Upgrades for IRS

[Craig K.]

Does anyone know of any good upgrades for the factory IRS?

Things I would like to know about are upper/lower arms, bushings and coil overs.

Also what about rear alignment, on the IRS is it adjustable or not, and if so what kind of racing specs are good?

I haven't searched much on the net, just seeing if someone has already done all the home work so I won't have to.

[Italian LX]

Things I would like to know about are upper/lower arms, bushings and coil overs.
We put the MM poly bushings in Joseph's Cobra. He says they made a pretty big difference.

Also what about rear alignment, on the IRS is it adjustable or not, and if so what kind of racing specs are good?
I know there are tie-rods to adjust toe, but I can't recall if there is any camber adjustments. I would imagine there would at least be some sort of eccentric bolt/bushing to adjust it some. :shrug:

[QWKSNKE]

yes you can do all the necessary adjustments for alignment on a IRS stang.

Like Brian mentioned, there are bushings, stronger braces, and halfshafts that I know of to upgrade the IRS equipped mustangs

[Craig K.]

Thanks Brian and Lee,

I checked out MM web-site, they look like they have a lot of new products for them as well, including delron busings and a solid adjustable front mount. They also have a coil-over conversion.

I haven't found any tubular Arms yet, I'll keep looking.

Is there any way to tell from the outside if it is an '99/'01 or a '03/'04?

[slvrbullit]

Pull a half shaft and check the splines, 03/04 31 spline shaft and larger diameter.

[Craig K.]

yeah, I knew the 31 spline (older have 28, right?), if this works out I'll pull one.

[QWKSNKE]

01's are 31 spline also

[Sendero]

According to Jack Hidley at MM, you don't have to do much to make it a performer:


Installed Delrin bushing in both the upper and lower control arm inner pivots. This must be done very carefully to ensure low friction pivoting.

Installed a coilover shock assembly.

Installed a bumpsteer kit to remove the Ford installed roll understeer.

Installed an oil cooler to keep the differential fluid temperature under control.

Installed a solid differential mount to remove compliance and set the pinion angle to zero.

Installed polyurethane bushings between the subframe and frame.


This is on their 91 LX Track car.

[Craig K.]

Thanks Nathan, thats what I was looking at fron the MM site, forgot about an oil cooler though

[TheJeanyus]

The bushings made a difference in wheel hop, but it doesn't seem to have changed my 60' times any (still a best of 2.0). It does seem to bite a little harder coming out of turns now, though. :yup:

[96GTS]

I haven't found any tubular Arms yet, I'll keep looking.

Kenny Brown makes 'em...
http://www.allfordmustangs.com/reviewpost/data//4/499-04-irs-cobra-kbp-49620.jpg
http://www.gotmustang.com/Portals/0/KB%20Cobra%20IRS%20new.jpg

[Sendero]

Kenny Brown makes 'em...


How much do they weigh? I haven't seen any extensive FEA analysis studies on the IRS structure or arms, but I would be interested to know what changes the KB arms make.

I do know that in NASA AI competition, replacement arms are illegal (for now).

[96GTS]

How much do they weigh? I haven't seen any extensive FEA analysis studies on the IRS structure or arms, but I would be interested to know what changes the KB arms make.

I do know that in NASA AI competition, replacement arms are illegal (for now).
The KB site is under construction, but I found this..
http://www.mustangweekly.com/2004/june/newproducts/np06-11-3rd.asp

[ChipR4cam]

Upgrades for the IRS?



A live axle.

[Craig K.]

Thanks guys,

I found the KB arms last night on their site, but could not find any pricing for them.

Concerning the comment on the live axle, the only reason why I am considering the IRS is because of the deal that I may get on it. For road racing I think I could get a better advantage out of the IRS compared to a live axle/watts/3 link, also again, for the deal I may get it would be worth it to try.
I will find out for sure over the next month or two if this deal will come together, but even if it does, the IRS will sit for several years before it goes into the '85, so for now I am just looking to see what is available.

As far as the tubular arms and the legality, I most likely will never again race in full blown competition again, I want to run HSR in their catch all group, that way I can run what I want, and do it just for fun.

[Sendero]

Given what I know now, go with the IRS. If the car could possibly make it to full-on race (ie gutted caged and blown), then stay live axle.

[Craig K.]

Given what I know now, go with the IRS. If the car could possibly make it to full-on race (ie gutted caged and blown), then stay live axle.

