18inc rims

[johnc]

Not necessarily, because a larger diameter profile (wheel and tire together) will have an increased contact patch which should provide better traction.

 

Actually the contact patch total area will remain basically the same. Contact patch size is determined primarily by weight and air pressure. 600 lbs. on a tire will require X number of square inches of contact patch (based on air pressure) regardless of the tires width, sidewall height, diameter, etc.

 

The shape of the contact patch varies based on tire and rim width and sidewall construction.

[B00STDZ]

Oops.. I forgot, you can only run halfway into the forest...... So, in the sense of scale, I made a gross error, but the bones of the matter stand. The more mass that sits further from the center of the rim takes more work to accelerate and decelerate.

 

Technical/performance reasons I have a problem with 18s (and again, this is my personal taste):

 

-mass issue

-sidewall flex issue. I drove my 75 around for about a year with some BIG TALL tires on it and I have to say, it was the loosest and most enjoyable year in that can on the street.. easy to snap out of control and right back in. Everything that I liked about the way a stock Z handles, handled more like that.

 

Aesthetically, I simply point out that the direct stylistic descendant of replacing our 215-60R14s with 255/40/18s, is the instant popularity of the black, bolted on fender flare. The fenderwell is missing too much negative space (because the wheel is so big and the tire sidewall so small) so you need to go buy:

 

-expensive wheels

-expensive tires

-expensive (because they're currently all the rage) flares.

 

 

Now, I have to say that one MAJOR reason that "small wheel guys" seem so defensive about this is, my point above about tire pricing. Now that these huge wheels are all the rage, performance tires in 13, 14, and 15 inch sizes are all but gone from the market. This is something of a sore point for a lot of us, so please bear that in mind any time one of you "big-wheelers" (sorry, couldn't resist) hears one of us old fuddy-duddies* griping about your spinners.

 

*I am only 29, but my tastes are old fashioned.

 

.

18" rims really arent even considered large! You guys act like we're talking about 24" rims...

[B00STDZ]

???

I have been told all that sidewall is unneccessary when talking about autox. Infact that is said to "slow you down".

[B00STDZ]

Actually the contact patch total area will remain basically the same. Contact patch size is determined primarily by weight and air pressure. 600 lbs. on a tire will require X number of square inches of contact patch (based on air pressure) regardless of the tires width, sidewall height, diameter, etc.

 

The shape of the contact patch varies based on tire and rim width and sidewall construction.

You can make the contact patch the same as a bigger rim, you just have to run a huge massive sidewall tire...

[Leon]

Technical/performance reasons I have a problem with 18s (and again, this is my personal taste):

 

-mass issue

-sidewall flex issue. I drove my 75 around for about a year with some BIG TALL tires on it and I have to say, it was the loosest and most enjoyable year in that can on the street.. easy to snap out of control and right back in. Everything that I liked about the way a stock Z handles, handled more like that.

 

Aesthetically, I simply point out that the direct stylistic descendant of replacing our 215-60R14s with 255/40/18s, is the instant popularity of the black, bolted on fender flare. The fenderwell is missing too much negative space (because the wheel is so big and the tire sidewall so small) so you need to go buy:

 

-expensive wheels

-expensive tires

-expensive (because they're currently all the rage) flares.

 

 

Now, I have to say that one MAJOR reason that "small wheel guys" seem so defensive about this is, my point above about tire pricing. Now that these huge wheels are all the rage, performance tires in 13, 14, and 15 inch sizes are all but gone from the market. This is something of a sore point for a lot of us, so please bear that in mind any time one of you "big-wheelers" (sorry, couldn't resist) hears one of us old fuddy-duddies* griping about your spinners.

 

*I am only 29, but my tastes are old fashioned.

 

I completely agree with Daeron. Tire compliance is a big issue when considering predictable handling. The shorter your sidewall, the less compliance you have.

 

Let's take it to the extreme:

 

 

Look at those tires! Do you see F1 cars running 20" wheels with no sidewall? Now I know that those tires are very different from what we run on the street, but if it was truly beneficial to run relatively big rims and small sidewalls then I think F1 would seek to do that.

 

Besides, for myself at least, even 17" is pushing it on an S30. 14-16" seem to fit pretty darn well, IMO!

[B00STDZ]

Haha this is what ive been trying to say leon. Sidewall on autox = BAD.

 

Conclusion:

15" rims lots of sidewall = Drag Racing only

18" rims Very little sidewall = AutoX and daily driver use...

 

Well I guess it is possible to run a 15" rim with small sidewall...

