Disk Calipers

[nickr]

I've just replaced the pads for the first time on my 2 year old Planet X London road. The brakes are SRAM HRD. The front one is fine but the rear wheel pads are rubbing on the disk. I have tried putting the old pads back in and getting brutal with a screwdriver, trying to push the pistons right back in, but still cannot get the wheel to rotate absolutely freely. Years ago I had the same problem on a motorbike (RD400) and the only solution was a new caliper. Is this the case with an SRAM caliper?

 

[I like Skol]

Not familiar with those calipers but go easy on the 'brute force'! Are the pistons definitely not fully retracting? It could just be that the caliper needs lining up properly to centralise the rotor between the pads.
If the pistons won't push back all the way then try opening the bleed nipple while pushing the pistons back, that can sometimes sort it.

 

[JhnBssll]

Is it possible the brakes have been bled at some point without the pistons fully retracted? This would lead to excess fluid in the system, preventing the pistons fully retracting. I'd open the reservoir cap on the lever and try pushing the pistons home again.

 

[fossyant]

Try what's been suggested - never had any issues pushing the piston's back on my SRAM Guide RS.

Might be worth downloading the SRAM manual and having a read.

 

[Vapin' Joe]

If the pistons have become corroded they will often refuse to retract into the bore (A problem I had on my car). A good clean of the piston will sometimes work if they are not too bad.

 

[iluvmybike]

If pistons won't go back then it might be helpful to let a little bit of fluid out of the system. Have found sram brakes come a bit overfilled from factory. Not a good idea to use a screw driver to push thenm back as you risk damaging the pistons themselves

 

[MrGrumpy]

Defo don’t use a screwdriver ;-) I can concur .

However I’m impressed you managed to get somlong out of pads ! I’ve gone through two sets of pads this winter alone on my commuter. Shimano resin pads mind.

 

[Julia9054]

Is your disc warped?

 

[nickr]

Thankyou people for your excellent ideas. I have to admit a degree of laziness, and took to bike out. After using the brakes in normal traffic and then a series of hard braking the problem seemed to have solved itself. After spinning the backwheel fast it carries on for about 40 seconds, way worse than the front one, but not terrible. After some fast riding I felt the disk, it was barely warm. I agree with someone's post above that the hydraulic system has probably been overfilled

 

[nickr]

Follow up post. I wasn't happy with slightly rubbing pads. Took them out did piston advance as per sram video

View: https://www.youtube.com/watch?v=KtkeJc5WfZ8

now perfect.

Oh yes and stupid little clip, that looks pointless. It stops the pads rattling.

 

[si_c]

Glad it's working again. I needed to replace the pads on my front caliper the other week, it was a bit of a mare. The bike hadn't been ridden in a month or so, and the pistons had been covered in a winters worth of road gunk from daily commuting. I had to take the caliper off the clean around the pistons properly and then used a piston spreader (rather than a screwdriver!!) to get the pistons to retract properly. Working fine again now, but it took a bit of patience.

Note to self, clean the calipers with greater frequency. Although in fairness if I'd been riding the bike daily the gunk would never have had a chance to gum everything up so much.

 

[nickr]

Yes, my note to self is - keep caliper clean and remove pads once per year and perform piston advance. I completely ignored this on my Specialized and it was fine, but these SRAM brakes need more care.