Vibration

[Kingbagpuss]

Hi I have a 2008 a3 cr170, it has developed a vibration that I can feel through the floor, it only happens between 60-70mph iv done the obvious had the wheels balanced, checked tyres, seized callipers anything else I should check? Any help will be greatly appreciated 

[Magnet]

Hello Chris,

When you say you have had the wheels balanced, is that all four?

Kind regards,

Gareth.

[Kingbagpuss]

Yeah, had all 4 balanced made no difference at all 

[Magnet]

Well that blows that theory then Chris! 

Normally vibrations felt through seat or floor is associated with rear wheel imbalance.

Tried shopping front wheels to back?

Kind regards,

Gareth. 

[Kingbagpuss]

Yeah that was my first thought! I haven’t no maybe I’ll try that next. I had a sticky nsf calliper but I feel nothing when braking through the pedal or wheel. It is a Quattro would a centre prop bearing cause this or would I get noise with that ? 

[cliffcoggin]

I agree it's most likely associated with the wheels such as worn bearings, mismatched tyre patterns, or loose wheel studs; however it could also be caused by a worn suspension or transmission joint, so your prop shaft bearing is a possibility.

[Kingbagpuss]

Iv had it jacked up and checked all ball joints, suspension, wheel nuts and bearings the only thing I could put it to is warped rear discs maybe for £50 I’ll chuck a set on at the weekend 

[Magnet]

Hello Chris,

Replacing warped discs? Not a logical way forward in my book. If the discs are that warped then you would feel, it as a pulsing pedal. 

65/70 mph is typical wheel balance/tyre territory, and without doubt, I would not be renewing anything until rear/ front tyres are swopped. 

Have you got matching make and tread pattern tyres, at least on the same axle? 

Kind regards,

Gareth. 

[Kingbagpuss]

I’ll swap the wheels over at the weekend and see how it goes from there 

[cliffcoggin]

Chris.

Is it a two part prop shaft? If so it should have a pillow or doughnut shaped rubber mounting near the middle, and if that is soft or damaged it can lead to vibration.

[Kingbagpuss]

I’m not sure I’ll have a look when I swap the wheels over

[DavidTdi]

The A3 TDi I bought and overhauled for my daughter in June suffered similar. Didn't test drive as it was bought privately during full lockdown and was in the middle of the city so wouldn't have got it above 30mph. Bought with leeway to do work but I was shocked once up to speed on the motorway driving home to feel a dreadful vibration from 60mph. Felt more through floor than steering wheel... as if the driveshafts were bent or the gearbox was about to fall out! Worse I've known in decades of driving and not a typical wheel balance feeling.

Tyres were first check and were actually due for replacement as mixture of Chinese brands and I always fit premium. Both front tyres showed a degree of out of round/tread distortion when jacked up and spun with a fixed point just touching the tread to judge the distortion amount.

So I swapped front to rear as a test and 90% of the vibration went. Then fitted a new set of tyres and smooth as silk.

The amount of tyre distortion seen wasn't as great as the feeling of vibration indicated and you could easily have just balanced the wheels...still had the vibration... and moved onto wheel bearings, driveshafts etc... thinking the tyres OK.

I've seen this quite a bit over the decades and tyre fitters often swear blind they can balance anything out but if it ain't round it might show as balanced in free air on the machine but once back on the road still no good..

Fingers crossed a front to rear swap will prove the point for you... assuming the rears are running true!

 

 

 

 

 

[Kingbagpuss]

Hi sorry for tHe late reply, I’ve swapped wheels and still a wobble. What do you recommend to check next ? Checked all the obvious stuff 

[cliffcoggin]

You're not giving much information away Chris. What obvious stuff are you referring to? Did you look at the prop shaft bearing and rubber mounting? Are the tyres matched?