Edited March 6, 2010 by B00STDZ

[Leon]

Haha this is what ive been trying to say leon. Sidewall on autox = BAD.

 

Conclusion:

15" rims lots of sidewall = Drag Racing only

18" rims Very little sidewall = AutoX and daily driver use...

 

 

That is not my conclusion, nor is it what I say. You seemed to have misinterpreted my post. Take another look at it...

[B00STDZ]

 

They look like 18's to me...

[Leon]

They look like 18's to me...

 

Possibly, but I would not call those sidewalls "very little." Tire compliance is necessary, and you especially do not want a tiny sidewall for a race tire. As Jon mentioned earlier, you gotta put those big brakes somewhere.

[Leon]

I have been told all that sidewall is unneccessary when talking about autox. Infact that is said to "slow you down".

 

To the contrary, you want sidewall, just not soft sidewall. This "I have been told" talk is also not proof of anything. I have been told also, except by a former Formula One senior engineer and he doesn't agree with you.

[rat_ranger]

From my experience even on a daily driver you want some sidewall. suspension can only do so much, tires have to be able to take up some small imperfections on the road. I know it isnt a datsun but my ranger has 285/30r20s and you can really feel the ride quality diference. It is alot more harsh and small bumps are transmittied to the suspension which is too stiff to soak it up, resulting in a rougher ride with more chassis upset. I personally would want a 35-40series tire at the shortest after my experience. for ride compliance, and handling.

[B00STDZ]

... Im running 245/35/18's on my 260z

[roger280zx]

No one is still addressing my question, and it's not just looks and SUVs. Manufacturers continue to increase the diameter of wheels on performance vehicles. I did a search and found that a 2009 Ferrari 599 GTB Fiorano has 19" diameter wheels on the front and 20" diameter wheels on the back. This car is all about performance so if it would perform better with smaller diameter rims it would come with them from the factory. I'm also not talking about the aftermarket here which generally favors upgrading wheel sizes. Here's a site that talks about aftermarket reasons for getting 'plus fitments': http://www.toyo.com.au/tech_info8.htm

 

I think that as horsepower increases brake and wheel sizes can correspondingly increase as well. Since I probably have 3 or 4 times the horsepower my car had when it was stock, I think that running 18s isn't unreasonable. For those people that don't like it, I don't really care. I already have enough people that don't like that I have a Chevy V8 in my car - so get in the back of the line.

 

 

Yeah, this car is all about performance. Thats why it weighs a full 1400lbs more than the F40 from over 20 years ago. Granted it has 150 more hp, a plush interior, more brakes and bigger wheels to slow all that mass down with. The point is every single new car has bigger wheels now, but they also weight substaintially more. It is just the natural evolution of the industry. Sure, the new Z has 18s or 19s. I don't see any of them getting down under 2000 lbs with out quite a budget though. It may be my personal rant, but I joined Hybridz and purchased my first Z because I don't want to push around 3000-3500 (or more) pounds of flashy wheels, plush interior, high power stereo, and multiple airbags! Even the 911, once the epitome of a stripped down sports car, has a ton of; unnecessary eloctronics, sound deadening, airbags, and cup holders. I'm not knocking anyone's automotive enthusiasm however it differs from my own. I have friends with 80hp minitrucks that run 20" wheels... thats fine, but if you like it only for the way it looks call it what it is. After all this is america where we drive our big fat a$$es around in our big fat cars/suv's and park them in front of our big fat houses. I'll keep my 10 pound 14's with 19 pound tires. Rant over.

[Leon]

Very good point Roger, and it reminds me of something along the same lines.

 

Compare a Z to a 599 that was mentioned and the weight differences are relatively huge (~2300lb vs. ~3700lb)! The effective mass of the wheels will affect Z-car performance (i.e. time-to-speed) much more than a heavier car, meaning that the effective mass of the wheels is a higher percentage of total mass of the Z vs. Ferrari. Thus, the effect of larger wheels is much less noticed on heavier, more highly powered cars. Conversely, a reduction in weight of a Z's wheels will affect performance more than a reduction of the Ferrari's wheel weight.

[roger280zx]

I guess that simplifies it a bit. Please forgive my ranting but I was in a partial tryptophan coma and desperatly needed sleep. I was just happy to get up this morning and see my post actually made sense. Gotta love the bottomless Brazilian grills! Back to the wheel debate.

 

Oh yeah, "simplify and add lightness".

[Daeron]

And, to get back the the OP's question, I would summarize by stating this:

 

In America today, profit is King.

 

High diameter, low profile tires sell at a premium price.

