Rear brake disc sizing query

swod1

I've had my mega tr built up now for a couple of months and its great however the rear brake has been annoying me for a while now turns out the rotor is warped and is rubbing the pads no matter how many times I adjust the caliper.

So I'm looking at new disc rotors and would I see any benefit from fitting a 180mm on the rear?

I just transferred over parts from my hard tail which used 160mm on both front and rear. I've seen a big improvement with fitting a 180 on the front but now just wonder if there is any benefit to a bigger disc on the back.

I know downhillers use 203 front and back but I'm not doing that so still wonder if 160 rear is enough, what do you guys use on your trail bikes?

cooldad

160mm is plenty for me on the back of all my bikes.

The Rookie

You should be able to lock a 160 just fine (?), the only reason for going up to a 180 is greater heat capacity, so unless you are riding in the Alps or other similar long downhills you don't need it.

swod1

The Rookie wrote:

You should be able to lock a 160 just fine (?), the only reason for going up to a 180 is greater heat capacity, so unless you are riding in the Alps or other similar long downhills you don't need it.

yeah the 160 seems fine for general riding I do, however did some rides in peak district recently and the 160 did seem small on some long runs down.

I just thought as I need to replace the disc I would up the size to 180. there's not much price difference so I may just buy the 180 disc and be done with it.

I've a floating rotor on the front so going to fit one on the rear not come across the issue of it fouling the caliper yet.

The Rookie

I wouldn't bother with floating, they wear and rattle and achieve nothing measurable.

Don't forget you'll need an adaptor, the Shimano 'straight through' design with longer bolts (and CPS washers above the calliper only) is a nice neat solution if the frame is PM mount.

gt-arrowhead

It depends on what you like i suppose. Unless you feel that youre lacking power its probably worth sticking with the sizes youve got. Personally i have 203 front and 180 rear for XC riding and i love it, id never go down sizes at either end, eventhough ive never tried any other combination on my bikes.

Forget floating rotors. I think they are just too expensive for what they are. The benefit of floating discs is to reduce the risk of warping due to overheating, and to dissipate heat better, but thats rarely a problem on a bicycle unless youre riding some insane hills.

The only reason id want to get one/a pair is because they often come in some nice colours...