Banging noise/feeling above 37mph, gulp....

[Gerlewis]

Hi all,

Has my luck finally run out?

We took out Cayenne to a local wheel-refurbish company, and asked them to swap some tyres around (and fit some part warns) as ours were getting a bit bald.

Since we have had the car back the car lacks a bit of throttle response (gentle 20% throttle) between 0-30mph. At this time, when steering, the Traction Light flashes ('A' in a circle with an arrow).

Then when I go above 37mph, this is when the fun really begins:

The car starts a thud,thud,thud,thud,thud fairly quicky (5 per second), you can hear it and feel it in the car, almost like putting a shoe in a washing machine, which initially prompted me to think there was something in one of the tyres.

And as you increase speed to 45mph the thuding becomes LESS rapid, more like: thud, thud, thud, thud (2 per second). After 45mph, the thudding is the same frequency, regardless of increasing speed, or if I down-shift.

The previous owner told me the cardan shaft was changed about 25,000miles ago (although I dont have proof).

Any ideas what this could be?

Although speed related, the noise doesnt change directly proportionally with the speed of the car, or with the engine revs.

My limited guesses would be: cardan shaft, driveshaft, hub, gearbox, dislodged electical connection. But they are guesses!

Any experienced viewpoints? Before I take it to the specialist?

Thanks! and I will keep you posted!

Ger

[pugs2bb]

Considering that the traction light flashes, check your tire sizes, not just on the sidewall but measure the circumference. If the difference is more than an inch, the abs may be reacting. The sound you describe could be the careen shaft also.

[trollybus]

I would visually check all the tyres sounds like one may have delaminated or even two? The traction control light is the yellow flashing triangle which may be a poor fitting tyre that has not sealed properly, had thus with mine when I went round left hand corners at speed transpired the rim had a small crack which meant the bead would not seal. Hope this us of some use

[Gerlewis]

Thanks guys - Im thinking after a visual check - the natural next thing to do would be to go back to the alloy wheel refurb guy, and ask him to fit my original tyres, for a fair test.

How can I visually diagnose delamination?

[Gerlewis]

Ive just looked and the front tyres are 274/40/20 but the rears are 275/45/20

Im guessing this would be the cause?

[Hilux2400]

The 274 seems odd, sure it's not 275. Your back tyres have a different rolling circumference from the front tyres. The second figure is the aspect ratio. It measures the height of the tyre off the rim as a percentage of the width. The "45" tyres are bigger and therefore these wheels turn slightly more slowly than the wheels with the "40" tyres for any given speed. If this difference exceeds a certain tolerance the ABS senses something is amiss. I don't know what that tolerance is.

Having said all that it, could be a slack wheel nut as that can cause knocking noises also.

H

[Gerlewis]

Thanks.

Yes, 275 sorry, typo.

Im going to get the old tyres put back on as a first step. Hopefully its a case of me purchasing the wrong tyres!...

[Hilux2400]

Try the wheel nuts first - it will not take a minute with a wheel brace. Even one slack wheel can cause a lot of noise.

[Gerlewis]

Well, it was the incorrect tyre size (aka me rushing ordering tyres!).

Thanks for all your input - feel like I've dodged an expensive bullet!

Ger

[Hilux2400]

Da Iawn