1993 face lift v12.
I had a slight steering wheel wobble when braking but as time went on it got to the fix it point. On removing both front discs i found a badly discoloured area ,red/blue on the outer face approx twice the length of the pads. On the inner face and opposite the discoloured section an area where the pad was only in contact on the outer edge.
So new discs and pads, also i fitted new inner and outer bearings. The frustrating part was putting the shims back. It is vital to note where they are located and the quantity. They are approx the dia of a two pence piece and very thin. I found two on the top short bolt and one on the lower long bolt but not all cars are the same. After an hour and a half i gave up, i could not get them to either go in or stay put, i smeared grease on them to no avail. What to do next, A son who is an Engineer and his Engineers super glue ,he bonded the shims to the calipers and ten minutes later job done. Re wire the two bolts, wheels back on, a few pumps of the brake pedal check the fluid.
The brakes are as they should be and no steering wobble. My local Jaguar independent garage charges £400.00 plus vat to do the same work. The materials cost £88.12 and some frustration, but i would recommended Engineers super glue.
Ralph S.
Steering wheel wobble when braking.
Moderators:davidr, BigCatXJS, dhdove
Steering wheel wobble when braking.
..well I've too got a steering wobble when braking come back again, and I can't figure out why... first noticed it a while ago, I too had the discoloured areas, on each disc, so I changed the discs and the pads. Which got rid of the wobble for a few weeks... until it came back again. Ah I thought, must be bad pair of discs, they were cheap pattern ones. So I paid a little more this time got another pair, plus another set of pads.
OK, I fitted the new new discs, but didnt replace the pads, only been on for a few weeks. Good riddance to the wobble I thought, no wobble when braking.... until it came back again after a few weeks again!
So.... I'm a little baffled now. If it was buckled wheel it'd have to be on both sides. Loose wheel nuts, nope.
One thing I've noticed just recently is that when you use the brakes gently and softly, the effect gets progressively worse overall, so the ntural thing to do is to brake more gently to avoid it. But then if I stomp on the brake quite hard when braking, the overall effect then gets progressively better. Now maybe..... it's not been the discs after all and something else.
A freind said he reckons 'it's the caliper'. Or maybe it's lack of cooling? Perhaps the discs are getting glazed. Anyone have any ideaas please?
OK, I fitted the new new discs, but didnt replace the pads, only been on for a few weeks. Good riddance to the wobble I thought, no wobble when braking.... until it came back again after a few weeks again!
So.... I'm a little baffled now. If it was buckled wheel it'd have to be on both sides. Loose wheel nuts, nope.
One thing I've noticed just recently is that when you use the brakes gently and softly, the effect gets progressively worse overall, so the ntural thing to do is to brake more gently to avoid it. But then if I stomp on the brake quite hard when braking, the overall effect then gets progressively better. Now maybe..... it's not been the discs after all and something else.
A freind said he reckons 'it's the caliper'. Or maybe it's lack of cooling? Perhaps the discs are getting glazed. Anyone have any ideaas please?
XJ-S 3.6 230k miles +
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HerefordMark
- Posts:51
- Joined:Sat Jan 07, 2006 7:40 pm
Steering wheel wobble when braking.
The discs are probably OK but you'll get the same effect if they are refitted out of true. You need to have them set up with a dial gauge to make sure they are rotating only in 1 vertical plane. That should cure it.
Re: Steering wheel wobble when braking.
Anyone have any ideas
Wheel bearing a little too loose perhaps, it may have bedded in a bit since you changed the disks.
Pop
Wheel bearing a little too loose perhaps, it may have bedded in a bit since you changed the disks.
Pop
Steering wheel wobble when braking.
Funny about the wheel bearing connection, the pulsing brakes seem to all started around the same time new bearing/stubaxle either side fitted. Before replacing bearing and stubaxle, the wheel bearing was always loose and couldn't be tightened because of the worn stubaxle. Since the repair the wheel bearing is perfect and is still now. Maybe I should loosen the bearing off to like it was before, and put up with the loose steering again! Maybe the loose bearing allows the disc to float a bit more?
