bleucamaro

I guess I'm trying pretty hard to justify this, but at $35 bucks a tire, I probably should just try it.

Matt H

This is simply wrong but for some reason I am unable to get you to understand that.

It doesnt matter if it baloons a little or a lot, either way it is not ideal. The tire was designed for Camaro/Firebird platforms, for the record.

Look it is simple, do whatever you please it is your money. I will tell you that tires are my business, it is what I do every single day of the week. You are going to have a hard time finding someone on here who knows more about tires than I do.
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Serge944

Dan, you really are overthinking this. Personally, Id run 225s all around before putting 255 50's on the back. Yes, it will fit, but its simply the wrong tire for these cars.

mgmarsh39

i go with good ol 225 40 18 front and 295 30 18 rear

bleucamaro

Thats because its not wrong. Please read the following, then get back to me, and explain to me why its wrong.
http://www.insideracingtechnology.com/tirebkexerpt2.htm
http://www.tirerack.com/tires/tirete....jsp?techid=10
Fred Puhn's How to Make Your Car Handle.

The benefits of a shorter tire are as follows: gearing, less rotating inertia, less unsprung weight, lower center of gravity.

The benefits of a taller tire are: more grip, more compliance.

I never said that the benefit of more grip will out-weigh that of a shorter tire, but I don't think I'll be taking steps backwards going from a 53lb wheel & tire in the rear with slippery Pirelli's to a much lighter Hoosier R3S04.

bleucamaro

How much do those weigh? How bad do they rub, or if they don't, what offset do you have? I have 275/35-18's on the rear now and they rub pretty bad on the inner fender above the control arm

Serge944

Compliance isn't an issue for your average street car. Tires in F1, for example, are so big because they ARE the suspension.

The sprigrate on f1 cars is almost infinitely high because it has to cope with an incredible amount of downforce.

The main issue here is the fact that 8" wheels, idealy, are not supposed to fit such wide tires (even though some do it anyways) and that it's simply the wrong size for a 944.

Finally, I remember you had some oversteer issues with your car (even though you run heavily staggered tires). The extra inch in diamater will heighten the CG of the rear and that will mean even more oversteer.

If you REALLY want to use the 255s at least get a 9" rim.

xsboost90

well put some big ol honkin tyres on there and when your car wont move at the autox and you get stomped on youll know why. The problem is you dont have the gearing to over come those big tyres. Besides that, they are too wide for the wheels. Besides tons of sidewall roll like a truck, youll chance popping a tire off. My d90's had 205's and 225's. Handled excellent factory sizes. If yours are 245's stick w/ that width i had skinys. Sometimes just cuz somethings cheap doesnt mean its the best answer. Save for some better correct sizes my opinion.

MTM

Hey, is that why Formula 1 tires have a very tall profile, to increase the size of the contact patch?

johne

I agree with the above recommendation of running 225/50's all around. When you go with a taller sidewall you get more tire roll in the corners. Also when you go with a tire wider than the wheel you get a large increase in tire roll in the corners. F1 gets away with running pretty tall sidewalls by having wheels, which are significantly wider than the tires. This minimizes the amount that the sidewalls can roll over. Ok, how about I let MSPaint do the talking.

-John

Serge944

Look above.

"Tires in F1, for example, are so big because they ARE the suspension.

The springrate on f1 cars is almost infinitely high because it has to cope with an incredible amount of downforce."

In slow motion over bumps, you'll see a lot of tire compression/decompression.

Robby

I understand all the points in this thread, BUT, the gearing shouldn't be THAT bad- 1st off, the 951 could use a little taller 5th as is... 2nd, for a street car, it's not going to matter that much anyway- taller gearing DOES have it's benefits. 3rd, redline in 5th is normally 167, but, w/that tire, it's 175.5 at redline in 5th.... the rest of the gears will be a percentage basis.... anyway, that said, I would rather have a 255/45 on a 16, IF that's an option- I'm running the standard 968 M030 way- 225/45/17 & 255/40/17's. Eventually would like to run 235/40/18 w/275/35/18's.... that's just my opinion.... I want an S2 5th (.78) to get to almost 180mph @ redline- not that i have that much HP, but, for slightly relaxed 5th crusing w/out cutting into the rest of the gears... OF course, w/350+RWHP (which I hope to have some day) I would like slightly taller gears all the way up w/a 5th of closer to 190 or so... I'll worry about that when I get the engine though.... BTW- this has been edited- I hit the wrong key on my calculator the first time & got the wrong #'s....

Those 295's are HUGE! How does the car feel w/only 225's up front...? does it really understeer much...? I was kind of worried about the dif b/t 235 & 275, but, maybe not so much now....

xsboost90

but autox is mainly 1st and 2nd gears.

tifosiman

Listen, Dan, myself, and Matt all know what we are talking about. BTDT. I actually did a few autocross events with rear tires that size on some 16X8's (they were free with the wheels and RA-1's, so I thought I would burn them up and then get the proper size). Trust me, they were too tall, the car handled like crap, and you could feel the difference in gearing. It was a slug in 1st and 2nd, which are the gears that you are typically in at every autocross.

You asked for our advice, you got it. Everyone else here can wax poetically about crap that they don't have firsthand experience about. Shees.

Rant Off.

Tom R.

my turn,
I bought a set of near new dunlop 8000s off a 911 widebody for my S2 and have them on my 968 rims. 205/245 setup. Matt said it will handle like a truck, matt is right. too much understeer. I use the car only for autox and DEs. I drive to the DEs. I played with the tire pressures a bit and i think i found a nice balance. I dont change my tire pressure when I autox because the handling gets tempermental. since I am in the green run group i am not too worried and like the cushion of the little extra understeer.

when i change tires I will probably go 225/245 on the 7/8" rims, partly because I am a little rice and llike the look of the wider tires, not because of performance.

some 20+ years ago I put a set of bilsteins and addco sway bars on my 77 celica gt liftback, i topped it off with a set of phoenix stahflex tires in the stock size. but for the 90 hp motor mated to the auto, the thing stuck like glue and out handled my buddies new 280ZX. the better narrower tire is the way to go.