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As soon as my springs show up, I can start my suspension swap and get the car aligned. I'm not really liking the fitment of the 265-35-19 Trofeo-R on my 9" front wheel, so will prob use a 245-35-19 instead and free the car up with alignment since I have a 325-30-19 rear. The variation in size between a Hoosier, MSCP2, and Trofeo-R in a 265-35-19 is huge. Car looks like it almost has reverse rake with this tire fitment. Looks dumb. Could go with a 265-30-19 but then front ride height is crazy low, or you run tons of fender gap. Lack of correct diameter 19" tires is frustrating.
Probably going to start around -3F and -2.5R to see how the balance is, and take it from there.
As soon as my springs show up, I can start my suspension swap and get the car aligned. I'm not really liking the fitment of the 265-35-19 Trofeo-R on my 9" front wheel, so will prob use a 245-35-19 instead and free the car up with alignment since I have a 325-30-19 rear. The variation in size between a Hoosier, MSCP2, and Trofeo-R in a 265-35-19 is huge. Car looks like it almost has reverse rake with this tire fitment. Looks dumb. Could go with a 265-30-19 but then front ride height is crazy low, or you run tons of fender gap. Lack of correct diameter 19" tires is frustrating.
Probably going to start around -3F and -2.5R to see how the balance is, and take it from there.
Same holds true on 19” RS fitment. No good options on slicks that don’t result in major TCS/ESC intervention.
I'd like to see someone run a car with 1.8 negative and chalk the sidewalls... and then 2.5 and chalk the sidewalls. The fronts just don't roll that much on these cars and I don't see these cars needing more than 2' degrees negative in the front.
The rear, on the other hand... completely see it liking additional negative camber.
Will be interesting to see others setup and tire wear.
I'd like to see someone run a car with 1.8 negative and chalk the sidewalls... and then 2.5 and chalk the sidewalls. The fronts just don't roll that much on these cars and I don't see these cars needing more than 2' degrees negative in the front.
The rear, on the other hand... completely see it liking additional negative camber.
Will be interesting to see others setup and tire wear.
Best Regards,
Dave
I'm going to start on 1.8 square then do some skidpad and autocross with chalk and a probe pyro. It will be interesting to see where the rrar ends up. I don't want to compromise the ability to put power down, which I believe matters in these cars.
It is also interesting to note that cup cars run a lot of camber, but my only experience is iracing so far.
I'd like to see someone run a car with 1.8 negative and chalk the sidewalls... and then 2.5 and chalk the sidewalls. The fronts just don't roll that much on these cars and I don't see these cars needing more than 2' degrees negative in the front.
The rear, on the other hand... completely see it liking additional negative camber.
Will be interesting to see others setup and tire wear.
Best Regards,
Dave
Think the problem here is there are too many variables to truly assign a "best fit" camber number.
Variables that come to mind that would affect an ideal camber number:
1. Track - tight/technical track? High speed momentum track?? - I run high speed tracks and the car responds more to camber at a loss to slow speed turn-in
2. Driver Style? Like a loose or tight car? - I like a loose car personally
3. Which tire are you running? Dunlop Sport Maxx? SC2 N0 Spec? N1 Spec? - All respond differently to camber due to sidewall stiffness - SC2's I find respond more to camber than Dunlop's.
4. Hot pressure are you running? - SC2's I find at 32hot the SC2's set slower and have better lateral grip but not as good brake grip. I find best brake grip at 35psi hot on them. - Depends on if I need more lateral grip or more trail brake
I'm not trying to argue your point but I think there's more at play than just assuming all cars don't need "x" degrees of camber. I am guessing that you're very experienced and know when not to overdrive your car. Therefore, you're likely not rolling over your tires.
I can show you my tires after a full day at COTA with -2.5 and definitely shows wear to the outside edges. I don't overdrive my car but I am showing 1.48 lateral g's through the carousel at COTA with an exit speed around 110mph. I assure you that corner needs more camber to hang the car through the set.
Anyhow, great data points and observations. I do think a shorter technical track likely doesn't need as much camber, but my faster speed tracks in my locale necessitate more camber for my driving style. I do like a slower set.
Obviously the best way to test the tires would be to read temps across the tire with a pyrometer. I didn't bring mine with me last time at COTA.
Think the problem here is there are too many variables to truly assign a "best fit" camber number.
