You can adjust a solid axle's camber and toe by bending it. So, sorta.
You can adjust a solid axle's camber and toe by bending it. So, sorta.
A while back in Trans Am the cars could run IRS or solid axle. There was very little if any performance difference between the two.
The IRS can't have more than 25% (roughly) anti squat which is what makes it so bad for drag racing. A stick axle can be set up to have over 100% meaning the rear of the car rises on acceleration, excellent for drag racing.
Broken pavement: the stick axle's greater inertia makes it a poor choice. But on really BIG stuff, like Baja jumps, that's negated because a stick axle has less stuff to break and can be set up for huge suspension travel which outweighs the inertia issue. The rear engine buggies have to run IRS and they work well, but they do not have the amount of sheer travel the Trophy Trucks do.
Road racing/AX: set up properly, either can be a winner. My last car had a completely homebuilt SLA IRS, the current rig has a 3 link stick axle with Panhard. The Abomination is an EXCELLENT handling car, the Jensenator has some bugs to work out yet before I can say whether it's as good as the IRS. But at this point none of the problems can be proven to be a result of using the stick axle, it's more a product of the wrong spring rates and insufficient front suspension travel.
I like a 3 link / panhard set up like a 3rd gen Camaro. Better articulation than a 4 link. Factory 5 uses a 3 link as an upgraded over the fox suspension.
One thing about a live axle, it has NO camber or toe change under suspension travel. Those tires are always straight up and down. Now, 0 camber may not be ideal all the time, but it's perfect under acceleration (especially under squat - an IRS would have camber gain, and that squat would cause a reduction in traction patch). Plus, don't most IRSs have a wee bit of toe-in for stability? How are you supposed to properly hoon if you have a tail that doesn't want to step out?
What I've always been curious about is if there's a semi-dependent suspension that has camber change with suspension travel unless both wheels are moving equally. Basically, under something like straight-line braking, you would keep your static camber, but body roll would cause dynamic camber change.
Well, you do need to figure that there is "toe change" in practically all solid axles, or at least, there is roll steer. It's intentional.
FWIW, the maximum Motorsports shop car runs IRS now and typically runs lap times on the order of seconds quicker than when it ran a solid axle.
It goes like this in terms of mustang suspension for the 79-04 cars. MM Optimized IRS > MM TA/PHB solid > stock IRS > stock solid
I don't really care which type of axle it has, as long as that's the way that the power goes.
iceracer wrote: One upon a time the "unsprung weight" thing was big. Now with new technology, this no longer seems to be as big an issue.
Really?
In reply to EdenPrime:
I asked some folks about this when I was picking a Celica. Thought a GTS with IRS would be the way to go, but I think getting the solid axle was the right call. As I understand it, it's not a IRS vs. SRA thing, it's this rear suspension vs. that rear suspension. The IRS in the Celicas was a semi-trailing arm. Lots of toe change when it moves, so I'm told. So, you pretty much have to make it so it doesn't move. The SRA is a four link. Of course, as with any SRA, to make one side not mess up the other, you pretty much have to make it so it doesn't move, but it weighs a lot less.
That seems to be a pretty common theme. The IRS in a load of cars wasn't really designed to give more performance. It was designed not to take up too much interior room and make the car ride better. For a daily, I'd take the IRS. For autocross, the SRA sounds like it's usually easier to get working. I bet if you had A arms in the rear, it would work better. But you don't see that all that often.
fast_eddie_72 wrote: I bet if you had A arms in the rear, it would work better. But you don't see that all that often.
You mean like an SLA or like a Chapman strut?
iadr wrote: You will chew off your tires, and have unpredicatable handling, no matter how many hours were spent on supercomputers. IRS Sucks sucks sucks.
Seriously? 
93EXCivic wrote:iadr wrote: You will chew off your tires, and have unpredicatable handling, no matter how many hours were spent on supercomputers. IRS Sucks sucks sucks.Seriously?
I'm saying this as nicely as possible; I don't think I would pay much attention to that comment.
