Suspension & Brakes - Dreaming of IRS

I know that the C4 corvette IRS transplant to F-body has been kicked around this board once or twice, but there are other, stronger, simpler suspensions out there. This one is a 9" ford center and the whole mess attaches to a simple crossmember. (there are 2 other supports, but they could easily go where the LCA's go)

http://kitcarmag.com/howto/p44959_image_large.jpg

This one costs about $4,000 and is more money than I would spend, but is it feasible?

Well, you definitely have my attention... If for nothing more than the fact that it looks like an interesting project.

I would love to have IRS!!!!!!

The one thing is that it would have to be designed for our car and the suspension points matched to optimise it for our car. Roll centers, camber gain, Motion ratios, etc...

the Solid axle is somthing i dislike very much... Unsprung weight, no camber change, and not to mention the stock 10 bolt is very weak. :drive:

Have fun working on thoes brakes. Looks like you would have to damn near tear the thing down to replace the pads.
If it were me I would try it with a cobra IRS and basicly back half the car.

Well, that's one way to kill a stang... :P

Here is Factory Five's IRS, its price is a little more reasonable at $2000 but is not complete (requires 8.8 center section, cv joints, brakes from 90's fords like the thunderbird)

http://parts.factoryfive.com/newcatalog/chassis/pictures/irs.jpg

I'm with you DanO... I traded a C4 for the SS (wanted a NEW car with an ls1 and 6-speed) and would be completely satisfied if it only had an IRS... shoulda just waited for the GTO

http://www.corral.net/99mustang/99cobra/IRS.jpg

Looks like you can fabricate a way for the arms that would normaly mount in the mustang lower conrtol arm area to fit an F-body with little to no work. It just all dpends on how wide the set up is. If you have atleast a 4pt roll bar in the car, it should be too hard to get it all squared away.

I'm no fan of solid axles either, I wish GM had made it atleast an option on the fbody. No matter how much you do there's no getting around the fact that like a see saw one side of a sra goes up, and the other side goes down -- make rearend jumpy.

I understand the whole, sra transfer power better than an IRS, you'll make better time, less involved in maintence. But my car is a street machine, not a drag car. Plus at shows you can't beat the cool of all that stuff under the rear. You'll have other fbody guys ooohing and ahhhhing.

I've been saving for this project. I'm probably going to have Rick Roush, in Dayton Ohio, do the work. I've already contacted him, and like Wayne Due he's done first gen Camaros. I'd rather have a shop that's done this work before for the reasons metioned above -- tuning it to get it to work right for your car. If you are going to use a C4 IRS with a Dana 44, you'd better snatch one up fast. Damn hot rod guys are snatching them up, everyone I see at salvage yards is $1,500 and up!

It would be a great idea if it could be done right. That is, supporting the IRS properly, and without adding excessive weight to the car. I've heard the Mustang setup is pretty heavy.

My vote is for a design like this:

Here is Factory Five's IRS, its price is a little more reasonable at $2000 but is not complete (requires 8.8 center section, cv joints, brakes from 90's fords like the thunderbird)

http://parts.factoryfive.com/newcatalog/chassis/pictures/irs.jpg



I say if one is to develop a kit, it should be designed with coil-overs in mind, since it is to be a performance oriented part. A plus would be that it could reuse some of the SRA Camaro components (i.e. rear brakes, aftermarket shocks) or better yet, use some components off of C4, C5, GTO, or CTS-V. Questions that comes to my mind would be:

1. is there enough room underneath for all necessary modifications in order for it to be a reliable part (if not bulletproof)?

2. If there is no loss in unsprung weight, then would the IRS capabilities be definitely worth the tradeoff?

Coilovers with the setup I'm using are given, just have the cups welded on and ditch the transverse leaf. I'm sure something will obstruct the carrier, since that sticks out towards the back more than the 10 bolt diff cover. Mounting points for the control arms will have to be reinforced I'm sure too, boxed or something. Don't know all the details, but R.R. thought this this setup could work well. I'm sure that the IRS will have to be mounted to spots that weren't designed with absorbing suspension stress in mind.

