pvdw

Right ET wheels came in last week so fitted the new wheels with 245 325 tyre combo.
No fitment issues on first test run

Heigth effect :
Front + 0.350 cm
Rear + 0.600 cm
Rake + 0. 250 cm

Track effect:
Front: ET =0 + 0.5cm tyre = + 1 cm Total
Rear: ET =0 + 1cm tyre *2 = + 2 cm Total

So wondering why no-one else seems to be running this setup ? ( that I found at least )

Will be adjusting camber still but even at -1.32, fitment doesn't seem to be an issue.Ride height is pretty much standard 100 mm front 130 rear ( prior to tyre change)

Before and after pics :




Running Trofeo R so will definetly add camber but it seems there's two general opinions...
-2.7 front with -2.3 rear and then there's some running more in the back then the front ? For example -2.3 front and -2.8 back ? Any advice for this specific setup is welcome
Thinking that will set sways to middle position in back and front and start from there.
Will try @ Franco Fun on Spa this Tuesday

Serge944

The only thing that prevents me from going to these tire sizes is the taller gearing from the 325/30. These cars have enough traction for full throttle first gear acceleration, so I don't know if the potential increase in ultimate cornering grip is enough to offset the loss in acceleration.

Report back your thoughts.

mdrums

BEAUTIFUL GT3!!!!

997gt3north

unless you are track ONLY, fast and running Hoosiers or slicks, you don't need -2.3 rear negative camber

-1.7 to -2.0 is a good range (front can be -2.3 to -2.7)

that rear tire looks like it may on a big bump have a bit of a sidewall touching fender issue - if it does a very slight fender pull with a baseball bat levering off the tire is likely all you need - or removing your 5mm spacer if you are still running it

if you do remove it, or if you leave it because the tire fits, I would look to add a 5, 7 to 10mm spacer up front as well

ghst868

I'm running almost the same setup. 245 & 325 (Michelin Sport cups) on my narrow body GT3.

For a little bit I ran 2.5 front and rear and had no issues. The car felt great on the track. No rubbing in the rear.

triode

I went to 245 fronts w/no issues. So far have stayed with 305s out back.

pvdw

Ok here's after one day, 5 sessions, dry weather @ spa francorchamps, the greatest circuit of all times :-)
No too many people so not very crowded on track, ideal conditions

Removed the rear spacer prior to heading down this morning as it did have some rub. Still does under heavy load but minimal really

Tyres are amazing, Pirelli really did a great job on thes trofeo R tyre, grip is endless and predictable handling when going over grip level


I managed a new best of 2.50.99 which is about 7 seconds better then I hoped for !
Lap timer shut down on me because of overheating but fortunately the V-box kept data logging :-)

997gt3north

- what is your rear offset - OE is 68?

- if it is only the slightest of rub then you can very easily fix this by merely levering the fender slightly away front tire - not sure if you have a wood baseball bat but it is the perfect tool
- you just slide it in there and use the tire as the lever point and very gently and slowly lever the fender out slightly
- you will likely have to put a jack on the rear jack point and raise the car ever so slightly to get slightly more space between the tire and the fender
- if it is only 1-2mm of needed clearence it will work perfectly
- warm day, warm metal, will only take 5 to 10 minutes

- also try putting the 5mm spacer on the front wheels as it looks like there is plenty of space up there

delanobe

Wow, 2.50 is a big improvement
How did the car feel with the semi slicks compared with the PS2's?

Did you do an alignment before you went to Spa?
Also, where did you go for the alignment?

Thanks

pvdw

Grip seemed endless :-)
Kept them at 2 bar all day and there was no overheating, some minor slides (double gauche) and one too late braking point @ bus stop chicane but really, great tyre

Will post a picture or two to show wear.

