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I decided to fit new pads and rotors to my road bike as I didn't like the Paceline rotors that came on it and I ordered new wheels so decided to make them all matching.
So I ordered the SRAM Centreline rotors and some SRAM organic pads. I fitted them all (using the SRAM spacer tool to set the gap etc and following the SRAM instructions) and when I had finished I could not get the rotor in between the pads on either wheel. So I used a SRAM bleed block and basically did a lever bleed to get the pistons right back in the calliper. An amount of fluid came up into the bleed tube as I inserted the bleed block and pushed the pistons right back so I thought this might sort it but no. I still could not get the rotor in cleanly, it did go in though this time but the pads are touching the disc on both sides and there is no way I can get the piston any further back.
It seems very odd but both new rotors are the same and the bike is only 2 months old so the callipers are in good condition. The pistons aren't stuck at all. I followed the SRAM guide for resetting the pad gap as well but no change. I have been out for a quick spin to bed them in and they are a bit better but by no means spinning completely without touching the rotors They are Rival levers and callipers.
Is this normal with SRAM road discs? Do I need to sand the pads?
A very slight rub is normal, as long as they aren't actually dragging.
Have you tried centering the calipers?
I often fit one new pad and one old pad to each caliper and then ride it for a bit to wear the new pads down. After a few rides, try fitting the remaining new pads. This also means you still have one bedded in pad in each caliper so you don't get such a dramatic change in performance as the new pads bed in.
Or try sanding the pads down slightly.
open the bleed screw and push the pistons back.
Have you tried centering the calipers?
Yeah done that. Perhaps I’ll try sanding lightly then. Maybe the Centreline rotors are slightly thicker when new than the PaceLine ones as well.
open the bleed screw and push the pistons back.
do you mean the calliper one? I’ve opened the lever one and pushed the pistons back as far as they will go. There is a tiny bit further they can be pushed (1mm) but they just spring back again even with the lever bleed port open.
I’d check the specs of everything / rotor and pad thicknesses vs spec etc. are you using the right rotor and pads for the brakes themselves?
There is a tiny bit further they can be pushed (1mm) but they just spring back again even with the lever bleed port open.
There’s probably something in this. I’ve never seen a hydraulic system where the pads intentionally spring back. Is there air in the system? Next step for me would be a full system bleed to ensure that everything is as it should be.
Have you physically measured the old vs new rotors?
And/or, have you bought thicker MTB discs by mistake?
...but they just spring back again...
whatgoesup +1 If anything they're designed to spring more open
I had those issues on old Hope Evo X2 brakes, but not on my SRAM road callipers. All fits fine.
…but they just spring back again…
whatgoesup +1 If anything they’re designed to spring more open
it’s the pistons I’m talking about - they push back into the callipers so they are flush with the body but then spring out 0.5 to 1mm. It’s probably just the seal compressing.
The rotors are the same thickness as the originals.1.85mm and the new pads are the same part number as the previous ones. New ones are 4mm and old ones were only slightly worn and measure 3.4mm so the difference is 1mm.
I think what’s happened is the system was over filled when the bike was built from new (a few weeks ago) and it may have some air in it (I did a couple of air bubbles out of the levers when I had the syringe attached whilst pushing the callipers in). Having bedded them in and re aligned the pads etc they are almost perfect now so probably a combination of the above…👍