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Fitting Larger Tires on a Fox Body Mustang

Written By: Connor MC

Shop Fox Body ('79-'93) Tires

Having the right rubber under your Fox Body can be the difference between winning a race, or regaining control on a wet road. Be sure to equip your Mustang with the right tires for your planned use.

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Curious to find out if those bigger tires you've been eyeing up will fit your Fox Body Mustang? This guide shows you exactly what you'll need to do to fit those meaty radials or sticky slicks on your modified or stock Fox Body.

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Modifying Your Fox Body Mustang to Fit Bigger Tires

Say you want to get a massive 275/50 rear tire on your Fox Body Mustang. There are a few modifications that need to be done to accommodate this. In a previous article we confirmed a stock Foxbody (1987-1993) could not accommodate a tire and wheel larger than 245/50/R17 without modification (17x9 wheel) – otherwise the tires could rub or scrape against certain suspension and frame members. If running a 245/50/R17 tire/wheel combo isn’t enough for either your aesthetic or performance needs, it's possible to go bigger. However, as stated, it isn’t as simple as mounting the tire on the wheel and securing the wheel to the vehicle. Looking for different tire sizing calculations, or just want to see how much those new rims are going to throw off your speedometer? A tire size calculator will help you solve fitment and spacing issues, as well as give you insight into measurements and differences between tires.

  • The most cost-effective way of fitting big tires on a Fox Body is by rolling the fenders
  • Flipping the quad shocks around in conjunction with rolling the fender lip will allow you to fit a larger tire in the back
  • A stock Fox Body (1987-1993) can not accommodate a tire and wheel larger than 245/50/R17 without modification
  • Aftermarket control arms are the best method to increase room for bigger wheels and tires while beating the stock control arms in virtually every way possible

Needed Fox Body Rear Modifications

Roll the Fender: First and foremost, the cheapest (and most rudimentary) way to get a little more room in the fenderwells involves a hammer or baseball bat. Generally speaking, pulling out the hammer should be the last resort. In this case here, however, using a hammer to carefully roll the inner fender edge flat can yield a previous centimeter or two of additional clearance. What is meant by the inner fender edge? Well, if you reach up into the fenderwell and run your hand along the top most edge (do so carefully, it can be sharp), you will notice there is an outcrop of sheet metal perpendicular to the fender flare itself. During fabrication, Ford never bothered to flatten this edge down. A note of caution: quite often when hammering this area, the paint can crack. Using a heat gun to heat the area first can help, or better yet, there are specific automotive tools available to help the process (Some popular fender rolling options go for ~ $225 USD). Rolling the fenders will help fit a larger tire, but it will also give some extra vertical room for those that have lowered or will be lowering their Mustang.

Rear Fender Well of a Stock Foxbody
This particular car is running stock tires and wheels, so it has plenty of space. Note the quad shock visible behind the wheel (blue).

Additional Options For Fox Mustangs

Flip the Quad Shock: Further working with the idea to make what's already on your Mustang workable, if your car is equipped with quad-shocks, flipping them around in conjunction with rolling the fender lip will allow you to fit a larger tire in the back. Some guys go as far as to remove the quad shock completely, but this isn’t recommended as the quad shock is there for a purpose – to control the wheel hop allowed by the flimsy stock control arms during hard acceleration.

5-lug Conversion and Clearance

A popular mod for Foxbody owners, a 5 lug conversion will affect your Mustang's clearance. As mentioned earlier, a stock Fox Body (1987-1993) cannot accommodate a tire and wheel larger than 245/50/R17 without modification, which means you will have to adjust the suspension/wheel well areas if you are looking to fit a 255 tire of 18 inch wheel. However, a 5-lug conversion will allow you to fit larger brakes, giving you enhanced braking. If you are looking to fit larger tires on your Foxbody by means of a 5-lug conversion, be sure to first consider how you will modify your Mustang to accommodate it, whether that be rolled fenders or new suspension parts.

Replace the Stock Control Arms

The best solution also happens to be the most expensive (go figure!). The biggest problem in the rear of a Foxbody Mustang is the stock control arm geometry and accompanying quad shock. As stated, it isn’t a good idea to remove the quad shock and leave the stock control arm. However, replacing the stock control arms with an aftermarket design has a plethora of benefits. First off, aftermarket control arms no longer need the quad shock due to their superior design, strength, and geometry. With an aftermarket control arm, the quad shock is no longer needed (and probably won’t even mount). Secondly, aftermarket rear control arms are better packaged, meaning they take up less space in the wheel well. Even better, many aftermarket arms relocate the bottom coil spring perch slightly for maximum wheel clearance and better vehicle ride characteristics. So not only do you get more space for some massive rubber, but you also improve over the stock design in every department possible! Not a bad deal.

Working the Mustang’s Front

The front fenderwell of a Fox isn’t as big of an area for concern as the rear, namely because it is uncommon (and not particularly beneficial) to throw some fat tires up front. If you do need some extra space, the modifications necessary pretty much are the same as the back. The first thing to do is of course roll the fenders. Those with ‘91 and up Foxbody Mustangs are a bit luckier. As of 1991, Ford enlarged the front wheel wells, so you may not need to be as aggressive with your modifications.

After this, the major restrictions you’ll encounter are the front control arms and steering gear. Tight turns will often see the tires, and even the inside of the wheel, rub against the lower control arm. You can get additional clearance by installing aftermarket control arms. Like the rear, aftermarket units are not only stronger, but generally revise the geometry in a positive way as to augment handing and load transferring characteristics.

Front Fender Lip on a Fox Body Mustang
Looking straight up from the ground, you can clearly see the outcropping ledge on the inside of the fender. Rolling that flat will net some additional clearance both horizontally and vertically (the latter is great for lowered Foxes).
Fitment includes: 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, GT, Cobra, LX, SVO