Car aligned prior to heading over, was done by Porsche center Antwerp, camber adjustments:
Front -1'40"
Back -2'40"
Was a little last minute alignment so no time too get more camber up front, need to check strut rotation or shim solution
Need to look up toe values etc but pretty close to 0'4" front and 0'16 back I believe.
Adjusted sways to middle position in the back and middle front
Think next step will be stiffer still with more camber front

Used to run mpsc on the 993 4s but would definetly rate the Pirelli's a step or two up

All in all great track day, look forward to 11 July for the next one

pvdw

ET is 68 , same as OE
Not sure about spacer front without additional camber first, at full lock steering wheel, slight rub as well, need to figure out whether if in or outside

Does anyone know how to determine strut position, rotated or not without disassembling ?

997gt3north

by the looks of your pictures, and from experience, you are not rubbing on the inside, you are likely rubbing on both the fender liner at the edge of the fender given your low camber and load generated from sticky tires and also possibly if you hit a big bump because the tire is a taller tire and the gt3.mk1 has a low front spring rate

i think you will find the car better to your liking if you run a camber setup that most people have settled on - more in the front / less in the rear than your current setup

as you are already experiencing rubbing in the front, more camber will help but a shim only approach will add a lot of caster and likely make the rubbing slightly worse

as I have gone through everything you are about to go through let me make a few suggestions:

1) -2.3 front, -1.8 rear
2) rotate your front strut (it is not rotated or your wheel would be further inboard) - buy shims before you go to the shop if they don't have them, and INSIST they add shims to the lower control arm once the strut is rotated to get the desired -2.3 camber- this will widen the track AND it will add caster back closer to 8.0 spec - if they just use the eccentric your caster will be 7.5
3) once the strut is rotate your wheel will be further inboard - either relocated the rear spacer you took off up front or buy 7-10mm spacers for the front

If you were running a shorter front tire I would say just shim the car to get your desired camber - as the tire is both taller and wider that is were strut rotation will work 'better'.

As you seem keen on improving your car for the track (like most here) other 997.mk1 owners have put a slightly firmer front spring on the car (even without revalving) - that little bit extra will help with the above situation - the mk1 front spring is 'only' 220#s - the mk2s are close to 250#s and never experience the front tire fitting issues that the mk1 car's do as that tiny bit of additional spring makes all the difference

Finally, I mentioned the baseball bat to lever the inner edge of the front and rear fenders out ever so slightly - it works and is very easy to do.


good luck

Serge944

If you are rubbing in the front with just -1.4 degree front camber, your struts are not rotated.

Also, every degree of negative camber gives you roughly 5mm more space at the fender lip.

Regarding rotating the strut...it if desirable to NOT rotate, provided that you don't have excess rubbing at the desired camber setting. When you rotate, you lose valuable caster. Personally, I'm willing to deal with a tiny bit of rubbing in order to not sacrifice performance. I was able to achieve -2.2 on my 996 with shims only and no audible rubbing (although you could visually see the marks on the liners).

pvdw

I understood the trofeo's need / want a -2.5 camber in the back in order to work/wear properly ?

Thanks for all the advice, it is a long learning road ahead but I intend to enjoy the ride :-)
Car is 90% track as I drive Volvo's on a daily basis ....

997gt3north

on a 325 width rear 19" tire you need to be generating near pro levels of slip to get equal tire temps across that wide of a tire - and if you were, your car would be ploughing through every corner as the front at only -1.4 wold not be working in concert with the rear

also, since tires are expensive, there is no reason to be wearing out the inner edge of the tire prematurely

since the car is a track only car, -2.5 front / -2.0 rear is a perfect setup for you - even at that I believe you will find that the first part of the tire that goes is the inner edge of the rear tire - you are just burning unnecessary money and generating less rear grip than possible if the outside edge is underused


i agree with the above poster about caster and that is why I mentioned shimming the control arms to gain the caster back - i ran a -2.7 camber front car with shims only and it worked with a 235 tire - when I went to the taller 245 and dropped the ride height that is when I rotated the strut and added shims