IRS modification question

kenewagner

Registered User
I have researched among a lot of old threads on mounting the IRS solid to the cars body. Seems most threads are geared to eliminating wheel hop on manual equipped cars. On a automatic equipped car running over 400 rwhp is this a useable modifacation as well? Kind of wanting to see what the concensus is out there on this, for automatc equipped cars not manual, pro-cons? Looking to start winter projects soon and lowering my 60 foot times some with suspension mods seems like a start. Keep it bolted on with solid discs, weld it off solid, modifing attachment points. What say you all??

Ken
 
What I am going to do is check that. I am going to mark the rear with lines on the mounts and subframe its self. Kind of like a valve spring. If that moves, (don't think it will) is address that with some sort of extra bolt/mount. Kind of like a torque box on the frame rail. Front and rear if it requires it.

I have said it many times. From what I have witnessed is the top of the rear knuckle walking all over the place. I am pretty sure that the single mounting point on the top is what is causing it. I am going to box the rear of the "frame" and run a trailing arm to it, and run the other end to the outer part of the UCA. Heims at both ends will allow for the rotation and will keep it in place...like a front pointing pan hard bar.

I already bought the bars and got them too long. Mine may have a problem with deflection, but maybe not. These are the same setup my buddy runs for the FRONT UCAs on his roundy round race car. I can get some pix when I get my computer back as to what I have in mind if you are interested.


SWS
 
Wheel hop is not the issue here. What is the issue is wasted movement within the body/suspension. If you deflect a part during launch, that is energy not making it to the ground. I would weld the mounts solid within the subframe so that it still bolts to the car but that no movement is possible.
 
Anything that will prevent excess movement of the suspension and transmit power to the tires, instead of wasting both power and time in bushing wind-up, will help.

Start with LCA and knuckle bushings though, they're the real culprit. Solidly mounting the sub-frame without changing the suspension bushings will probably not make that much of a difference, other than increasing the NVH.

The reason the top of the knuckle moves is that the inner LCA and lower knuckle bushings are too soft.
 
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I have said it many times. From what I have witnessed is the top of the rear knuckle walking all over the place. I am pretty sure that the single mounting point on the top is what is causing it. I am going to box the rear of the "frame" and run a trailing arm to it, and run the other end to the outer part of the UCA. Heims at both ends will allow for the rotation and will keep it in place...like a front pointing pan hard bar.

I already bought the bars and got them too long. Mine may have a problem with deflection, but maybe not. These are the same setup my buddy runs for the FRONT UCAs on his roundy round race car. I can get some pix when I get my computer back as to what I have in mind if you are interested.


SWS

Someone else had pictures posted of the same thing and I thought it was a great idea that had strong merit. My problem might be that I have no room for the bars going back due to my new A1000 fuel pump is back there on the outside of the frame rail where the bars would have their attachment point. Have to get the car up in the air and check that out for sure. I might have to relocate the fuel pump to make that work. I read a thread where Dave Dalke has welded the IRS to the body and it strengthens both and I assume eliminates flex. But once again these are all mods to help the manual guys eliminate wheel hop. How much would it help a auto equipped car. I am just running a set of Monroe shocks under the rear as well so I assume they need to be address too. Any photos of your idea would be great

Ken
 
Ken,


As been said. Tighten up the control arms with some delrin bushings then move on to the subframe bushings. I have that setup i my car...WHAT A DIFFERENCE. Currently Im running a poly rear mount and factory rubber fronts on the IRS.

Your certain to reduce your 60' times..My bushings wernt even worn and I noticed a huge difference in feel
 
I believe the subframe I am using now has the Delrin control arm and knuckle bushings. I have been 1.52 in the 60. Maybe DLF can tell me what bushings Mike Viverette bought from him?
 
I believe the subframe I am using now has the Delrin control arm and knuckle bushings. I have been 1.52 in the 60. Maybe DLF can tell me what bushings Mike Viverette bought from him?

I don't recognize the name, but if he bought bushings from me, then they're Delrin.
 
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