Help Rubbing or scraping on right hand bend?

[CtrMint]

Guys,
I need some advice or recommendations regarding looking at an issue with the 7 as I'm a little stuck.

In short I've noticed if I drive quickly around a tight right-hand bend, with an incline or decline and I have a passenger I'm experiencing a rubbing or scraping noise.   I don't appear to notice it without a passenger.  The Gooseneck on the TT course is a great example of the sort of bend I'm experiencing this on.  Video supplied as an example of the bend, Gooseneck reference,

I've had a good look under the car and can't identify anything.  Initially I thought the sound was similar to a wheel rubbing in the arch but I can't see how that would be possible as there is a fair gap and there is no evidence or signs on the arch itself.

So I'm a little stuck.  While I have previously complained about a noise diff etc this noise should defo not be there, it's rather alarming.  Hopefully, with the experience here in BC, someone can point me at places to check.   If it helps I do have the wider rear tyres.

Thanks

[ChrisC]

So initial thoughts, have you checked you exhaust tip and seat bolts.   Scrapped my seat bolts a few time with no significant visible damage.  The exhaust tip is well know, I have seen some race cars had a D shaped exhaust after excessive scraping. 

[Nick Chan]

Possible rubbing on cycle wing stays as the tyre flexes?  Have a look for some witness marks on the tyres as a polished band. Also i had a handbrake cable touch the prop in the tunnel very lightly under high speed corners, I suppose the cable was swinging over very slightly and needed a cable tie to help keep it in place

[Jonathan Kay]

As above

+ balance weights on wheels meeting de Dion ears, but that sound is usually described as "ticking".

Jonathan

[ChrisC]

Even stones get caught between the wheels and the de Dion tube / ears.   Scratching the inside of the wheel. 

[Jim 123]

Can you replicate it in a car park holding a tight right hander to get a better clue where the noise is emanating from?

[CtrMint]

pics

This one is surprisingly deep

contact patch on the tube.

 

[CtrMint]

Thanks all for the support.

I've been and had a look.  The exhaust looks fine, no signs of rubbing or marring from contact with the ground or other surfaces. My seat fixings are the countersunk type which go up into the floor rather than downward, and also look fine.  The tyres, both front and back show no signs of rubbing as far as I can tell, and I can't see anything on the arches or cycle wings.  The handbrake and shafts also look fine with no signs or marring from contact either.

I did find what I would describe as scoring on the near side rim, aligned with the back of the Dedion tube, both the tube and wheel have picked up marks.  Could this be it?

I am surprised about how little clearance there is between the rim and tube, I'm assuming this is correct and I've not made a mistake during the build, say fitted the ears backwards, something daft like that.

I'll attach some pics.

[Jonathan Kay]

I am surprised about how little clearance there is between the rim and tube, I'm assuming this is correct and I've not made a mistake during the build, say fitted the ears backwards, something daft like that.

...

I did find what I would describe as scoring on the near side rim, aligned with the back of the Dedion tube, both the tube and wheel have picked up marks.  Could this be it?

Yes. Several reports in the archives and some fixes by judicious removal of material: 1, 2.

Jonathan

[CtrMint]

Surprisingly little clearance.

 

[CtrMint]

Jim, 

Might go and try, probably end up doing my first doughnut 

[CtrMint]

Just got back from a run around the course, it's definitely much less pronounced with only a driver, I only just heard it on a single bend.  Not sure why two up would make a difference. 

As I can't find any other evidence it would seem to be the dedion tube against the wheel, and the solution is to take a grinder to the tube? 

[Jonathan Kay]

... and the solution is to take a grinder to the tube?

Did you have a look at the two discussions linked from #9?

Jonathan

[CtrMint]

yeah read both through, but they seem to reference a mix of older cars and setup options.   Obviously I run a the current S3 chassis with the 13" Apollo wheels, but it still seems to be rubbing. 

[aerobod - near CYYC]

I don't think it is the deDion against the wheel causing the scrapping sound, other than a brief transient scrape that wouldn't be repeatable when a stone gets in there. There won't be enough deflection of the wheel unless the wheel bearing is knackered and even then it would scrape the whole wheel circumference in a fraction of a second if it was contact due to deflection. It is normal with the 13" wheels to do this. I considered grinding the ear down a bit but thought it will just let larger stones get in there and I'm loathe to remove any of the weld strength. Both my rear wheels are scraped like this all the way round, in the past I have removed rubber balls with small stones embedded from the deDion ear after a track day, showing me that they are the cause of the scraping:

[Mark w]

Have you got a rear exit exhaust ?

If so check the section behind the silencer / drivers seat area where it passes behind the offside wheel . Ride height settings / spring rates can lead to bottoming here if not set up correctly  .

Obviously worse two up .CC had to fit race dampers to their 620s demo car after it kept bottoming out on track day demo rides .

If its a side exit exhaust ignore these pointless comments 

[CtrMint]

It's a side exit, standard 420 stuff..

[CtrMint]

Aerobod are you suggesting its not the dedion on the rim?

[aerobod - near CYYC]

Correct, it is stones that occasionally get trapped between the rim and ear that cause the scratching, not the ear touching the rim itself. Once it has happened over a few thousand kilometres / miles you will just end up with a continuously scraped area about 15mm wide all the way around each rim, but it won't cause any issues other than cosmetic damage where the powder coat has been removed.

[CtrMint]

OK but why is it worse with 2 up and in a corner?

[anthonym]

Been following this saga. Wheel balance weights?  I was once told my gearbox had seized because the wheels wouldn't go round; all it was was the weights jammed against the calipers (or something) So a very mild version of this? Though I don’t see how a passenger changes things.. f w i w.  My favourite was the exhaust touching the ground. 

Passenger seat mountings - is it on rails? 

All seems to be covered in earlier posts. 

[CtrMint]

The passenger seat is fixed and is also using the countersunk upward screws, they seem fine,  There isn't a mark on the exhaust and it's perfectly smooth, both on the exit and the silencer section.

Wheel weights are well clear, much further inboard and there's no sign of contact to them.  See post 8

W.r.t to the issue relating to a passenger.  The wife and I went over the Mountain road yesterday, and through the Gooseneck, since the wife was in the car and the speed limit in place at that section my speed was some where between 30-40 if that, and the car made an alarming noise.  I've been out this evening to test, to see what I can replicate, with the one-way removed and the speed limit removed also I carried more speed into the bend and nothing.  I lifted so any noise wasn't drowned out by the engine/exhaust.

[anthonym]

how about she drives and you passenger? see if that gets different clues

seat belt scrawping on something? does the seat flex with someone in it? Tillets? "Not Tillets" (I only know Tillets)

[aerobod - near CYYC]

If the noise is brief (like a quick "squawk", "graunch" or "squeak") that isn't reproducible and only happens in a corner, it could conceivably be a stone being fired from the front wheel while it is turned across into the barrel of the diagonally opposite rear wheel, causing the stone to briefly be wedged between the ear and the wheel rim. If this is the case you should have the same number of scapes on the wheels as the times the noise has occurred. Perhaps it is just coincidence it has happened only with a passenger in the car.

Have you also checked that the tyre isn't contacting the watts linkage on the rear suspension on one side and that the links have the indents facing the wheel? That could be dependent on a passenger being in the car.

[CtrMint]

She won’t drive it unfortunately, said she would but that’s yet to happen.

We’ve got carbon seats and harnesses and while I’m not dismissing your suggestion I think we’d have heard something during bump roads etc, which there are plenty on the IOM.  I’ll check the seat and harness tomorrow, but I suspect they’re good.  I’m also convinced the noise was around the arch, and not so much inboard.