Strange noise on a spider

[wadgebeast]

It sounds like a hole in the exhaust as it's a deep bass note and is definitely coming from the rear of the car, doesn't sound like anything is grating. The exhaust looks ok, and the wheel bearings should be ok too - it was only mot'd last month and when you grab the wheels, they don't shake. Rear brake pads are due to be replaced, but the noise doesn't get any worse or any better when you apply either brake. Nor is the car's performance dented, so I don't think it's a brake binding.

Noise seems to be related to speed as you hear it above 25mph and is independant of revs, ruling the exhaust out again. And yes, the tyre pressures are ok.

Any thoughts?

[RicksAlfas]

If it was a 147/156 I would bet you a large can of WD40 that the rear tyres have worn to a certain point which is causing the noise. I don't know why they do it, but they do. It wouldn't surprise me if Alfa have given the Spider a similar "feature". Cheapest way to find out is to swap the tyres front to back and see what happens.

If it's not the tyres could it be one of the fancy rear suspension mounts that's gone?

[wadgebeast]

Tyres have only got a few thou on them, but swapping them around is simple enough to do! Ta.

Hopefully not one of the rear mounts.... does seem to be the lhs, where the exhaust exits.

[xyyman]

I would bet its the rear tyres feathering on the inside edges. Happened to mine on the original fit Firestones after a few thousand miles. Had suspension checked and all OK. Changed tyres to Toyo Proxes T1R's and all still OK and better wear rate all round, evn the fronts and this is on a 3.2!

[jamieboy]

If it's a 916 Spider then I'll go along with everyone else, because I had the same thing with my GTV when the tyres were a bit worn.

RicksAlfas said:

If it was a 147/156 I would bet you a large can of WD40 that the rear tyres have worn to a certain point which is causing the noise.

That's reassuring - I didn't realise the 147s had the same issue, so it's hopefully not a wheel bearing that I'm hearing in ours.

[wadgebeast]

Yep,916 spider. Goodyear Eagles GSDs on, about 2000 miles on thenm tops but it is enthusiastically driven.

I'll swap the fronts for the rears tomorrow; if it works, then it can be recorded here as a solution for weird noises not made by exhausts. That's provided the insides of the fronts aren't worn in the same way - the tracking was done at the same time.....

[wadgebeast]

Tyres swapped; noise has moved to the front, problem solved. Thanks to all.