Tyre contact with arch liner on compression

[Lee]

After a wee bit of advice:
On track I quite often suffer from the tyre rubbing against the arch liner (fender) during compression of the suspension. This is causing a braking effect which is upsetting the rear end during high speed corners, and also makes the steering very 'grabby' i.e. not smooth.

Set up:
Car: GT86
Front ride height: ~330mm / 13" (wheel centre to wheel arch)
Rear ride height: ~342mm / 13 1/2"
Sway bars: stock (I have not fitted adjustable endlinks)
Suspension: KW clubsport (6kg springs I think)
Alignment: Front -2.5 degrees, Rear -1.4 degrees
Wheels & tyres: 17x9 ET 42, 235/40R17 Nankang NS2R tyres
Misc: Whiteline roll centre adjusters / bump steer kit fitted up front. SPL Titanium rear arms. Stock bushings. Left side rebound adjustment siezed on full soft (although still had rubbing when it wasnt siezed pre winter)

Thoughts:
Sway bars - one size up both front and rear (I like the balance as is, would allow me to tune the set up a bit easier)
Raise ride height - dont really want to - I dont feel the car is too low
Revalve for stiffer springs with a rebuild - Scottish roads are not as flat and well kept as american roads, and whilst the car is currently my main car I dont want to go too extreme with spring rates to make the ride intolerable for the majority of my time (closest track being 3hr drive, 2nd closest being 6.5hrs)
The car does seem to 'roll' a bit.

youtube channel link is in my signature which has some videos where you can hear whats going on.

[mav1178]

What tires/tyres are you running?

[Lee]

Wheels & tyres: 17x9 ET 42, 235/40R17 Nankang NS2R tyres

First post updated

[cjd]

More negative camber an option? It should be a net benefit to handling too.

If Scottish roads are worse than what I deal with in Chicago I can only be aghast at the image it brings to mind. I've gotta get out there some day, see for myself, and visit the "family" castle (long since politicked to another family...) while I'm at it.

[glamcem]

I had some rubbing issues with the same tire, wheel size and similar drop (about 1 3/4")..
FYI, I have 9k Front/ rear spring rates so yours should be even worse since springs are softer.. you can definitely consider raising the car a bit (1/2" should help), you can try adding a bit more neg cambers to the front as well but not as much as the springs and/or the ride height.. in my case it helped me but I still rub at times when the elevation changes are instant (like the corkscrew at our local track)..

good luck

[Lee]

More negative is an option, but it wont help with whats happening. I am not rubbing at the edge of the arch - its the black plastic 'fender liner' that is getting torn to shreds and rubbed away. pretty much in the centre between the spring perch and wheel arch.

[glamcem]

assuming you have camber plates in the front since 1.25" drop alone shouldn't be enough to get ~-3.0 neg camber

[Lee]

Originally Posted by glamcem

I had some rubbing issues with the same tire, wheel size and similar drop (about 1 3/4")..
FYI, I have 9k Front/ rear spring rates so yours should be even worse since springs are softer.. you can definitely consider raising the car a bit (1/2" should help), you can try adding a bit more neg cambers to the front as well but not as much as the springs and/or the ride height.. in my case it helped me but I still rub at times when the elevation changes are instant (like the corkscrew at our local track)..

good luck

Cheers, do you still have the stock bars?

Originally Posted by glamcem

assuming you have camber plates in the front since 1.25" drop alone shouldn't be enough to get ~-3.0 neg camber

Yep - camber plates and camber bolts are fitted.

[glamcem]

Originally Posted by Lee

Cheers, do you still have the stock bars?



Yep - camber plates and camber bolts are fitted.

yes, I still have the stock roll bars (sways)

[tahdizzle]

I read that post with the voice of

in my head.

[strat61caster]

I remember reading that the engineers claimed that a 20mm drop is ideal from stock configuration in early press kits and interviews and such.

You've dropped the car ~40mm, and added some tire.

Is raising it up 5-10mm (0.25"-0.5") really that bad?

[cjd]

Shoot. The middle!

Maybe I should be glad I have so much spring (at 35mm drop, ~1.4") I wasn't particularly after that much drop, but it's the recommendation so...

Sometimes it's too smooth, but sometimes it's a bugger.

Heat gun and reshape the liners for more clearance? Though, if 5mm is enough, why not?

[glamcem]

Originally Posted by strat61caster

I remember reading that the engineers claimed that a 20mm drop is ideal from stock configuration in early press kits and interviews and such.

You've dropped the car ~40mm, and added some tire.

Is raising it up 5-10mm (0.25"-0.5") really that bad?

Originally Posted by cjd

Shoot. The middle!

Maybe I should be glad I have so much spring (at 35mm drop, ~1.4") I wasn't particularly after that much drop, but it's the recommendation so...

Sometimes it's too smooth, but sometimes it's a bugger.

Heat gun and reshape the liners for more clearance? Though, if 5mm is enough, why not?

Where do you guys read these recommendations?
mind sharing the link?

[strat61caster]

Originally Posted by glamcem

Where do you guys read these recommendations?
mind sharing the link?

I thought it was in a magazine but struggling to find it, I did find these two posts here though, I'll update if I find the magazine, thought it was C&D or R&T...

http://www.ft86club.com/forums/showt...894#post538894

http://www.ft86club.com/forums/showthread.php?t=2787

(Note the second link, they have a 130mm ground clearance on the 86, many sports cars have 110mm...)