IRS vs Live Axle

[38sho]

Most IRS diffs seem easier to work on as well, you can usually drop them from the vehicle quickly and have all the room in the world to work on the innards.

where as a bigger solid axle is definitely cumbersome


I must say I'm a solid axle truck lover too, but they have made something decent with independent suspension.... are you all forgetting the Hummer? That is a fairly capable vehicle.

 

[MrHorspwer]

Quote:
Of course Ford went BACK to live axle for the Shelby cars....... What that says, I'm not sure


There may be a very interesting tale behind this. Some folks say that this is why John Coletti left Ford. He officially "retired," yet went on to form his own automotive firm. Strange, isn't it, that someone who "retired" would immediatly go right back to work in the same field.

The rumor goes, Coletti was dead set on IRS for the new Mustang. The IRS in the SN-95 was always a compromise, made to fit in a location that was designed to hold a live axle. Coletti wanted a proper, from-scratch desgined IRS for the new Mustang in 2005. With the competition (Camaro/Firebird) gone (at the time, at least), the bean-counters at Ford said no way. To the bean-counters, the proposed IRS was too expensive to implement, too expensive to manufacture, too expensive for parts, and that without any competition, ride and handling would be *acceptable* with a solid axle. Coletti left just after the launch of the 2005 Mustang.

 

[BeanCounter]

Originally Posted By: 38sho
Most IRS diffs seem easier to work on as well, you can usually drop them from the vehicle quickly and have all the room in the world to work on the innards.

where as a bigger solid axle is definitely cumbersome


I don't even have to pull the 9" to work on it.
Wheels off, axle shafts out, then the 3rd member iss yours for the taking. Pretty easy, which explains one of the many reasons many NASCAR series still run it.

 

[BeanCounter]

Originally Posted By: Gary Allan

I didn't see that said anywhere. I saw (essentially) that you would have to tweak the suspension on a solid axle to get it to handle. You would have to tweak IRS to give it comparative strength.

..but I may not be reading enough into it..


When he replied about modifications, he was responding to a comment I made strictly about being able to build a solid axle stronger for less money.
I agree with the underlined comment above for the most part though, so I think we are on the same page.

 

[Papa Bear]

The simple fact that we are debating this issue shows me that there is no clear winner ....

I have no intent on racing/Bajaing/off-roading my Chev Uplander, my main goal is to put the grandkids and kids in it and go for a picnic.
My preferred suspension setup would be the cheapest, simplest and most durable rear( probably a solid rear axle with leaf springs ) and the front suspension that the van has now seems OK

 

[ARB1977]

Live axle no dought. IRS if built right can be pretty strong too. My father inlaw has a 427 Shelby Cobra with a Jag rearend...its IRS.

 

[dailydriver]

Originally Posted By: Gary Allan
Originally Posted By: BeanCounter
Originally Posted By: Gary Allan
Quote:
It appears most the items you mentioned for a solid axle have nothing to do with the unit but rather the suspension.


Which handling, if I read the original post correctly and mind read for intent, would be the only thing that one could adapt. The axle itself is a fixed object.

I saw no reference to "putting blown out ultra tweaked hp to the ground that was never offered off of the show room floor" in the original post.




Read my comment that he responded to, Gary.

Quote:
. That was never part of the comparison as far as I was aware. And a full float setup is needed to get as strong as an independent setup? Reality must be severely skewed...

I didn't see that said anywhere. I saw (essentially) that you would have to tweak the suspension on a solid axle to get it to handle. You would have to tweak IRS to give it comparative strength.



..but I may not be reading enough into it..



YES, you 'got' my point, he did NOT!!
I was NOT stating that a full floater was needed to get a solid axle as "strong" as an IRS, just that it might be needed to get a solid to handle as well as a properly sorted IRS (as well as the other mentioned solid axle add ons/mods).

 

[Steve S]

Originally Posted By: ARB1977
Live axle no dought. IRS if built right can be pretty strong too. My father inlaw has a 427 Shelby Cobra with a Jag rearend...its IRS.
The Shelby has to be an incredable car.

 

[Steve S]

I would rather have a live axle it is simpler.

 

[dailydriver]

Originally Posted By: BeanCounter
Originally Posted By: Gary Allan

I didn't see that said anywhere. I saw (essentially) that you would have to tweak the suspension on a solid axle to get it to handle. You would have to tweak IRS to give it comparative strength.

..but I may not be reading enough into it..


