IRS recommendations

[fastd]

don't see that this topic has been brought up recently.



thinking about an irs for my 72 bird.

looking at heidts/art morrison/anybody else's? please let me know what your experience has been. thanks.

[dhutton]

David Pozzi installed an Art Morrison IRS in Mary's second gen Camaro. A lot of fab to get it in there. Should be in a thread on this site.

Don

[dhutton]

Here you go:

http://www.superchevy.com/how-to/cha...ependence-day/

Don

[fastd]

Thanks for the info.

I am leaning more towards the Heidts set up:
1. Cheaper than AME; $10k includes the brakes, ford 9", and coilovers. AME doesn't include the brakes or coilover (but it does include the Strange 60 3rd member I think); so AME is more like $13-$14k.
2. Installation of the Heidts is pretty easy and I think allows me to keep the back seat. AME requires a lot of fab work, is not custom fitted for my '72 Firebird and doesn't keep the back seat.
3. Wondering about the frame rails; are they strong enough with the Heidts set up to hold that IRS in there? Anyone install and drive the Heidts/AME. I know that D Pozzi installed AME and is impressed with it; not sure if it was primarily due to the inboard brakes because they are harder to cool - but Daves/Marys needs are different than mine; they have a dedicated track rate; mine will be 90% street/10% road course where I run 25 minutes at a time...

I was thinking of the DSE Quadralink but the Heidts seems it fits better (DSE pretty much loses the rear seat I think and needs to cut up the floorboards in the rear), includes the 3rd member/axles that I would have to upgrade if I got the DSE so the cost really isn't much different, so why not get the IRS?

[Mean 69]

The biggest concern with any IRS system is the dynamic response, especially in terms of toe changes in bump and droop. It is the same thing as bumpsteer on the front, but the biggest difference is that the front has two more adjustable items that the rear doesn't - the steering wheel and driver - which can make small changes to keep the car mainly where you want it to be. The early Corvettes were diabolical due to toe changes under heavy braking. There is evidence that the new Corvettes can also have this tendency on certain platforms, which seems incredible that this could be.

There is a Heidts unit under a car at my bud's shop, looked at it a bit. I am personally not a fan of inboard brakes on a car that has outboard brakes on the front, the ratio of front to rear unsprung weight is significant and doesn't make high performance tuning any easier. It looks super cool for street rods, no denying. I'd find someone that has the system and has actually tuned and measured toe changes. Even the AME system is apparently very difficult to tune - this from someone that has significant experience with the system in a second gen.....

Would love to hear what you learn on this. By the way, would you be welding the kit in, or is it a bolt in deal?

Mark

[fastd]

thanks for your comments mark.

the kit is a bolt in but no reason not to weld in the saddles onto the frame rails...

[Mean 69]

You bet. And if you CAN weld, DO weld it.

[fastd]

Thanks everyone for your helpful comments.

FYI, I decided to go with the Chassiswork 4-link (g-link), FAB9 axle housing and a Ford 9"; adding their strong rear frame rails, double adjustable varishocks front and rear, helwig sways.

Felt like this was a safer (i.e. proven), slightly less expensive way to go. Oh, yeah, installation seems pretty simple also.