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Discussion Starter #1
Trying to decide wether or not it's worth it to get anything larger than a 17 X9 or 18 X 9 wheel at all four corners. I like the idea of having some big tires in the back to get a little more traction, but would a 315/35/17 tire be too big on a 10.5" wheel? would the traction gains for autocrossing or road racing be greater or less and would that size tire even fit on an '03 Gt? Just wondering, tell me what you guys think.
 

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Im running 265 35 18's on the front and 305/30/18's on the back. Kumho v700's Very happy so far.

Stan
 

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Discussion Starter #4
I am currently running the stock bullit wheels (17 x 8) with Nitto 245/45/17's up front and 275/40/17's in the rear. I was looking to get some nicer looking wheels to go with the paint job I have and was thinking about the 10.5" rear wheels that i saw online on a couple other cars. I thought they looked good, but if it would hurt more of the performance of the car then I'll just go with a nice set of 17 x 9's all around with 275/40/17's of a stickier tire.
 

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SCCARACERGT said:
...thinking about the 10.5" rear wheels that i saw online on a couple other cars. I thought they looked good, but if it would hurt more of the performance of the car then I'll just go with a nice set of 17 x 9's all around with 275/40/17's of a stickier tire.
Generally speaking, a Mustang suffers more from understeer than oversteer. This is very evident when autocrossing. Using a larger rear wheel/tire combination will exacerbate the problem. Not only that, but if you don't match the circumferences of the front and rear tires you can cause your ABS to malfunction. For those reasons and the fact that tire rotation can't be performed I would recommend using the same size tire/wheel on both ends.

I have found that a 17x9 Cobra R wheel is an excellent wheel for a very reasonable cost, I have three sets of them myself. The Victoracer V700 in a 255/40/17 or 275/40/17 is a good fit to the 9" wheel and will make the car a lot faster in autocross. The Victoracer is also a tire you can drive on the street, like to an event, without too much trouble.

Another good choice would be the Ecsta V710 in a 245/45/17 size. The V710 tends to run a bit wide and is a good fit on a 9" as well. I would not recommend using the V710 on the street as it is too soft and has no tread so it would be very dangerous on wet surfaces. In any event, I would suggest keeping your stock wheels for daily driving and getting a set of 17x9 wheels for autocrossing.
 

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Glenn,

One thing you told me was that in order to have a big overweight car corner like a smaller lightweight car that you have to have big tires underneath it. I don't understand how bigger tires and wheels would increase understeer(unless you mean more weight) I always thought the bigger contact patch the better.

I am running the V700 ecsta's the model that came out after the victoracer but before the 710. It does have some grooves and handles decent on the street in the rain and might be another choice for someone who wants to drive two and from the track on them.

Stan
 

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You can have greater overall grip and still have a car with more understeer.

By running a staggered tire setup, the increase in rear grip is disproportionate to the increase in front end grip. Front tires have a larger slip angle at the (now greater) limit, more understeer.
 

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If you decide to run larger rear tires plan on adding some rear bar like the steeda adjustable add on bar. That will cure the understeer. I run larger rears and ended up getting a lot more speed out of the corners due to less spin and got dang near double the tire life out of the wider rears. Before I added rear bar it would push the front end right out from under you with the larger rears.

The offset on the 10.5" wheels will not work on the front without spacers. This has been covered several times recently.
 

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Han Solo said:
The offset on the 10.5" wheels will not work on the front without spacers. This has been covered several times recently.
Unless you spend the necessary cash to get some custom wheels. A 10.5" wheel will fit up front if it has 6.25" backspacing.

Han Solo is correct about the adjustable rear sway bar. With a good rear bar you can tune out a lot of the understeer. I run the MM bar which IMHO is the best one you can get for a Mustang. It is available in 5 different sizes and is adjustable to 4 different levels of stiffness. However, I still prefer running the same size tire/wheel front and back to allow for rotation. Rotation will greatly extend your useable tire service life.
 

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Yeah I was referring to the off the shelf wheels like the wheel replica brand.

Glenn has those high dollar CCW's in 10.5 or 11 with a custom offset. When I add up all I've spent testing different sizes of the cheapies I could have probaly bought a set of CCW's and been ahead of the game.
 

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Han Solo said:
Yeah I was referring to the off the shelf wheels like the wheel replica brand.

Glenn has those high dollar CCW's in 10.5 or 11 with a custom offset. When I add up all I've spent testing different sizes of the cheapies I could have probaly bought a set of CCW's and been ahead of the game.
Heh heh heh... maybe so. They are CCW's in a 10.5" and I got a really sweet deal on them by driving up to Daytona and talking to the business owner, John Purner. Turns out he was an avid autocrosser some years ago and knows a lot of the very same guys I race against. We chewed the fat for a while, then he gave me a tour of the factory. Really nice guy, oh...and did I mention he gave me a really sweet deal on the wheels? :)
 

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huesmann said:
But you'll still have a greater limit, which is the point, isn't it?
Well, no. Balance is the point. An unbalanced car, e.g., one with massive understeer, is a ***** to drive at the limits.

Bigger in back is fine for the street where looks trump performance (you really shouldn't be testing understeer/oversteer limits on the street, now should you :) ).

