sb427f-car

How's hung an IRS under their hotrod or classic muscle car? I'm seriously considering going the IRS route in a 7 replica and have been doing massive amounts of reading on chassis/suspension design and theoretical fundamentals.

If you've gone the IRS route, what went into your suspension geometry, fabrication, ect? Did you fab your own control arms, uprights, ect.?

Additionally, anyone that has a good upright idea along with a way to do bearings in them, I'm very curious about that too.

Thanks!!!

v8bug

If I was ever going to bo IRS in a full size hot rod, don't think I would for $ reasons, I would start looking on ebay for full corvette rolling chassis. I have seen them for under $10K with the rear end trans!

This would take all the thinking out of the equation (for the most part) You would have to make upper control arm mounts it look like, but thats no big deal. For the time and money your could sink in something else, GM has done the work for you.

http://cgi.ebay.com/ebaymotors/97-Co...QQcmdZViewItem

my $.02


7 replica, you talking about them little lotus things?

sb427f-car

Yeppers...and this isn't starting for quite a while...so the research and dreaming is half the fun. The "trans axle" has crossed my mind, but due to space constraints in these things has been ruled out. I'm probably not even going to go with anything that's already been designed (same basic space frame, but with many variations).

I really want to do my own suspension work, and there is something to be said in a car that was designed for certain weight, certain cross weight, track width, ect. That's half the problem that people run into in building these cars, that is not being able to get the geometry right for things like bump steer and ackerman steering angles.

Besides...corvette stuff is money. Quality for the money, sure, but I want to be able to have full adjustabilty and knowledge that it'll do what I want it to do... No worries though, ideas are still ideas and NOTHING is set in stone.

Quick Double Nickel

iTrader: (5)

C4 vette, or you could do the old-school hot rod thing and go Jaguar. I don't know how strong those are though. I think there might even be an IRS-version of the Halibrand Quick-Change, but I'm not sure.

sb427f-car

I was also thinking off the shelf center sections like Expidition, Cobra, Caddy, GTO.

digitalsolo

iTrader: (24)

Lots of guys use 3rd Gen (93-2002) Mazda RX7 rear subframes. Strong differentials, and dual A-Arm setup.

jsconiers

iTrader: (2)

I have a 68 fire bird with a wayne due c4 IRS. It was a bracket kit that welded in place and allows you to attach a c4 dana 36 / 44. Check out the chassis from http://www.schwartzperformance.com/products.htm. For $2495 you a get a full bare frame which in my oppinion is pretty good. Adapting a c4 (even GTO style) IRS should be fairly easy. Also there is TCI who makes an IRS kit but I don't know anything them.

v8bug

I would look at places like this:

http://www.kitcarmag.com/

Seems they do alot of the 7 replicas. You should run an all aluminum turbo ecotec, power to weight is insane, like in their ECOCAT project car.

just some more info

as for a rear end, I dont know, I would assume lighter the better right?

superchargedbandit

The Irs Scare Me. I Dont Want To Get Audited!

sb427f-car

I'll have to look into that...

Thing to consider is that I will not be using a "sub-frame" for the build. It will NOT coinside with the frame geometry in the most likely case.

v8 bug...thanks for the kit car mag thing...I guess I should really pick up a copy of that somewhere and start reading it...and yes the ecotec captured my attention for a while but I've come to the determination that I want this thing to be "right" in my mind which includes the sound, the tq, the v-8 rumble, shake, feel, ect. I'm sure that I'd have a blast with an ecotec, but I won't be 100% "happy" with my build.

jsconiers, you didn't read my post very carefully I'll be building my own frame...I just need center section, upright, and other suspension ideas...

99c5vert

I was looking under a caddy CTS the other day. Pretty nice looking diff in there.

RX-7s and cobra rears are tried and true.

sb427f-car

Man, both of those have crossed my mind now...along with the CTS stuff...more after dinner.

sb427f-car

The CTS-Vs have had issues with wheel hop and breaking diffs, but they'd also be 2xs the weight as anything I'd have. Not only that, but I can take the time to set up a proper suspension to stave off any sort of wheel hop problem. I don't know.

99c5vert

well, the wheel hop is a matter of suspension design, not the diff itself. Often the hop is a result of busings being too soft. Also, just because there is hop issues in a 3000 lb car, doesn't mean you'll have it.

What I would love to do is have inboard brakes to go with it.

ls1coupe

iTrader: (2)

look into the 03-04 cobra irs rearends

sb427f-car

Problem with inboard breaks on these cars is where do you put the fuel cell? There ain't much room back there to begin with, add brakes on the inside and where is it gonna go?

I agree with the suspension design being the primary culprit of causing wheel hop. Couple it being 400 horse, 400 lb ft of tq AND stressing it with 2 tons of fun from a steady state mass to in motion, and yeah, you do the math,

LS1coupe...I know the 03-04 cobra irs rearends have been discussed on some of the 7 boards as well. So have explore / expidition rear housings. Trailblazer is IRS too now isn't it?

99c5vert

On the Rotus there'd be plenty of room, but then again, It's [cough]an oversized[/cough] seven. I think it's been done in a normal sized seven.

NO-OPTION-2002

iTrader: (2)

Nope, still solid axle with coils / control arms.

sierrac3_s2000

iTrader: (6)

Someone mentioned using the Ecotec engine. The CTS rearend is used in the Pontiac Solstice / Saturn Sky which is powered by either a turbo or NA Ecotec engine and the car weighs in at 2900lbs. Seems like that would be a good option for your car.

Project GatTagO

iTrader: (7)

If gear ratio selection is a factor, nothing will beat a diff out of a Cobra or Explorer. The housings are different but the guts are ideantical in both rears. The internals are the same as solid axle 8.8 rear ends and use 31 spline axles. There is huge aftermarket support for these rear ends with all kinds of diffs being offered along with just about any gear ratio you may need. Stock 03-04 ratio is 3.55, not sure about the Explorers.

Andrew