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To have an IRS, or not


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Posted

If one were faced with o/w similar 98 & 99 cobras, as AI starting platforms

and prices were maybe $6,750 and $10,000 (respectively), live-axles model

and if either purchase was o/w destined for equal SLA, etc buildups . . .

 

How much of an advantage would the newer car have because of it's IRS??

Enough to justify the extra $3,000?

 

Thanks,

Jesse

Posted
How much of an advantage would the newer car have because of it's IRS??

Enough to justify the extra $3,000?

/quote]

 

advantage? It wouldn't , and certainly not for $3,000 dollars

Posted
How much of an advantage would the newer car have because of it's IRS??

Enough to justify the extra $3,000?

/quote]

 

advantage? It wouldn't , and certainly not for $3,000 dollars

 

Only advantage the newer car would have...with a live axle , is the C headed motor over the B headed 4V motor. Better torque down low and better flow up high and you don't have to screw with the dual intake runner. there are also a lot more aftermarket body parts for the newer cars.

 

I would buy the newer car, do a live axle/Irs swap with someone and some of their cash, then go forward with a 3 link setup or TA/PH bar. Penalty with IRS is you have to run a diff cooler setup, parts are nearly non existant and too many more parts to fail and a lot of added weight...however, two IRS cars were on the podium last year at nationals...?

Posted

Go to MustangEnthusiast.com and look for "Project Phoenix". We are building a 99 Cobra Bondurant Racing School car into an AI car. Roush built 20 99 Cobras for Bondurant and they removed the IRS for stick axles in every case.

 

They were looking for reliability rather than performance, but its worth considering their reasoning.

IMG_4006.jpg

Posted

We all know how REAL performance road racing cars have stick axles..........right??????

 

I would go with a Cobra IRS in a minute for top performance. It would take some $ to upgrade the bushings, bump steer it, and add a cooler, but it would be worth it in my book after driving both.

 

Brian

  • 2 weeks later...
Posted

If I had the option of chosing an IRS or a live axle, I would take the IRS in a second without even thinking twice. I think guys that don't like IRS cars have never driven IRS cars. I raced an IRS car for years and have not been in a live axle car that was as good.

 

If you're building an SN95 car, the best price vs. performance setup is going to be Max Motorsports front suspension with IRS rear. You should use '03-'04 Cobra IRS if anything. The steering geometry is better and the axle shafts are stronger. I don't understand the $3k difference in price. You can get a good used '03-'04 Cobra IRS for about $1,000 most anywhere. You'll spend more than that on a good 3 or 5-link setup for a live axle. Oh yeah, don't mess with the LCA bushings. Leave them stock '03-'04 Cobra. Go stiff on the uppers.

 

Some guys think the added 100 pounds of the IRS is a disadvantage. I don't understand that... The unsprung mass in the IRS is lighter than teh Live axle. and that 100 pounds is in teh rear IMPROVING your weight distribution and putting the weight in a good spot. Have you ever taken the esses at VIR FLAT in a live axle car? I'll bet not...

 

You do need a diff cooler. Rehagen Racing has a really nice kit that is cheaper then the MM kit. Just a little more weight to put in the back right corner of the trunk...

 

I'll take an IRS please.

Posted

if you would like to upgrade later. kenny brown is back in business and has done alot of research on the irs and has come up with a lot of upgrades. virtually the only company that has.

Posted

IRS is better in anything other than a mustang. The IRS used in Cobras is a bandaid made to fit in the constraints of the stick axle mounting points. The geometry is all wrong and the unsprung weight is massive. Do a live axle swap with a good watts link setup and call it a day.

 

My Panoz has a trailing arm setup with a watts link and it handles better than my setup Z06.

Posted
IRS is better in anything other than a mustang. The IRS used in Cobras is a bandaid made to fit in the constraints of the stick axle mounting points. The geometry is all wrong and the unsprung weight is massive. Do a live axle swap with a good watts link setup and call it a day.

 

My Panoz has a trailing arm setup with a watts link and it handles better than my setup Z06.

 

 

This is AI....build your own using the diff housing as a start and go from there...

 

Personally, it's too much to change and spend money on from what is already working in the car. To each their own though.

Posted
This is AI....build your own using the diff housing as a start and go from there...

 

Personally, it's too much to change and spend money on from what is already working in the car. To each their own though.

 

I wouldn't do that if I were you...

 

Rule 6.1:

 

© (1) 1999-current Mustang Cobra with factory IRS is allowed and updating of 1979-current live

axle Fox Body or SN95 cars to factory IRS is allowed. “Factory IRS” is defined as: (a) the

unmodified OEM installed rear IRS cradle that attaches to the chassis and serves as a mount for

the center differential and uprights; (b) uprights; and © differential housing. Control arms and

bushing material are unrestricted, but the location of the cradle cannot be changed in relation to

the OEM mounting point. The OEM brackets must remain in place and the IRS cradle must

mount to the chassis using those points in the OEM location. Bushing material for the brackets

and mounts is free (Aluminum, Delrin, etc.) but the mounts must remain as stock.

(2) Other IRS cars allowed are MN12 chassis Ford Thunderbirds/Mercury Cougars, Cadillac

CTS, and 2004-up Pontiac GTO’s with factory IRS. “Factory IRS” is defined as: (a) the

unmodified OEM installed rear IRS cradle that attaches to the chassis and serves as a mount for

the center differential and uprights; (b) uprights; and © differential housing. Control arms and

bushing material are unrestricted, but the location of the cradle cannot be changed in relation to

the OEM mounting point. The OEM brackets must remain in place and the IRS cradle must

mount to the chassis using those points in the OEM location. Bushing material for the brackets

and mounts is free (Aluminum, Delrin, etc.) but the mounts must remain as stock.

Posted
This is AI....build your own using the diff housing as a start and go from there...

 

Personally, it's too much to change and spend money on from what is already working in the car. To each their own though.

 

I wouldn't do that if I were you...

 

Rule 6.1:

 

© (1) 1999-current Mustang Cobra with factory IRS is allowed and updating of 1979-current live

axle Fox Body or SN95 cars to factory IRS is allowed. “Factory IRS” is defined as: (a) the

unmodified OEM installed rear IRS cradle that attaches to the chassis and serves as a mount for

the center differential and uprights; (b) uprights; and © differential housing. Control arms and

bushing material are unrestricted, but the location of the cradle cannot be changed in relation to

the OEM mounting point. The OEM brackets must remain in place and the IRS cradle must

mount to the chassis using those points in the OEM location. Bushing material for the brackets

and mounts is free (Aluminum, Delrin, etc.) but the mounts must remain as stock.

(2) Other IRS cars allowed are MN12 chassis Ford Thunderbirds/Mercury Cougars, Cadillac

CTS, and 2004-up Pontiac GTO’s with factory IRS. “Factory IRS” is defined as: (a) the

unmodified OEM installed rear IRS cradle that attaches to the chassis and serves as a mount for

the center differential and uprights; (b) uprights; and © differential housing. Control arms and

bushing material are unrestricted, but the location of the cradle cannot be changed in relation to

the OEM mounting point. The OEM brackets must remain in place and the IRS cradle must

mount to the chassis using those points in the OEM location. Bushing material for the brackets

and mounts is free (Aluminum, Delrin, etc.) but the mounts must remain as stock.

 

 

pffff...stupid rule. You can do 9 million things to the front of the car but can't do ANYTHING to the rear? LOL!!!

 

Actually, reading entirely too much into that rule.....can I put a GTO subframe under the rear of a mustang and use the GTO rearend?

 

ah....still too much work!

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