For auto-cross/track work equal size tires/wheels will almost always work better on a Mustang (one exception might be for those with very high horsepower). A point of data, Dave Schotz won ESP at Nationals a few years ago running 275/17 in front and 265/16 in back.

For those wondering how big is too big - there are three very quick local Camaros (one won ESP at Nationals but was DQ'ed for a modification that was done wrong) running 335's front and rear! I'm not claiming that's the hot ticket for a Mustang, though.
 

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Discussion Starter #14
Thanks guys. I think I'm going to go with the maiximum motorsports 18 x 9.5" wheels all around. They weigh only 24 lbs. and look awesome. I do have the Steeda adjustable rear swaybar all ready so I'll stick with that for now. One of my gifts for this holiday, which I'm not supposed to know about, is the 5-link system. So with that on my rear will pretty much be set. The reason I asked more about the rear of the car oversteering is because I had installed the koni single adjustables all around, not knowing the difference at the time between the single and doubles,

with the front on the stiffest and the rear backed off a dew nothces, the car realy wants to oversteer. I do not yet have a front swaybar in it, which will come soon, but man does it want to swing around on me. I thought it was my driving at first, getting a little too happy comming out of the turns, but I've been adjusting my style and it still feels the same way, not as bad but still wants to come out.

The car does have 3.73's in the rear and makes a little over 300 hp, so i don't think it's too much power. The only other thing I can think of is the tires themselves, which obviously will also be changed with the new wheels.
Once again thanks guys, I realy do appreciate the help. Later.
 

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Why run the 18s on the track? Do you like spending $50-75 extra per tire for the 18" rim?
The 17" Konig Villains are the better choice, IMO. You'll be able to buy 5 275/40r17 V710s from tirerack.com for what 4 275/35r18s will cost you. This hobby costs alot without trying to make it more expensive. Ultimately, its your call but the 18s on the track would put me in the poor house. I'll run them on the street but thats it. Good luck and post pics of what you decide on. Anthony
 

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SCCARACERGT said:
I do not yet have a front swaybar in it.

The only other thing I can think of is the tires themselves, which obviously will also be changed with the new wheels.
You don't have any front bar at all on the car?

While some Mustangs may carry a bit too much in the front stabar department, I have never heard of anyone attempting to run auto-cross or track events without one. I know drag racers sometimes drop the front bar for weight loss/transfer reasons. I can't imagine trying to sort out handling before fitting a front bar. Little wonder it oversteers.
 

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I have the steeda adjustable rear swaybar as well. What setting is best for us with it?

Stan
 

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Discussion Starter #18
I have the stock front swaybar on the front right now. The last time I ran in an autox event was a little over a month ago, and all I had was Steeda sport springs, koni's, strut tower brace, and c.c. plates. Since then the car has been in and out of the shop with mods as my budget will allow. Now the car has the 5-link with the adjustable rear swaybar (which I haven't figured out the right setup for it yet), I just ordered the front swaybar, aluminum rear lower control arms, full length subframe connectors, ball joints, bumpsteer kit and some cobra brakes with brembo rotors all around. So the car is not done yet, and won't be done for at least another 3 weeks, or whenever the stuff arrives. I do most of the work myself with my brother, except for welding. After all that stuff goes in I plan on tackling the wheels and tires.

I did a little more reasearch on the tires and you're right rfloz, I don't want to realy spend that much money on tires. So it'll be some 17 x 9 wheel, as soon as I make up my mind on which ones to buy.
 

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SCCARACERGT said:
I did a little more reasearch on the tires and you're right rfloz,
ramnstang said:
Why run the 18s on the track? Do you like spending $50-75 extra per tire for the 18" rim?
The 17" Konig Villains are the better choice, IMO. You'll be able to buy 5 275/40r17 V710s from tirerack.com for what 4 275/35r18s will cost you. This hobby costs alot without trying to make it more expensive. Ultimately, its your call but the 18s on the track would put me in the poor house. I'll run them on the street but thats it. Good luck and post pics of what you decide on. Anthony
I gets no respect I tell ya, no respect :shakehead
 

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SCCARACERGT said:
I have the stock front swaybar on the front right now. The last time I ran in an autox event was a little over a month ago, and all I had was Steeda sport springs, koni's, strut tower brace, and c.c. plates. Since then the car has been in and out of the shop with mods as my budget will allow. Now the car has the 5-link with the adjustable rear swaybar (which I haven't figured out the right setup for it yet), I just ordered the front swaybar, aluminum rear lower control arms, full length subframe connectors, ball joints, bumpsteer kit and some cobra brakes with brembo rotors all around. So the car is not done yet, and won't be done for at least another 3 weeks, or whenever the stuff arrives. I do most of the work myself with my brother, except for welding. After all that stuff goes in I plan on tackling the wheels and tires.

I did a little more reasearch on the tires and you're right rfloz, I don't want to realy spend that much money on tires. So it'll be some 17 x 9 wheel, as soon as I make up my mind on which ones to buy.


What adjustable rear sway bar do you use with your 5 link and is it a 5-link 1 or 2?(I'm assuming you are talking about the steeda 5-link)
 
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