17" vs 18"

[jdmblood]

I'm planning on doing intake exhaust headers and tune. Dont plan on dropping the car. What do you guys think?

[Gary in NJ]

I think you should do what you want. In the end YOU have to be happy. But be an informed purchaser and understand the choices before you.

[ciotime]

What about going to a 19"? Im thinking about upgrading from stock to a 19" 57Xtreme...aside from improved looks what about the ride and speed?

[FR-S Matt]

My 18x9.5's with Continental DW tires don't weigh a lot and have improved my driving. Weighs less than stock still and they look fantastic. Don't let someone talk you out of 18's unless you track your car all of the time.

[Rayme]

Daily driving, the harshness of low profile 18" is what's the worst to live with, especially if you have a bumper area. Just weight the pros and cons.

[wparsons]

Originally Posted by tonyfrs86

i would only go 18" if you're using a turbo, like myself..i need a bigger/wider tire. i break traction pretty easy with nitto motivo's when i romp on them..in the wet taking a turn, have to keep it steady or back end comes out.

if you're not pushing alot of power and want steering response and all then then stick with 17" but looks and power got 18"

Wheel diameter doesn't effect that nearly as much as wheel/tire width... as for breaking traction in the wet taking a turn, no amount of tire is going to help you there, stop getting on the gas at the wrong time if you want to stop that.

I'm running dunlop Z2's that are VERY sticky and can take right hand corners at 50+ km/h with zero slip at all (60km/h is possible at most intersections, but it's not slip free ), BUT I can also get the back end to kick out very easily in the same corner at like 30km/h just by hammering on the gas too soon in the corner. All this in bone dry conditions, if it's wet it takes even less to get it sideways if you're on the gas too soon.

[raul]

Originally Posted by FR-S Matt

My 18x9.5's with Continental DW tires don't weigh a lot and have improved my driving. Weighs less than stock still and they look fantastic. Don't let someone talk you out of 18's unless you track your car all of the time.

What wheels and what tires? There's not many setups that can achieve that claim.

[FR-S Matt]

Originally Posted by raul

What wheels and what tires? There's not many setups that can achieve that claim.

Enkei RPF1's on 245/35/18. I absolutely love this setup.

[raul]

Originally Posted by FR-S Matt

Enkei RPF1's on 245/35/18. I absolutely love this setup.

Lol yeah, you went with one of the lightest wheels in the market with possibly the lightest tire in that particular size. That setup is like 39.7lb total, any other tire would put you above stock weight. When you pick an 18in wheel that isn't a TE37, TC105n, RPF1 or PF01 with a light tire, you're almost guaranteed to go over. That is unless you cheat and go with an undersized tire and stretch it.

[Suberman]

Originally Posted by Gary in NJ

There is a common misconception that an 18" wheel setup fills out the wheel well better then a 17" setup. If you keep the circumference (or height) the same to maintain the stock gearing and speedometer reading, then the outer measurements are the same.

Not only that, there is also a common misconception that larger tires or larger wheels "put more rubber on the road" which is a myth.

Contact patch area is determined by vehicle weight and tire pressure. Modest differences result from tire design but those differences aren't affected by tire size. Tire pressure is pretty much limited by the tire carcass design. Tire pressure is selected to optimize the contact patch shape at expected tread temperatures.

Furthermore, even if you could get more rubber area touching the road it wouldn't increase tire grip because the coefficient of friction doesn't work that way. That's why it's called a coefficient.

There is little point putting larger and heavier wheels on your BRZ expecting improvements in tire grip. Also, the current fashion for "filling out the wheel wells" is cosmetic only. The only way you can actually do this and keep the same rolling circumference is by dropping the ride height, just pushing the tire outwards in the fender well is most likely to reduce performance of the car.

Shorter sidewalls just give the same grip level at lower slip angles but cannot increase total grip as that depends on the tread compound. The shorter sidewall tires will give you sharper turn in and quicker transient maneuvering at the expense of twitchier handling, slightly inferior braking and noticeably inferior acceleration grip. You will reach the limits of tread compound grip more quickly but you will not likely improve maximum grip assuming the two different sized tires have the same tread compound. These effects result from the wider but shorter contact patch.

Switching from stock to 225/45x17 Michelin SuperSports or Bridgestone Pole Position S4 max performance tires will have much more significant improvement in grip than switching to 18x8 and 225/40x18 but using only the high performance level tires. On the other hand, going up in wheel and tire size and moving up to max performance tires will have little effect on total performance and might actually diminish performance, as compared to just fitting the better tires on 17 inch wheels.

This car is so well balanced I'm inclined to fit 225/45x17 onto 17x8 wheels for summer use and get some high performance snow tires in 225/45x17 size for the skinny stock wheels. The narrower stock wheel should improve the snow tire performance by softening the sidewall flex a bit. I might even get better snow grip with the slightly wider tire as a result of fitting it to such a narrow rim.

[wparsons]

^^ Just a slight clarification, if you actually drive in snow you'll want a narrower tire. You need something that will sink through the soft stuff to something that will give you grip, too wide of a tire you'll just float on the surface and slide around more.

[enjoyminutemaid]

@Suberman
Are you suggesting that wider tires won't improve grip (with all other factors the same)?

[lex tech]

If you increase the over all height of the tire you will change the rear end gearing at the same time. The bad part is you will have slower acceleration. But on the highway the rpm will be lower.....better gas mileage.

[jdmblood]

will it be a really noticeable decrease in acceleration?