In reply to iadr:
That's funny, I would never consider a stick axle for any car I would drive on the street. I just rented a v6 mustang last weekend and I was appalled! It drove like a truck; a big nasty truck. It took less than 5 minutes for me to be shaking my head. IRS all the way for the street. Yeah, maybe engineers need to stop trying to improve on a perfect rear suspension... you know, a stick. Hamid
AverageH wrote: In reply to iadr: That's funny, I would never consider a stick axle for any car I would drive on the street. I just rented a v6 mustang last weekend and I was appalled! It drove like a truck; a big nasty truck.
Whatever. I live with a Mustang GT on a daily basis and it's just fine, as was my Fiat 124 Spider and first gen RX7. But then again I'm not some stuck up princess that can feel a pea beneath 10 mattresses, with an axe to grind about how my RWD car is suspended. It's no worse on the street than my BMW 7 series with the IRS or my stepson's 3 series.
I'm getting really tired of princesses masquerading as car enthusiasts. 
^ bwahahaha pwned
pres589 wrote:93EXCivic wrote:I'm saying this as nicely as possible; I don't think I would pay much attention to that comment.iadr wrote: You will chew off your tires, and have unpredicatable handling, no matter how many hours were spent on supercomputers. IRS Sucks sucks sucks.Seriously?
I'm going to give this a big +1.
Chris_V wrote:AverageH wrote: In reply to iadr: That's funny, I would never consider a stick axle for any car I would drive on the street. I just rented a v6 mustang last weekend and I was appalled! It drove like a truck; a big nasty truck.Whatever. I live with a Mustang GT on a daily basis and it's just fine, as was my Fiat 124 Spider and first gen RX7. But then again I'm not some stuck up princess that can feel a pea beneath 10 mattresses, with an axe to grind about how my RWD car is suspended. It's no worse on the street than my BMW 7 series with the IRS or my stepson's 3 series. I'm getting really tired of princesses masquerading as car enthusiasts.
Yeah dude, my Turbobrick had a stick axle, that worked fine - the Cruiser has one, works fine. The only vehicle I own without a stick rear axle is the minivan!!
AverageH wrote: In reply to iadr: That's funny, I would never consider a stick axle for any car I would drive on the street. I just rented a v6 mustang last weekend and I was appalled! It drove like a truck; a big nasty truck. It took less than 5 minutes for me to be shaking my head. IRS all the way for the street. Yeah, maybe engineers need to stop trying to improve on a perfect rear suspension... you know, a stick. Hamid
I think a lot of the truck-like feeling has to do with the absolutely horrid stock damping. The standard V-6 dampers are extra floaty and the GT/V-6 Performance Pack. dampers are little better. I understand Ford has to make this things to a price point and to appeal to a mostly baby-boomer/drag racing audience, but my impression of the V-6PP is that it is Ford's attempt to dip its toes in the Millenial waters before the IRS-equipped world Mustang drops. Wafting along the road on a cloud ain't gonna cut it; kids like me like our suspensions taut.
I have some Koni Yellows waiting to be installed into my 2013 V-6PP. That should help control body motion a lot. S197 racers including Sam Strano also report good experiences replacing the Panhard bar with a Watt's link. Since the motion of the axle is controlled in a straight line with the Watt's link instead of in an arc with the PHB, the axle motion is much better controlled and symmetrical. A Mumford link could possibly be even better, but AFAIK no one makes one for the S197 and they need to be carefully designed to reduce the chance of binding.
One big advantage of a properly designed IRS: adjustability. But then Chapman's Law rears it head: 'have you seen how bad someone can screw up a Weber with a screwdriver?'. 
Fuel for the fire: The bench racing is finally over. It turns out that despite a huge horsepower deficit and higher curb weight, the irs Camaro ZL1 trounces the new solid-axel Shelby GT500 as soon as the road bends.
http://www.insideline.com/chevrolet/camaro/2012/2012-chevrolet-camaro-zl1-vs-2013-ford-mustang-shelby-gt500-comparison-test.html
"Nothing is more humbling than watching a car with 100 fewer horses and the extra weight of an NFL running back disappear into the distance on a back road. But that's exactly what happened when we brought the two cars together to establish which is the best-driving pony car ever. The answer, as improbable as it seemed, was as obvious as the Camaro's shrinking taillights. Every corner was another opportunity for the Camaro to drop trou and wave its giant bowtie-emblazoned butt in the GT500's face."
