Tire, Wheel and brake questions.

tommyroc said:

255/40/18 front and you can squeaze a 285/40/18 in the rear, thats what I'm going to put on when I get those same rims from my friends GT. As for road noise thats subject to individuals, what might be noisy to you might be fine for me. I'm going with a set og BFG KDW the ones with the "shark fin" like tread, they're soft so they wont last long but I here from a lot of people with different cars that they GRIP!.

Click to expand...

jlisle01 said:

I have run the KDW's (the traditional tread, not the funky new tread design) on the track and yes, they are great for cornering. Anyway, I'd ditch the stock wheels first thing. One of the best improvements you can make in every department is wider wheels and tires. I love the deep dish look, but if you are planning a brake upgrade those stock rims or deep dish aftermarket rims will seriously limit your choices. I'd look around for wheels that fit the GT500. They're the right size for the car and will leave you with the Shelby brakes as a possible option later on.

Click to expand...

LV51FER said:

As a sort of rule of thumb, a 255 is a good width for an 8" rim and something like a 275 for a 9" rim. The idea is to have the sidewalls reasonably vertical to the rim bead.

Personally, I tend to go with 275s for maximum grip without making the car look over-tired but a 255 is perfectly adequate and it's worth distinguishing her ebetween grip and handling. Grip is something any car can have but handling is the ability to catch and control the car through corners and ultimately, balance. A car with no grip can be a fantastic handler (Mini, Lotus Elan, Lotus Elise) as long as you can catch it and power through a corner in a balanced way. Cars with too much understeer just plough straight on and cars with too much oversteer will spin.

A car with a surfeit of grip isn't necessarily a good handler either because when the grip runs out, the car can snap into oversteer and if the steering is too slow or too quick (TVR), the car is lost.

Right, so the Mustang has good balance and is a good handler so do you want lots of safe grip with little chance of snapping the tail out or do you want to have a little more fun with less grip.

On the tire front, softer tires will give you more grip but wear faster. Low profile tires will indeed take some of the slack out of the steering. The stock 55 profile tires flex and the car will ultimately feel less responsive as the tire flexes. Like anything, the less something can flex, the more immediate the response. However, as there is more wheel and less air, the cushioning effect is less and it will transmit more noise. Tires vary as to the noise they make so you'd have to read some reviews on that score.

I'm in the UK so not sure what you have over there. Goodyear GSD3s get great reviews. I use Dunlop Sportmaxx tires. Not tried the BFGs or Nittos.

Click to expand...

jlisle01 said:

Whoa! Lot's of questions. First off, no, most of the big brake kits will not fit the factory Mustang GT wheels and the "deep dish" type wheels. You can probably mount a 265 to a 8.5 inch wide wheel but it will bulge out a little and as someone else has pointed out, you want the sidewall to be straight down from the rim bead. I suggest you look up the specs for various tires from the manufacturer. Here's the specs for the ever popular BFGoodrich GForce KDW, which by the way, is also very quiet for a tire with this level of grip.

http://www.bfgoodrichtires.com/specs/g-force-t-a-kdw/22.html

Most tire manufacturers have this data available on their websites and it's a good source of information. Besides the range of tire widths that will fit on your wheels you'll also find the number of tire revolutions per mile for each size tire. That is the number your flash tuner will ask you for when you calibrate the speedo. At least, that's how my XCaliber tuner works. A tuner is a great tool, I'd recommend one to anybody who's going to mod their car. Another great source of information is The Tire Rack. They are very active in grassroots racing and most of the guys that man the phones there are autocrossers who know their stuff.

I really hate to recommend wheels and tires because peoples tastes vary greatly and what I think looks great may look like a die cast turd to you. However, I'll refer you to the Tire Rack again here:

http://www.tirerack.com/tires-techpage-1/58.shtml

You'll notice that to decrease under steer (which the Mustang has in abundance) they recommend a wider tire in the front than in the rear. Now, that's obviously going to look pretty stupid so I wouldn't go that far but for that reason I would not recommend staggered wheel sizes. If you want to set your car up for handling, keep the wheels the same size all around! I run a 18x9.5 inch wheel all around. It's a Kazera KZA in the silver painted variety. I like them and they are just about the largest wheel you're going to fit in the front wheel wells. It's also the same size that Steeda runs on their Q series and that Ford puts on the GT500. Steeda also makes a number of wheels that will fit the S197 Mustangs. Whatever you get, if it will fit a GT500 then you can go to a Shelby brake setup later. There are several people (GEF Racing comes to mind) that sell the Shelby brakes as a package deal and as far as I can tell, that's one of the most cost effective ways to get a set of Brembos on your car. And that's about enough so I won't even start on the whole brake cooling thing!

Click to expand...

LV51FER said:

Powersliding is over-rated and there's no reason you should ever do it on a public road because it so easily goes wrong.

To calculate the difference in rolling radius and speedo error, put in the original tire size here and then put in your alternative tire to see the difference in your speedo. Often, it's not so far out it matters:

http://www.tyretraders.com/Tyrecalculator/

This site tells you all you need to know about tires:
http://www.carbibles.com/tyre_bible.html

This explains something about the theory of tire suitability:
http://www.dunloptire.com/care/widthRatio.html

This will tell you the rim width for a given tire from which it seems 255 is the max you can get on an 8.5" rim.
http://www.tyresite.com/tyrecalc.asp

Click to expand...

jlisle01 said:

Oh, by the way, I'm glad to hear someone else who's interested in doing some real driving in a (gasp) Mustang. I'm going to warn you though, putting a car like this on the racetrack is addictive. Don't say I didn't warn you, but just sos ya don't lose interest here's a teaser. Oh, and this was on a set of KDW's. In the vid, I'm a little exasperated because I've been following these two guys for a whole lap now and the guy in the Roush just won't point me by. At the Shelby meet you were required to get a point by from the other driver, which really stunk. Anyway, that supercharged Roush 427 was pulling me on the straights but was holding me up in the corners, hence the foul language. Sorry. And before anyone asks, yes, my little pass in the corner move there (not to mention it being without a point by) did earn me a "wee chat" with the corner worker after the session.

http://smg.photobucket.com/albums/v727/jlisle01/?action=view&current=MyMovie.flv

Click to expand...

jlisle01 said:

Well, yes, but it has more to do with my knowing the track better than it has to do with the car. Still, it's gotta bring a smile to your face as you watch the $150,000 Ford GT recede into the distance in the mirror of your $28,000 Mustang. Ha Ha! The joys of corner carving after a few rides with an instructor. Which brings me to my last piece of advice and it's one I feel assured you will not be able to find fault with....money spent on track time with an instructor will beat an equal amount spent on mods every time. No B.S.

Click to expand...