IRS swap, or build up current Live axle:

[Chris_Red_V6]

I've been offered a stock 03 Cobra IRS for my 8.8"/3.55s right down to the brakes if I do the swap.

My car is a daily driver with a drag strip visit once or twice a month, and I would like to begin to learn open-track and auto-x.

Right now, the car is stock with the exception of C springs in the back. Up front has a lot of work, but I've yet to begin working on the back.

My original plans were to get a MM panhard bar, some pro3i adjustable perch lower control arms, and strange 10 way shocks. Later down the road compelte the setup with a torque arm, removal of the upper arms, and higher rate springs.

Would I be better off taking this? I've never driven on 03 cobra, so I have no clue how an IRS mustang feels, but I do know I want to have a good handling car, with emphasis of handling ability of drag ability.

It seems that if this is a good upgrade, then I could be saving a lot of money over the rear suspension I mentioned above.

If I decide this route, what all has to be modified on my car for this to work?

I know the cobra may have to have a couple bolt holes enlarged, but other than that, I am not sure.

Also, I read http://www.angelfire.com/bug/irs0/index.html

[Evil Ash]

I'd do it just for the brakes alone. The 03 is the 31 spline setup and the most delevoped against wheel hop and toe problems.
I've completely done my rear suspension and exhaust and would still do it for stock 03 IRS.

[RagingGrandpa]

Well I love to dig up threads so here are a few relevant ones for you:

http://www.corral.net/forums/showthread.php?t=263607
http://www.corral.net/forums/showthread.php?t=505346

[Gimpstang]

if you decide not to take this offer, give me the persons contact number
Ive got an 8.8 with 3.55s ready to load on a truck and drive down there

I would get the IRS somply for the drivability of it, if nothing else. it makes the rear end infinately more stable when cornering over bumps

[Chris_Red_V6]

I worked it out with the guy, however, if I end up not liking it, I'll hit you up with my info.

[SSinfull]

lol...

The next mod Im doing is getting rid of my stock POS joke of an IRS for a solid axle.

The 03 is the 31 spline setup and the most delevoped against wheel hop and toe problems

If my car wheel hopped any more it would be a freakin kangaroo!

[Chris_Red_V6]

for the money, I'm still better off.

I'm saving $1500+ over a setup that's marginally better ($2000 if I left the IRS stock, I plan on tackling that wheelhop issue).

[Evil Ash]

Originally Posted by SSinfull

lol...

The next mod Im doing is getting rid of my stock POS joke of an IRS for a solid axle.







If my car wheel hopped any more it would be a freakin kangaroo!

Well I did say most developed.

If I wasn't constantly in the throws of deciding whether to sell the car I'd be working something out with you.

[92SilverStang]

You're better off just throwing a pallet of bricks in your trunk because thats what you'll get with an IRS a LOT more weight. Not to mention weak axles, more moving parts to break, no forward bite, a high roll center, wheel hop, rear steer in fast corners and your car will now go out of alignment all the freakin time! Highly recommend a Torque Arm , Panhard Bar, Subframe Connectors, Lower Rear Control Arms and throw your uppers away.

[Jon A]

Originally Posted by 92SilverStang

a high roll center,

The Cobra IRS' roll center is quite low. Quite a bit lower than any of the common solid axle setups.

[92SilverStang]

It may be lower than a stock solid rear axle setup, I'm not sure, but it sure isn't close to a Torque Arm, PHB setup. Roll center is determined by the suspension attachment points and a TA, PHB is about as low as it gets, and adjustable with the right ones.

[fastmustangs1]

If the car is a daily driver I and does see some drag strips than I would do a biuld up on a soild axle. On the other hand if you wanted to autocross or road race a IRS rear would be more adequite.

Matt 01 stanger

[92SilverStang]

NO, INCORRECT! Road Racers and Autocrossers benefit even more from ditching the IRS. A solid rear with a Torque Arm, Panhard Bar is better for both. PERIOD

[Jon A]

Originally Posted by 92SilverStang

It may be lower than a stock solid rear axle setup, I'm not sure, but it sure isn't close to a Torque Arm, PHB setup.

99 Cobra IRS, lowered 1":



The IRS has plenty of problems but a high roll center isn't one of them.

[Chris_Red_V6]

I'm probably stil going to do the swap. My bushings are 10 years old, and I won't have a lot of money to throw at it immediately.

I will get some bushings for the IRS to help control some issues and higher rate lowering springs, but I think it should easily outhandle a dated 10 year old live axle (we're talking stock shocks, stock bushings, stock arms. The guy getting the IRS for me has already bought parts to help this live axle)

I'm already using c springs and 03 cobra dampers up front, I think the IRS stockstuff (besides the taller spring) will match up just fine.