Yeah I'd say that's fuel if you are making that statement off one slalom through some cones and a skidpad as opposed to on a track with laptimes. I am sure those will happen soon enough. Now I expect the camaro WILL best the shelby in handling, maybe not on laptimes due to power differences. But I think this is due to the fancy MR shocks and the aero built into the car not the fact its IRS is magic
nderwater wrote: Fuel for the fire: The bench racing is finally over. It turns out that despite a huge horsepower deficit and higher curb weight, the irs Camaro ZL1 trounces the new solid-axel Shelby GT500 as soon as the road bends. http://www.insideline.com/chevrolet/camaro/2012/2012-chevrolet-camaro-zl1-vs-2013-ford-mustang-shelby-gt500-comparison-test.html
I will pay attention to that when it is done by a magazine that doesn't suck. Either way I would take the GT500 by a mile anyway.
ReverendDexter wrote:fast_eddie_72 wrote: I bet if you had A arms in the rear, it would work better. But you don't see that all that often.You mean like an SLA or like a Chapman strut?
Yeah, thinking SLA more than Chapman strut, but yeah. Basically, I was thinking anything that's not a semi-trailing arm.
It seems a lot of cars with IRS use semi-trailing arms. Near as I can tell, all they're really good for is a nice ride on the street.
Miatas are A Arms all around, aren't they? I'd guess that's a big part of what makes them work so well. Shoot, I'm going to have to get one of those things someday.
Chris_V wrote:AverageH wrote: In reply to iadr: That's funny, I would never consider a stick axle for any car I would drive on the street. I just rented a v6 mustang last weekend and I was appalled! It drove like a truck; a big nasty truck.Whatever. I live with a Mustang GT on a daily basis and it's just fine, as was my Fiat 124 Spider and first gen RX7. But then again I'm not some stuck up princess that can feel a pea beneath 10 mattresses, with an axe to grind about how my RWD car is suspended. It's no worse on the street than my BMW 7 series with the IRS or my stepson's 3 series. I'm getting really tired of princesses masquerading as car enthusiasts.
Sorry Chris V but I'm not convinced. A true enthusiast can admit to the downfalls of certain suspension designs. One of my cars is a Spitfire, and I damn well know the weaknesses in the rear suspension! It was WAY obvious how bad that Mustang felt. My wife had it worse while sitting in the back seat; she complained of the bouncy ride nonstop. I didn't like that her headrest was the rear window either, but that's another story. I've owned enough stick axle cars to not want to own one again. Trust me, I was really hoping to like it but I was really disappointed. I have no problem with people liking stick axles, I'm just not one of them. Yes, I am a princess. I daily drive a Miata.
Hamid
RexSeven wrote:AverageH wrote: In reply to iadr: That's funny, I would never consider a stick axle for any car I would drive on the street. I just rented a v6 mustang last weekend and I was appalled! It drove like a truck; a big nasty truck. It took less than 5 minutes for me to be shaking my head. IRS all the way for the street. Yeah, maybe engineers need to stop trying to improve on a perfect rear suspension... you know, a stick. HamidI think a lot of the truck-like feeling has to do with the absolutely horrid stock damping. The standard V-6 dampers are extra floaty and the GT/V-6 Performance Pack. dampers are little better. I understand Ford has to make this things to a price point and to appeal to a mostly baby-boomer/drag racing audience, but my impression of the V-6PP is that it is Ford's attempt to dip its toes in the Millenial waters before the IRS-equipped world Mustang drops. Wafting along the road on a cloud ain't gonna cut it; kids like me like our suspensions taut. I have some Koni Yellows waiting to be installed into my 2013 V-6PP. That should help control body motion a lot. S197 racers including Sam Strano also report good experiences replacing the Panhard bar with a Watt's link. Since the motion of the axle is controlled in a straight line with the Watt's link instead of in an arc with the PHB, the axle motion is much better controlled and symmetrical. A Mumford link could possibly be even better, but AFAIK no one makes one for the S197 and they need to be carefully designed to reduce the chance of binding.
Thanks for the info RexSeven. It really bounced around everywhere! I hope your mods improve the feel. With how popular the new Mustangs have gotten, I really felt that I needed to give them a try. My neighbor has a Saleen Patriot Special Edition Mustang and at some point I'll go for a ride. He pops the hood a lot but I don't think it has left his garage once in the last several months. I think a lot of Mustang owners can be that way!
-Hamid
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