IRS vs solid axle
 

Hey guys,

Just asking a general question here, but realistically which is pound for pound dollar for dollar better? I know IRS is ultimately better. But in a "retro-fit" application which is better? I'm not discrediting roadster shop or art morrison by any means (I'm a huge fan of both) but is the upwards of $10k really better than a well engineered 3 link or like wise solid axle set up? And on the same lets use a cobra IRS set up for example. Is the added weight (just assuming, IDK the exact weights of both) of packaging this system really worth it? What's you guys take?

As I said sorry for such a general and vague question but I'm just thinking out loud and looking for opinions.

Thanks
Kody

A Ford 9" with no floater and 14" rotors, 6 piston calipers weighs 195 lbs.
A Ford 9" with floater and 14" rotors and 6 piston calipers weighs 220 lbs.

To compare to the Morrison, you would need to know the weight of the shock mount bar, panhard bar, brackets, and 3 link equipment.
According to Morrison, their IRS is 30-40 lbs heavier total than a Ford 9" with suspension, but it has an even larger ring gear & is stronger. The added weight is low and to the rear which is the best place to add it if you have to add weight. The un-sprung weight drops from 150 lbs per wheel to 80 lbs assuming a 50 lb wheel and tire.

In terms of ride, IRS wins hands down, it's way way smoother riding & you will enjoy driving the car so much more on the street, it isn't funny.

In terms of autocross times, IRS will beat a stick axle with equal tuning time invested. How much? I don't know if it's a second faster, but somewhere close to that.
How much better on a road course? I don't know, but if it's a bumpy track the IRS will be faster, since lap times will be longer on a track, I think easily a second faster, maybe more, but I'm guessing. You will feel more confident going over rough sections of the track.

For a car to drag race, the stick axle probably has an edge in theory, more anti-squat could be used, but there are plenty of late model Corvettes doing pretty well at the drags.

Kody, first I think you are off a bit on that $10K?? I think the A/M unit is almost $12K just for the unit and then if you can't install it yourself you have another $6-8K in labor to install it. Now again you will close to that to install most of the 3-4 link setups as well so more of a wash on the labor end.

As for the Roadster Shop setup your not just buying their IRS your buying a complete chassis but if you start adding up all the cost of ALL of your suspension its not that far off with the added cost of labor compared to installing the RS frame.

Now as far as the rest I have know idea but as most would say, what are your goals? Have fun look cool, or are you looking to be at the front of the pack?

I know your just kicking around the question but to think about for sure, but great topic for sure, especially with all the opinions we have today from a lot of great company's making awesome products!!

David you bring up a very good point that I didn't even consider in unsprung weight on the tires. I didn't even think of that! And also a lot of good input.

And I didn't know that the IRS was that light. I know a 9" can be a hefty chunk of weight.

David I know you guys have the A/M IRS in Marry's car is there any potential limits on rear tire size with the A/M rear clip?




Rick I know I came in a little low on the price, I just pulled a bare RS clip with no options and that was the price so I just threw that one up there lol.

As far as install, I'm building my whole chassis myself and plan on just buying the rear suspension as a "clip" doing it myself so I'm only looking at the parts prices.





Also what is every body's thoughts on a C6 IRS swap and using the trans axle?

Wow, building an IRS yourself. Quite an undertaking, your going to learn a whole bunch.

There are a few cars that have been built with C4 corvette rears. As long as you plan to use the stock hub to hub width it is a pretty easy swap, just go with coil-over shocks instead of the transverse spring. Stay away from narrowing the rear width too much, as other issues start to crop up and need to be resolved.
Look for the Beach Cruiser first gen Camaro and the P1800 on this site. Full custom installs, using much of the factory parts with custom install mods to fit the build.
https://lateral-g.net/forums/show...ighlight=p1800
https://lateral-g.net/forums/show...ghlight=camaro

Regarding the C5/C6 rear end and transaxle, that setup tends to blow out the back seat of most cars. There is one build on this site (1960's vintage XK120 Jaguar) where they mounted the C5/C6 Vette IRS suspension and brakes on narrow frame rails, and are using a 5th gen Camaro gear case, with modified torque tubes. https://lateral-g.net/forums/show...ghlight=jaguar

Hot Rod Magazine did a comparison of systems in existence a few years ago. It gives some good points of consideration when thinking about an IRS swap, especially limitations of the different set ups. http://www.hotrod.com/how-to/chassis...or-musclecars/

If you are looking for an outright swap with a complete rear, there is a first gen Camaro that is using a Nissan 350Z rear end (build thread is on protouring.com), lots of other cars and trucks using 1990's Ford Thunderbird IRS, and I've even seen a 69 Camaro that has an IRS from 7-series BMW, with cantilever shock set up. http://pacificfabrication.com/barrys-camaro

Got your work cut out for you. Just picking the type of IRS is a chore by itself.

No limits on tire width.
If your horsepower will be high, the selection gets more limited. The C4 uses the Dana 44, which is good, but I don't know if it will handle 600hp. Newman offers a beefed up aluminum case for them. The 8.8 is probably pretty strong.

At this point I'm really leaning towards the C6 transaxle and IRS to help move some weight to the rear and because I know it can hold the power it's also almost a perfect match width wise. I'm only looking to make at the most 650-700hp.

Gm takes special care to not induce wheel hop, so if you can do that, it may work. How would you deal with the torque tube input shaft?

I spoke with Rodger at ironworks a long time ago about this set up and he said he would cut the factory tube and make a new driveshaft and then weld in a new longer/shorter tube to reach the desired length.


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very interesting thread, subscribed. :innocent: