Why Wider Tires are Better

[Chrsx]

Most racers have figured out that wider tires allow for more lateral grip, but most people have no idea why.

The most common myth is that a wider tire has a greater contact patch... which it doesn't. If the internal pressure and vertical load are the same for a narrow tire and a wide tire, the contact patch will still be same. A=F/P (area=force/pressure).

The key is the SHAPE of the contact patch. A narrow tire will obviously have a longer length (narrow width), while a wider tire will have a shorter length (wider width).

Deformation builds along the length of the contact patch until the restoring force of the tread and carcass exceeds thread grip... and sliding begins.

Where on the patch a tire begins to deform is roughly the same distance from the leading edge with a narrow contact patch as with a wider one. But the shorter contact patch has more of its length stuck to the road than the longer, narrower contact patch; and therefore a larger portion of its overall area is gripping! A larger portion of the contact-patch area gripping means more total grip.

So, for the same load and slip angle, a wider contact patch generates more grip than a narrower patch.

This table presents changes in contact patch (CP) length at various tread widths. I'll assume slip starts 1.5 inches into the contact patch. The load on the tires is 500 lbs and the tire pressure is 20 psi:

Tread Width: 6
CP Length: 4.17
CP Area Gripping: 36%

Tread Width: 8
CP Length: 3.13
CP Area Gripping: 48%

Tread Width:10
CP Length: 2.50
CP Area Gripping: 60%




Source: Mostly from my own understanding of physics, suspensions, and tires, and the calculations from "The Racing & High-Performance Tire" By Paul Henry.

[anewbreedx008x]

cool :thumbsup:

[LickyMYwalker]

good stuff!

[JohnBlaze]

makes u go hmmmm...

[gordo27]

I'm not gonna lie and say I understood the whole thing, but I think I got an overall understanding... nice post..

[beowulf7]

I also thought that a wider tire is "stickier" b/c it has more surface contact with the road. But apparently that's not the reason why. So what's the fattest tire that will safely fit on a stock 2002 RSX rim (16") and won't throw off the speedometer? Perhaps 225/50-16? The stock tire size is 205/55-16. TIA.

[Chrsx]

I also thought that a wider tire is "stickier" b/c it has more surface contact with the road. But apparently that's not the reason why. So what's the fattest tire that will safely fit on a stock 2002 RSX rim (16") and won't throw off the speedometer? Perhaps 225/50-16? The stock tire size is 205/55-16. TIA.
Yeah, you can get that size on the RSX-S. I autocrossed a few different types of tires with that size and never had problems related to it.

I also used to think that it generated a wider patch, but it really doesn't. It just changes the shape.

[beowulf7]

Yeah, you can get that size on the RSX-S. I autocrossed a few different types of tires with that size and never had problems related to it.

I also used to think that it generated a wider patch, but it really doesn't. It just changes the shape.
That's good to know. I've never bought non-stock-size tires before for any car. So hence my newbie-ish questions. I'm leaning toward the 225 size rather than 205. I would've like to have gone to 17" tires, but they'd cost even more, weigh more. And of course the main reason: I gotta cough up $ for a new set of wheels. But it is tempting.

[clsixspeed]

good info...thanks

[beowulf7]

Chrsx, I just wanted to get your opinion on what DTD says (http://www.discounttiredirect.com/direct/brochure/info/tmpInfoPlusSizing.jsp) about wider tires.


Plus sizing is one of the easiest ways to achieve enhanced performance and improve the appearance of your vehicle. In the example above, a 15x7 wheel with a 205/65R-15 tire is considered the O.E. (original equipment) size. Converting to a plus 1 size would mean increasing the wheel diameter by 1" (16x7.5) and selecting an appropriate tire to fit (225/55R-16). Likewise, moving to a plus 2 fitment would result in a 17x8 wheel and a 245/45R-17 tire. It is important to note that although the wheel diameter is increasing, the overall diameter of the tire remains about the same.

A couple of things happen with the tire to increase performance when we begin to move into plus sizes. First, the tire is wider (section width) and therefore gives us a wider contact patch. Second, the sidewall becomes shorter (aspect ratio) and more rigid. The two added together give better lateral stability and increased steering response.

The sentence I bolded indicates that wider tires have a wider (which I assume is same as greater) contact patch, which is contrary to what you mentioned.

