New IRS for Fox Body Fords Makes Corner Carving Less Taxing
Speaking as Hagerty’s resident Fox Body fanatic (1979-93), there’s not much you can’t do with Ford’s versatile vehicle platform. But there’s always been a final frontier: to make these lightweight, highly customizable vehicles inherently more refined with a fully independent suspension (IRS).
While Ford did us all a solid by adapting the IRS from their MN-12 platform to the 1999-04 SVT Mustang Cobra, those parts are thin on the ground in 2024. Plus they are all used by now, and benefit from aftermarket upgrades to handle track use and high horsepower powertrains.
RideTech now has a solution that seems to check all the boxes, and it’s based on the well regarded 2015-23 Mustang rear suspension. This suggests RideTech’s kit will be readily available, well-engineered, and possibly even affordable compared to prices for used Cobra IRSs online. But at $4500 plus ancillaries, perhaps two out of three is good enough?
What you see pictured above is $4500 from RideTech, but you still need a 2015-23 Mustang differential ($350-ish used from LKQ), custom CV axles ($395), caliper brackets ($120), coil overs ($840), 99-04 Cobra cat-back exhaust ($800-ish), and a rear anti-roll bar if so inclined (for $375). A total of about $7380 for an independent rear suspension upgrade isn’t necessarily cheap, but plenty of big dollar Fox Body builds will only get more appealing with this IRS in their portfolio.
And it’s not just Mustangs, as the Ford Fairmont (1978-83) and the Ford LTD (1983-86) are known to readily accept any Fox Body Mustang rear suspension upgrade with ease. (Other Fox Body derivatives may require a bit more massaging to work, in my experience.)
There’s a chance that RideTech’s IRS system might spur similar efforts from famous Fox Body suspension gurus like Kenny Brown and Griggs Racing, but for now RideTech seemingly owns the (after)market. So if your Fox Body is ready for the final frontier, RideTech has what you need to finish the mission.
I recall being at the Pontiac headquarters in the early 90’s. A gold Trans Am rolled in and had a C4 suspension in the rear.
The engineer said the 4th Gen was designed for it but they never got the go ahead.
Imagine a WS6 with that?
That would have been such a fun car. I would be curious to see this on a Fox body LX car or something like a Lincoln Mark VII
I had an 89 and 91 5.0 Mustang, and despite their reputation, I never found them to be particularly poor handling cars. It will be interesting to see if someone comes up with any numbers (e.g. skid pad g’s, comparative lap times) of these IRS packages vs solid axles to see if they are really worth a healthy chunk of the value of the car.
They aren’t poor handling, but they aren’t good, refined handlers. IRS fixes a lot of that (the rest is addressed with components that tweak the front end geometry).
I just saw a YT video of Ridetech’s test mule. It has this IRS set up, and a short/long arm (SLA) front end! That’s what I want to complete my ’93 LX suspension upgrades. I have a Griggs set up on the backend. It would be too much to switch to the IRS. But a professionally made IRS would be sweet!
I have a 89 Fox Body GT
That would be cool in a Lincoln mark vii, but sadly not worth it
Not poor handling cars, AWFUL handling cars would be more like it. Junkyards were full of these cars in the late 80’s. There’s a reason the Mass. State Police called them “kid killers”. Short body, solid rear axle, drum brakes and awful weight distribution. They were cheap but dangerous as hell! You get what you pay for.
The weight distribution was bad, which meant they could get very loose on overly aggressive acceleration. A useful handling characteristic in the right hands, but nothing a novice driver should be messing with… and of course that is primarily who drove them back in the day
Charles B – I can imagine someone doing an IRS Mark VII . Why wouldn’t you if the cost wasn’t of any real consequence.? The LSC still has a certain sporty elegance. Formal but not too uptight. If you rubbed on one enough I’m sure you could probably surprise more than a few people with just catalogue parts and be the only kid on the block. As an investment no. As a some days driver… go for it I say!
Well, I suppose that there are a few retired guys that realize that they have more money than years left and buy things like this, but the average Joe can’t even entertain the thought of this upgrade. I’ve been driving my 90 convertible daily for over 30 years now. It’s kind of a sleeper with a blown 351, but it’s just a good fast and fun cheap car to own. I do notice that there are very few left on the road. Surprising that anyone is making kits like these- it’s nice to see, though, when generally performance parts are not as available as they were in its heyday.
Mercury Zephyrs also can utilize this IRS.
Ford SVO department wanted to put an IRS setup on the 1986 SVO Mustang. Ford had different ideas because it was too expensive