Post trackday noises...

[Inferno]

Just come back from a day out at Brands. Towards the end of the day the car developed a knocking noise - it sounds similar to a woodpecker tbf, but it's intermittent.

At first I noticed it on the exit of Clarke Curve with full power being applied and thought it was something to do with the suspension (AST's), but that can't be the case as it's now making the noise in a straight line!

I've had all the wheels off and had a look under the car. I can't see anything obviously broken and the exhaust appears to be solid.

As I've said the noise is intermittent, but in a straight line I can make it re-appear in a hit and miss type way at around 4000rpm. Sounds like it's coming from the rear, but I find it's very difficult to figure out where sounds are actually coming from in a car.

Any ideas of what it could be would be most appreciated!

 

[Inferno]

Hmmm, definitely not engine or exhaust related, but it is speed related. The faster I go the more it happens.

All I can think is that it's the excess rubber that I've picked up on cool down laps or when moving over for faster cars removing itself and hitting the arches, but it's so loud!?

 

[iimushroomzii]

Jack the wheels up and give them a spin and a wobble one by one see if you notice anything out of the ordinary?

 

[Inferno]

Already done that first thing this morning, nothing appears to be loose or out of place.

 

[Steve]

Does it sound like going over rumble strip?

 

[jon_r]

No trim come loose underneath? My Cup did that. Mind you hitting the fox at 85 mph didn't help.

 

[Inferno]

Does it sound like going over rumble strip?

No, nothing like that. It's like one of those clicky things used for dog training repeated very quickly.

 

[iimushroomzii]

No trim come loose underneath? My Cup did that. Mind you hitting the fox at 85 mph didn't help.

I had the same thing, Hit a fox and then found the archliner melting on the tyre!

 

[Inferno]

No trim come loose underneath? My Cup did that. Mind you hitting the fox at 85 mph didn't help.

Only things that look loose are the two most rearward arch liners that locate inside the rear bumper, you could move them with your hand and hit the bumper, but I'm not sure if they've always been like that or it's just that I noticed because I was looking.

 

[powey]

heatshield?

 

[Inferno]

heatshield?

I had a quick look at the rear heatshield and it looked pretty solid, but I suppose there is the possibility that the wind could be catching it at certain speeds. I'll have another look at that tomorrow.

 

[Steve]

Stone in rear tyres?

Get that report done now you've done a trackday

 

[Inferno]

Stone in rear tyres?

Get that report done now you've done a trackday

I knew that was coming! Will do! (It's good news) There were a few stones that I picked up (no trips to the gravel though) and they're quite easy to identify when they hit, but this is totally different.

 

[rob_clio197rs]

definatly sure its not the exhaust knocking on subframe? mine use to do it only when the rpm picked up. you say its speed related have you tried knocking it out of gear at hi speeds so the engine is just idling or is it only happening when the rpm is high aswell as speed?

 

[Inferno]

definatly sure its not the exhaust knocking on subframe? mine use to do it only when the rpm picked up. you say its speed related have you tried knocking it out of gear at hi speeds so the engine is just idling or is it only happening when the rpm is high aswell as speed?

Yep, was going along at 70mph with the engine at idle and the noise was loud and clear. Did it a couple of times just to be sure.

 

[rob_clio197rs]

and you say its from the rear? strange that, i was thinking maybe drive shaft but ruled out if its from the rear. not sure then dude

 

[Inferno]

and you say its from the rear? strange that, i was thinking maybe drive shaft but ruled out if its from the rear. not sure then dude

Sounds like the rear, but it can be so deceptive. Wouldn't the noise be there all the time if it was a driveshaft?

 

[mark123]

I have clicking that I reckon is drive shaft. That is intermittent but definitely sounds like it is coming from the front.

How about cracked rear disc?

 

[Kiev85]

I have clicking that I reckon is drive shaft. That is intermittent but definitely sounds like it is coming from the front.

How about cracked rear disc?

that sounds like an idea...

i had a crack...(VERY difficult to see)...clicking noise at high speed...

 

[Jay Payne]

could just be tyre pickup. old rubber stuck to the tyre. makes a hell of a noise & can be intermitant.

 

[Inferno]

I have clicking that I reckon is drive shaft. That is intermittent but definitely sounds like it is coming from the front.

How about cracked rear disc?

that sounds like an idea...

i had a crack...(VERY difficult to see)...clicking noise at high speed...

Will check the disks again in the morning, I assumed a crack would be pretty obvious.

could just be tyre pickup. old rubber stuck to the tyre. makes a hell of a noise & can be intermitant.

I hope so!

 

[Jay Payne]

Have a look at the tyres, if there is loads of bits of rubber stuck to them then im pretty sure that will be it. Takes a few miles but will eventualy stop.

Or swap tyres front to rear and light the boy up :rasp:

 

[Inferno]

Have a look at the tyres, if there is loads of bits of rubber stuck to them then im pretty sure that will be it. Takes a few miles but will eventualy stop.

Or swap tyres front to rear and light the boy up :rasp:

There is a lot of crap stuck to the tyres, but I'll be surprised if the excess rubber can be louder than stones! However I do like the lighting up idea - playtime tomorrow...

 

[Jay Payne]

Trust me it can be mental loud. I got my rear tyres off a mate who had used them at Brands. For the first 100miles it sounded like a machine gun going off randomly.

Be great if thats all it is, let us know

 

[ado]

Mine made quite abit of noise from the crap on the tyre flicking up aswell after every trackday. Hopefully thats your problem.

 

[Inferno]

Trust me it can be mental loud. I got my rear tyres off a mate who had used them at Brands. For the first 100miles it sounded like a machine gun going off randomly.

Be great if thats all it is, let us know

Mine made quite abit of noise from the crap on the tyre flicking up aswell after every trackday. Hopefully thats your problem.

It does appear that small bits of rubber can make such a noise! Obviously I'm pleased that's all it is!

Looks like the long strips of rubber are starting to come unstuck at one end and are slapping against the arch liners for a number of wheel revolutions until the whole section finally gives way to the centrifugal forces and disappears down the road.

I've done my fair share of track days, but never noticed it before - looks like the factory sound proofing does actually work quite well!

 

[Jay Payne]

it depends how 'dirty' the track is. if its rained hard since the last race meeting its normaly washed the marbles away

 

[Inferno]

Might have well been a race meeting on the day, there were a couple of these things pounding the track almost constantly all day...

There were four race teams carrying out full on testing as far as I could tell. Various cars.

 

[Steve]

Thats why i asked about the rumble strip sound, my trophy on 888's when dirty used to make a loud whiring sound like doing 100mph in an old land rover.
Just the old rubber stuck to tyres

 

[Kiev85]

anyone got any pics of this rubber build up??

sounds absolutely crazy (i dont do track days)...it would be interesting to see...

im assuming its noticable on the tyre??

 

[Jay Payne]

I may have a pic somewhere, cant look right now coz photobucket is on strike.

Yes it is noticable, Its all the crap that is off line on the circuit. Marbles they call it sometimes in race comentry