'03 IRS brace install

[biminiLX]

I ordered an '03 IRS brace from FordPartsNetwork.com to install with my springs/shocks/struts/IRS bushings/CC plates, but the brace does not come with any mounting hardware. I haven't looked under the car yet, but does the brace use existing bolts on the IRS? Anyone who has done this, help appreciated. -James
ps--The AFS chrome '03 18s are on (9" front/10.5" rears with 275/35s front 295/35s rear) These look absolutely killer, and I'll post before and after pics once the Cobra is lowered.

 

[Snake Eyes]

This should help.

http://www.shane.roberts.net/irsbr.htm

Good Luck,

Kyle

 

[TeamDOHC4point6]

Does the php 03 IRS brace upgrade fit on the 01 IRS? If so how does it cost over the cost of a 03 IRS brace?

 

[Snake Eyes]

All versions of the IRS are structurally the same. Yes any brace will fit any year IRS. Forget Paul's brace it costs a lot more than the 03 brace and they do the exact same thing. You can pick up the 03 brace cheap here.

Good luck,

Kyle

 

[TeamDOHC4point6]

Thx dawg.

 

[Mach0ne351]

www.fordpartsnetwork.com 03 cobra IRS brace is $79.99 will be ordering one soon

-marek

 

[Snake Eyes]

Already have that link up top man.

 

[biminiLX]

Thanks for the replies guys. The link for the install was excellent, and as stated above, I think the best deal is the factory '03 brace. The one question I still have is the mounting of the brace to the IRS. The brace does not come with any hardware, so I'm assuming I'll use bolts already on the IRS to secure the brace. Please let me know if I'm mistaken. Thanks, James

 

[Snake Eyes]

You will need Steeda's Polyurethane Differential Bushings (link). The install can be done with the stock bushings but that kind of defeats the purpose.

Let us know how it goes,

Kyle

 

[elyrain]

t does this brace actually do, and how well does it work.

 

[Snake Eyes]

Basically when you are trying to accelerate, your drive shaft turns, applying torque to the differential. Which in turn converts that power to the two half-shafts which are attached to the wheel. Well in the Cobra with the IRS the differential is not structurally (the solid axle) attached to the hubs and wheels. So the differential must be held in place while the wheels are allowed to move independently (on the A arms). Well as it turns out, the mount and bushings that SVT used were quite compliant (soft) and allowed the differential to rotate a few degrees under hard acceleration due to the rotational torque applied to it by the drive shaft.

So this brace was modified from it's original form to add 2 additional mount points for the differential. SVT also used higher durometer (harder) bushings to stiffen up the movement of the IRS components for the 03 cobra. So adding these pieces helps reduce pinion wind-up, which in turn lessens the wheel hop. Here is a summary of IRS suspension break down. This is what William R Mathis (author: Mustang Performance Handbook: Engine and Drivetrain Modifications for Street, Drag Strip or Road Racing Use) says. The only point I disagree with is that replacing all four subframe bushings doesn't increase NVH that much, many have done all 4 MM bushings with great results.

There are three basic IRS systems used in the Cobra Mustang, each with its own set of problems. The 99-01 IRS was designed for a smooth ride and low NVH. To achieve this, soft bushing were used in the subframe and the control arms. Although it is natural for Cobra owners to do burnouts, this series of IRS was never designed to handle this type of use. Ford mandated that the car ride smoothly and so soft springs, dampers and bushings were used. The second type of IRS was installed in the 2000 Cobra R. It had very high durameter bushings in the control arms as well as a pinion brace, amoung several other durability and road racing modifications. Additionally, it was equipped with 750 lb/in springs and road racing valved shocks. Although a significant improvement over the "smooth ride" version that was in the 99-01 Cobras, it was not intended to be used for drag racing. The latest rendition found in the 03 Cobra was designed with handling in mind. The control arm bushing are higher durameter than the previous Cobras, although less than the Cobra R. The 600 lb/in springs and semi road racing valving do not make for great drag racing launches. Given the basic designs of these, depending on which version you have, there are a few things that can be done to improve the function of the IRS and eliminate the wheel hop.

First, if your Cobra does not have the pinion brace, add it. Although Paul's is a good unit, the Ford piece fits perfectly and is both cheap and strong. I would recommend the harder Maximum Motorsports or Steeda bushings. Second, replace the front IRS subframe bushings with a polyurethane or Delron material and a steel sleeve. Do not replace the rear bushings unless the car is a track car only. NVH and high speed gear noise will increase significantly when the rear subframe bushings are replaced. These bushings are the same as the pre '94 Mustang trailing arms, so if you have a set of the Energy Suspensions items, use them. When you replace these bushings, replace the mounting bolts with standard 14 mm bolts instead of the stepped 12 mm pieces. The stock 12 mm bolts allow the subframe to move and should be replaced.

If your car has a 99-01 IRS, you will need to upgrade the control arm bushings, as the stock units are very soft. If your car is a street car where listening to tunes is important, install the 03 Cobra pieces, else, install Delron with the metal sleeve. Also, the knuckles (uprights) are much stronger on the 03 unit. You will need a VIN number from a Cobra R to get the R units and a VIN number from an 03 Cobra to purchase the 03 control arms.

Next, fabricate a bracket from 3/16" x 4"x 4" Flat ASTM A108 steel that will be welded to the outside edge of the rear subframe mount bracket and extended up inside the wheel well to a point approximately 1.5" above the level of the trunk floor. Drill two 3/8" holes through the bracket and wheel well into the trunk area, approximately 0.75" above the trunk floor. Install grade 8 bolts, nylon insert nuts and W series, type B, washers. You will have to massage the plate to conform to the wheel well. This modification is very important to the elimination of wheel hop. The cantilever bracket that mounts the IRS subframe to the frame bends considerably under heavy throttle or cornering loads. Additionally, you should replace the shocks with AFCO 7" stroke, double-adjust stock car shocks. This will require the fabrication of a small bracket for the upper mount. These shocks are inexpensive and provide excellent frequency control. Finally, be sure to check the pinion nut and all the center section mounting bolts. These have been known to be loose with little or no mileage on the car.

One of the side benefits to these modifications is a significant improvement in steering compliance. The car actually becomes pretty neutral and the off-center compliance is much quicker. If cornering is important to you, slot the upper control arm mounts for the uprights approximately 3 mm inboard. Modify the cam bolts to allow negative camber settings. You should see approximately 1.2 - 1.3 degrees of negative camber with this modification, and a noticable improvement in corner transition.

Hope this helps,

Kyle

 

[BadMoFo]

subscribbing, I want to do the same thing so I need to know if I got to get additional items. also who has replaced their bushings and is it worth it and how difficult is it?

 

[wolves]

Is the IRS Suspension Bushings (324-IRS-100) the same item as the Maximum Motorsports IRS Suspension Bushings (MMIRSU-1)?

I am also trying to help on teh wheel hop deal.

Thanks.

 

[biminiLX]

Thanks for the continued input guys. I spoke with my friend and we will be doing this on a lift HOPEFULLY this coming weekend, I have the IRS brace, MM IRS bushings, CCplates and subframes, '03 Bilstein dampers, and modified Eibach Pro-kit springs (front cut 1/2 coil). I can't wait to finish the install and post pics/info. I'll let you know. Later, James

 

[Snake Eyes]

biminiLX: I hope you know that if you are doing all that at once, and on a lift you should just drop the rear subframe out from under the car and work on it like that. It will be much easer!

Kyle

 

[shadow]

I plan on doing the MM bushings and the 03 brace.
What is the expected time to do these two mods ??

 

[GordsFord]

ttt

Gord