Why do so many people want bigger wheels?

I thought that from an engineering standpoint the bigger (more weight) a wheel has the worse it makes the car perform. Unsprung weight is about the worst weight to add. It is harder to control by the suspension and the added inertia makes it harder to accelerate or brake.

The taller wheels also lift the car. The higher center of gravity also hurts handling performance.

I am a fan for wider wheels and tires since they provide more contact area with the ground, but the taller wheels can't help the performance.

I understand that some people like the look, but for me it doesn't make it look better have a tall wheel.

Any comments or opinions?

 

To each his own. I guess we all have our fine line of wheels that are too big or too small.

 

Heard of SLIP ANGLE? Bigger wheels with lower profile tires tend to have a lower slip angle - makes transitions quicker and smoother. This is coming from an autocrosser's standpoint - I run 18" wheels on my BMW autocross car because of this.

A light 18" wheel with a tire will weigh less than a 16" wheel with the same width and tire tread width. All depends on how much $$ you're willing to spend...

Ever wondered why ALMS, cup cars etc run such low profile wheels? Same with exotic cars ... not as critical for nascar since there isn't much transitioning - you load the tire, and keep it loaded through a turn. F1 cars are so light, it doesnt matter to them since there is no slip angle in the tires.

Now, for straight line performance, a smaller wheel with a fat grippy tire probably wins...

 

The aftermarket 18's with a 335 tire weigh less than the 17's with a 315 tire that the car came with. The ride height is about the same give or take 1/4 of an inch. I notice a better turn in with the 18's as well. That's just my experience with it.

Daniel

 

good stuff! I was going to say lower profile tires, "upsizing" as they call it in the tire biz, makes the overall diameter the same if done correctly. But the lower profile tire will give less "flex" as well- as you call it, 'Slip Angle'. I like that, learn something new everyday.

I've noticed that alot of C4 owners make the mistake of trying to get a wider tire, especially in the front, and get 275/35/18 as an example, on a 8.5" wide wheel and you can see the side walls 'jet out' away from the rim-to me, giving it more flex.

Learned this from experience as I put 275 series on a 8.5 (C6 wheel) after having 9.5" stock front wheels and not only did I not like the look (didn't match the rear tire side profile) but the front end was "mushy". Ate a shiz sandwich on those tires and bought the right size the next day (245s).

 

Thanks for the comments.

I would not have guessed that the bigger wheels and tires weigh less.

It also sounds like your experiences with the bigger wheels have been good for performance too.

 

 

To clear big brakes. You're not going to get 17's on a new ZR1.

Other than that I think they are getting bigger because cars are generally getting too big.

Also, as far as bigger wheels weighing less, they still move the weight farther away from the center of the wheel which is probably worse than a lighter overall package. But if there are other possible benefits to be had then you do what you need. It's all about compromises.

 

There is no compromise, bigger lighter rims, lower profile tires = less weight. Bigger brakes = better stops. All and all a big win

 

 

Ok I been thinking of replacing my stock 16 inch rims on my 86 to the 17 inch rims due to more tire to choice from ok how wide of rim should I get I like to have the same front and rear and what are the best tires size to get so it not mushy for a 17 inch rim thats ?? wide HELP.

Wider would be nice also if I going to fork out the money to do this.

 

My 18" c5z06 track wheels with tires weigh considerably less than my 17" stock wheels with tires so I've lowered my unsprung weight. Since either set is exactly 25.5" in diameter (according to the tire manuf) where have I raised the car? where have I changed anything other than the rim diameter?
I'm running a 275 tread width on both (I'll admit those R6's look a lot wider than 275 but thats what is on the sidewall).

Nice thing about the 18" rims I can run over a 3xx tire even though its prohibitive points wise in my race class.

 

My LT1 with 18" handles better than my LT4 with 17".

I had problems with the 18" but, if anyone lowers the Vette and planning on upgrading to 18", you'll need 35 tires, 40 tires would rub your front fender.