Also would like to keep TCS and ABS active. I know C4's came with traction control and abs (obviously).

Not sure about a rear sway bar. I know many vettes didn't come from the factory with one. But if there is clearence maybe. Since shocks and control arms aren't the only thing holding the rear drive assembly to the body; What kind of gain or loss would there be having, or not having one with this setup?

I guess im just looking for a lotus elise/exige with an LS7... hmm...

This is probably being made out to be more complicated than it seems. Plenty of hot rodders and first gen guys have done this swap. Granted it won't handle like a vette, but it'll probably be an improvement over the solid. How much so depends on how and where you are driving it. Any pro rod builder could probably makes this work very well. For the $$$ of course.

Well there's a reason that PRO rod builders charge quite a bit of money for a swap like this. It does take a lot of thought and perfectionism to get something of this magnitude right, especially for a race oriented car. If they're setting up a street cruiser and the owner wants IRS for a smooth ride and bragging rights, that's a bit easier than a beefed up reliable race oriented design.

Well there's a reason that PRO rod builders charge quite a bit of money for a swap like this. It does take a lot of thought and perfectionism to get something of this magnitude right, especially for a race oriented car. If they're setting up a street cruiser and the owner wants IRS for a smooth ride and bragging rights, that's a bit easier than a beefed up reliable race oriented design.

No doubt you are speaking the truth.

My goal is a fairly unique setup, that can handle a very moderately modded ls1, and that is more refined than the sra -- and has bragging rights of course.

I don't mean to hog this thread either. Just want to get people talking about this swap to see who else is curious, and get people to float their ideas.

Im curious....but im broke too, lol.

I don't mean to hog this thread either. Just want to get people talking about this swap to see who else is curious, and get people to float their ideas.

Absolutely, I'm really curious about this. I can't remember hearing too much about IRS swaps into an LS1 F-body and I'm really wondering what it would take. Maybe this is a step towards innovation. :cheers:

Maybe this is a step towards innovation. :cheers
and hopefully a bolt in kit, lol.

Speaking of all this IRS...

Does anyone have the front suspension points and overall CG location?

This is very beneficial in choosing a suspension setup... Do they use underground or above ground roll centers.. what kind of Kingplin inclination, scrub radius... etc.

Hrmmm, more information for me to start collecting for the massive massive database of technobabble I'm starting on... :D

and hopefully a bolt in kit, lol.

Hehe, I'll build a bolt in for ya... just show me the money... :D Hey, I've been lookin for a job anyway. :P

While you're dreaming of IRS, why stop there? To really make it work effectively, you would probably need a completely new chassis design. So the best thing would be to to just gut your fbody and put it on a tube frame, but pick one that is designed to be mid-engined, so you have the LS1 right behind the front seats. You could even use the rear hatch for engine and transmission access. Then the car would have a true 50-50 weight distribution, as well as four wheel independant suspension.

While you're dreaming of IRS, why stop there? To really make it work effectively, you would probably need a completely new chassis design. So the best thing would be to to just gut your fbody and put it on a tube frame, but pick one that is designed to be mid-engined, so you have the LS1 right behind the front seats. You could even use the rear hatch for engine and transmission access. Then the car would have a true 50-50 weight distribution, as well as four wheel independant suspension.


FYI... a 50/50 weight distribution is not always optimal... especially on mid engined vehicles.. i have designed those vehicles.

And why we would stop there is because the IRS is somthing that could be accomplished without tearing the entire vehicle apart and focusing on one major performance hinderance of the design... and while your at it... why dont you just say that we should all be driving around Formula 1 cars... I appreciate the snide remarks.

vettes have 50/50....and have the engine up front...as well as 4 wheel independent.

FYI... ... why dont you just say that we should all be driving around Formula 1 cars... I appreciate the snide remarks.
My comments were not intended to be snide. As someone that has designed cars before, you should know that the fbody was not designed to have a IRS, and it's unit body is not stressed for that. My point was, you have to practically start over on the chassis design to do it right and make it function as more than eye candy. And the easiest way for most of us to do that would be to buy a pre-designed tube frame to drop the body on.

why dont you just say that we should all be driving around Formula 1 cars....
Belive me, if I could, I would.....and no there is no sarcasm.

