phile

Alot of people who auto-x go for 17" wheels. Are 17" optimal for a roadcourse? I'm looking to get some lightweight rims that look decent without having to spend a fortune. In another thread someone recommended 9.5 fronts and 10.5 rears for widths...And what tire sizes would be a good match?

Or say I went 9.0 width fronts and 10.0 width rears...what tire sizes would be a good match for these.

I'm not willing to go higher than an 18". I don't want to sacrifice performance.

King Tut

iTrader: (1)

They go with 17" because the race rubber selection is the best for 17" wheels. The second best choice is 18". I decided to go with a cheap set of OEM 18x8" wheels and some Dunlop SP Sport Race rubber same size all the way around for my road course setup.

phile

Why didn't you opt for wider rears?

jakesford

just a couple of things to think about, if you aren't required to run a spec tire then go with the lightest wheels you can get that clear your brakes and will support your tire selection. This generally means running a smaller diameter wheel.

I would go with 17's that clear your brakes -->
1. Lighter
2. More tire choices

In all honesty on the street a nice wide wheel and tire in the rear looks great, but unless you are trying to put down a lot of power then all your doing by running a 285+ tires in the rear is creating more understeer. The Z from the factory has some understeer, you don't want to make it worse. I would go with some 17x9's and run something like 255's all around, this will save you money on wheels and tires and you can rotate the front to rear as needed.

phile

I thought a stagger in width negates a little understeer? -i'm not sure about this

But I do remember reading thata stagger in diameter gets rid of some understeer... once again I'm not sure though.

jakesford

basically understeer happens when the front looses grip, when you put lets say a 285/245 combo you're just adding more grip in the rear the front end is going to give up long before the rear.

Now if your trying to put lots of power to the ground, when you come out of a cornor in 2nd you try to nail it your going to loose grip in the rear and create oversteer, so a wider tire might help some.

You didn't really mention if your buying these wheels for a second set of "track wheels" or not...

If you are just get some 17's and track tires and go at it... If this is your daily and you want it to look nice and you just do a little AX every now and then, go and get some good looking staggered 18's and put some fat meats in the rear because you can't beat the look...

apharmdb

iTrader: (1)

That's almost what I have. 17x9 MB Motorsport (A-Tech) Competitions with 275 all around. Pretty economical setup that clears my Stoptechs.

phile

I'm not entirely sure waht I want to do yet But so far it's sounding like getting the same widths all around is the way to go for the track. If I had FI then I might want a staggered setup to balance things out, right?

Kolia

iTrader: (2)

It all depends on how you drive.

On a high speed course, I'd rather drive a slightly understeering car. Same size all around if fine for AutoX. But on a road course, I'd stick to a staggered setup, the way the car was designed.

phile

True. But only the track model has a staggered setup.

dirtroad

iTrader: (1)

they all do, even my base had 225F,235R.

phile

I'm talking about wheel widths, not tires.

Kolia

iTrader: (2)

Rim width isn’t much of a factor. It will affect steering response and feed back.

It’s the tire width that counts, and the overall tire diameter to some extent.

The Track and Performance (and GT ?) models are just a bit more staggered.

All Z (from a same model year) have the same suspension.

I was running 235/40R18 (f) and 255/40R18 (r) last year and I could spinout really easy if I drove like an idiot. And I still got plenty of wheel spin on corner exit.

phile

I have a performance Z.

Wider rims allow for a wider tire size and hence a more significant contact patch. I wanted to try to find the optimal wheel width stagger and the optimal tire width stagger for that particular wheel width, for the purpose of improving cornering and off-the-line acceleration at the same time.

Kolia

iTrader: (2)

I have 17x9 +35 rims with 255/40R17 (f) and 17x10 +35 rims with 275/40R17 (r) for my track only setup.

It quickly becomes a question of personnal preferences.

phile

What's your street setup?

Kolia

iTrader: (2)

Street setup is 235/40R18 (f) and 255/40R18 (r) on OEM Track wheels (18x8 and 18x8.5)

phile

What are the main differences in handling between your track setup and street setup? If say you were to track both setups.

Kolia

iTrader: (2)

I haven't tracked the track setup yet.

But it can't be compared anyways. I tracked with Falken Azenis RT-615 last year and it was great (235/255). These tires can get greasy if overdriven so it's good trainning in smoothness.

The Track setup now is on Toyos RA1. Dot R-compound will kill any street compound, no matter the width.

King Tut

iTrader: (1)

Yeah I am only running 235 width Dunlop SP Sport Race tires all the way around versus my street setup of 245/275 Dunlop SP 9000 tires. I already know that once warm the race tires stick infinitely better than my street tires. Can't wait to hit a couple HPDE events this year.