This is for the '85, it is already fully gutted with a full cage, and will only see road racing tracks for the rest of it's life. ;)

What is the power hold capability of these, does anyone know?
I thought I have seen were some '03/'04 Cobra are running low 12's/11's on an untouched unit.

My racing will never be the powertrain shock of a launch from the line, but I would like to perhaps some day see 600 h.p. at the wheel, is this too much :shrug:

[Italian LX]

What is the power hold capability of these, does anyone know?
I thought I have seen were some '03/'04 Cobra are running low 12's/11's on an untouched unit.

My racing will never be the powertrain shock of a launch from the line, but I would like to perhaps some day see 600 h.p. at the wheel, is this too much :shrug:
I would think a road racing apllication would have a lot higher HP limitation due to less shock on the drive train. :shrug:

[Sendero]

If its for the '85 you will most likely come out cheaper doing a TA/PHB or Tri-Link/Watts with a tad more performance. Unless you get a super-bubba good guy deal on a 01+ IRS.

[TheJeanyus]

This is for the '85, it is already fully gutted with a full cage, and will only see road racing tracks for the rest of it's life. ;)

What is the power hold capability of these, does anyone know?
I thought I have seen were some '03/'04 Cobra are running low 12's/11's on an untouched unit.

My racing will never be the powertrain shock of a launch from the line, but I would like to perhaps some day see 600 h.p. at the wheel, is this too much :shrug:
I've seen videos of 10 second '03 Cobras with stock IRS. :yup:

[QWKSNKE]

I've seen videos of 10 second '03 Cobras with stock IRS. :yup:

I saw one at Montgomery. Kid showed the car no mercy. Made several 10.50 passes on slicks

[Craig K.]

If its for the '85 you will most likely come out cheaper doing a TA/PHB or Tri-Link/Watts with a tad more performance. Unless you get a super-bubba good guy deal on a 01+ IRS.

I'll tell you after the fact (if it goes through).

So based off of the drag results, I think for my needs it should take the power.

I just hope it goes through

[ChipR4cam]

I've seen videos of 10 second '03 Cobras with stock IRS. :yup:


Russian Roulette.

[Italian LX]

Russian Roulette.
:rofl:

:werd:

[TheJeanyus]

Russian Roulette.
:werd: I didn't say that I would do it with my car - just that others have done it successfully.

[broke]

What kills the stock shafts on the 03/04 cobra's is wheelhop, plain and simple. Im workin on 33k miles on my stock shafts and probably close to 150+ passes mostly in the 1.7 & below area. I drive my car daily, and beat it daily. I have been as quick as 10.61@132 as well, and 60ft'd 1.51 as well my car makes 600+whp and 700+tq on the bottle and weighs 3700+lbs

I think a stock 8.8 solid will break just as easy as a stock IRS equipped cobra if not properly taken care of on a good sticky tire i.e drag radial or ET Street or Drag. I wouldnt even waste my time with stock components in a solid axle swap, I would go straight for a 33 spline strange setup.

The only mod I have done to my IRS is adjustable shocks and a rearend girdle from www.billetflow.com which attaches the rearend to the subframe threw a metal plate attached threw the rearend cover & the housing instead of the stock cast cover. Its fairly cheap and it deters the deadly complete rearend blowout experienced on some IRS cars.

Unfortunately bad drivers have given the IRS a bad name, and thats hard to get away from, if proper precautions are taken, it can take you a long way.

[TheJeanyus]

What kills the stock shafts on the 03/04 cobra's is wheelhop, plain and simple. Im workin on 33k miles on my stock shafts and probably close to 150+ passes mostly in the 1.7 & below area. I drive my car daily, and beat it daily. I have been as quick as 10.61@132 as well, and 60ft'd 1.51 as well my car makes 600+whp and 700+tq on the bottle and weighs 3700+lbs

I think a stock 8.8 solid will break just as easy as a stock IRS equipped cobra if not properly taken care of on a good sticky tire i.e drag radial or ET Street or Drag. I wouldnt even waste my time with stock components in a solid axle swap, I would go straight for a 33 spline strange setup.

The only mod I have done to my IRS is adjustable shocks and a rearend girdle from www.billetflow.com which attaches the rearend to the subframe threw a metal plate attached threw the rearend cover & the housing instead of the stock cast cover. Its fairly cheap and it deters the deadly complete rearend blowout experienced on some IRS cars.

Unfortunately bad drivers have given the IRS a bad name, and thats hard to get away from, if proper precautions are taken, it can take you a long way.
:hmm: I wish you hadn't posted that - I'm trying to save money for another project right now. :D