I did check the runout before and after fitting disks. I can't remember the exact figures, but disks removed were warped alright, the limit is 4 thou. The new ones seating surfaces were spotless clean, the bolts torqued evenly and as I expected no 'abnormal' runout was seen (I can't remember the figure, but I'd of removed it and shimmed it with ali foil at the time if it was out).
The strange thing is that there was no hint of brake pulsation for quite a few weeks after replacing the disks on both occiasions.
Now I've discovered that after habitually using the brakes as lightly as possible over a period makes the tendency to pulsate worse, and at the current rate of increase, the effect will back to just before I replaced discs No2 for No3!.
..But on the other hand I've just found that doing a few high speed stomp-on-the-brakes-down-to-20mph cycles has almost completely cleared the brake pulsation.
Well I'll carry on giving the discs a regular dose of stomp-on-brakes treatment when needed and I'll keep you posted. In the meantime I'm still baffled!
I did check the runout before and after fitting disks. I can't remember the exact figures, but disks removed were warped alright, the limit is 4 thou. The new ones seating surfaces were spotless clean, the bolts torqued evenly and as I expected no 'abnormal' runout was seen (I can't remember the figure, but I'd of removed it and shimmed it with ali foil at the time if it was out).
The strange thing is that there was no hint of brake pulsation for quite a few weeks after replacing the disks on both occiasions.
Now I've discovered that after habitually using the brakes as lightly as possible over a period makes the tendency to pulsate worse, and at the current rate of increase, the effect will back to just before I replaced discs No2 for No3!.
..But on the other hand I've just found that doing a few high speed stomp-on-the-brakes-down-to-20mph cycles has almost completely cleared the brake pulsation.
Well I'll carry on giving the discs a regular dose of stomp-on-brakes treatment when needed and I'll keep you posted. In the meantime I'm still baffled!
XJ-S 3.6 230k miles +
Steering wheel wobble when braking.
I've got a '92 facelift and its exactly the same. I've tried 2 sets of discs, pads, bleeds etc etc. Still wobbles at the wheel during gentle braking and is OK during "test stops". I've got no idea why either.
The IAM observers look worried pulling up to roundabouts though!!! Shame they don't like hard braking
The IAM observers look worried pulling up to roundabouts though!!! Shame they don't like hard braking
Steering wheel wobble when braking.
I had a similar problem on a Range Rover a few years ago. I thought the obvious cause was warped discs, changed the discs and the problem came back a while later. Didn't happen under hard braking, though.
The problem turned out to be a slightly sticking piston which was OK to move under really severe braking (or else the other piston was pushing so hard that it didn't let the disc vibrate slightly?)
Anyway, I stripped and cleaned the pistons, put some caliper grease on them and hey presto, no vibration!
It may not be that, but it's got to be worth a try.
Paul
The problem turned out to be a slightly sticking piston which was OK to move under really severe braking (or else the other piston was pushing so hard that it didn't let the disc vibrate slightly?)
Anyway, I stripped and cleaned the pistons, put some caliper grease on them and hey presto, no vibration!
It may not be that, but it's got to be worth a try.
Paul
1995 XJS 4.0 Convertible
1980 XJ-S Pre-HE
Jaguar 4.2 Supercharged engine (but not with a Jaguar body..)
1980 XJ-S Pre-HE
Jaguar 4.2 Supercharged engine (but not with a Jaguar body..)
Steering wheel wobble when braking.
Paul,
Thanks for the suggestion. I'm sure things were OK when I put the latest discs etc on, but it was a while before the judder returned so it could be the cause is a "recently developed" sticky piston(s). I'll whip the calipers off and have a look.
Thanks for the suggestion. I'm sure things were OK when I put the latest discs etc on, but it was a while before the judder returned so it could be the cause is a "recently developed" sticky piston(s). I'll whip the calipers off and have a look.
Steering wheel wobble when braking.
