Question on wheels sizes. Please read.

[rnln]

edited: I read my post again and think it's hard to understand, so I edit a bit...

I don't have the turbo power but I do have the wide body and 16"x7"x9" with some adapters. I know I have more disadvatange than advantage going bigger wheels (regarding speed), do to the weight. So if I upgrade wheels to 17"x10"x12", how much (speed) will I loose? Alot? A little? Please advice.
I don't want want my car to be much slower than it is now.
Thanks in advance.

[Noah930]

Won't that depend on how much your new tire/wheel package weighs (compared to the current set)? Usually, "bigger" wheels will weigh more. But if you replace a heavy set of "smaller" wheels with a lighter set of "larger" ones, that difference may be minimal. It would be slightly difficult, though not impossible, to actually get lighter larger wheels.

[RarlyL8]

I did that with my car before the engine swap. What I noticed was that the handling fealt "heavy". The car was not as tossable as before the big heavy meats were added.
You'll get used to it and your car will handle and brake better with more rubber on the ground.

[Danny_Ocean]

16" x 7" x 9"

17" x 10" x 12"

Are you measuring the box the wheels came in?

What does wheel size have to do with speed?

I have 18 x 12's in the rear and 18 x 8's in the front...my car is plenty fast.

[RarlyL8]

Gear advantage.
It is assumed (sometimes incorrectly) that if you go up a size in wheel diameter that you also increase rollout circumferance. If that is the case then you loose a gearing advantage.
You also loose top end and accelleration with the increase of unsprung weight.

What size meats you got on those 12x18s?

[Danny_Ocean]

Originally Posted by RarlyL8

Gear advantage.
It is assumed (sometimes incorrectly) that if you go up a size in wheel diameter that you also increase rollout circumferance. If that is the case then you loose a gearing advantage.
You also loose top end and accelleration with the increase of unsprung weight.

What size meats you got on those 12x18s?

If the circumference of the tire/wheel combo is the same as the smaller sized wheel/tire, then what is the difference? Larger wheel, smaller sidewall... My rear tires have almost the same circumference as a 255/60-15 (27.2 vs. 27.0).

My rear 18 x 12's are Michelin Pilot Sports from a Viper...I believe they are 335/35-18.

[rnln]

Originally Posted by Danny_Ocean

... then what is the difference?

Dan, that is one of my original kind of questions. I have heard all the time, "bigger wheel base, better handling, worse speed/acceleration" because more contact surface to the ground, more friction, if not heavier (but for sure tires will be heavier). I am no expert that why you see my question here. Let me know if I am wrong. If I am correct, then I wonder how much do I loose.
umm.. afer searching on tirerack I found no tire available. If you are running 335/35/18, I should be looking for 335/40/17 or 325/40/17, etc. None is available on tirerack. Easier to shop for tire is the first reason brough me to wheels, but look like this wheel size defeat my primary purpose.

Rally, yes, they are 17x10x12 (not 18"). I saw them on the classified section and called. I plan to see them tomorrow unless someone tell me it's a no no.

[Danny_Ocean]

Originally Posted by rnln

Rally, yes, they are 17x10x12.

The suspense is killing me. What is a 17x10x12 wheel? Are they square?

[rnln]

dan,
front 17x10 rear 17x12. Sorry.

[Jeff Alton]

Most of the 17 inch wheels I have built for the 930 are being run with a 315 tire.

Cheers

[David]

Are your flares bigger than 930 flares? I could only fit an 11.5" rear wheel on mine. I have 9" on the front and I could go to 9.5 or 10", but it would be a tight fit.

[Bill Verburg]

while the bigger wheels will likely be heavier, that won't be the primary influence on the feel of the car or the speed in gears.

The diameter or the tire is the #1 issue.

Your car now rides on 245/45 x16 tires which have the following specs
nominal height (in) 24.6
Revs/mi 844
dynamic loaded radius (in) 11.9
dynamic loaded height (in) 23.9

any tire taller than that(lower revs/mi) will change the torque curve delivered at the wheel. A taller tire will delay peak torque to a higher speed, i.e. the car will feel slower at lower speeds.

for a 12x17 wheel you will need a 335/35x17 tire minimum
specs are
nominal height (in) 25.7
Revs/mi 811
dynamic loaded radius (in) 12.4
dynamic loaded height (in) 24.9


Here you can see what happens to the speed in gears



@3k rpm the 16 will be doing ~70mph the 17s ~74. That doesn't sound like a lot but in reality it is.

My advice go to a narrower wheel in 18, say a 10or11x18 and use a narrower tire, say a 285/30x18
specs
nominal height (in) 24.8
Revs/mi 836
dynamic loaded radius (in) 12.1
dynamic loaded height (in) 24.1
w/ the above wheel and tire the speed in gears and torque curve at the wheels will be pretty much the same as what you now have. There will be a slight degradation in performance from any weight increase but not much that will be noticeable at normal speeds.

[rnln]

Bill,
So I will/might feel like I lose a little at low end.
Thanks for the info.

Thanks guys. I appreciate it.

I looked at the wheels/tires this morning, used. Front wheels front spacing is closed to 4", rear wheels front spacing is about 5.5". Look like they don't just bolt right on, but I am not sure what sizes of adapters I need (or different halves sizes). I will have to come back another day to amount them on, he suggested. Very nice seller. Current tires on the wheels are 275 front and 315 rear, cost lot more than the current tire sizes on my car.
Again, thank you for all the info.