Ive been seeing a trend with people running crappy times (high 14s low 15s) that are using 19s (bad for launches). But I think it might be the weight more than the size.

Anyone with 19s please post your wheel specs (type, weight, etc..) along with your time slips.

 

It is more than just the weight. Up to 50% of the power to accelerate a car (and brake it) goes into spinning up the wheels. So it is not the static weight, but the rotational inertia. For racers, we should choose the brakes required for a track, after maximum ducting is applied, and then put on the smallest wheel that will fit over them. It is more complicated than this with tire choices, usually race tires come in odd sizes of 13", 15" and 17", and handeling issues need to be accounted for, but it is a good starting guidline. 19" wheels could take as much as 25% more power to spin them up than 17". That could be 10% of your engines power. I have not run the numbers on this system, but when I went from 15" to 13" on my RX-7, I droped the rotational inertia of the car, including engine and drivetrain, by about 60%. This lead to head snapping accereration from a 170hp car. I use 17" wheels with race tires, 275/40, since 16" wheels and tires are limited. Some autocrossers are using 16s.

 

my 19s were 8 pounds (total) lighter than stock

 

The stock wheels are garbage, except for the Rays track. And again, it is the mass distribution, not the weight. I'm watching Formula 3000 and they are using 13".

 

good point on teh mass distibution, although if a wheel/tire combo were a few pounds lighter, I would doubt that it would be that much heavier on the perimeter (where it matters) to make that much of a difference.

BUT it is a good point, and EXACTLY why I spent a few hundred more on Toyos than Bridgestones (they are 3-6 pounds lighter per tire)

as an avid mountain biker I know that rotational wt (mass) is very important

 

Guess this is going to put me off from getting 19" volk GTCs...would have been nice.

No one with quarter mile times (with 19s)?

 

I have 1/4 mile time slips.. My times stayed the same but here is the catch...

Stock which I was consistent

I ran 14.3 @100mph with a (2.3-2.4 60 foot)

With Volk GT-7 and Big Brake Kit

I ran 14.3 @98mph with a (2.1-2.2 60 foot)

What I am saying is with the 19" I got better traction and the car launches nice but with stock tires I was spinning them so you can see the difference in the MPH.

 

most sport cars come wtih 18s stock....19s is something new and its usually purely for sport

 

I wouldn't let this put you off from getting the Volks. If you're that serious about dragging your car, then put on the stock 17s with race rubber for when you go to the track. Better still, get a set of CE28Ns in 17" and then put a set of sticky tires on.

 

Guys, 2003z already did a real good comparison of this using dyno numbers. Interesting results, although it is not on the strip.

https://my350z.com/forum/showthread....&highlight=19s

 

Taller wheels, with lower profile tires are worse for traction. That's a fact.

19's are actually worse than 18's or 17's for handling as well.

Rule of thumb- low sidewall flex is great for handling, but terrible for acceleration

Lots of sidewall flex is great for accleration, terrible for handling.

There's a reason that drag cars use 15" wheels, with huge tires that flex like mad.

 

Dude, that middle part contridictes (sp?) everything else in your post. I do agree with you, the 19s are better for handling cause of less sidewall flex, and the 17s are better at the strip.

 

Sorry, but what do you mean by side wall flex?

 

VQ35DES, the lower the profile the side of the tire has, the less sidewall the tire has that can flex one way or another. Now this is relative to the similar tire constructions and such, cause some tires are just better than others. But when you have a 35 series on a 19" rim, you have less sidewall than a 50 series on a 17" rim. When you corner, the G forces put a lot of pressure on the tires, and they have a tendency to lay down on their side under this pressure.

 

19's look better but the numbers dont lie your better off with 17' or 18' due to alot of reason not just weight or rotational mass but more selection or tires and if you go through alot of rubber it will save you in the long run. Not to mention slightly quicker in acceleration..if you want to better looks get the 19's or 20's. Like someone posted above this is a new trend hence limited selection in tire sizes and choices 19".

I acually thought toyos were good but i have heard alot of negative comments about them ..def not good at the track with the soft sidewalls. Anyone have good experience with toyos on the track?

 

Can anyone in real world terms tell me how much of a difference 18 vs 19's will make? For argument sake we keep everything the same just change the height of the rim and the tires to keep the same tire height. I like the nismo wheels and the look of the new 19's but I like them in the 18" size too. I don't want to loose performance to get a 'look.'

 

I believe zoasis did back to back runs with track rays? (maybe standard 18s) and iforged 19s. He lost .2 seconds.

My best is a 14.490 on my iforged. That was with injen cai and technosquare ecu being only performance mods, and about 85% and very humid. My biggest problem seemed to be traction, as I got a lot of wheelspin.

Going back on the 19th with Borla dual and M/T ET Street, 26x10.50 on light 16" wheels. Hopefully should do a lot better!

 

when go from a bigger rim from a 18 to 19 you are messing up your gearing which will slow you down..

 

not if the outer diameter of your new tire is the same. going from a 245/45-18 to a 275/35-19 will have no gearing change.

 

thats not always true.. I went from a 245 17 45 to a 275 17 40 and my tire got taller and wider..