 

High diameter, flashy looking wheels sell at a premium price.. (almost WHOLLY regardless of weight.. wheels that are heavy are by NO means necessarily inexpensive.)

 

If the advertisers and the marketing types can convince enough people to go "Joe Cool" and buy these wheels, then they can start phasing out tire options for smaller sizes and begin a New Era where they get to charge premium prices for just about every tire and wheel sold. I must also add that the TIRES are where the major revenue generation is. Wheels you buy once, tires you buy over and over again.

 

All that being said, I have yet to see an ounce of evidence that justifies the expenditure alone. Forget the aesthetic points, forget rules compliance, and forget weight versus performance, this question is first and foremost and economical one.

 

Sure, maybe you happen to have $2000 for a set of wheels and tires, and you don't mind paying $800 for new rubber when you need it. Why does that justify limiting selection of original equipment size performance radials?

 

 

 

Profit. A cadre of MBAs somewhere asking "What's in it for me?"

Edited March 8, 2010 by Daeron

[Bartman]

...

In America today, profit is King.

 

High diameter, low profile tires sell at a premium price.

 

High diameter, flashy looking wheels sell at a premium price.. (almost WHOLLY regardless of weight.. wheels that are heavy are by NO means necessarily inexpensive.)

 

(If you want to see the entire post look above...no need to copy everything again)

What a highly biased load of bologna. Why do people that don’t want to run larger rims feel it’s necessary to continually bag on people that do? Clearly there are some issues regarding larger diameter wheels, but there are some benefits as well. The next thing you know you large wheel haters are going to tell me that large diameter wheels are going to create a block hole that will ultimately kill everyone on the planet.

 

You haven’t even proven that smaller diameter wheels = better performance and you deliberately discount any evidence that doesn’t conform with your expectations. This isn’t a conspiracy and I don’t believe it’s all about big corporate profits. I would like to see real world data that specifically supports the theories about larger diameter wheels causing performance issues such as the experiment that johnc described in an earlier post. By this I mean something realistic like comparing 17s to 18s on the same vehicle.

[johnc]

You haven’t even proven that smaller diameter wheels = better performance and you deliberately discount any evidence that doesn’t conform with your expectations. This isn’t a conspiracy and I don’t believe it’s all about big corporate profits. I would like to see real world data that specifically supports the theories about larger diameter wheels causing performance issues such as the experiment that johnc described in an earlier post. By this I mean something realistic like comparing 17s to 18s on the same vehicle.

 

Well, first we would need to define "performance" and that's something that not many agree on - as evidenced by this thread.

[JMortensen]

You haven’t even proven that smaller diameter wheels = better performance and you deliberately discount any evidence that doesn’t conform with your expectations. This isn’t a conspiracy and I don’t believe it’s all about big corporate profits. I would like to see real world data that specifically supports the theories about larger diameter wheels causing performance issues such as the experiment that johnc described in an earlier post. By this I mean something realistic like comparing 17s to 18s on the same vehicle.

You're right, we need to do more proving. We have the formula to prove the assertion that the smaller wheel takes less force to accelerate. What we need is someone with some math skill that can work it out to figure out the disadvantage between a small diameter and larger diameter wheel. I'm not that guy unfortunately, or I'd do it myself. To really make that accurate you'd have to figure out exactly how far out the center of mass is, but I'd be willing to bet that there would be a noticeable difference on the same weight tire/wheel combo with just a couple inches difference in the center of mass.

 

Here's an anecdote for you though, and this is not the first time I've told it. My friend wanted to trade me my Caroll Shelby 15x7's which are astonishingly heavy, probably 20 lbs each, for her 14x6 6 spoke wheels which are 14 lbs. I agreed after SPECIFICALLY WARNING her that they would make her car slower. I swapped out the wheels and she drove home (about 180 miles) and called me on the phone saying "my car is slower and the brakes don't work as well." I asked if she wanted to switch back, she said no, and she still has those heavy mesh 15x7's on her Z today.

[Bartman]

You're right, we need to do more proving. We have the formula to prove the assertion that the smaller wheel takes less force to accelerate. What we need is someone with some math skill that can work it out to figure out the disadvantage between a small diameter and larger diameter wheel. I'm not that guy unfortunately, or I'd do it myself. To really make that accurate you'd have to figure out exactly how far out the center of mass is, but I'd be willing to bet that there would be a noticeable difference on the same weight tire/wheel combo with just a couple inches difference in the center of mass.

...

I don’t mean proving on paper, I mean real world proof. I agree with some of the specific data that’s been posted, but I don’t think everything is being taken into account. The only results that really mean anything comes when the rubber meets the road – literally.