Brake judder - opinons please
Discussion
jeremyh1 said:
LuS1fer said:
Front discs are warped on my Mustang, MOT man keeps reminding me and it feels juddery when braking.
Good example We know why they are wrapped ! It is always hard braking or towing a load such as a caravan !
You not been pulling a caravan ! ?
HustleRussell said:
That's a bad idea! A number of people, including two with direct first-hand experience of this problem on BMW 3-series, have said that this problem can be caused by a sticking brake caliper. Guess what happens when you replace or skim the discs and fit new pads without properly investigating the cause?
If the caliper isn't moving freely it drags on the disc and gets very hot, when the disc, piston, pad backing etc etc gets hot it expands which causes the brake to drag more, this causes it to get hotter.... and then you leave the motorway and stop at the lights, the pad welds itself onto the now stationary disc leaving a nice patch of friction material on the disc, rinse and repeat...
I'm not ruling anything out but in the absence of a conclusive diagnosis I'm minded to start with the cheapest/most likely causes. I first noticed the issue a couple of weeks after I bought the car, since when I've done about 8000 miles in 10 months. It hasn't got any worse and the discs and pads look new and both sides look the same. A sticking caliper seems unlikely and it won't be the end of the world if I waste £80 on skimming.If the caliper isn't moving freely it drags on the disc and gets very hot, when the disc, piston, pad backing etc etc gets hot it expands which causes the brake to drag more, this causes it to get hotter.... and then you leave the motorway and stop at the lights, the pad welds itself onto the now stationary disc leaving a nice patch of friction material on the disc, rinse and repeat...
I've had a sticking caliper before on another car. It was obvious, I could feel it once it got bad and the pads on the caliper were shot.
I thought I'd update this since I've finally gotten round to getting it looked at and somebody may find the info useful in future.
I took it to a garage that has this kit:
http://skimmydiscs.co.uk/
They put it on the MOT brake tester and found a vibration on the N/S rear with brakes applied. So they skimmed both rears and the judder is 100% cured. I don't know what caused it so hopefully it won't come back.
I took it to a garage that has this kit:
http://skimmydiscs.co.uk/
They put it on the MOT brake tester and found a vibration on the N/S rear with brakes applied. So they skimmed both rears and the judder is 100% cured. I don't know what caused it so hopefully it won't come back.
It seems to me that the problem of brake juddering may have several causes but I feel that the primary cause is that the brake disc does not run parallell to the brake disc.In other words the brake disc is "out of . true." When the problem occurred on my Kuga, I replaced the discs etc at 70,000 miles. Shortly afterwards the problem occurred again.This is what I found and what I did. Reasoning out how to find out whether the new discs were out of true. I first tested the new discs with a micrometer.They were ok. Next I removed the caliper as others have said and tested the disc with a DTI by rotating them through 360 degrees. There was a .03 mm variation. but that was on the outside edge. Wanting to clarify what I was seeing, I then found a convenient spot on the brake caliper support bracket and measured the distance between the disc face and the bracket face adjacent to the disc face with feeler gauges and rotated the discs through 360 degrees. There was total variation of .007 0r 7 "thou". fr0m the highest to lowest spot.
I removed the disc and repeated the operation with the DTi on the hub. There was a simliar swing on the hub which meant that the hub was also out of line with the face of the bracket and therefore the pads..The wheel bearings were ok and so I remedied the out of alignment by locating the lowest point on the hub and then making metal shims of about 4 thou and placing them over the wheels studs. By a process of trial and error I reduced the wing on the DTI to less than .01 mm. Reseraching this problem further, I found that this is the practice which is used to solve this problem. Manufacturers standards seem to imply that a 2 thou tolerance is allowed at manufacture but I do wonder whether this actually takes place at all times. In any case just a liitle wear in the bearings can lead to small errors elsewhere in time which will be increased at the discs extreme edges. Thin shims can be obtained on a popular on line auction. In theory the shims should be tapered but as they are only very thin anyway, that does not really matter for the average motorists vehicle. Problem soved.
I removed the disc and repeated the operation with the DTi on the hub. There was a simliar swing on the hub which meant that the hub was also out of line with the face of the bracket and therefore the pads..The wheel bearings were ok and so I remedied the out of alignment by locating the lowest point on the hub and then making metal shims of about 4 thou and placing them over the wheels studs. By a process of trial and error I reduced the wing on the DTI to less than .01 mm. Reseraching this problem further, I found that this is the practice which is used to solve this problem. Manufacturers standards seem to imply that a 2 thou tolerance is allowed at manufacture but I do wonder whether this actually takes place at all times. In any case just a liitle wear in the bearings can lead to small errors elsewhere in time which will be increased at the discs extreme edges. Thin shims can be obtained on a popular on line auction. In theory the shims should be tapered but as they are only very thin anyway, that does not really matter for the average motorists vehicle. Problem soved.
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