Brake Juddering
Discussion
rObArtes said:
Coming back from a trip out today, I noticed my brakes were juddering at speeds around 60+ mph. lower speeds feel fine. any ideas? would have thought it would be hard to warp them, as I'm no mad driver
Truly warped brake discs are rare.I goofed up my VW Golf's brakes once by parking the car with wet brakes. I washed the car and let it sit. When I next drove the car I had an unexpected occasion to make an emergency stop shortly after I pulled out of the driveway and before I had used the brakes to scrub away the rust that had developed. The car stopped just fine but afterwards the brakes exhibited a slight judder, a light pulsing when used lightly at low speed.
What happened in my VW's case was the the emergency stop left the hot pads in contact with the hot rotors and material was deposited on the rotors where the pads were in contact with the rotors. This deposition of material affected the rotors' coefficient of friction. I tried re-bedding the brakes some but it didn't help. The only cure would have been to refinish the rotors or replace them.
This behavior remained with the car for the over 140K miles I drove car and it was there the day I sold car. The buyer noticed it on her test drive. It never bothered me cause I braked a bit more aggressively to avoid the behavior. (Since then I always make it habit to drive my car after washing to dry the brake hardware to avoid this risk.)
The above I supplied by way of detailing how brakes can develop a judder/pulsing without the need to warp.
So time to get back to your car's brakes.
As I said above, truly warped brakes are rare. The rotors undergo many heat cycle which stress relieves them (if they weren't already stress relieved -- often times after casting but before machining cast iron parts are just left outside to age and naturally stress relieve on their own) so it is out of character for these to upon being used at one particular time to warp due to uneven stresses being removed which causes the rotor to change its shape, develop a kind of potato chip (crisp?) shape.
For the brakes to manifest juddering at 60+ mph and not at lower speeds is weird.
This reads more like a tire balance problem if you tell me you feel some judder or vibration at speed without using the brakes. Or if you only feel the judder/vibration when using the brakes then more likely it is an alignment problem. Alignment gets the nod because when the brakes are applied at 60+ mph the alignment is such that the braking causes the tires/wheels to move out too far from the acceptable alignment and the juddering is the tires fighting against the incorrect alignment.
Alignment has me back on the subject of one of my cars's again: I have experienced a self inflicted alignment problem -- pulled too far into a parking space and bumped both front tires against a low curb which caused some slight toe out to develop -- with my Turbo's front wheels/tires and while braking feel was unaffected the tires howled at speed above 75mph. Fearing a wheel bearing I arranged to have the car checked out and the tech told me the tires were howling, and had me feel the tread surface. Sure enough I felt the signs of feathering of the tire tread blocks. An alignment -- done after I got the car home -- had the tires quiet again but it took some driving to wear away the goofy tread wear pattern the tires had developed when out of alignment.
For alignment check the tire tread surface for any signs of feathering or roughness that would arise from the wheels/tires being out of alignment.
Check tire inflation pressures. If these are too far out it can cause tire issues that (to me) feel like an imbalance problem.
Check for any missing tire weights.
Check for any tire damage. Even if you didn't hit anything a tire can experience a problem with its sidewall. A belt failure is possible but harder to diagnose.
Consider having the tires rebalanced. It is not unknown for these tires -- it is not limited to Porsche tires it can occur in tires for other cars too -- to go out of balance as at the tire wears. The tread material wears away and heavier/lighter regions wear away and this changes the balance. (This too I have encountered with my cars. The car develops a faint tire imbalance vibration at highway or higher speeds. The Boxster has this now as the front tires are quite worn. My dealer usually gives me a free rebalance if as the tires have worn they go out of balance but since the front tires are so worn I'm going to replace them, soon, rather than waste any time rebalancing them.)
Last but not least you can check for a warped rotor if you know how (or you can take the car to someone who knows how).
A shade tree mechanic's way of checking for warped rotors is to drive the car at slow (walking) speed. Oh, have the A/C off, the cabin vent fan off, the radio off, the windows down. If a rotor is warped you should hear a tick tick tick as the rotor cause the pads to move in and out. In case the warped rotor is on the other side you can have helpers one on each side the car listening for this noise.