When he replied about modifications, he was responding to a comment I made strictly about being able to build a solid axle stronger for less money.
I agree with the underlined comment above for the most part though, so I think we are on the same page.



NO DOUBT one can built a stronger solid axle for less money (I would NEVER argue otherwise!!).
What I was stating was that it would take some coin/mods to built a solid axle to handle as well as a properly sorted IRS (on anything other than glass smooth road/road course), just as it would not be cheap to get an IRS as strong as an already bombproof soild axle.

That's all.

So I guess we are on the "same page" after all?

 

[fdcg27]

I've had some of each over the years, and it doesn't usually make that much difference.
Semi-trailing arm IRS can be either nasty or great, depending upon both car and driver.
For most road cars, a live axle is simple and durable and works perfectly well.
A good IRS is probably better.
For example, I really liked my old W123s, and my old Vanagon was worlds better than our current (now old) Aerostar.
Still, most of the time in most applications, there is no dramatic difference.
The driver adjusts to and works with whatever the car may have.

 

[artificialist]

The biggest limitation of a driven solid axle rear suspension is camber. It has to be next to zero, but and independent RWD suspension can have -2.5 camber if it is needed.

It really amazes me how many FWD cars have the equivalent of a solid axle in the rear, rather than use a 4 wheel independent suspension. That in mind, such suspensions can be built with negative camber.

I would simply take this as a sign that the auto maker was being cheap, but the Nissan Maxima built between 1995 and 2001 was loved for its feel, and it had a solid axle.

 

[labman]

I am on my third small GM FWD. Since the rear does so little in a FWD, it is a good place to save money both initially and upkeep. Drums and the semi independent beam axle are cheap in the first place and cheap to keep up and still work fairly well.

 

[Shannow]

Originally Posted By: artificialist
The biggest limitation of a driven solid axle rear suspension is camber. It has to be next to zero, but and independent RWD suspension can have -2.5 camber if it is needed.


Aussie V-8 supercars run heaps of negative camber on the back, and have adjustable toe on their solid axle rear ends.

http://www.motorsm.com/motorsport/auto/AUS_V8_Supercar/Oz_V8_cars.asp

In the early day's they'd turn the axle splines into a sort of CV joint, by machining a radius on the spline.

If I was building a kit car or the like, I'd favour dedion.

 

[edwardh1]

Originally Posted By: artificialist
The biggest limitation of a driven solid axle rear suspension is camber. It has to be next to zero, but and independent RWD suspension can have -2.5 camber if it is needed.

It really amazes me how many FWD cars have the equivalent of a solid axle in the rear, rather than use a 4 wheel independent suspension. That in mind, such suspensions can be built with negative camber.

I would simply take this as a sign that the auto maker was being cheap, but the Nissan Maxima built between 1995 and 2001 was loved for its feel, and it had a solid axle.


the rear of that maxima would not hold the road well. the front steered tight, but hit a bump in a turn and the rear skips- cheap design

 

[ARB1977]

Originally Posted By: Steve S
I would rather have a live axle it is simpler.

For sure. What sucks about the Shelby is the brakes are inboard....meaning near the diff. In order to change the brakes the axle shafts need to come out.

 

[labman]

Originally Posted By: Steve S
I would rather have a live axle it is simpler.


That is why I like the flexible beam. It has the simplicity of a solid axle, yet some of the advantages of the IRS. The incremental improvement with a full IRS isn't worth the expense. A fine piece of engineering given little respect.

 

[dailydriver]

Originally Posted By: ARB1977
What sucks about the Shelby is the brakes are inboard....meaning near the diff. In order to change the brakes the axle shafts need to come out.



Which "Shelby" are you speaking about, the original AC Cobra versions??

 

[artificialist]

Originally Posted By: Shannow
Originally Posted By: artificialist
The biggest limitation of a driven solid axle rear suspension is camber. It has to be next to zero, but and independent RWD suspension can have -2.5 camber if it is needed.


Aussie V-8 supercars run heaps of negative camber on the back, and have adjustable toe on their solid axle rear ends.

http://www.motorsm.com/motorsport/auto/AUS_V8_Supercar/Oz_V8_cars.asp

In the early day's they'd turn the axle splines into a sort of CV joint, by machining a radius on the spline.

If I was building a kit car or the like, I'd favour dedion.

How durable is that on a daily driven car?

anyway, there was another independent rear suspension that I don't remember being mentioned: The swing axle type found on the Mercedes Gullwing and similar other IRS cars.

I heard that the large camber changes made those cars difficult to control.