While you're dreaming of IRS, why stop there? To really make it work effectively, you would probably need a completely new chassis design. So the best thing would be to to just gut your fbody and put it on a tube frame, but pick one that is designed to be mid-engined, so you have the LS1 right behind the front seats. You could even use the rear hatch for engine and transmission access. Then the car would have a true 50-50 weight distribution, as well as four wheel independant suspension.

FactoryFive took you up on your suggestion!

http://www.factoryfive.com/table/ffrkits/GTM/concept.html

Tube frame: Check
Mid-engined: Check
LS1: Check
50-50: Check
fully independent suspension: Check

FactoryFive took you up on your suggestion!

http://www.factoryfive.com/table/ffrkits/GTM/concept.html

Tube frame: Check
Mid-engined: Check
LS1: Check
50-50: Check
fully independent suspension: Check
Yeah I've seen (and drooled over) that car already. Looks kinda like a Ford GT-40, only with a LS1 in place of the heavy Ford engine. Factory Five makes some nice stuff; a guy I autoX with has one of their Cobra's.

[QUOTE=Cal]fbody was not designed to have a IRS, and it's unit body is not stressed for that. QUOTE]

That comment certainly isn't in the spirit of this board, or any one who's run the car hard on the street or strip. Look at all the sh*t people do to turn there street ready camaro and firebirds into to balls to the wall drag cars. BBC and crazy small blocks with turbos, and sc's. Many pushing 600hp or way more....was the frame designed to take that stress? How much twist does that put on the chasis, frame, and the cars various other parts? No one hear thinks in terms of what it was designed to do, they want to see what it can be made to do, and how can I get it do it?

Granted an IRS in the fbody won't be as clean and smooth as ferrari, vette, porsche. I'm not asking it to be able to run 12 hours at sebring, or 24 hours at le mans. However, with a good welder, a shop that understand suspension geometry, and frame reinforcement it can be made to handle COMPETENTLY, functioning more than just eye candy. Atleast close to GTO and as well as the Cobra. You see these changes being made to trucks, hot rods, and older muscle cars.

http://www.classictrucksweb.com/tech/0303CT_IndThinkII/
http://www.rickroush.com/
http://www.waynedue.com/web/Products/irs.html
http://www.seattlestreetrods.com/index.htm
http://www.rodandcustommagazine.com/techarticles/86279/index.html
http://www.pro-touring.com/waynedue/chris_baldwin_69_firebird_project.htm

IIRC, the test mule for the Cobra IRS development was a completed GT. A chassis that arguably "wasn't designed for the stresses of IRS". They didn't seem to have much problem. It just needs to be reinforced as and where necessary.


As for MR - I'll keep my engine upfront thanks. Shoot for 50/50, but not too worried if it's not dead on. The big weight towards the front makes it safer and easier to control once you go past the limit.

IIRC, the test mule for the Cobra IRS development was a completed GT. A chassis that arguably "wasn't designed for the stresses of IRS". They didn't seem to have much problem. It just needs to be reinforced as and where necessary.


As for MR - I'll keep my engine upfront thanks. Shoot for 50/50, but not too worried if it's not dead on. The big weight towards the front makes it safer and easier to control once you go past the limit.


The Ford IRS is a complete unit. It's designed to place the chassis loads in the same locations as the solid axle setup. Therefore, it's heavy, a bit clunky and not really optimal, but it is independent (there is a 99 GT with an IRS swap that stays at my place....belongs to a room mate). It's not any worse than the solid axle, but I'm not sure how much better it is (than ours, not theirs. The stock GT suspension design sucks from a handling standpoint). It's a bandaid solution, but it's still better than what we got.

fbody was not designed to have a IRS, and it's unit body is not stressed for that.

That comment certainly isn't in the spirit of this board, or any one who's run the car hard on the street or strip.[/url]
I'm not saying that a good job could not be done with the hot-rodder's approach of "cut and try" and "modify what's already there." It just hasn't been done by very many people yet (if any) so this approach is going to take quite a few itterations to yield the best results.

