A6 vibration at high speed

[krishcanag]

Hi guys

Wonder if anyone can comment on this.

I bought a approved used A6 3.0 tdi 204hp from main dealer, 62 plate, 26k on it, 4 new tyres on it as well.

When I brake there is a juddering noise, nothing great but a little and no steering wheel shake, so took it to local main dealer, who said the disks are vibrating and need changing together with the pads. hoping for cost to be bourn my main dealer I bought it from up north.

Second issue is I had also noted at around 95 mph!! (I drive in germany at times so need high speed) there is a general vibration in the car but not on the steering wheel. It is at this speed it is worse at 100+ it seems to reduce and again below 85.

My local dealer has re-balanced the wheels it is still there, so the QUESTION!!!

Will changing the disks stop this vibration as well as the juddering?

cheers

krish

[Whippy53]

And the answer is, possibly. You may however require further investigation. Try finding a specialist who can balance the wheels ON the car.. There is also the possibility that one of the tyres is ever so slightly out of round. At over 100 it don't take too much.

[Pikey Narna]

I had a 3.0ltr Mondeo ST and had 4 new tyres fitted. Went down a dual carriageway and the vibration was so bad I almost crashed. Took the car back to National Tyre Service rechecked the balance and all appeared to be spot on. Went down the road the same thing.
In the end took it to a garage who put the car on a ramp started up the car and at speed we noticed a bulge on the inside of the brand new tyre.
It was a defect in the side wall, tyre replaced F.O.C and all was well.
As whippy said if your doing speed try to get them balanced on the car.
Andy

[krishcanag]

Ok, well dealer changed all disks and pads, brake juddering sounds gone, but again from 90mph - 100mph (cannot go any higher !!!) vibration is there, how can anyone know its a dud tyre or maybe something like a unbalanced driveshaft from some front end accident? The tyres were also re-balanced

krish

[ukgroucho]

I had a dud tyre on a brand new Cavalier SRi company car 25+ years ago... same symptoms but at lower speeds... anything over 70 mph and it vibrated. Apparently it was a bulge caused by a manufacturing defect, something to do with the way the "plys" are lapped over each other in a cross-ply tyre.

You need to start by getting the dealer to check the tyres out properly - which probably means taking them to a tyre shop that has the right equipment to do it.
Balancing means nothing... if the tyre has a bulge then it's gonna cause some vibration and it will increase the faster you drive.

What you might try, just to see if it is the tyres, is to rotate your wheels front to rear and see if it changes the nature of the vibration - if it does then it's definitely a tyre issue.

[Pikey Narna]

As said, put the car on a lift start it up and put it through the gears. We had our checked twice on a wheel balancing machine and it didn't show anything. Put it on
a free wheel lift took it up to speed and there it was the size of an egg. I would not believe it could happen if I hadn't seen it with my own eyes.
Andy

[krishcanag]

Ok, touch wood, may have found the issue, will have to update after a week to be sure.

I just took it and checked the tyre pressures, the recommended for not fully loaded car is 35psi front and 32 rear. It was 33 front and 30 rear. Now so I increased it and no more vibration!!! I find it hard to understand why such a small change could cause this unless as most of comments seem be tyre related, must be one tyre is not good maybe is that the real reason why?

krish

[Pikey Narna]

Hope it works for you Krish, I know how annoying it can be

[krishcanag]

Ok, the vibration is still there, but I now no more about it.
If you accelerate fast the vibration is felt from 80-95+.. cannot keep going... and also when you then just take your foot totally of the pedal and cruise down. If on the other hand you just let the speed build up slowly, you hardly notice any vibration though not totally free, well sometimes you fell nothing at some times you do feel a little.

So over to any one with more experience as to what is it caused by.

regards

krish

[N16E]

Hi,

Just a thought, have you had the wheels checked for buckles. My car had similar symptoms after I hit a pothole. 2 wheels £1700 later it was fixed. Thankfully the council paid out.

N16e


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