I've been wondering for quite sometime now what people's opinons are regarding rim size for track use. What are the advantages & disadvantages for 15" and 16" rims.

What do you guys run?? I'm just curious...

BTW the car is a Civic Hatchback w/ jdm 4.785 final drive.

 

..b/c I've been debating the same questions; for my '99 prelude though. Anyone else?

 

Hubert,

Why put smaller rims than what comes OE on the car?

 

roll with 22''s ..... the only way to roll yO....make sure you have your stunna visor on too

 

..to drop the gearing a little, and to lessen the rotating mass. But, it was just a thought.

 

That was productive.

 

Smaller, always better...

 

The only possible negative to smaller wheels is it generally leaves you running higher profile tires. This is generally only an issue on the street as race tires have very stiff sidewalls by design.


... oh yea, if for some reason you feel the need to run 16" rotors or something like that, then yea... bigger wheels. Many of the racing series you see running large diameter wheels are doing so because it's a series requirement.

 

<-----has 13.5 inch ROTORS in garage.....that would be why i'd run 22's yO dAwG.......so i can out brake you!

 

Chad, stop being a jackass, or im going to lap you at CMP...

 

Don't worry dude, we'll do that anyways.

Warren

 

 

what if.. the 15 and 16 inch wheels were almost the same in weight (the actual rim itself) wouldnt the 15 use a heavier tire as opposed to the 16 (assuming you wanted to keep a relatively close total diameter) ?

 

You would still want to run the 15 inch wheel primarily b/w the weight will be closer to the axis of rotation, the further you move the weight away from the axis of rotation, the greater torque is needed to rotate that mass; at least that's what all the physicists will tell you. So, the more torque needed to move the mass, the greater the drag/loss; get it?

 

When some of you state smaller is always better I think you are being way to general with your statement. In some situations the bigger wheel/tire combination can be as good or better than a smaller setup. In the instance of a 5th gen Prelude you can go with a 225/50/15 or 225/45/15 in 15" size and you can also go with a 225/50/16 in 16". The smaller combos will be lighter and give you better gearing and the 16" will give you a bigger contact patch. However with some wise wheel and tires choices you can get the weight of the larger combo within a couple of pounds of the smaller combo. And with a lower final drive you can always make up for the gearing. So in this case if your car was modded correctly the bigger combo might be faster primarily because of the larger contact patch.

 

How will a 225 width tire in a 16" diameter give you a bigger contact patch over a 225 width tire in a 15" diameter?

That doesnt work.

Besides, on race tires you dont need to worry about a lower/shorter sidewall (like from a +1 wheel/tire), they're so damn stiff anyways.

 

You need to think about the rolling circumference of a taller tire vs. a shorter one. Given the same PSI lets say both tires have a 5 degree angle from the center of the wheel that they are in contact with the road. Since the taller tire has more distance from the center of the wheel to the ground that same 5 degrees would be a greater area hence a bigger contact patch.





[Modified by DR, 11:19 AM 7/19/2002]

 

I don't understand. A 5 (percent or degree?) angle from the center of the wheel to what? Or do you mean like if you drew a triangle from the front of the contact patch, back of the contact patch, and the center point of the wheel (where the angle at the top would be 5 degrees)? Thanks for the clarification.

The way I see it, smaller is better for acceleration because like bb6h22a said, it's easier to rotate, but then requires more energy to keep it rolling at a certain speed because it would revolve more times than a larger wheel. Since you're never really at a constant speed on a race track, I would think smaller would work better on a race track so you can accelerate out of a turn. Unless you're on street tires, then sidewall stiffness might be more important.
I was looking on tirerack and they did a comparison between 15, 16, and 17" wheels on a Civic. 3 drivers, 10 runs each with each wheel on an autocross course. The 17s turned in the fastest times, which leads me to believe that with street tires, sidewall stiffness advantage overcomes the disadvantage of acceleraton loss.
[Edit: damn html tags]


[Modified by Steppin Razor, 9:11 AM 7/19/2002]

 

Yes I meant degree not percent So yes draw a triangle from the center of the wheel to the front and rear of the contact patch. Given the same PSI that bottom side of the triangle, which is the contact patch, would be larger as the circle, which is the tire, gets larger. Simple trigonometry really.


[Modified by DR, 11:28 AM 7/19/2002]

 

Whatever is lighter.

If you get a killer deal on some ultralight 16's, ******* buy them. If not, get some 15's.

Simple as that. I've got 15" Kosei K-1 because they are cheap and light, the tires are cheaper in smaller sizes, and lots and lots of race compound rubber is available in 15" sizes if I ever decide to put some hectic sticky **** on them.

But then, the philosophy I'm building my car against is "bang for the buck."

Kosei K-1's, AEM CAI on a blowout sale for $170, Kumho 712's, KYB AGX, H&R Sports. Benen tie bars that were sitting the tuning shop I use for a year or two so I got them for $75 apiece. Tenzo-R strut bar that was sitting on the shelf in the shop for years so I got it for $40. B&M short shifter.




[Modified by Mojo-Jojo, 9:44 AM 7/19/2002]

 

Well my situation is as follows...

I have 15" spoons & 205/50 Azenis tyres. That setup will require me to use an 8mm spacer to clear the spoon calipers.

What I am considering is 16" spoons & 215/45 Azenis. Which will eliminate the need for spacers.

But the latter is heavier by quite a bit.

Confused in Cali.




[Modified by Mario, 2:04 PM 7/19/2002]

 

Well spacers suck unless you get longer lug bolts and the added width of the tires will make up for the slight weight gain. I would go with 16" in your case.

 

I agree. What I should have said was go with the lightest wheels that your brakes will fit under.

:D


[Modified by Mojo-Jojo, 2:00 PM 7/19/2002]

 

Nope. The size of the contact patch is strictly a function of the weight of the car and the inflation of the tires, as long as the inflation of the tires is holding up the weight of the car. If you have a 3300 pound car with the tires inflated to 33 psi, the size of the four contact patches will equal 100 square inches - regardless of whether the tires are skinny 185 mm wide or wide 245 mm wide, regardless of whether they are on 14" wheels or 18" wheels. People who choose wider tires do so because it changes the SHAPE of the contact patch (wider side-to-side, narrower front-to-back), not the SIZE of the contact patch.

Also - not that it's relevant here - but usually tires are selected to have the same outer diameter and rolling circumference, regardless of whether they are on a bigger wheel with a lower aspect ratio, or a smaller wheel with a higher aspect ratio. Regardless, this has nothing to do with the size of the contact patch.



[Modified by nsxtcjr, 6:51 PM 7/19/2002]

 

I'm glad that someone mentioned this. The shape of the contact patch changes laterally or longitudinally with the rotation of the tire under different tire sizes, but the contact patch area does not change.

However the "inflation" of the tires (in terms of Psi) is not what actually holds the car up. The sidewalls of the tire are what actually "hold" the car above the ground. The pressure from the enclosed air molecules keeps the sidewall shape/position from deforming.

Keep in my mind that the density of a wheel (mass per unit volume) is greater than that of most tires (summer/performance tires, that is). The difference in weight (and the density) between a 205/50 15 tire and a 205/45 16 is very slim, and can sometimes be offset by the differences in tire construction.
I currently work for Discount Tire Co. (I'm 20...it's a summer job) and I handle a lot of tires everyday. I've noticed that the 16" equivalence (same overall diameter) of a 15" tire "feels" though it weighs more. I could only attribute the difference to the construction of the tires, most notably in the sidewalls. Note: just some empiracal data I've picked up lately.