Vibration when braking

[duffcooper]

Has anyone got any ideas I have a S class 430 - I have changed all 4 discs and pads and lower control arms. I also had it MOT tersted this week, with no problems.

My problem is that I have a vibration at no matter what speed I am doing, under braking. This vibration can be quite violent and can be felt all over the car.

There is also a vibration when I hold the speed between 75 and 80 m.p.h

Any suggestions as to what this can be ?

 

[Ellsy Tanners]

Has the problem only been since your disc and pad change or was this why you changed them?

 

[television]

Some firms are hopeless at wheel balancing, that could cause a vibration under normal driving, especially if you can drive into it and out of it.

I have known faulty disc even when new for the braking problem, there is nothing else

 

[Silver Arrow]

If it occurs only under braking, then it is probably a defective disc.
If it happens at a particular speed, with no braking, then it is likely to be wheel imbalance.
My 123, and Volvo estate were prone to disc warping. It didn't happen when they were new, but replacement discs, with current pad material seemed to cause the discs to warp after about a year.
Send the discs back to the supplier and get them to replace them.
My independant claims to be able to feel the difference between a front and rear discs the way the pedal moves. (I can't).

 

[MIW615]

If, when braking you feel the vibration through the steering wheel then it's the front disc's - if you feel the vibration through the car (driver's seat) then it's the rear discs.

When fitting new discs it's important to make sure the hubs are clean so that the new discs fit squarely onto the hub's surface

 

[television]

If it occurs only under braking, then it is probably a defective disc.
If it happens at a particular speed, with no braking, then it is likely to be wheel imbalance.
My 123, and Volvo estate were prone to disc warping. It didn't happen when they were new, but replacement discs, with current pad material seemed to cause the discs to warp after about a year.
Send the discs back to the supplier and get them to replace them.
My independant claims to be able to feel the difference between a front and rear discs the way the pedal moves. (I can't).

Thats interesting as I have from with Volvo disc

 

[stevesey]

When fitting new discs it's important to make sure the hubs are clean so that the new discs fit squarely onto the hub's surface

Also check for rust on the hub mating surface. Had a similar problem on my Vectra, corrosion between the disc and hub meant new discs wouldn't run true on one side. Swapped discs over, checked runout, and the fault stayed with the hub, closer inspection revealed rust/blakened magnatite on the mating surface of hub (and old discs - still in garage bin). Bit of careful elbow grease later - problem solved.

 

[David Nock]

Could it be a tyre flat spot, caused by the previous discs being warped and now a tyre's setting up it's own vibration? Try swapping front to back? Check all wheels and tyres carefully.

 

[kth286]

If it has only happened since the change then it will be because the mating surfaces were not cleaned properly between the disc and its seating face. There is debris in there and the disc is not on flat against the mating surface.

It is a wheel off job and you need to check each disc for run out.

If you do one at a time it may be the first one and problem solved and you do not need to take the other wheels off.

Use a pencil and steady your hand on the hub and hold the pencil a very small distance from the disc (16th inch say) and get someone to turn the disc to see where it touches the pencil. That will show it is not fitted properly if it touches the pencil in one part and not another part.

If it is even all around then move onto the next front wheel etc.

Let us know how you get on as it is the only way we all learn.

 

[hmang]

when checking the run out it's important to fasten the disc to the hub using all 4 bolt holes .

the original wheel bolts with suitable spacers will do.

this will keep the disc flush to the hub and avoid false readings

 

[whitenemesis]

If, when braking you feel the vibration through the steering wheel then it's the front disc's - if you feel the vibration through the car (driver's seat) then it's the rear discs.

When fitting new discs it's important to make sure the hubs are clean so that the new discs fit squarely onto the hub's surface

SEAT issued a service tech memo that when renewing discs on the Alhambra (Galaxy -Sharan) the hubs must be renewed also. Seems corrosion on the mating surfaces is a big problem.

 

[wireman]

Better check the run out with a dial gauge since only 0.05mm (2 thou) of run out will cause trouble, be sure that the front wheel bearings are correctly adjusted or the disk run out may be swamped by bearing end float.

 

[robh]

In my experience, warped discs can usually be felt through the brake pedal. The pedal kicks under foot when braking. Warped discs can be caused by a sticking piston .