While like I said above this condition is rare it is possible.
mm450exc said:
If you done hard track on standard brakes they could be warped.
Otherwise just resin or other deposits on disc.
^^^ ThisOtherwise just resin or other deposits on disc.
Try the bedding-in procedure for new pads/disks to clear the issue. Whilst the exact recommendations for this procedure vary a little depending on who you ask, in principle it works as follows:
1) Warm the brakes by normal use for a few miles, gradually working the brakes harder.
2) Literally stand the car on its nose from approx. 100 mph down to 50 mph (where safe and legal, of course) 6 times in succession. Don't worry if there's some graunching, really bad burning smells (and even smoking) from the pads - this is what should happen.
3) Now drive normally for a few miles to let things cool down a little
4) Repeat the same six 100 mph to 50 mph braking events again. This time there should be less complaining from the brakes as you do them.
5) Drive several miles to let everything cool down slowly.
This procedure will clear any deposits/glaze from the disks and also transfer a new layer of brake pad material to the surface of the disk. Your braking performance should be better than it has ever been, once completed.
You dont need to spend any money. Just get up early on Sunday or go out late when the roads are quiet. Get the car up to speed safely and complete several medium brake pressure stops from 70mph to 5mph. Then repeat with full pressure braking just at the ABS threshold. Again , do not let the car get become stationary at any point.
Once the brakes have got nice and hot almost to the point of fade or smoking go for a drive for 20 mins without touching the brakes to let them cool completely - your problem should be sorted and all the pad deposits suitable burnt off the rotor.
Once the brakes have got nice and hot almost to the point of fade or smoking go for a drive for 20 mins without touching the brakes to let them cool completely - your problem should be sorted and all the pad deposits suitable burnt off the rotor.
Far Cough said:
You dont need to spend any money. Just get up early on Sunday or go out late when the roads are quiet. Get the car up to speed safely and complete several medium brake pressure stops from 70mph to 5mph. Then repeat with full pressure braking just at the ABS threshold. Again , do not let the car get become stationary at any point.
Once the brakes have got nice and hot almost to the point of fade or smoking go for a drive for 20 mins without touching the brakes to let them cool completely - your problem should be sorted and all the pad deposits suitable burnt off the rotor.
20 mins without touching the brakes? In the UK? I bloody wish.Once the brakes have got nice and hot almost to the point of fade or smoking go for a drive for 20 mins without touching the brakes to let them cool completely - your problem should be sorted and all the pad deposits suitable burnt off the rotor.
rObArtes said:
the car is in the garage a week on friday to have the window regulator sorted will ask them to have a look.
the car brakes fine, other than the juddering. worth getting the alignment/balancing checked ?
You can try the bedding in process. In my VW's case it didn't help. But in your car's case it might. the car brakes fine, other than the juddering. worth getting the alignment/balancing checked ?
Since it doesn't cost you anything it is cheaper than having someone start wrenching on the car.
I'm not sure I'd do more that 2 or 3 hard slow downs -- do not bring the car to a stop! -- during the bedding in process. Get the car up to speed then apply the brakes hard. No skidding the tires, no ABS trigger, but hard nonetheless. Slow the car down as much as you from it high speed say to maybe half its high speed then release the brakes speed up and do the braking again. Repeat this one more time, that's 3 times.
If the juddering ain't gone then you need to consider some of the other things I and others have offered.
rObArtes said:
the car is in the garage a week on friday to have the window regulator sorted will ask them to have a look.
the car brakes fine, other than the juddering. worth getting the alignment/balancing checked ?
If the juddering is only evident when the brake pedal is applied, there is no reason to have the wheels balanced or suspension geo checked. the car brakes fine, other than the juddering. worth getting the alignment/balancing checked ?
rObArtes said:
The brakes are not new and the car is used as a daily. therefore unsure if this will make no difference??
The fact that it is used as a daily and therefore not often subjected to hard braking is all the more reason why it could be pad deposits causing your juddering.Clean up the discs as oulined above and if that doesn't cure it check the rear faces of the discs for rust.
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