So, why a cobra IRS

[cavepony]

As many of you recommend, I am looking at the end result before I go mod crazy or just buy a snake.

I have been looking into supension mods for the GT for months now. The availability of Cobra IRS's make it pretty tempting. In fact, I had a dude within 75 miles of me who was willing to swap for my live axle. I called Steeda, since they are pretty much half way between us, to see if they would do the swap and what they would charge. Their answer was pretty blunt.
"Other than the wow factor, why would you want to do that?. You can make the live axle handle better."

I have read everything I can get my hands on and what I think I have concluded is that unless you go with an aftermarket IRS (like Griggs -$$$$$) you cannot make a stock Cobra IRS (even modded) handle noticeably better than a live axle (modded) if you put roughly the same money into both.

Now, I like to drive hard, but there isn't much of a challange in S Florida.

I am not likely to notice the difference if it is at the extreme end of the spectrum.

I think the IRS may ride better and may be better on a bumpy turn (which are non existent down here). They also add weight to the rear and decrease the unsprung rate.

What does the peanut gallery think?

 

[tomustang]

I have been looking into supension mods for the GT for months now. The availability of Cobra IRS's make it pretty tempting. In fact, I had a dude within 75 miles of me who was willing to swap for my live axle. I called Steeda, since they are pretty much half way between us, to see if they would do the swap and what they would charge. Their answer was pretty blunt.
"Other than the wow factor, why would you want to do that?. You can make the live axle handle better."

The stock Live axle can never fell the same as the IRS, and for handling it's another ballpark. Live axle will take alot to catch up to a IRS, Mildly modded Live axle is not as good as a stock IRS.

Go for the IRS if you're not getting a Cobra.

 

[cavepony]

The stock Live axle can never fell the same as the IRS, and for handling it's another ballpark. Live axle will take alot to catch up to a IRS, Mildly modded Live axle is not as good as a stock IRS.

Go for the IRS if you're not getting a Cobra.

So is Steeda just trying to push 5 links? That would suck if that's the case.

I lwould prefer an IRS, but the Cobra IRS is kind of a compromise.
Do you have any specifics on why it's better? Most of what I have read points to a LA advantage on skid pads, slaloms, and road courses, or not a significant difference. (talking stock mustangs here) I would love to see a real heads up comparison if you can find a link. I would jump all over an IRS if it is really that much better. May even get me to buy one of those reptiles.

 

[tomustang]

The best thing to consider that your car isn't a 24/7 race car. It says Hi to every road bump and pothole, Any Solid Axle is worse than an IRS in a street prediciment because when one tire (Solid) hits a bump it will affect the opposite tire. resulting in a negative affect on handling. Now in a IRS only one tire will feel the bump while the other side (not being connected) won't even know there was a road bump cause it didn't hit it.

 

[tomustang]

So is Steeda just trying to push 5 links? That would suck if that's the case.

Of course, 5 Links are great for a track, But 3 Links are better. But still you can mod out an IRS to have a better overall handle on track and street.

 

[dew22]

03 gt with 04 cobra IRS and I couldn't be happier.

 

[White Stang]

Live axle if your going to make power Alot cheaper to build up and alot less to break under heavy load. If you want to say you have a Cobra IRS and use it as a daily driver do the swap. The guy wanting to swap is probally making good power and needs to get it to the floor at the drag strip. Personally I would not even consider that swap But I drag race

 

[DBMSTNG]

you can make the solid axle handle just as good as the IRS. it's not hard to do. the only real advantage to the IRS is the ride comfort and control over bumpy surfaces. the IRS actually weighs quite a bit more than the solid axle. anyway, i'd probably switch to an IRS if i got a good deal.

 

[hognutz]

The road tests I have seen on the cobra IRS is not overly impressive. If I remeber the f-bodys with a live axel held more g's on the skid pad than the cobra.

I would be that a MM or steeda modified live axel would hand a cobra it ass around the track. I could be wrond though.

now if You get the kit for free and do the install youself it may be worth it as it is free.

Although ultimatly a modded out IRS is the best setup if money were not object but the ford stock IRS is no amazing solution.

 

[cavepony]

The road tests I have seen on the cobra IRS is not overly impressive. If I remeber the f-bodys with a live axel held more g's on the skid pad than the cobra.

I would be that a MM or steeda modified live axel would hand a cobra it ass around the track. I could be wrond though.

now if You get the kit for free and do the install youself it may be worth it as it is free.

Although ultimatly a modded out IRS is the best setup if money were not object but the ford stock IRS is no amazing solution.

Yeah,
DB and you must be reading the same stuff I have or maybe you have real world experinece, I would just love to see a heads up LA vs IRS in stock stangs.

