LOL a Pirate Z ! :P

DC350ZTRACK, which track is that ?

 

I guess I have to share too. 19s are not the ideal setup for track - but for me, I wanted a good mix between performance and looks:

How is it that 19"s are a good mix of performance & looks???? 19"s are not performance oriented at all.

 

I also have the Rotora 14" 4-wheel kit. I gave up on trying to find 17" wheels to fit and went with 18" SSRs. My 17" 5Zigen FN01R-Cs wouldn't fit. Though Rickdogg supposedly got them to fit his car - still don't know how he did it.

Back to the first question at hand - definitely 18" is a better choice for track wheels than 19", for all of the reasons that have already been posted.

 

I believe the 19" NISMO wheels weigh approx. 2 - 2.5 pounds more per wheel (if I'm not mistaken - though I didn't weigh them both before I installed the new wheels) than the stock '04 track wheels. So, the increase in diameter did not kill my performance. And because I've done power mods as well (intake, plenum spacer, underdrive pulley, high-flow cats, true-dual exhaust), the increase in overall wheel weight and unsprung weight hasn't slowed me down at all.

 

Those picture were taken at Summit Point Motorsports Park in West Virginia.

http://www.summitpoint-raceway.com/

 

18's are lighter than 19's. 1 lb of unsprung weight is equal to 8 lbs of sprung weight. Also, 18's will give you better gearing than 19's. For the track, 18 is better than 19.

 

Doesn't work quite like that, unless you're driving a train...

 

I agree with Kolia, it doesn't quite work like that.

1 pound of unsprung weight might be equal to "a few" pounds of spring weight, but 8 is rather excessive.

Also, gearing would be determined by overall wheel AND TIRE diameter - not just wheel diameter.

 

get what your budget will support.

 

I disagree. You do get better gearing for accelleration with a smaller diameter tire. Top speed is decreased, but accelleration is increased. Works the same (but to a lesser degree) as having a different geared rear end.

 

From all the track days/racing I've done, I've always heard the 1 to 8 ratio. I do a lot of track days, I do SCCA racing and this is always what instructors and other racers tell me.

Yes, gearing is determined by the overall OUTSIDE diameter, which would be the tire. My assumption is that when getting 18's, he wouldn't get 50+ aspect tires. Since we're talking track tires, 18 size tires SHOULD have a lower overall diameter than 19's. I didn't call this out because I assumed that would be everyone's assumption. So, Yes, gearing would be better with 18" track tires, vs 19" track tires assuming they were both low profile (265-35-18 vs 265-35-19).

 

You sound like you had the exact same experience. I also went with SSR's GT7's, what did you end up with? And the wheel and tire combo are so light I can almost mount my 295's with one hand!! OH, and my wheels are gun metal and the Rotora calipers are blue.

 

Kolia - does your number 375 mean anything? Also, the rear end of your Z would look better without the rear windshield wiper.

 

Also, from the pictures - looks like Black is the color of choice for people who track their Z.

 

i've never heard a unsprung to sprung ratio, but heart the power to weight is 1hp/10lbs.

yeah.. i drive an SB as well.. haha. you guys running 19s at the track must be ballers. i complain about the price of a 17" r-comp.

 

Unsprung weight is one of the most critical factors affecting a vehicle's road-holding ability. Unsprung weight is that portion of hte vechicle that is not supported by the suspension (wheels, tires and brakes) and therefore more susceptible to road shock and cornering forces. Reducing unsprung weight provides more pecise sterring inputs and improved "turning in" characteristics. Also, by reducing the weight of the vehicles rotational mass you get more responsive acceleration and braking.

The ratio you are talking about 1# of unsprung is worth 8# of sprung is just a generality. Yet, the overall point is true. It is far better to focus on reducing the unsprung vs. focusing on the sprung weight. Yet, sometimes you must make sacrafices, like a larger rotar will weigh more, but will be a larger heat sink and less likely to have brake fade.
The wheel size is a long arguement, so I will just go with this, for a track wheel, go with a 17" if it will fit then go up from there if it won't . This is all due to the cost of the tires, since on road tracks this will be by far you largest expense. And track tires go up in $ exponentially with wheel size!

 

I have always heard 1 pound unsprung is approx. equal to 4 pounds sprung. Still significant. Also have heard that depending on the track and car, 10 pounds of car weight can equal 0.1 seconds per lap (a lot of uncertainty there given all of the variables), but weight certainly matters. Look at what lower weight does for F1 cars as they burn off fuel weight, even as their tires get worn.

MoodDude, I have several sets of wheels. I have a nice set of 18x9.5" Rotas with 285/30 Hoosiers mounted on all four corners. Not super light (22.5 pounds) but farily cheap for a wide wheel. I have a set of SSR Comp-H's (18x8.5 front, 18x9.5 rear) that I use for open road racing (VERY light) and some car shows. I also have recently purchased a set of SSR GT-2s (18x9 front, 18x10.5 rear) that I will use as my time attack wheels - got a decent deal on some used ones (but excellent condition). Still light, but not quite as light as the Comp-H's. I am still waiting (intentionally delaying) to mount tires on these - I want to get NEW tires for the next time attack - I need every advantage that I can get. I am waiting to see what will be the BEST street tire available at the time.

My Rotora calipers are also blue - that's their signature color, and the one that Rotora wanted me to use (as one of my sponsors,) so I said "sure!"

 

Almost right. It is the over tire diameter that will change gearing. But the rim size doesn't have any direct effect on the tire since you can (and should) select a different sidewall ratio to maintain the gearing. 265-35-18 to 265-30-19 for exemple (provided these tire sizes exists).

This is why I was teasing you about the train wheels. The rim itself is irrelevent to tire diameter. (Within limits of course... a 28" rim kinda limit the tire sizes availlable).

 

Aside from the discussion of gearing which I agree with improved performance on a smaller diameter there's also the issue of availability of tires.

I run 275/35/18 Nitto NT-01 R-compounds front and rear. I'm thinking about getting 17x9 or 9.5 wheels so I can run Kumho V710s that aren't available in the 275/18. Probably gram lights in 17x9.5.

Good luck finding any r-compounds in 19". R-compounds also don't last very long and the expense of a larger diameter tire is a killer. I believe 275/40/17 is a perfect size for our Z's and offers a lot of choices in tires and are a lot cheaper.

After running r-compounds for some time now, I would never run street tires in autox or on the track. The level of grip and progressive feel of r-compounds makes running street tires an exercise in greasy overheated frustration.

 

Lucky. How about spreading out some love to your fellow Z's and hooking me up with some free Rotora brake pads ?