eric n

So I absolutely love my 2011 5.0. But as with most all mustangs, not nearly enough contact patch. It seems even with the significantly sticky pirellis grip is a major issue. The other day I hit third really hard abusing an on ramp. The **** on this car jumped out like it wanted to get sideways. Let me say again 3rd gear.

So....I would love to have a little more contact patch/traction in the back. All of the hp in the world is useless if you can't effective translate that to forward propulsion. I know there are several of you running 275's and even 285's.

What is the downside (handling wise) to going with a wider rear tire?

How does changing the circumference affect launch/effective gear ratio?

Is it easy using an sct to dial in your speedo?

Does the added rotational mass defeat any advantages gained in increasing traction?

I'm sure I'm showing my ignorance, but being as I'm happily married, I'm used to being wrong! Thanks in advance for your collective wisdom.

RaceRed12

Good questions. I would like to know as well.

Hawaii 5.0

Well from my understanding wider tires equals a wider contact patch, so more traction. Less risk of spinning and all that poqer is going right tothe ground so i would think that your gears and everything woild work a lil better since youre puttin that oomph right into the ground. As for the tune i think ford has a speedo re-calibration tool that is built just for this reason. Im no expert here but this is just what ive picked up
As for rotational mass im not sure. If you have a heavy rim then the unsprung weight could cause a very slight performance loss but that really onlu matters is you track your car frequently

MRGTX

+1
I would add that going wider in the back would lead to a great tendency to undsteer...which some would argue is a safer situation than having the car snap around and swap ends on you... But I think most "enthusiasts" find this o be less enjoyable..

Plus more tire means greater unsprung weight which means a less responsive suspension and some detriment to acceleration, traction being equal...

The only other drawbacks would be expense (wider usually = $) and greater rolling resistance which will cost you more at the pump...which may or may not matter.

Double-EDad

The wider the tire in the front, the heavier the steering. So if you are interested in being able to rotate your tires (a nice feature to even out wear), then you'd want fronts & rears to be same size, and the front would be your limiting factor. As well, MRGTX already pointed out how wider in the rear promotes understeer, a safer but less fun dynamic, but which you indicated in your O.P. that you needed a little more of.

This may not matter to you, but thought I'd point it out because I've owned a car with staggered wheels/tires (BMW 540i 6MT) and multiple times I regretted not being able to rotate the tires. Got expensive replacing tires. But MAN, it had an awesome stance!

lemarin

To go wider will give you more grip for sure, but for the previous reasons, you will not want to put wider front tires. Yes the steering will be too heavy, but there's no advantage to wider's tires up front. Of course if you stagged your car, you'll not be anymore able to rotate front and rear tires.

The best would be to take 285's at the rear, just like the Shelby. But there again, you need wider rims to accept wider tires. Per example, the 19's on the CS Mustang, are juste 8.5" wide so 255's is the widest you can go....not interresting ?

Then if you want to know heigh/speedo difference between tire's sizes, here's an interresting link:

http://www.miata.net/garage/tirecalc.html

going for broke

Well first off a wider tire doesn't always give better grip. It depends on the compound of the tire. Secondly most of the time when people go with a wider tire they will also go with a lower aspect ratio to give the wheel a similar circumference to the stick tire size. For example say your stock tire is 245/45/19 you could Run a 275/40/19 so the the overall diameter is similar so a recal wouldn't be necessary.
I would play around a little with air pressures so see if that will help combat the wheelspin. Also just shifting smoother will limit the amount if spin you see when you shift. If you can match the revs better you will have less wheel spin.

MRGTX

Oh yeah. That's possibly the most important point of all...you could go wider and have less traction I you pick the wrong compound.

Reviews are subjective...ratings don't help much. If you can, hang out with some guys who race Mustangs in street classes to find out what works best.

Modshack

Wider tires do not necessarily equate to more grip. The shape of the contact patch simply changes since it is primarily determined by weight on the tire



Tread compound change is the best way to get more traction. Here's a good site that has an explanation of this as well as numerous calculators for sizing. Several pages worth, just click the links at the top for various tire subject areas:

http://www.carbibles.com/tyre_bible_pg3.html

As to disadvantages, a wider rear (staggered set-up) will result in more understeer which needs to be compensated for (sway bars, spring rates etc) if you want to retain the Mustang's relatively neutral handling characteristics.

5 DOT 0

Eric, the Boss cars run 255/40/19 and 285/35/19 tires. The staggered setup is common on many high performance cars. Get some 9's and 10's with the above and you'll be set. Or go 18's or 20's in the same width and adjust profiles accordingly. The Boss setup will work well on your car and there will be no need to adjust the speedo. Which wheels are you looking at? I really like the BBP wheels too bad there is no 10" wide version. I've been looking at the Ford Racing SVT PP wheels along with Forgestar F14's and CF5's. Good luck.

Kona

Wider tires would be worse on slick surfaces like cold/wet/ice/snow.

5 DOT 0

He lives in Bakersfield CA. You've obviously never been there before.

2012GT

Gus from Steeda told me that I could Run the 285 40 Nitto dr's on my stock 18" rims. I am satisfied with the rims on my car for now. I like the sleeper look. I assume it will be ok. They (steeda) run 275 dr's on on their 17x8 rim.

Everett

I have 275/40R17 on my stock rims. They bulge slightly but the traction difference is night and day

lemarin

look at the specs of the tires you're looking for and you'll see the range of rim width you'll need. 275's on 8" wide rim is really strange...

Of course cheaper wider doesn't means more grip, but here we're comparing wider tires for the same brand/model per example....

Everett

They look great and hook right up. Cheap *** sumis. I am pretty happy

SolidAxle

Eric,
I'm running a 275x40-19 Toyo rear tire which has a diameter (nominal) of 27.66" vs. the stock 245x45-19, which has a nominal diameter of 27.68". So, only .02" difference won't have any effect on the speedo, traction control, ABS, etc.

Without increasing front tire width, it is true that there is a tendency toward more understeer. I'm running a 255x40-19 in the front and don't notice too much difference. You can always install a slightly stiffer rear anti-roll bar (or less stiff front bar), or stiffer rear shocks/springs to counteract this.

The wider rear definitely helps w/ traction, I get much less intrusion from the traction control now although going from the all-season Pirellis to sticky Toyo rubber accounts for some of that I suppose. I haven't really noticed a loss in MPG, though I do have 3.73 gears and have never had stellar gas mileage anyway. Not much difference in ride quality either, slightly more jiggly I guess, but just barely.

BTW, my wheel sizes are f19x9, r19x10.