Solid rear axle on a Mustang.

May 16, 2005 12:28 PM

The new Ford Mustang, just like the last one, "features" a solid rear axle. Ford (and her enthusiasts) claim that such a design is for "performance reasons." Is this plausible?

I always thought that an independent rear suspension was superior. So is Ford just making shit up, or is there some sort of trade-off (other than cost) of which I am unaware?

posted by Kwantsar to Science & Nature (11 answers total)

Best answer: No trade-off that I'm aware of. Ford spent a huge amount of money and engineering to make the SRA setup handle "just as well" as an independent one, and most reviews that I've read have said that you can "barely tell" that it uses such an archaic driveline. Ultimately, though, it seems that the reason they're using a SRA is the same reason that Corvettes still use a pushrod V8: American car companies are terrified of innovation in their "icon" models, and prefer to keep things the way they were back in the glory days, at any cost.
posted by saladin at 12:52 PM on May 16, 2005

Best answer: The reviews I've read -- while very positive about the Mustang -- all point to the solid rear axle as a place where the Evil Accountants got their way.
posted by ROU_Xenophobe at 12:57 PM on May 16, 2005

Well, people who prefer seat-of-the-pants acceleration (re: drag racing) prefer solid rear axles. Unless you have all-wheel-drive, which the Mustang will definitely not, a solid rear axle helps keep the most rubber planted on the pavement during hard acceleration. So when you take off at the beginning of a drag (or from a stoplight) with the most standard horsepower a Mustang GT has had, the solid rear axle keeps both rear wheels planted, thus the most power is transmitted to the pavement. You get the fastest, hardest start that way. I'm no pro drag racer, but you could probably look up things like 'weight transfer' along with solid rear axle and you might find out more about the pros. Also, I've read that all-wheel-drive can cure some of these traction issues. But no AWD for the Mustang as it is an economy, everyperson sports car.

For those who would say a Corvette, with IRS would beat a Mustang GT in the quarter mile, I would agree. But the Corvette isn't for people who drag race, nor does it have four seats. And it's quite a bit more expensive. Etc., etc.

I have a 86 Mustang SVO, which should have gotten IRS as it is more designed for autocrossing... You can transplant in the IRS from a 99 Cobra I've read.

But, again, I imagine this has most to do with Ford's belief that the Mustang's performance word-of-mouth (re: whether young men will like it and recommend it to other young men) will depend heavily on how well it does when you take it to a dragstrip. Or race at the stoplights.
posted by Slothrop at 2:01 PM on May 16, 2005

Well an independent rear is superior for handling but a solid rear is better for a drag car. I personally think the difference between the two probably isn't very significant for a street car.
posted by 6550 at 2:04 PM on May 16, 2005

In other words, do you live somewhere with corners? That's basically it: a solid rear is better in a straight line, not so good coming out of a bend. No bends, no worries.
posted by DangerIsMyMiddleName at 2:22 PM on May 16, 2005

These comments are a little too cynical IMHO...a solid rear axle has the advantage that the two rear wheels are always parallel. This has the effect noted above of being good for RWD drag cars. But is also is quite effective for road cars on smooth pavement. With a more sophisticated linkage (Panhard rod), solid axles are not bad at all.

IRS suspensions have an advantage on bumpy roads because of less unsprung weight and because the wheels move independently.

Ask anyone with an old Alfa racecar: solid rear axles can be very good indeed! And don't knock the new Mustang. Saving $200 on the suspension wouldn't have been done without a lot of thought. They already had an IRS in the old SVT Cobra and it wasn't that well loved....

BTW, I own Honda's, Toyota's, and a Mazda Miata race car (all with IRS), so no real bias....
posted by Instrumental at 4:12 PM on May 16, 2005

The "Best Answers", while appearing to confirm the author's own misconceptions/bias, are flatly incorrect.

A solid axle is better for drag racing, plus it's cheaper.

Independent rear suspension is better for handling and ride quality, so is generally considered "better" for street cars by car magazines, etc.

Mustang fans have historically been more interested in budget straight-line performance than handling & ride-quality, so YES it could be considered a feature.

I have both drag raced and road raced. on tracks, of course.
posted by LordSludge at 9:18 PM on May 16, 2005

LordSludge, it's only a "feature" if the car has enough power to be a competent drag racer. However, the vast majority of the Mustangs that will be sold to the American car buying public will be the wimpy V-6s, not GTs or Cobras, and in V-6 trim, the 'Stang is hardly a thrilling drag car. I could certainly be argued that the GTs and Cobras would benefit from a SRA in a straight line, but the base models?

Not only that, but Ford sunk a lot of money into trying to get that SRA to handle like an IRS. From what I understand, this new suspension is actually costing more than a comparable IRS as a result of the sophisticated engineering involved in producing it. What's the point, when 80% of the cars they're going into would have performed just as well, if not better, with a parts-bin IRS set-up? Automotive journalists have been asking this question since the new 'Stang was previewed last year, and the general concensus is that, by and large, a solid rear axle represents a historical continuity decision, not a performance one.

Sorry if I'm sounding too cynical, because I'm actually a big fan of the new Mustang, having test driven a GT a couple of months ago. I just sense, as others have before me, an over-reliance on tradition in the American sports car industry, at the expense of innovation.
posted by saladin at 6:19 AM on May 17, 2005

Response by poster: Hey, sludge, I marked those as best by accident. Actually, I marked the first one as best by accident, and marked the second to be consistent. Then I dropped the marking altogether.

Thanks, everyone, for your answers.
posted by Kwantsar at 7:54 AM on May 17, 2005

Best answer: Oh, great, Kwantsar. Thanks. Now I've got to take off my BEST ANSWER party hat and go and find the NOT BEST ANSWER YOU FUKCING LOOSER shotgun.
posted by ROU_Xenophobe at 9:33 AM on May 17, 2005

Hats off to ROU_Xenophobe, for a very impressive two "best"s in one thread!
posted by saladin at 1:03 PM on May 17, 2005