I'm coming round to the idea it may be calipers too. Maybe a sticking piston prevents 'float' and the 4 thou (in-spec) runout then becomes significant. The stomp on brakes problem clearing must also be something to do with this somehow!
XJ-S 3.6 230k miles +
Steering wheel wobble when braking.
Got an update on the brake judder..
Measured disc run-out with dial gauge = less than 0.1 mm (4 thou). None of the 8 pistons are sticking. According to that the discs are straight.
Found out something about disc brakes from a racing driver, that is it's not just a metal disc being squeezed either side by pads, more to it than that.
You see on the disc there's a thin coating of brake pad material a few 10'ths of a thou thick on it, which the pad engages with, if that coating is patchy the brake judders, commonly mistaken for a warped disc. A warped disc needs to be running out at least 12 thou or more.
There's 2 modes brakes work in: 'abrasion' and 'adhesion', the former is the one without the coating and a weak braking effect, the latter more braking effect which is supposed to be the normal condition.
When the brakes are above a certain temperature, the pad smears itself over the disc and provides 'adhesion mode' braking where the pad rubs against the deposited pad material on the disc. Depending on the type of pad it can from as low as 80 degC, or from above 500 deg C if a racing brake. When below the adhesion mode temperature, the brake is working in abrasion mode. Somewhat above adhesion mode (around red hot) is another mode where the brake effect fades away (I guess you could call that one 'oh-s**t!!! mode'!) when the pad material sublimes and outgasses or something like that.
To get a disc unjuddered there is a technique that can be used, that is warm up the brakes into the adhesion temperature range, and then do one or more rapid decelerations from 70 mph (faster if possible) down to almost stopped, and allow the brake to cool below the adhesion temperature. While having the hot brakes, avoid stopping completely, or if you have to, don't hold the brakes on one place on the disk otherwise it might undo what you've been doing.
Another update:
A theory I ahve that it could be due to the type of Brake Pads themselves being cause of the brake judder persistently returning. If so replacing with an entirely different make of pad should make a difference. The pads I have been using are 'Allied Signal- Jurid' brand in a blue-coloured box. The brand I had before that (no judder then) was 'Bendix' branded.
Measured disc run-out with dial gauge = less than 0.1 mm (4 thou). None of the 8 pistons are sticking. According to that the discs are straight.
Found out something about disc brakes from a racing driver, that is it's not just a metal disc being squeezed either side by pads, more to it than that.
You see on the disc there's a thin coating of brake pad material a few 10'ths of a thou thick on it, which the pad engages with, if that coating is patchy the brake judders, commonly mistaken for a warped disc. A warped disc needs to be running out at least 12 thou or more.
There's 2 modes brakes work in: 'abrasion' and 'adhesion', the former is the one without the coating and a weak braking effect, the latter more braking effect which is supposed to be the normal condition.
When the brakes are above a certain temperature, the pad smears itself over the disc and provides 'adhesion mode' braking where the pad rubs against the deposited pad material on the disc. Depending on the type of pad it can from as low as 80 degC, or from above 500 deg C if a racing brake. When below the adhesion mode temperature, the brake is working in abrasion mode. Somewhat above adhesion mode (around red hot) is another mode where the brake effect fades away (I guess you could call that one 'oh-s**t!!! mode'!) when the pad material sublimes and outgasses or something like that.
To get a disc unjuddered there is a technique that can be used, that is warm up the brakes into the adhesion temperature range, and then do one or more rapid decelerations from 70 mph (faster if possible) down to almost stopped, and allow the brake to cool below the adhesion temperature. While having the hot brakes, avoid stopping completely, or if you have to, don't hold the brakes on one place on the disk otherwise it might undo what you've been doing.
Another update:
A theory I ahve that it could be due to the type of Brake Pads themselves being cause of the brake judder persistently returning. If so replacing with an entirely different make of pad should make a difference. The pads I have been using are 'Allied Signal- Jurid' brand in a blue-coloured box. The brand I had before that (no judder then) was 'Bendix' branded.
XJ-S 3.6 230k miles +
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