Variables that come to mind that would affect an ideal camber number:
1. Track - tight/technical track? High speed momentum track?? - I run high speed tracks and the car responds more to camber at a loss to slow speed turn-in
2. Driver Style? Like a loose or tight car? - I like a loose car personally
3. Which tire are you running? Dunlop Sport Maxx? SC2 N0 Spec? N1 Spec? - All respond differently to camber due to sidewall stiffness - SC2's I find respond more to camber than Dunlop's.
4. Hot pressure are you running? - SC2's I find at 32hot the SC2's set slower and have better lateral grip but not as good brake grip. I find best brake grip at 35psi hot on them. - Depends on if I need more lateral grip or more trail brake
I'm not trying to argue your point but I think there's more at play than just assuming all cars don't need "x" degrees of camber. I am guessing that you're very experienced and know when not to overdrive your car. Therefore, you're likely not rolling over your tires.
I can show you my tires after a full day at COTA with -2.5 and definitely shows wear to the outside edges. I don't overdrive my car but I am showing 1.48 lateral g's through the carousel at COTA with an exit speed around 110mph. I assure you that corner needs more camber to hang the car through the set.
Anyhow, great data points and observations. I do think a shorter technical track likely doesn't need as much camber, but my faster speed tracks in my locale necessitate more camber for my driving style. I do like a slower set.
Obviously the best way to test the tires would be to read temps across the tire with a pyrometer. I didn't bring mine with me last time at COTA.
- Chris.
Agreed, I would be interested in tire temps, that would help. I think you're right, the tracks I've ran so far in the GT3 have been 'flatter/technical' courses, only pulling about 1.44 G's. I haven't been able to run it on the higher speed, and banking courses, as you have, so could just be the course dependency to your point.
Today, I'm running the OEM Cup 2's... On my actual race car, I run Hoosiers, and do prefer a 'loose' car over a 'tight' car.
I'd like to see someone run a car with 1.8 negative and chalk the sidewalls... and then 2.5 and chalk the sidewalls. The fronts just don't roll that much on these cars and I don't see these cars needing more than 2' degrees negative in the front.
The rear, on the other hand... completely see it liking additional negative camber.
Will be interesting to see others setup and tire wear.
Best Regards,
Dave
yes that would be a good comparison...however...it’s moremthan just camber...with the MPSC2 is the tire pressures that guys are running are mostly to low compared to what Michelin recommends.
Again, although my 2017 GTS isn’t a GT3 it is however a 991 with rear steering and at the track it’s on MPSC2 GT3 sizes...I’m running -1.6 which with Sport PASM is the max for this car...BUT...I’m running the higher hot pressures that Michelin recommends....lowest worked too and the rears got up to 38 and that’s when it slightly started to slip a little.
I belive with the lower pressures no matter the camer the tire is not supported properly and it cords or chunks.
yes that would be a good comparison...however...it’s moremthan just camber...with the MPSC2 is the tire pressures that guys are running are mostly to low compared to what Michelin recommends.
Again, although my 2017 GTS isn’t a GT3 it is however a 991 with rear steering and at the track it’s on MPSC2 GT3 sizes...I’m running -1.6 which with Sport PASM is the max for this car...BUT...I’m running the higher hot pressures that Michelin recommends....lowest worked too and the rears got up to 38 and that’s when it slightly started to slip a little.
I belive with the lower pressures no matter the camer the tire is not supported properly and it cords or chunks.
I think my MPSC2 got up to about 36 Frt and 38 Rear by the end of the session.
As I had previously posted, you can simply add Tarett race camber plates and get all the camber you need/want without any additional shims, and your caster stays on the low side of spec, about 9.3, which is what I wanted. No shims, no solid/adjustable caster pucks, no caster arms needed to achieve this. JUST camber plates. Must easier to adjust camber for your shop, no track width changes, and much better inner strut clearance. Plus, you get to retain the compliancy of stock rubber if desired. There is no downside IMO. I set mine at -3.2, but these plates let you go to -3.5 without any additional shims.
This also allows you to add caster if you want, by simply using shims, instead of decking the plates fully inboard for camber, so shimming adds caster and camber if you want higher caster, say 10. Spec is 9.5 to 10.5, and I want to be on the low side anyway.
Here is the initial alignment setup, we'll see how it goes on track and adjust from there. I'm on 572/1140# springs, so the additional camber will be put to use
So done some tracking now with my .2 gt3's. Also a raceprof has been using it for testing and teaching me how to be faster.
We both find it to totally UNDERSTEER.
So very thankful for any advice what to do to make it not so understeer. My raceprof recommends more camber and a slight (2mm total) Toe Out.
02-04-2018, 12:23 PM
