So i'm apparently having an Argument about the Mustang.

I'm on the FT86Club forum and have suddenly been shunted into this argument/debate about the Mustang. I'm submitting that i believe the Mustang should have IRS and that the Live Axel is really holding it back.

These guys are not thrilled about that-- telling me to cite where it's proven IRS is better. And they argue that it's way more expensive and that they could pick out something similar to gripe about in every car.

Am i really in the wrong here? I've heard on this forum how the suspension is pretty dismal until you dive into it with new struts, springs, sways, ect.

The live axle in the new Mustangs is pretty good.

The Mustang GT vs M3 comparo proved that around a track. Would an IRS be better around a bumpy track? More comfortable as a DD, possibly.

But I don't think it's worth the added cost.

IRS is better if you want more interior room, or more road isolation.

People aren't terribly thrilled with the IRSs used in the late model GMs. Or the IRS in the Cobra.

Generally speaking, the added weight of an IRS setup negates the improved handling.

A well setup live axle system will usually be so close to an IRS that it doesn't really matter.

Have a look at how competetive a Lotus Super 7 can be even though the design is over 50 years old.

Shawn

I'm no expert but I hear the Cobra IRS was far inferior to the live-axle setup.

Ironically, guess what noteworthy 'handling first' sports car had a live axle out back? The Toyota AE86...

If you were talking about the '85 Mustang GT I once had, I'd agree with you. But Ford has done an incredible job with the live axle setup on the new mustang. I don't think it's holding it back at all. And for drag racing it's preferred.

Oh man. I'm wrong. ..I know what i have to do-- burn down the FT86Club Forum.

If anyone asks, i was never here.

I sure don't see IRS cars dominating any of the autocross pony car classes. On a track, the only advantage I see from IRS is rear camber. And if you really want to, you can camber a solid axle, too.

One upon a time the "unsprung weight" thing was big. Now with new technology, this no longer seems to be as big an issue.

Will wrote: And if you really want to, you can camber a solid axle, too.

...and it can be done on a challenge budget

It's hard to care much about shaving unsprung weight when you're putting 20" wheels and 13" rotors on a 4000lb car.

if I remember correctly, one of the problems with the Cobra's IRS was that they were forced to use the Live Axle's pickup points?

Yes, in theory an IRS is better. Yes, in reality the S197 has a pretty damn good live axle.

It's kind of a loosing argument either way.

A crappy live axle set up will be bad. But so can a crappy IRS be.

An interesting reference, which I'm biased toward, of course...

Back in the early 60's, Alfa was getting very done with the 750/101 chassis, and working on the later 105/115 car. In the middle of that was also the transition from the SZ to the TZ cars- SZ being late 101 cars. If you look at teh TZ's close, you can see a somewhat early front suspension for the 105 cars- traiing upper link with a lateral, lower A- decent for '63. The rear was an IRS set up. Not a great one. It had a major fault that it would toe out under compression, which made handling very tricky- which ended up being a lot harder to set up than the stick. The 105 ended up with a live axle.

Full blown race cars later did have full independant, but the GTA, GTA Jr, and GTAm's all used a axle....

I digress. IMHO, the current live axle in the mustang is very good. Not great, though- pretty darned close- but there are some great live axle set ups out there.

In reply to mad_machine:

Yes. That IRS is supposed to be easy to swap into any of the Fox body cars. I've heard of some folks swapping them in for ride quality improvements over the stock live axle in SN95's and such and the biggest thing to change is getting a Cobra cat-back exhaust.

I think a better route is a Steeda 5-link or the Maximum Motorsports torque-arm or other similar setups and keeping the live axle but if someone was handing over a Cobra IRS for no money it might be a tempting swap as long as the car is only seeing street use and no track time.

V8Supercars, Nascar and many more National and International high powered tin top classes use live axles exclusively for the $ savings, simplicity and strength.

IRS is hands down better on rough surfaces but on a good condition road, there is little, if any, advantage.

If you are talking fox body, its a bit like arguing between having a pimple in the middle of your forehead, vs a pimple at the tip of your nose. Neither is really debilitating, but you really can't make much use of either one without some pretty serious makeup.

Having IRS means you can adjust toe,camber, and other stuff out back, something you can't do with a solid axle. Outside of road racing, I don't see IRS having a big advantage over a solid axle, and for drag racing, it's actually worse. It also helps to have a well designed IRS over something thrown together to fit an application. Best advice is to stop getting sucked into stupid arguments with people who don't know what they're talking about.

As a former owner of an 1999 Cobra, the IRS Ford designed for that car was a compromise at best. Yes, it handled broken pavement pretty well but due to the packaging restraints, it was pretty poor as far as IRS setups go.

And you guys are correct, it was designed from the get-go to utilize factory solid axle mounting points. You could bolt that IRS into pretty much any Mustang built after 1979 with minor modifications.

1999 and 2001 were the worst versions. 2003-2004 had lots of changes, including stiffer subframe bushings to reduce wheel hop and stronger halfshafts. Something in my '99 was always breaking. I grenaded the differential assembly twice and broke the driver's side c-clip twice. I wanted to swap a GT owner straight across for their solid axle 8.8. All the IRS parts were damned expensive to boot. Funny thing was is that the Lincoln Mark VIII used the exact same aluminum differential case and halfshafts as my Cobra. Guess which parts were cheaper?

Forget drag racing with that IRS. I would get wheel hop so bad it would shake the transmission out of gear. You couldn't launch that car at all.

I'm still kinda bitter about that moneypit LOL

ncjay wrote: Having IRS means you can adjust toe,camber, and other stuff out back, something you can't do with a solid axle.

Ah, but having a solid axle means you don't have to screw with any of that...

The way I see it, all of the best front engine/rear drive rally cars were solid axle, even in the Group B era where links to production cars were tenuous at best. These are cars that need to be fast and reliable over real roads. If IRS would have been a performance improvement, it would have been used.

Oh and I forgot all of the drivetrain slop. Driving in a parking lot in first gear was a herky-jerky affair. Too many mechanical couplings...

Well setup solid axle > poorly designed IRS

Knurled wrote:

ncjay wrote: Having IRS means you can adjust toe,camber, and other stuff out back, something you can't do with a solid axle.

Ah, but having a solid axle means you don't *have* to screw with any of that... The way I see it, all of the best front engine/rear drive rally cars were solid axle, even in the Group B era where links to production cars were tenuous at best. These are cars that need to be fast and reliable over real roads. If IRS would have been a performance improvement, it would have been used.

group b rallying? The top runners were all IRS cars. Most of them were mid/rear engined.. kinda makes it hard to use a solid rear

Note qualifier front engine/rear drive. Yes, mid-engine cars like the 037 had no choice, did they?

The Celica performed rather well despite its not having all wheel drive. The Manta 400 did EXTREMELY well, despite being 2wd and down on power compared to the competition.

or these

ncjay wrote: Having IRS means you can adjust toe,camber, and other stuff out back, something you can't do with a solid axle. Outside of road racing, I don't see IRS having a big advantage over a solid axle, and for drag racing, it's actually worse. It also helps to have a well designed IRS over something thrown together to fit an application. Best advice is to stop getting sucked into stupid arguments with people who don't know what they're talking about.

Well, actually it's turning out that i'm the one who apparently don't know what i'm talking about. :/

Also, can you really not adjust the Mustang's rear camber at all?