Front brake disc run out
Discussion
Hi,
Fitted new EBC rotors to the front brakes this weekend as the old ones were causing steering vibration under braking.
I understand that the vibration can be caused by disc thickness variation caused by excessive disc run out when fitting.
I have a dial gauge but not a suitable clamp at the moment to test the run out but with the new discs fitted, run out is visible when looking at the clearance between the pad carrier and the disc as it is rotated. I guess if I can see it by eye, the run out is probably excessive. How can I correct this? I spent 2 hours a side fitting these, making sure that all the mating surfaces were scrupulously clean, using wire brush. I also did this and then witha file to make sure carrier mountings and washers that fit between the carrier and the hub were flat and clean. I guess the disc to hub surface is the most important one for the run out.
Cheers, Matt
Fitted new EBC rotors to the front brakes this weekend as the old ones were causing steering vibration under braking.
I understand that the vibration can be caused by disc thickness variation caused by excessive disc run out when fitting.
I have a dial gauge but not a suitable clamp at the moment to test the run out but with the new discs fitted, run out is visible when looking at the clearance between the pad carrier and the disc as it is rotated. I guess if I can see it by eye, the run out is probably excessive. How can I correct this? I spent 2 hours a side fitting these, making sure that all the mating surfaces were scrupulously clean, using wire brush. I also did this and then witha file to make sure carrier mountings and washers that fit between the carrier and the hub were flat and clean. I guess the disc to hub surface is the most important one for the run out.
Cheers, Matt
I trust you have the wheel attached to the hub and torqued up to see run-out??
Have you driven it and the vibration is still there??
Or, are you rotating the hub with disc, but no wheel attached??
If the latter, then re-attach the wheel - it locates the disc rotor!!
Not clear - to me anyway ???
Have you driven it and the vibration is still there??
Or, are you rotating the hub with disc, but no wheel attached??
If the latter, then re-attach the wheel - it locates the disc rotor!!
Not clear - to me anyway ???
K4TRV said:
I trust you have the wheel attached to the hub and torqued up to see run-out??
Have you driven it and the vibration is still there??
Or, are you rotating the hub with disc, but no wheel attached??
If the latter, then re-attach the wheel - it locates the disc rotor!!
Not clear - to me anyway ???
Hi K4TRV,Have you driven it and the vibration is still there??
Or, are you rotating the hub with disc, but no wheel attached??
If the latter, then re-attach the wheel - it locates the disc rotor!!
Not clear - to me anyway ???
No, I had two opposite wheel nuts on with washers to take up the space due to the wheel missing. The vibration has gone but from reading on this subject, it seems the run out isn't the source of the vibration. The run-out causes the discs to be worn thinner in one area than others, so the disc goes out of balance (a bit like a wheel with a new tyre before wheel weights added I guess) and it is the thinned disc that causes the vibration. The thinning process takes approx 3000 miles to happen, which is why discs with incorect runout always start to vibrate at around the same mileage use regardless of use or vehicle.
I don't understand how thinning of the rotor due to runout would cause it to go out of balance. Surely its thinning the rotor at the same rate all round.
Oddly, and the reason for me poking my nose in here, I have a set of EBC rotors under the bench which only lasted a few thousand miles before causing vibration under braking. I was going to get them skimmed but they've sat there for more than a year now.
Were your old rotors EBC GD150 (grooved and dimpled) by any chance ?
Oddly, and the reason for me poking my nose in here, I have a set of EBC rotors under the bench which only lasted a few thousand miles before causing vibration under braking. I was going to get them skimmed but they've sat there for more than a year now.
Were your old rotors EBC GD150 (grooved and dimpled) by any chance ?
Barreti said:
I don't understand how thinning of the rotor due to runout would cause it to go out of balance. Surely its thinning the rotor at the same rate all round.
Oddly, and the reason for me poking my nose in here, I have a set of EBC rotors under the bench which only lasted a few thousand miles before causing vibration under braking. I was going to get them skimmed but they've sat there for more than a year now.
Were your old rotors EBC GD150 (grooved and dimpled) by any chance ?
Hi Barreti,Oddly, and the reason for me poking my nose in here, I have a set of EBC rotors under the bench which only lasted a few thousand miles before causing vibration under braking. I was going to get them skimmed but they've sat there for more than a year now.
Were your old rotors EBC GD150 (grooved and dimpled) by any chance ?
The reason is this: the rotor is not lined up with the brake pad carrier, so as it rotates (with brakes off), the faces of the rotor come into contact with the pads but crucially only for a proportion of its rotation. For the rest of the rotation, the rotor is not in contact with the pad. This causes it to wear thinner over only a proportion of its circumference. This probably causes some degree of constant vibration (like a wheel would when out of balance) but it is usually only felt during braking where the changing thickness of the rotor causes the braking force to fluctuate as the rotor spins, causing brake pedal pulsing and steering to shake. Mine got so bad, the wing mirrors used to shake !
To answer your last question, mine were EBC 150 sized rotors so similar but not the grooved and dimpled ones. I think run out would affect any rotor in a similar way however, so this is not only an EBC rotor issue.
taylormj4 said:
Hi Barreti,
The reason is this: the rotor is not lined up with the brake pad carrier, so as it rotates (with brakes off), the faces of the rotor come into contact with the pads but crucially only for a proportion of its rotation. For the rest of the rotation, the rotor is not in contact with the pad. This causes it to wear thinner over only a proportion of its circumference. This probably causes some degree of constant vibration (like a wheel would when out of balance) but it is usually only felt during braking where the changing thickness of the rotor causes the braking force to fluctuate as the rotor spins, causing brake pedal pulsing and steering to shake. Mine got so bad, the wing mirrors used to shake !
