TRAKCAR

I am using R6 18" 255/40 front OD = 25.9 and 335/30 rear OD = 25.9. 345/35 would be a better fit at 27.0 OD, taller tire might be better, but I think they will be too wide. Maybe I'll try next time.

Hoosier 245/40/18 is OD 25.7 is an exact match.

OEM front OD = 25.7
OEM rear OD = 26.6

NJ-GT

Actually, the 2010 GT3 RS is pretty light.

A full tank of fuel is 110 lbs. 5/8 of a fuel tank should be around 11 gallons at 6.25 lbs/gal, so close to 69 lbs on fuel alone.

3,188 lbs with no fuel and all the stuff you have there is right on the spot.

The fire extinguisher and mount are typically around 10 lbs. The OEM rollbar is another 45 lbs. The harnesses 5 lbs for both. You have 16 lbs heavier tires than stock, and the Traqdude/camera another 3 lbs. If you take this 79 lbs from the estimated current empty weight, you end up with a 3,109 lbs stock GT3 RS, which is in the ballpark of the weight figures I have for the 2010 GT3 RS.

You should save 20 lbs on wheels, 20 lbs on tires, 40 lbs with either PCCB or a Brembo GTR brake system, another 40 lbs by deleting the side mufflers, another 35 lbs on a LW battery, you will be already under 3,040 lbs with no fuel, and you still have an A/C and Radio. If you delete the A/C (37 lbs) and radio/speakers (5 lbs) that should put you under 3,000 lbs.

rmag

Peter why did you go with the 245/40/18? While it's an exact match for front, your rear is still smaller by an inch? Your front to rear ration is going to be farther of than the 255/35

Stock
Front: 25.7
Rear: 26.7
Ratio: 0.963

245/40 335/30 combo
Front: 25.7
Rear: 25.6
Ratio: 1.004

255/35 335/30 combo
Front: 24.8
Rear: 25.6
Ratio: 0.969

.

TRAKCAR

Huh? I did'nt. I went with 255/35/18...

Rad, thank you for those numbers. Cool. I am very happy with the numbers for a bone stock, delete nothing car with all the needed track stuff added.
I hope that with the BBS and Hoosier and all the crap unloaded and an empty tank it will be 3100lbs. I gladly leave everything alone as-is for the last 100lbs and focus on eating and drinking less.

Fill me and the car up and we're back to 3460lbs...

rmag

Ah, good, you had me worried! Your post made it seem like you were going with 40s

TRAKCAR

Ahh, yes, I see. I better check, I know they are 255, not sure 35/40 now...

rmag

255/40s are even bigger ... have OD 26.2( the 245/40s have 25.7) ... not good.

Nizer

By going with 18" BBS and slicks?

mdrums

Remember reading on these forums something like you need to keep the front and rear diameter less than 4% difference. What confuses me is do you have to keep the overall diameter the same or can you downsize both fron and rear overall diameter in order to slightly lower the car and that would in affect lower the gear ratio for better acceleration.

On my car (997S) I use 245-40-18 and 305-35-18 and that is right there at the stock overall diameter front and back of my stock 235-35-19 and 295-30-19. I was wondering if 255-35-18 and 315-30-18 would work on my car? I know they will fit but will the overall smaller diameter mess up ABS and PSM?

Great forum here...sorry to butt in, but the GT3 crowd seems to know more about this type of stuff.

NJ-GT

He is running street tires 16 lbs heavier than stock. If you go with 255/35R18 and 335/30R18 Hoosier R6 and 1 piece 9"/12" forged wheels, you will save around 18-26 lbs (depending on wheel brand) from the stock weight of wheels/tires. In Peter's case this is 34 lbs to 42 lbs from his stock wheels and all-season tires.

If you go with slicks, you can run the 9"/11" Magnesium wheels with 240/270 Cup slicks and the proper front and rear spacers plus studs. In this setup I saved 53 lbs from a stock 235/305 MPSC-NSpec and 9"/12" 2007 RS, in Peter's car this setup would save close to 70 lbs on unsprung weight, massive savings.

The 2010 RS has 1 lb heavier tires and 1 lb lighter wheels, so wheel/tire combo weighs around the same than the 2007 RS.

TRAKCAR

Thanks!
One OEM rear wheel and General tire = +/- 62lbs, if I remember correct... I will put the BBS with Hoosier on a scale when I get them.
I used Tirerack weights to conclude just tires are 16lbs heavier.