Brake Vibration analysis - validation or suggestions?
Discussion
Hi PH mind hive!
I have an annoying braking issue, they vibrate on braking - light vibration on gentle braking, very noticable on hard braking. The feel is more through the brake peddle, and also the steering wheel but no as harsh.
Car is a 2012 Cayenne 3.0d
So far I have replaced the discs with quality MTEC ones, new brembo pads and this went away for a while but has returned.
If I remove the calipers & pads, clean the pins and regrease, remove discs, clean and refit it feels better, then gradually the braking vibration returns.
Discs * wheels are fitted to the hub with NO copper (or other) grease.
i dont think the discs are warped already, they lie flat on a true surface and steel flat rule is level across the discs.
last time i went through the strip clean refit procedure, I suspected some of the brake pistons may not be moving freely (6 per caliper) so worked them in/out etc to free them up. again brakes were ok for a bit and then return vibrating under braking.
My theory / question is - if some of the brake pistons stick or do not move freely, can that cause vibration under braking?
if not any other ideas as to what else I can try / troubleshoot?
thanks
I have an annoying braking issue, they vibrate on braking - light vibration on gentle braking, very noticable on hard braking. The feel is more through the brake peddle, and also the steering wheel but no as harsh.
Car is a 2012 Cayenne 3.0d
So far I have replaced the discs with quality MTEC ones, new brembo pads and this went away for a while but has returned.
If I remove the calipers & pads, clean the pins and regrease, remove discs, clean and refit it feels better, then gradually the braking vibration returns.
Discs * wheels are fitted to the hub with NO copper (or other) grease.
i dont think the discs are warped already, they lie flat on a true surface and steel flat rule is level across the discs.
last time i went through the strip clean refit procedure, I suspected some of the brake pistons may not be moving freely (6 per caliper) so worked them in/out etc to free them up. again brakes were ok for a bit and then return vibrating under braking.
My theory / question is - if some of the brake pistons stick or do not move freely, can that cause vibration under braking?
if not any other ideas as to what else I can try / troubleshoot?
thanks
If a clean and regrease gives you a temporary improvement then that suggests it isn't related to the friction surface. If it's a floating caliper, a worn slider might produce symptoms like that. You mention a slider, which suggests it's a floating caliper, but then you also mention 6 pistons which seems a lot for a floating caliper.
GreenV8S said:
If a clean and regrease gives you a temporary improvement then that suggests it isn't related to the friction surface. If it's a floating caliper, a worn slider might produce symptoms like that. You mention a slider, which suggests it's a floating caliper, but then you also mention 6 pistons which seems a lot for a floating caliper.
each caliper has 6 pistons, 3 per side / brake pad. I think OEM are maybe brembo?like this -
I assume you were referring to pad retaining pins then rather than caliper sliders.
You could check the caliper is square to the disk and no play in the wheel bearings but I'm clutching at straws here - this type of caliper doesn't suffer from all the flexing problems that a floating caliper does.
You could check the caliper is square to the disk and no play in the wheel bearings but I'm clutching at straws here - this type of caliper doesn't suffer from all the flexing problems that a floating caliper does.
Despite really good brake servicing eventually one of those pistons will start to seize, Landcruisers with the big 4 piston front calipers have the same issue, its the lower inner piston every time that lets the side down on those even if you annually service the brakes properly as i do (thought to be fair the original front calipers lasted 16 years), suspect this is whats happening with yours as you seem to have everything else covered,
You can sometimes gain a stay of execution for the calipers by exercising the pistons in their bores, ie remove 1 pad at a time and push one of the opposing pistons home as you do it should push the other unpadded piston out, rinse and repeat lots till all are free moving, if one piston is sticking block the free moving one and get an assistant to push the brake pedal...keep a lever in the pistons way so it doesn't ram up against the disc.
When the piston is out you can peel back the dust cover and see what condition the piston is in, permissable at that point to wipe a small amout of the correct red brake grease onto the piston itself.
If despite mutiple times you still end up with a sticking piston maybe its time for new calipers or getting yours refurbed.
Oh and yes, if a piston is sticking then the pad is being pushed unevenly onto the disc and will cause vibration.
You can sometimes gain a stay of execution for the calipers by exercising the pistons in their bores, ie remove 1 pad at a time and push one of the opposing pistons home as you do it should push the other unpadded piston out, rinse and repeat lots till all are free moving, if one piston is sticking block the free moving one and get an assistant to push the brake pedal...keep a lever in the pistons way so it doesn't ram up against the disc.
When the piston is out you can peel back the dust cover and see what condition the piston is in, permissable at that point to wipe a small amout of the correct red brake grease onto the piston itself.
If despite mutiple times you still end up with a sticking piston maybe its time for new calipers or getting yours refurbed.
Oh and yes, if a piston is sticking then the pad is being pushed unevenly onto the disc and will cause vibration.
Edited by Smint on Sunday 12th June 05:51
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