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R P - 03 Aug 2005 18:14 GMT

Why did Ford go back to a solid rear axle in the new Mustang? Are they
all that way? No options for IRS?

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Michael Johnson, PE - 03 Aug 2005 18:51 GMT

> Why did Ford go back to a solid rear axle in the new Mustang? Are they
> all that way? No options for IRS?

It never "went back" as is has always had one. The only Mustang to have
an IRS was the '99+ Cobras. The main reason they stayed with the solid
axle was for cost savings. They have redesigned the solid axle to
perform much better than on past Mustangs. Most reviews have praised
its performance considering its design is not IRS. One other reason is
that many, if not a majority, of Mustang fanatics prefer the solid axle
for its light weight, strength and simplicity for those that change
gears, axles etc. It really didn't matter to me which way they went
because I can see the value in both axle designs.

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R P - 04 Aug 2005 14:21 GMT

Thanks!.......I wasn't aware that only the cobra's were IRS. I thought
after 99 all were.
Years ago I had a Shelby GT-350, {66} I set the front-end up to "R"
model specs. & it handled very!! well.
Never should have sold it :(...........Ron

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Fao, Sean - 04 Aug 2005 14:53 GMT

> It really didn't matter to me which way they went
> because I can see the value in both axle designs.

For somebody that knows practically nothing, how much *cornering*
advantage do you actually gain by having an independent rear suspension?
I know a lot of the ricers like to brag that they have IRS, but most
of these cars are FWD so it's a little different.

For off-road applications, I can imagine that you'd have a major
advantage by going with an IRS. I'm not really sure about a Mustang,
though.

On a side note, I will mention that when I had my 02 Mustang GT
convertible (sold it back in November :-( ) there was this one section
of road that always seemed to throw me all over the place. It's a
right-hand corner with pot holes on the inside. If I didn't stay to the
outside of this corner, my rear end would bounce all over the place.
This was unlike my friends 1992 Honda Civic VX (which I would assume has
IRS since it's FWD) that was barely affected by the bumps. Would IRS
have helped me in this situation?

Signature

Sean

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Michael Johnson, PE - 04 Aug 2005 15:37 GMT

>> It really didn't matter to me which way they went because I can see
>> the value in both axle designs.
[quoted text clipped - 16 lines]
> IRS since it's FWD) that was barely affected by the bumps. Would IRS
> have helped me in this situation?

Yes it would have because the IRS is better when the road has
irregularities (i.e. potholes etc.) but on relatively smooth roads the
difference isn't nearly as great. While overall the IRS is a better
suspension from a handling aspect, like most things, it has trade-offs.
To make it as strong as a solid axle adds weight to a design that is
already heavier. It is more costly. Also, IMO, IRS can't touch a well
built solid axle at the drag strip. The '03-'04 Cobra owners that are
serious about drag strip performance ditch the IRS and plug in a good
old 8.8" rearend.

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Fao, Sean - 04 Aug 2005 17:12 GMT

> Yes it would have because the IRS is better when the road has
> irregularities (i.e. potholes etc.) but on relatively smooth roads the
[quoted text clipped - 5 lines]
> serious about drag strip performance ditch the IRS and plug in a good
> old 8.8" rearend.

That's what I figured. And I agree; I can't see how IRS could even
begin to be as reliable as a solid rear axle on the strip. That's why I
wanted to stress cornering abilities, as this is where I tend to believe
IRS shines.

Like you said, both have advantages and disadvantages. I'm personally
more interested in road racing (yes, on the track where that type of
driving belongs) than drag racing, which is why I'd probably opt for a
IRS over solid rear axle if I were building myself a race car.

Thank you for the information,

Signature

Sean

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