As far as running fbodys hard at the drag strip, that has been done since day one and by now everyone knows what works and what doesn't.

I'm not saying that a good job could not be done with the hot-rodder's approach of "cut and try" and "modify what's already there." It just hasn't been done by very many people yet (if any) so this approach is going to take quite a few itterations to yield the best results.

As far as running fbodys hard at the drag strip, that has been done since day one and by now everyone knows what works and what doesn't.


I'm willing to take that approach, but testing whether it handles well or not is subjective. I'm not a good tester since I won't be pushing it like an autox'er would. You might drive it and think it's just adequate or less so.


http://parts.factoryfive.com/newcatalog/chassis/pictures/irs.jpg


I've seen this product before. I wonder if you could use the GM parts, (half shafts, brakes, center section.... instead and just have the cage. Maybe factory five would be willing to test bed a few for the fbody. And eventually make a kit that would work with the gen III/IV Fbody's. There are so many birds and camaros, and we're prolly not the only ones who'd be interested in this.

For kicks I sent an e-mail to factoryfive asking about using GM specific parts in a cage designed for our cars. Pretty much what he said is they have no interest in taking on such a design. Oh well

The Ford IRS is a complete unit. It's designed to place the chassis loads in the same locations as the solid axle setup. Therefore, it's heavy, a bit clunky and not really optimal, but it is independent (there is a 99 GT with an IRS swap that stays at my place....belongs to a room mate). It's not any worse than the solid axle, but I'm not sure how much better it is (than ours, not theirs. The stock GT suspension design sucks from a handling standpoint). It's a bandaid solution, but it's still better than what we got.

The cobra IRS is considered worse than a solid axle torque arm/phb setup. Look on corner-carvers.

Some people need to realize that IRS does not always equal better than a solid axle. There is a lot of design and actual engineering work to take place before you do it.

The cobra setup is probably an example of design to fit, but not necessarily be light or work well. IRS is a better setup for some and not for others depending on what you will be doing with it. There are some who would want it to be a perfect auto race piece, others would want it just for looks, and a lot in between who just want it to handle well on the street. And there are plenty of muscle car guys who just flat out think that IRS is voodoo, and sacreligous to put in a muscle car. Will it work well, who knows...I hope to find out by July '06.

Looks and status are one thing, but in racing it may or may not help. It will probably add weight if the car wasn't designed with it in mind to start with. That hurts racing performance. An IRS is adjustable, so you can add negative camber and toe in which will help on a road course. But if you don't wind up with a good camber curve, you could actually loose camber in a hard corner. Solid axles usually have zero camber, but they don't give up any under load either. Another thing is, you can bend a solid axle slightly to get up to -1.0 camber without affecting the reliability of the axle (quote from Herb Adams.) Likewise, you can bend the axle for a little toe-in to improve rear end stability in a corner.

I think someone did a irs in a 3rd gen I just cant find it but I know I saw it.. They used the c4 setup... I dont know alot about chassis related things and fabrication but I do know I ran across it.. If i find it Ill post it up for ya guys

The cobra IRS is considered worse than a solid axle torque arm/phb setup. Look on corner-carvers.

Some people need to realize that IRS does not always equal better than a solid axle. There is a lot of design and actual engineering work to take place before you do it.

That's what I was trying to say. My statement was that it was probably better than the stock GT suspension, not the griggs (PHB/TA setup). That's what I was trying to say here (I don't think I phrased that very well when I said it):

It's not any worse than the solid axle, but I'm not sure how much better it is (than ours, not theirs. The stock GT suspension design sucks from a handling standpoint). It's a bandaid solution, but it's still better than what we got.

I meant that it is better than the bind prone stock GT setup, but likely not better than a torque arm/phb setup such as ours. And, that they got an IRS to experiment with and we didn't (I just hope GM would have done a better job on it if they had done it).

Gen III Camaro with IRS
http://www.thirdgen.org/techbb2/showthread.php?s=&threadid=223728