[teggei2]

Chrsx, I just wanted to get your opinion on what DTD says (http://www.discounttiredirect.com/direct/brochure/info/tmpInfoPlusSizing.jsp) about wider tires.



The sentence I bolded indicates that wider tires have a wider (which I assume is same as greater) contact patch, which is contrary to what you mentioned.

Read the sentence before the one you highlighted. That applies to plus sizing.

[gordykeefers]

Chrsx, I just wanted to get your opinion on what DTD says (http://www.discounttiredirect.com/direct/brochure/info/tmpInfoPlusSizing.jsp) about wider tires.



The sentence I bolded indicates that wider tires have a wider (which I assume is same as greater) contact patch, which is contrary to what you mentioned.
no, he said the contact patch is WIDER but SHORTER. Discount tire is only mentioning the part about it being wider.

[beowulf7]

OK, thanks guys. I just wanted to find out if there's a difference between the words "greater" and "wider" in terms of contact patch (also, is that the same as contact area or should we just call it "contact patch area"?).

[Chrsx]

Chrsx, I just wanted to get your opinion on what DTD says (http://www.discounttiredirect.com/direct/brochure/info/tmpInfoPlusSizing.jsp) about wider tires.



The sentence I bolded indicates that wider tires have a wider (which I assume is same as greater) contact patch, which is contrary to what you mentioned.
As what others have said, it is referring to a change of shape... not an increase in area.

The formula is quite simple: Area = Force / Pressure. Think about it: PSI = Pounds per square inch. If you increase your pressure and keep the same weight (force), your need less area to support it.

I mentioned it in the first post and in the title.

[NBP_RSX_S]

What about traction during straight acceleration? Do wider tires work better?

[Chrsx]

What about traction during straight acceleration? Do wider tires work better?
Hmmmm.... that's a good question. I know they do, but I'm trying to reason out why they do. Let me think on it a day, and I'll get back to you.

[cougar-magnum325]

I know i'm gonna get whacked for this but a little common sense says that if all the big companies that are racing in auto-X events and drags use monster sized 10 inch wide tires, they must be for a reason. It must be for extra grip cuz otherwise, it's just a whole crap load of extra weight.

[benjoewoo]

sorry if I'm not doing enough research/understanding (I went through the FAQ and this thread before I posted), but can you put a slightly wider tire on the same rim? I think an earlier poster tried and someone else said he/she did not have any problems. I sit on stock size tires 245/45/R17 and since wider tires are more efficient, figured if I could I would change to slightly wider on the same wheel. Sorry again if this is something illogical.

[03 TYPE-Sexy]

How wide is your wheel?

[benjoewoo]

whatever the OEM width is for 2005 Type-S. Sorry about my lack of knowledge.

[TYPEzachS]

So it will actually improve acceleration times?

[disturbedmtb]

yes, because you will have more traction when you launch, but once you get up to speed, it will be slightly slower because of the extra friction from more rubber. But faster overall

[C02SpitFire]

:thumbsup: nice

[DC5 rollin]

nice write-up +rep:thumbsup:

[gordykeefers]

sorry if I'm not doing enough research/understanding (I went through the FAQ and this thread before I posted), but can you put a slightly wider tire on the same rim? I think an earlier poster tried and someone else said he/she did not have any problems. I sit on stock size tires 245/45/R17 and since wider tires are more efficient, figured if I could I would change to slightly wider on the same wheel. Sorry again if this is something illogical.
if you have an 05-06, the stock tire is 215/45/17. You can safely fit 225/45/17 with zero problems; lots of people go that direction.
So it will actually improve acceleration times?

yes, because you will have more traction when you launch, but once you get up to speed, it will be slightly slower because of the extra friction from more rubber. But faster overall

He never said that. This thread is about lateral grip ONLY. I've been trying to figure out this question for awhile now, and I can't find any reason why wider tires would be better for acceleration. In fact, the only thing that makes sense to me is that wider tires are WORSE for acceleration from a stop precisely because of the reason they're good for lateral grip.

So I haven't heard any convincing arguments either way.

[DesiRSX]

thanks man now i know aha

[TYPEzachS]

So maybe just wider tire in the back? That way your front tires still get the same launching grip?

[gordykeefers]

No, that upsets the grip balance of the car.

Any time you're sizing tires, you need to know exactly what your application is. If you're doing anything other than dedicated track use (i.e. if you drive on the street at all) just get the same size tires F&R.