IRS vs. 3 link vs. 4 link

[Vimes]

I’ve considered this very thing.



My problem is I need to be able to see stuff already done to feel comfortable with it, and I don’t see a lot of mustangs with benz underpinnings. ��*♂️ LoL

In that case, I stumbled across this one this very night. Looks like a solution for you. It may be a solution for me depending on what the shop I'm talking to this time says, or rather doesn't, which seems to be par for the course for me. At least for this one I've got a guy not 5 miles from me that can do the framework for this one. It's a cradle that allows you to bolt a C5/C6 Corvette suspension into any car, and the price is pretty reasonable. My preference would still be an offset 3 link, but if that isn't meant to be, perhaps this is.

https://rick486.wixsite.com/dobbertinperformance

[dhutton]

In that case, I stumbled across this one this very night. Looks like a solution for you. It may be a solution for me depending on what the shop I'm talking to this time says, or rather doesn't, which seems to be par for the course for me. At least for this one I've got a guy not 5 miles from me that can do the framework for this one. It's a cradle that allows you to bolt a C5/C6 Corvette suspension into any car, and the price is pretty reasonable. My preference would still be an offset 3 link, but if that isn't meant to be, perhaps this is.

https://rick486.wixsite.com/dobbertinperformance

I’m using his front and rear adapters on my 56 Cameo pickup.

Issues and cost increase if you can’t live with the stock C5/C6 track width. I was able to squeeze it in.

Don

[Vimes]

What sort of issues?

[ICrombie]

What sort of issues?

I've got the rear adapter for my 69 Camaro, which has been narrowed 7". If you narrow it you need custom length half shafts (~1500 from Driveshaft Shop) and sway bar setup (easy to get from a place like Speedway Engineering). Clearance for the control arms could be a potential issue depending on your ride height and how narrowed it is.

I think the OEM mount for the diff gets wiped out if you narrow them more than 6", so you'd need to make brackets for that as well.

[Vimes]

Cool, nothing unexpected then. Issues to me would have been not as strong, can't handle as much power, doesn't handle as well, ect.

[Mark@lateral-dynamics]

My preference would still be an offset 3 link, but if that isn't meant to be, perhaps this is.

@ Vimes - What is your application?

[Vimes]

@ Vimes - What is your application?

2003 Dodge Dakota ext cab 2WD, and if I can ever get the suspension off the ground it will have a 427, possibly turbocharged, 8 speed auto. Building it to handle. But, I don't really want to be a post pirate, so if you want to discuss further PM me. My posts on this thread have mainly been aimed at getting the OP a path to an IRS system.

[Chad-1stGen]

Having driven a lot of cars on an autocross course and assuming equal levels of setup and tuning an IRS > 3 link > 4 link.

Especially if you want to also drive the car on the street. IRS puts power down on corner exit better than the others. Not to mention street friendly camber and toe.

That said. If you aren’t a suspension guru I’d take a proven off the shelf 3 link design over a home brewed or cobbled together IRS.

[gsxrken]

Sean at Street or Track makes a well regarded 3 link setup with tunable spring and shock rates, that will save you weight as well. It’s very on my radar.

I don’t get the IRS thing in a classic car. It can and has been done but it’s a ton of work, $$, and weight and when it’s all said and done it’s probably nowhere near dialed in for your car and you still have a flexible old muscle car around the rest of it.

Some people like to use their car like an artist uses a canvas and that’s fine. But a sorted 3-link will be an excellent comfort and performance upgrade.

[dhutton]

It’s too bad Mary Pozzi doesn’t come here anymore. She has been auto crossing her Art Morrison IRS for several years and doing well with it last I heard.

Maybe David Pozzi will give us an update. I’m not sure of the status of his 67 Camaro with IRS.

Don

[ilikeike]

It’s too bad Mary Pozzi doesn’t come here anymore. She has been auto crossing her Art Morrison IRS for several years and doing well with it last I heard.

Maybe David Pozzi will give us an update. I’m not sure of the status of his 67 Camaro with IRS.

Don

I thought I saw someplace she would consider selling it. Maybe on to other hobbies.

[anguilla1980]

I've been aganizing over what IRS to go with as well, and if I should do it with a full frame. I have a stock modified front subframe now with solid drop body mounts, welded in SFCs, and for now a leaf sprung rear end (built with all top-notch aftermarket components on the whole suspension that's well matched).

I worry the weight of a full frame plus the IRS will make it not any better than if I just swap in a 4-link (I need to keep my back seat). I've yet to see any full frame built specifically with weight in mind and the IRS options all seem on the heavy side.

[Pragmatist]

The lightest live axle will be a truck arm rear suspension provided you build it with composite arms. 12.5 lbs. each.
Even a three link weighs more.

https://www.youtube.com/watch?v=San17XlQCGM

[stab6902]

The lightest live axle will be a truck arm rear suspension provided you build it with composite arms. 12.5 lbs. each.
Even a three link weighs more.

https://www.youtube.com/watch?v=San17XlQCGM

I like the outside of the box thinking! Do you have any issues with axle wrap using the leaf springs as control arms? Typically you'd want the truck arms to be as rigid as possible to keep pinion angle under control during acceleration/braking.

[Pragmatist]

The truck arms are for a 3/4 ton truck so stiffness is not a problem. I've been driving it this way for over four years and I still leave two long black markers from the 315s on the rear at least once a week.

[stab6902]

The truck arms are for a 3/4 ton truck so stiffness is not a problem. I've been driving it this way for over four years and I still leave two long black markers from the 315s on the rear at least once a week.

Glad to hear it's working well! The leaf springs are a convenient shape for floor pan clearance, and like you say, nice and light.

[Skip Fix]

The Stagnaros in their old early Shelby with leaf spring solid axle kicked butt at the SCCA national level in CP for a lot of years and freaking hauled a$$ when I saw them.

[Rod]

fun thread the old IRS x 3 link x 4 link debate, you forgot to add your leafs into the mix....

[dontlifttoshift]

Certainly, you have something to add.

[David Pozzi]

It’s too bad Mary Pozzi doesn’t come here anymore. She has been auto crossing her Art Morrison IRS for several years and doing well with it last I heard.

Maybe David Pozzi will give us an update. I’m not sure of the status of his 67 Camaro with IRS.

Don

Mary still likes the Art Morrison IRS. It does keep the rear tire at a more optimum camber on corner exit. IRS flows over uneven pavement much better without upsetting the chassis. Street ride is much much better than a stick axle. One ride and I was sold. Off the line it may not be quite as good as a 3 or 4 link but the AME version has as much anti-squat as you can put in an IRS and it its very good. I'd say it's better than the late model Corvettes and they do quite well off the line. I think it's a matter of getting enough rear weight bias to promote rear traction. Her Camaro gained around 30 lbs but it's all sprung weight, low, and in the rear so not a bad trade off. The lighter the car, the more important it is to go with an IRS. A Ford 9" with floater axles and brakes weighs 220 lbs. Add 45 lbs each for wheels and tires and that's 310 lbs rear unsprung weight your car has to control.
My 67 Camaro has the suspension fitted but I've been working on my house and rental house so haven't done much on it the last year and a half.