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Originally Posted by dollarbill  I've never heard of 19X10.5s fitting on a stang. The biggest I've heard of on a 99-04 is a 18x10, which you can put a 305/30/18 tire on. If you wanted to stay with a 17 then 17x10.5 fit with a 315/35/17. I think if you go bigger than 18 then you can't get them as wide as with the smaller ones. |
Dollarbill has it pretty dead on. I run 10.5x18's on the back, and 9x18's on the front. I have seen a few people with 19's, but they were custom fitted, and I have see one or two show cars with 20's, but they had been extensively re-worked and probably not a good daily driver at ALL!
It is possible to run really wide tires IF you have wheels with the proper offset. This might result in the tires and wheels sticking out of the rear fenders a bit. Adding spacers to gain offset works the same way, allowing very wide tires to be run on the rear (FRONT wheels should NOT be treated this way, since steering is affected and they will hit suspension and body components as they attempt to travel through their normal steering arc). I know several folks running 335 tires on 10.5 or 11" wheels (the 11" wheels were custom made, though perhaps there are now some that come that size).
Tire width is NOT defined entirely by the metric size ratings (ie, 305, 315, 335, etc). Tires have different design characteristics that also get involved. I've seen 295 tires that are physically wider than 305's because their sidewalls bulge outward more. Tires with low profiles, stiff sidewalls, AND square shoulders will tend to be narrower through their cross-section than the same size tires with rounded shoulders and soft sidewalls. (Generally, drag radials have wider cross-sections than would be seen on a regular summer street tire). Contact patch varies for the same reasons.
IF your wheel/tire choice does make contact in the rear, there are several options.
1. Wheel spacers. If you re NOT going to be doing lots of high rpm dump the clutch launches, you can add a high quality spacer and gain the needed offset that way. If you ARE building for the drag strip, you are barking up the wrong tree and need to backup and re-think your ideas. 16 or 17" wheels are the correct size, and sticky drag radials or slicks are needed.
2. Reverse the quad shocks. By flipping the quad shocks around on their perches, you gain a little clearance at the top for the wheels and tires. This can often give you what you need.
3. Remove the quad shocks. This REQUIRES upgrading the LCA's (lower control arms) at the same time to keep the rear end under control. Since the LCA's are known weak points during quarter mile action on these cars, this will pay benefits in other ways as well.
As for dropping the front end more than the rear, this can be done safely without affecting handling TOO MUCH IF you do it just a little...
Say, drop the front 1" and the rear 3/4", or 1.2" front and 1" back. Extreme differences (2" front, none back) will upset the car's balance and hurt handling on the street.
OK, the short skinny about dropping the front end is that dropping it up to 1.2" is OK, but you are probably smart to simultaneously plan to replace your struts and insulators at the same time. The stock struts will wear quickly because the new, lower ride height will put a strain on them and wear them within a narrow band which they were not designed to operate within. If the car already HAS 80,000 miles on the original struts, they are shot anyway. Replace them with a quality adjustable strut that can offset some of the ride harshness which will come from the shorter, stiffer springs.
The same principals apply to the rear shocks.
If you are like most of us, you will end up setting the struts and shocks to their softest settings for everyday driving, and firm them up for the track (or set them full soft front, and full hard rear for the drag strip, etc, etc, too many variables to really guess).
1999 Mustang GT What is the widest wheels I can go with? 
