kujo

Let me start by saying, I know this has been discussed alot.
I did a search, but didn't come up with the answers.

Some say that an 18" wheel 'performs' better than a 19".

I feel, that my car has a much crisper, sharper turn in, with 19"s.
So, imho, isn't that a better performance attribute ?

I know that an equally weighted 18 and 19, the car will run quicker with the 18 due to less rotational mass.

BUT, if the 19" weighs say 20 lbs and an 18 weighs in at 25 lbs, won't the car launch quicker with the lighter 19" ?

I guess, the bsica question is this.

I'm going with a lightweight set of 19's for the street.

But, does an 18" wheel/tire package perform better on the track than a 19" package, IF the 19" package it lighter ?

I know that if the 18 has a stiffer sidewall, that'll help turn in, but is that the only thing ?

I want to start tracking this thing soon.
Was looking into the Track Wheel/tire options.

All you track guru's, what tire ?
What's your thoughts on the 18/19" debate ?

Thanks for your time, as always.

Kurt

Youreviltwin

Id like to knw too

04 Savant

Rotational mass is a big issue, so pay attention to weight. Turn-in will be sharper with 19s, but good tires will give you that as well, esp if you go with R-rated tires for the track. Sidewall will be more of a factor with tires than size, although 19s have less sidewall than 18s, allowing LESS flex. A BIG difference you allude to is rotational mass. A 1 inch increase in diameter results in a 4% loss in torque, which is why many use 17" rims for the track. Hence, I think you're better off with a lightweight 18" for the track. OZ SL is a solid, inexpensive option.

Please, anyone correct me if I'm wrong.

Captain Sheetmetal

It sounds like you have a pretty good grasp of the concept.

The only valid argument somebody could make against buying 19's is that if you bought an 18" version of your 19" rim, it would be lighter <i>still</i>.

Also keep in mind that 19" tires are heavier than 18" tires. My 19" rims are 5 lbs. lighter than my stock rims were, but when combined with the heavier tires, the total corner weight is about the same.

But assuming lighter corner weights (like 45 lbs. instead of the OEM 50 lbs.), a 19" tire will respond more quickly than an 18 incher (all other things being equal). Overall grip, assuming identical rubber compounds, would be the same.

[edit] And as 04 Savant said, watch your overall circumference.

oatzel

run 18's. tires will be cheaper

kujo

The 19" Toyo T1R's and the PS2's are also 22 lbs.

The wheels I was going to get for street will be 20 lbs, droping 9 lbs per corner, since the tire is the same as stock.

For the track, I was looking at a few cheaper cast wheels from Edge, in 18" and 23 lbs.

The Pilot Sport Cup tires, in 18" are also 22lbs, so not too much gain there and still a loss in 6lbs per corner for the track.

Does that sound like a smart set up for Street and Track ?

I also need to make sure whatever 18" wheel I look for, for track purposes will clear the 355 Stop Tech kit..

thanks for the info and for confirming what was in my head.

can't wait until she's broken in fully, so I can hit the track.

kj

Captain Sheetmetal

...are 235s, not 245s, correct? Just be aware that even <i>235</I>-series 19" tires are going to be slightly larger in overall circumference, but probably not enough to be noticeable.

808S4DRVR

Kurt,

Even if the 19" were lighter, you have to also take into account the weight of the tires. When the 2 are combined, the total weight may just be as heavy as the heavier 18".

Also, there was a formula, which I have conveniently forgotten, that could calculate the difference in rotational force. IIRC, in order for a 19" wheel to achieve the same or better rotational force, it should be at least &gt;= 5 lbs lighter. YMMV.

In terms of track performance, C&amp;D did a test 5-6 yrs ago, for rim sizes 15-18", showing that the best size for track events are probably 16-17". For DRAG, 15". They did notice that there was slightly better turn in and cornering ability with the larger rims, due to larger contact patch of the tires, but lap times were better with the smaller rims overall. In the end, they said that the best rims were 16" for both Track and Drag racing.

kujo

yes, they are 235/35/19's...

kujo

the +1 tires I'd use weigh in at the same as the 18" Conti's.
So, I'd be losing 9 lbs with the street set up and 6 lbs with the track 18" set up....

thanks for the info about the C+D test....

Just don't think I'd put 17"s on the S....