My head and experience with non Cobra IRS's want me to lean that way and like Tom says an IRS feels damn good,

But nothing I have read convinces me it handles enough that I would notice, except on a bumpy turn.

It might be worth it just for the daily ride though!

Edit: I am tempted to ask this question on Corner carvers but they would probably beat the crap out of me.

 

[Indiana]

The best thing to consider that your car isn't a 24/7 race car. It says Hi to every road bump and pothole, Any Solid Axle is worse than an IRS in a street prediciment because when one tire (Solid) hits a bump it will affect the opposite tire. resulting in a negative affect on handling.

AMEN!!

you can make the solid axle handle just as good as the IRS. it's not hard to do. the only real advantage to the IRS is the ride comfort and control over bumpy surfaces.

I"m not trying to start a fight, but WTF are you smoking? You said you can make the SA handle as good as the IRS, then you say the IRS has better control over bumpy roads.

I had the SA, and now I have the IRS. It is like night and day. The SA sucks for road driving, and it will never be as good as the IRS. Never. Cornering over a bump with the SA and hard springs is a nightmare.

If you are mainly interested straight line, keep the SA.

If handling is what you want, get an IRS.

 

[tomustang]

Edit: I am tempted to ask this question on Corner carvers but they would probably beat the crap out of me.

I am a corner carver. One thing you have to remember is if you want to cut turns with a SA on a bumpy road, you would lose control if you want to keep pushing the limit of the car.

I"m not trying to start a fight, but WTF are you smoking? You said you can make the SA handle as good as the IRS, then you say the IRS has better control over bumpy roads.

DB is saying you can modify a SA to outhandle an IRS with certain setups, but it won't be affective if there is bumps on the road.

 

[DBMSTNG]

AMEN!!




I"m not trying to start a fight, but WTF are you smoking? You said you can make the SA handle as good as the IRS, then you say the IRS has better control over bumpy roads.

I had the SA, and now I have the IRS. It is like night and day. The SA sucks for road driving, and it will never be as good as the IRS. Never. Cornering over a bump with the SA and hard springs is a nightmare.

If you are mainly interested straight line, keep the SA.

If handling is what you want, get an IRS.

what is so hard to understand? the 05 GT race cars use a solid axle and are beating IRS equipped cars. why? obviously because they handle pretty damn good. add bumps tho, and it shifts towards the IRS's favor. i've driven IRS Cobras and on flat corners, they don't have much of an advantage in a flat corner over my GT with nothing but bullit shocks and springs. you can easily make a SA out corner the stock IRS. get the point? no one races (atleast i hope not) on bumpy surfaces, therefore the debate turns more into ride quality than handling potential.

 

[cavepony]

No frost heaves or potholes or bumpy roads down here. Unless I play Dukes of Hazzard.

Then again, not too many curvy roads either.

I would think a coil over set up would allow some softer springs and help reduce the chatter.

Making a stock IRS handle better doesn;t sound like a cheap proposition either.

Even Kenny Brown cuts the thing out and remounts/replaces parts of it to compete against a decent IRS. Short of that, what do people do to their stock IRS to improve handling? TA's, Coil overs, Better control arms?

 

[Indiana]

You can adjust the camber and toe on an IRS, I'm not aware that you can do that on a SA.

A little toe-in on the rear suspension can reduce oversteer.

Camber can be adjusted with the IRS also. Cars corner better with a little negative camber. i.e. the top of the tire angle "in" a little bit. When you corner the tire deflects a little and negative camber keeps the tire flat on the road. On solid axel car the tire that is on the outside of a turn (with all the weight on it) be lift on the inside giving less traction.

The harder you corner, the worse it gets. This is not a problem with a good IRS (yes, even the Mustang one).

Both of these things make the car handle better FLAT, SMOOTH roads.

As far as racing goes. If you actually watch a road race, they pretty much run over the "warning strips" on most turns. That's a pretty big bump.

Also, the Mustangs are doing well in Grand Am, but if you watch they don't handle as well as the Porsches, BMWs etc, that they are racing. One of the big reasons they are doing so well, is that they have a crap load of power. I have yet to see an 05 Mustang in GT racing.

If solid axels were as good as IRSs on smooth roads, Porsche, Ferrari, Lambourghini, BMW, F1 cars, Le mans, Indy, champ, Toyata Atlantic etc would use them. They don't.

All else being equal, the IRS will always handle better.

 

[jasonh_86]

I had a chance for a free IRS setup and install in exhange for my Solid rear, but at the time I figured i'd be making my car more of a drag car setup but i've got a little tired with racing.. we have horrible roads here in Arkansas, bumps everywhere, especially on corners. I feel sooooo stupid for turning that IRS down. Now it's gone and I don't know where to find another one for free like that