad the front bites nice but the back doesn’t I’ve also realigned the caliper there’s not leaks . As I’m a big lad I was wanting to go bigger at the rear the same as the front but i think the frame won’t take a 203 as I purchased the correct 203 adapter. The caliper bolts down through the adaptor from above and not through the frame . Sorry not sure how to attach pictures which would show what I’m talking about . If this is not possible then will stick to the 180 and replace the brakes with saint . Many thanks

cycleclinic

Try different pads. The issue you are encountering is not down to rotor size. Shimano make pads with different compounds and ebc make excellent pads.

Rear brakes will never be as sharp as the front that down to weight transfer.

swod1

You mentioned deglaze the pads.

I think you’ve just gone wrong on the bedding in of the pads and it’s given you a bad impression of the brakes.

I had a similar experience with the shimano pads you can easily glaze them.

I would try some different pads first before buying new brakes.

Try some organic pads from one of the aftermarket suppliers. I use uberbike semi metallic or race matrix.

cobba

W6llace wrote:

Sorry not sure how to attach pictures which would show what I’m talking about

Upload some photos on a image hosting website and post a link to the photos.

https://makeawebsitehub.com/free-photo-hosting/

billycool

I have the same SLX brakes on my HT. I run 180 F and 160 R and they work really well (IMO they are just as good as my XT brakes on my FS bike).

As others have said - pad choice and bedding them in correctly can help. I prefer to run sintered F & R. I tend to use Clarkes as they work well for me.

https://www.amazon.co.uk/gp/product/B00 ... UTF8&psc=1

When you have new pads and are bedding them in, you need to be careful not to drag your brake too much or you can glaze them. They usually bed in really quickly if you just give them a few firm brakes on some DH but don't drag.

I know you say you are a big unit, but if the brakes are set up correctly, what you have should work ok. The front will always offer more braking power but give it a go and see how you get on.