To answer your last question, mine were EBC 150 sized rotors so similar but not the grooved and dimpled ones. I think run out would affect any rotor in a similar way however, so this is not only an EBC rotor issue.
Sorry to be a sceptic. I don't buy wearing of the rotor because it's not lined up!!The reason is this: the rotor is not lined up with the brake pad carrier, so as it rotates (with brakes off), the faces of the rotor come into contact with the pads but crucially only for a proportion of its rotation. For the rest of the rotation, the rotor is not in contact with the pad. This causes it to wear thinner over only a proportion of its circumference. This probably causes some degree of constant vibration (like a wheel would when out of balance) but it is usually only felt during braking where the changing thickness of the rotor causes the braking force to fluctuate as the rotor spins, causing brake pedal pulsing and steering to shake. Mine got so bad, the wing mirrors used to shake !
To answer your last question, mine were EBC 150 sized rotors so similar but not the grooved and dimpled ones. I think run out would affect any rotor in a similar way however, so this is not only an EBC rotor issue.
The pads would just wear themselves to suit, even with "soft" cheap rotors!!
Most brake vibration is simply warped rotors from localised over-heating and despite being a reasonable make, I'd bet they failed from poss bad heat treatment allied with localised overheating!!e.g. A v fast stop and then not releasing the footbrake (in a queue on a hill??), the pads/rotor, creating warping.
Experienced it myself when Sprinting at Castle Coombe on more than one occasion, horrendous vibration from initial pads gassing then the rotors warped - mine were 283mm Cossie discs, but only £21 each (inc VAT) !!
Unless you have gone through 3 or 4 sets of pads, I doubt wear would start to be an issue with brake pedal pulsing?? You've got warped discs!!
Just my penny worth (£21 x 4 so far)!!
Trev
'Fraid I have to agree with Trev. my EBC's warped on my Range Rover. Auto box so forced to keep foot on the brake. It is down to poor heat treating and can affect any disc. Mine only warped the offside rotor so shudder under breaking also caused a slight pull to one side. You can get the disc skimmed but this will only really be a temporary fix as the initial heat treatment has not applied to the rotor evenly. So will warp again when you next heat it up.
Matt
Matt
yes, you could be right. I did read that warping can also be caused by the pads stopping on the discs. I guess the acid test would be to put some accurate calipers or similar over the discs to see if they are thinner at any points. I did notice the outline of a pad on one of the discs which suggests the pad deposited on the disc as it stopped. This is set number three now. I did look into larger discs or discs by others but decided to stick with the EBC discs and try yellow stuff pads, as before the disc problem I was finding the braking to be moderate at best. The yellow stuff pads seem to give better initial bite so far but still wearing them in so no heavy braking tests yet.
Interesting responses guys anyhow thanks. Always happy to hear others points of view.
Interesting responses guys anyhow thanks. Always happy to hear others points of view.
How sorted is the rest of the braking system?
Don't forget the rears. If they aren't working as they should all the braking effort will be on the front brakes and could easily be overheating them.
On my pre-cat Griff I had standard brakes but they were downright dangerous.
I've left the rear brakes standard but upgraded the fronts with later 500 spec calipers, EBC GD150 rotors and yellow stuff pads. I've also got braided brakes all round and DOT5.1 fluid.
I can now stand the car on its nose with a bit of effort and it has nice road manners normally.
Don't forget the rears. If they aren't working as they should all the braking effort will be on the front brakes and could easily be overheating them.
On my pre-cat Griff I had standard brakes but they were downright dangerous.
I've left the rear brakes standard but upgraded the fronts with later 500 spec calipers, EBC GD150 rotors and yellow stuff pads. I've also got braided brakes all round and DOT5.1 fluid.
I can now stand the car on its nose with a bit of effort and it has nice road manners normally.
Barreti said:
How sorted is the rest of the braking system?
Don't forget the rears. If they aren't working as they should all the braking effort will be on the front brakes and could easily be overheating them.
On my pre-cat Griff I had standard brakes but they were downright dangerous.
I've left the rear brakes standard but upgraded the fronts with later 500 spec calipers, EBC GD150 rotors and yellow stuff pads. I've also got braided brakes all round and DOT5.1 fluid.
I can now stand the car on its nose with a bit of effort and it has nice road manners normally.
Hi Baretti,Don't forget the rears. If they aren't working as they should all the braking effort will be on the front brakes and could easily be overheating them.
On my pre-cat Griff I had standard brakes but they were downright dangerous.
I've left the rear brakes standard but upgraded the fronts with later 500 spec calipers, EBC GD150 rotors and yellow stuff pads. I've also got braided brakes all round and DOT5.1 fluid.
I can now stand the car on its nose with a bit of effort and it has nice road manners normally.
I have braided lines on the front as the old ones cracked so I had them replaced but the rears are still rubber. Others have said that this will affect braking so I'll get them changed when finances recover from just having to have a clutch replaced ! I'd also heard DOT5.1 is better, why is that ? Do the older types of fluids compress very slightly losing braking effort or something ?
Cheers.
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