I understand the live axle + PHB + T/Arm is the best stangsetup, itsjust going to be a while before I can afford the setup, and when I can, it won't be a big deal to get a used 99+ 8.8 when I need it.

[95 GT RR]

Originally Posted by 92SilverStang

NO, INCORRECT! Road Racers and Autocrossers benefit even more from ditching the IRS. A solid rear with a Torque Arm, Panhard Bar is better for both. PERIOD

Why? I know and have read about several auto Xers and road racers who do very well with a modified IRS, and some have only minor mods.

Do you mean a TA and PB solid axle is better than a stock IRS or a TA & PB solid axle is better than a modified IRS ? Because there is a huge difference. This has been beat to death, but why would compare a heavly modified solid axle to a stock IRS?

[92SilverStang]

I'm not going to beat a dead horse on this issue. In order to get any type of Road Race worthy rear suspension you simply ditch the IRS. Look at American Iron wins with a Torque Arm, PHB setup. The roll center in the above picture is based on a 1" drop, I was talking stock but that doesn't matter. Now post a chart on a TA, PHB setup with adjustable low roll center, and coil-overs.

[95 GT RR]

I don't intend to go round and round on this issue either. However, in the OH/IN region of AI/AIX there have been only two cars running an IRS in the last two years. Neither of these cars have many races, but each has atleast two wins. Run the numbers and calculate the percentages and they look pretty good for the IRS. Considereing that atleast 80% of the total cars use a TA/PB set up and less than 5% use the IRS. My point is, it can and has been done, and will continue as more cars begin to tune the IRS. It may not be the Holly Grail, but it can be made to work.

[92SilverStang]

Hey, more power to em'. I would be surprised to see any IRS Mustang be competitive towards a series win, those are the only percentages that matter to me. I've seen a few AI, AIX races and looked under a few cars.

[MFE]

Go ahead and beat it up. The more tech there is, the less of a welcome mat exists for people who mistake random assemblies of characters masquerading as tech as something necessary or even desirable to post here.

[95 GT RR]

Originally Posted by 92SilverStang

Hey, more power to em'. I would be surprised to see any IRS Mustang be competitive towards a series win, those are the only percentages that matter to me. I've seen a few AI, AIX races and looked under a few cars.

Our region is being broken up into two seperate regions next year, so I'm not sure how that will effect series points. But, check on the two Mid-west regions next year, becasue there will be some competitive IRS cars in AI/AIX, hell, there already is.

edit : grammar

[92SilverStang]

Hey, bring those tractors to the West Coast and see how they do against some REAL cars!

[Jon A]

Originally Posted by 92SilverStang

The roll center in the above picture is based on a 1" drop, I was talking stock but that doesn't matter. Now post a chart on a TA, PHB setup with adjustable low roll center, and coil-overs.

Stock height:



MM's PHB is more than twice as high. Neither Griggs' adjustable WL or PHB will go anywhere close to that low.

[95 GT RR]

Originally Posted by 92SilverStang

Hey, bring those tractors to the West Coast and see how they do against some REAL cars!

You've made some lame, vague statements, but this one clinches it for me.
"Uncle"

Good luck
Dave

[95 GT RR]

Originally Posted by Jon A

Stock height:



MM's PHB is more than twice as high. Neither Griggs' adjustable WL or PHB will go anywhere close to that low.

Jon,

Great information.

Dave

[92SilverStang]

Let's see one with NO upper control arms. Also, that is only a 1" drop, there is much more adjustability with coil-overs. What setting is that Panhard Bar on?

[MFE]

that's an illustration of the IRS at ride height.

[92SilverStang]

Ya, I know but to make a comparison you have to have relevant information.

[MFE]

Well, you asked which setting the PHB was on and obviously there is no PHB on an IRS so it seemed a clarification was in order.

[92SilverStang]

I was just refering to the note at the bottom of the chart, "MM's PHB is more than twice as high, neither Grigg's adjustable WL or PHB will go anywher close to that low."

[rfloz]

Originally Posted by 92SilverStang

I was just refering to the note at the bottom of the chart, "MM's PHB is more than twice as high, neither Grigg's adjustable WL or PHB will go anywher close to that low."

I think the quote is just comparing roll centers with various setups.

[93SVTCobra]

I'll put my KB IRS equipped AI car against ANY AI car in the country without ANY hesitations. If you have anyone on the east coast you'd like to put me up against please feel free to name the time and place.

P.S. In addition to my KB equipped 04 Mustang I also have a 93 Cobra R with the full Griggs suspension and I can easily say that the IRS is superior.

[92SilverStang]

Don't blame it on the car. That #26 should be at the front!

[93SVTCobra]

Why?

[CMCRacer302]

If the IRS is so bad why is it now outlawed in AI?? And only allowed in AIX??