Braking woe......
Discussion
Hi all,
I had new discs and pads on my 93 Mayfair in August due to the original discs been warped, causing heavy judder when breaking, paticularly from high speed. All was fine and dandy, but in the last month, I have started having juddering again when braking, possibly even worse than before. Discs shouldn't warp this quickly, any idea what could cause this?
I had new discs and pads on my 93 Mayfair in August due to the original discs been warped, causing heavy judder when breaking, paticularly from high speed. All was fine and dandy, but in the last month, I have started having juddering again when braking, possibly even worse than before. Discs shouldn't warp this quickly, any idea what could cause this?
Yes discs can worp that quickly. It may not be you problem but it is worth checking. Brake calipers sticking, cheep discs and hard use (stoping quickly and leving you foot on the brake) cauld also worp the discs. But also check the ball joints and fixings around that area. DO you know how to check if the discs are gone?
The "warping" could actually be DTV (disc thickness variation)which takes time to show itself up .
Basically when you fit new discs sometimes its worth checking their trueness with a dti gauge , if out, the pad will wear the disc thinner in the spot where it is rubbing and eventually show up as judder . Don't always blame the disc , check your drive flanges and make sure the mating surfaces are spotless.
Basically when you fit new discs sometimes its worth checking their trueness with a dti gauge , if out, the pad will wear the disc thinner in the spot where it is rubbing and eventually show up as judder . Don't always blame the disc , check your drive flanges and make sure the mating surfaces are spotless.
As 'cone' says, it could well be defective discs or the mounting face for the disc, i.e. the drive flange, not running true.
You really need a Dial Test Indicator (DTI)to check this. You fit the DTI onto the calliper or hub, put the arm onto each disc face in turn and measure any run-out by turning the disc slowly. Note the max and min positions of the DTI reading and repeat for the other side of the disc. note whether the max and min figures occur at the same point on each side of the disc. if there is, say, a 0.004" error each side and the low/high points are the same (in opposition, obviously) both sides, then the disc is out of true or the drive flange is not square to the axis of rotation. Check the drive flange with the DTI.
If the disc is of varying thickness, then that's the problem and you need new discs. Back in the 80's Fords used to suffer from DTV a lot and we had a brand new Escort with 0.007" variation on one side.
If the disc is of constant thickness, but not running true, the calliper pistons may move in and out slightly to compensate, but could well still cause a judder. You need to either change the disc, if the disc is not square to the axis of rotation, or change the drive flange if that is the fault.
Alternatively, you could have a sticky piston in one of the callipers which could cause uneven disc wear.
It's a matter of measurement and investigation, I'm afraid.
I hope this helps.
Peter
You really need a Dial Test Indicator (DTI)to check this. You fit the DTI onto the calliper or hub, put the arm onto each disc face in turn and measure any run-out by turning the disc slowly. Note the max and min positions of the DTI reading and repeat for the other side of the disc. note whether the max and min figures occur at the same point on each side of the disc. if there is, say, a 0.004" error each side and the low/high points are the same (in opposition, obviously) both sides, then the disc is out of true or the drive flange is not square to the axis of rotation. Check the drive flange with the DTI.
If the disc is of varying thickness, then that's the problem and you need new discs. Back in the 80's Fords used to suffer from DTV a lot and we had a brand new Escort with 0.007" variation on one side.
If the disc is of constant thickness, but not running true, the calliper pistons may move in and out slightly to compensate, but could well still cause a judder. You need to either change the disc, if the disc is not square to the axis of rotation, or change the drive flange if that is the fault.
Alternatively, you could have a sticky piston in one of the callipers which could cause uneven disc wear.
It's a matter of measurement and investigation, I'm afraid.
I hope this helps.
Peter
If you cant get a DTI (this is not a replacment but just to give you an idear of what is going on). Clamp a pen to the cliper and look at the gap. It dose not give you a true reading but just an indication of if the disc has gone. Then you can take it some one how has got a DTI or look for other problems. As coper man sead a DTI is best if you can get one.
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