 

I think they look good and perform better as well, if done properly. I just hate those goofball cars that have a wheel that looks like it belongs on a stage coach instead of an Impala. And those pickups with the GIANT wheels have to be dangerous when it comes to brake leverage. It makes the brake disk look like a little pie pan trying to stop a riverboat side wheeler!

 

Wow there is a lot of incorrect information here.

First, slip angle isn't about wheel size or tire size it's about the angle the car is sliding at to achieve maximum grip from the tire.

Second, there's no such thing as low profile wheels. There are low profile tires that can be used with any wheel size. Minimizing the sidewall is a good thing for handling.

Third, an 18" wheel and tire WILL weigh more then a 16" in the same width. Plus the weight will be out on the end, ever hear of moment of inertia? You don't want more weight out on the end, it takes more force to turn. This is what the OP is talking about and most of the responders don't understand.

There are two good reasons to use a larger diameter wheel, one for looks and the second for clearing different brake calipers.

As noted above you can get the same overall diameter tire so the car height isn't changed. The larger wheel will fill out the wheel well better. As we all know some folks like huge wheels 20" or more. And others do not.

PLRX, so the two cars are exactly the same otherwise? I doubt it..

 

GOOD READ

 

Well said.

 

This, by itself is a good reason. The 255/50/16 is becoming a rare bird...and with that a 50% increase in price over 17" and 18" tires.

275/35/18s some were as low as $109 each. No 16"s for anything under $150.

The Sidewall collapsing on higher profile wheels are not desired for cornering at all.

The weight issue?? Sprung weight or "rotational" weight could be an issue....but you'd have to have two of the exact same design wheels to actually find out the difference......the smaller profile tire would win hands down if you compared weight.....especially since I just put 18" on my car......the old tire O.D. was 26.06" and I am looking for other 18' tires with the same O.D...simple observation would tell that the low profile 18" has less meat on it than the same O.D. tire in 16"

So it comes down to wheel and the design. If we had three piece wheels we could disassemble the wheel and actually weigh the difference in hoops from 16 vs 18

Then we could weigh the spokes. There would certainly be a difference as each spoke would be at least 1" longer for the 18" wheel..

Now.....will the low profile tire make up the difference for a hoop with 2" added in O.D. and ~5 spokes that are 1" longer??

That would be the question that needs to be answered.

 

After a little more research, I think the 'slip angle' is symantics between your post and the other poster. The original poster is correct and so are you, to a point. Slip Angle is not the 'angle a car is sliding', it is the measurement of the angle at which a tire either breaks loose or oversteers (tread on the ground) and optimum Slip Angle is "0", (between the front and rear of the car).

Optimum 'slip angle' is achieved by adjusting the 'Roll Center'- ie, lower profile tires, wider tires (less flex in the sidewall, more tread on the ground) along with sway bars, endlinks (stronger for both) to keep the car from 'sliding' out. The goal is to get both the front and rear of the car with less than 1% difference (which I couldn't tell you how to do that).

So, to acheive a good 'slip angle', you want to work on your roll center.

As far as lower profile wheels, I don't see anywhere above that was ever mentioned- only lower profile tires.

Regarding PLXR cars, for the most part, these cars would be the same. HP is at the high end of the band, so there's little difference in these. I think he's finding that the 'slip angle' is better with the lower profile tires.

Regarding tire weight, the difference between a 275/40/17 (stock on C4) and a 275/35/18 (up sizing-overall same diameter) is negligent. 40 series weighs 29.4 lbs, 35 seried weighs 29 lbs. Not sure what the wheel weight would be and would probably be a moog point since most don't buy 18" sawblades

 

Quoted for you.

Here, I took a quick picture from a driving book.



We know nothing about the two cars mentioned above. It's a poor example. They could be very different, due to wear, or whatever. PLXR knows as much about slip angle as you do. So I doubt he's finding that.