View Full Version : IRS Brace Questions

06-26-2006, 04:51 PM
Okay, so on the new SC I hope to buy soon, I'm probably going to leave it mostly stock (intake, headers, true dual, suspension drop and stiffening, blower overdrive, EEC tuner). I will, however, convert the rear end to 3.27 (it's a 5-speed). I noticed in my old 35th that on hard take offs, especially in wet conditions, the car would jump around like mad and not go anywhere. SCP has an IRS brace that supposedly works well to stop this. Can I get some feeback on whether it's worth it or not?


06-26-2006, 05:07 PM
I built a few IRS braces simular to the SCP setup, but much more heavy duty.
My buddy with a 35th 5 speed wanted one, so I made it for him when he switched to a 3.27 rear end. He said it helped out his launches and the rear end feels stiffer, but it doesnt completely cure the problem 100% as there is still some flex areas in the rear IRS aside from the differential.

I will be using one I built on my 94 5 speed but I havent tested it yet as the engine isnt finished being built.

You need to make sure you also have good IRS bushings or poly ones. The passanger side top bushing compresses, and the driver's side moves downwards - so I can imagine the brace helps out more on the driver's side. I was thinking about making a solid spacer instead of using a rubber bushing on the top passanger side to eliminate the flex completely.

- Dan

06-27-2006, 05:24 AM
I bought one of the original (red) pinion braces from MN12Performance. It "may" have helped a little bit with my Horrendous Wheel Hop (5-spd w/3.27's). I already had poly diff. bushings & poly rear diff mount (from tbird88). Bottom line, my diff. isn't moving at all, and I still have HWH.

The IRS Pinion Brace was developed because in SOLID AXLE CARS, the axle housing rotates counter to the axle, which changes the pinion angle. The axle housing winding up, & releasing is what causes wheel hop IN SOLID AXLE CARS. IRS cars have No axle housing attached to the outer springs. Our diff. housing can do the freakin' Watusi all day long, & it won't affect the cars suspension. A set of poly diff bushings & poly rear cover bushing will accomplish "almost" as much as adding the Pinion Brace to the mix.

If you DO decide to install the Pinion Brace, you will need 3 strong guys to break the lower control arm nuts loose. You can't get a conventional socket on it. I bought a set of BIG combination wrenches from Harbour Freight. I forget the size, but it was about 1 3/16" if I remember correctly. Even then, I needed a cheater pipe to break the nut loose. You should soak it with BP Blaster for several days before you attempt to break it loose. Even with the correct BOX END wrench, & cheater bar, it took 3 of us to loosen it (& Ryan is a BIG MAN!!!) I ended up bracing my back against the opposite tire, and pushing with both legs, while Ryan or Rich was pulling with both hands.

I still can't figure out why Ford designed the lower control arm mount this way. The bolt is about 9/16" & the nut is tightened to 184 - 229 ft/lbs!!!!



06-27-2006, 11:10 AM
There are several braces for this.
The pinion brace keeps the differential up. The cover brace strengthens the case itself and the torsional load braces hold the subframe together.

06-27-2006, 11:22 AM
Question of thw year...WHich helps with wheel hop? :O)

06-27-2006, 06:13 PM
The torsional load brace is the only one I can see helping with wheel hop. The biggest change you can do on these is to remove the subframe and weld it up good with some bracing to the subframe. Adding the torsional load brace and some poly knuckle bushings will help but it's like trying to use a solid bar to hold 2 weak sides together. The factory welds are spot welds and not very good ones at that.

06-27-2006, 09:15 PM
The torsional load brace is the only one I can see helping with wheel hop. Alan
I bought my '89 XR-7 new. It did not hop at all, no matter how hard I hammered on it. Even when I shipped it back from Germany in '96, it did not hop. Sure, I've upped the hp/TQ of the engine since then, but I feel that something has changed in the rear suspension area.

I would like to see somebody test the "subframe rigidity" vs. wheel hop theory. I just don't buy that, but I'm willing to listen, if somebody can prove it.

So far we know LOTS of things that Don't work to stop the hop. Sure, every little bit helps, but nobody seems to have found the miracle cure, Except maybe "Manny the Inverted"!!!!! The entire wheel-hoppin' SC community is still waiting for Mannys diamentional drawings for his Subframe Bushings Cup Plates (Hint, HINT, Manny!!!!!)

My next wheel hop upgrade is Poly Knuckle Bushings, & boxed (NEW) UCA's (yes, I know how NOT to box them!). Possibly poly Inner control arm bushings.

I have not installed my coil air bags yet, but I'm pretty sure that they too, will NOT kill the hopping.


06-27-2006, 09:25 PM
The cover brace strengthens the case itself Alan
I believe that the cover brace strengthens the rear diff mount, not the differential case. It distributes the load from the rear of the alum. cover, to the circumference of the differential housing. I think you'd be hard pressed to find somebody who's broken a diff. housing in the rear. BUT there are several people who have ripped the OEM rear mount right out of the diff. cover.


06-28-2006, 09:54 AM
well the cover is a part of the case and there have been several pictures posted of busted covers.

06-28-2006, 11:04 AM
Being I am officially part of the wheel hop crowd I find this most interesting. Who make spoly knuckle bushing?...I;m doing that cobra brake upgrade might as well give em a try

06-28-2006, 12:50 PM
They were an mn-12 performance product. I got my set from Supercoupeperformance.