Live Axle vs IRS question
7/11/14, 08:52 PM
#21
Bullitt Member
As far as avoiding first-year models, that was really a thing of the past. Seriously. Everything has changed. Cars don't need to be broken in any more, at least not like in the old days. Tolerances are so much tighter than before. Cars are just made better, period. I bought the first-year 2005, and have had ZERO issues with it in 9+ years. It's never been back to the dealer. No recalls, no warranty problems, no issues. And this is a car that has been a daily driver until I got the Mini last year, and has been to HPDE track day events 7 times now. This first year car is definitely the most reliable car I ever owned in my life.
7/11/14, 10:47 PM
#23
I'd rather have a live axle RWD Mustang than a FWD car any day. I have a Mini as a daily driver, and it sticks like glue, but oh how I wish it were RWD - like God intended. :-)
That said, there is one scenario where FWD is better than RWD, and that's driving in snow. You can get by with a FWD and all-season tires, but a RWD with all-seasons is challenging.
There's a reason that almost every race car (other than AWD rally cars) are RWD.
That said, there is one scenario where FWD is better than RWD, and that's driving in snow. You can get by with a FWD and all-season tires, but a RWD with all-seasons is challenging.
There's a reason that almost every race car (other than AWD rally cars) are RWD.
Last edited by Astenax; 7/11/14 at 11:04 PM.
7/14/14, 08:10 AM
#24
Join Date: January 30, 2004
Location: DMV
Posts: 2,980
Likes: 0
Received 0 Likes
on
0 Posts
While the live axle can be, and has been, made to handle very, very well, or, to ride very, very well, the IRS will basically expand not only the rear axle's capabilities but overall performance envelope. In other words, it will allow increases in both handling and ride, much less of the either, or compromise required of the heavy live axle.
The IRS will also be able to maintain higher levels of performance, or safety if you wish to look at it that way, across a wider range of road conditions and surfaces, all while beating you up less.
If you liked that handling of the Boss 302's, imagine the 2015 exceeding its numbers while likely delivering a much better, more sophisticated ride over a far greater range of real world road conditions (not just smooth tracks). If the handling prowess of the Fiesta and Focus STs are any indication, the 2015 Stang should be an back road beast.
The IRS will also be able to maintain higher levels of performance, or safety if you wish to look at it that way, across a wider range of road conditions and surfaces, all while beating you up less.
If you liked that handling of the Boss 302's, imagine the 2015 exceeding its numbers while likely delivering a much better, more sophisticated ride over a far greater range of real world road conditions (not just smooth tracks). If the handling prowess of the Fiesta and Focus STs are any indication, the 2015 Stang should be an back road beast.
7/14/14, 08:19 AM
#25
Mach 1 Member
While the live axle can be, and has been, made to handle very, very well, or, to ride very, very well, the IRS will basically expand not only the rear axle's capabilities but overall performance envelope. In other words, it will allow increases in both handling and ride, much less of the either, or compromise required of the heavy live axle.
The IRS will also be able to maintain higher levels of performance, or safety if you wish to look at it that way, across a wider range of road conditions and surfaces, all while beating you up less.
If you liked that handling of the Boss 302's, imagine the 2015 exceeding its numbers while likely delivering a much better, more sophisticated ride over a far greater range of real world road conditions (not just smooth tracks). If the handling prowess of the Fiesta and Focus STs are any indication, the 2015 Stang should be an back road beast.
The IRS will also be able to maintain higher levels of performance, or safety if you wish to look at it that way, across a wider range of road conditions and surfaces, all while beating you up less.
If you liked that handling of the Boss 302's, imagine the 2015 exceeding its numbers while likely delivering a much better, more sophisticated ride over a far greater range of real world road conditions (not just smooth tracks). If the handling prowess of the Fiesta and Focus STs are any indication, the 2015 Stang should be an back road beast.
(although I still like the way my Boss handles) lol
7/14/14, 09:12 AM
#26
Cobra Member
While the live axle can be, and has been, made to handle very, very well, or, to ride very, very well, the IRS will basically expand not only the rear axle's capabilities but overall performance envelope. In other words, it will allow increases in both handling and ride, much less of the either, or compromise required of the heavy live axle. The IRS will also be able to maintain higher levels of performance, or safety if you wish to look at it that way, across a wider range of road conditions and surfaces, all while beating you up less. If you liked that handling of the Boss 302's, imagine the 2015 exceeding its numbers while likely delivering a much better, more sophisticated ride over a far greater range of real world road conditions (not just smooth tracks). If the handling prowess of the Fiesta and Focus STs are any indication, the 2015 Stang should be an back road beast.
7/14/14, 09:28 AM
#27
Cobra R Member
The Fiesta doesn't have a live axle. It has a twist beam rear setup, and front is independent. The twist beam suspension does allow for some movement, and really isn't the same as a solid axle (and is in no way "live" since it's FWD).
7/14/14, 09:32 AM
#28
Cobra Member
Join Date: October 12, 2004
Location: Milwaukee, WI
Posts: 1,188
Likes: 0
Received 7 Likes
on
4 Posts
One of the things Car and Driver mentioned in one of the articles on the new Mustang is how the IRS allowed them to tune out a lot of the dive and squat. One of the reasons I got rid of my 2005 Mustang is that when I hit the brakes the front end would dive like barge cresting a big wave. It felt so similar to my grand parents Buick that I had to get out of it. Now granted I had a V6 convertible which was set up with softer springs, but I've driven other convertibles (even the Chrysler Sebring rental) that didn't dive and wallow around the road like a mid 80's Cadillac. I am hopeful that the IRS will allow tighter handling in the convertibles than the live axle did. If not I at least have the performance pack as an option to hopefully tighten things up a bit.
7/14/14, 09:56 AM
#29
Bullitt Member
One of the things Car and Driver mentioned in one of the articles on the new Mustang is how the IRS allowed them to tune out a lot of the dive and squat. One of the reasons I got rid of my 2005 Mustang is that when I hit the brakes the front end would dive like barge cresting a big wave. It felt so similar to my grand parents Buick that I had to get out of it. Now granted I had a V6 convertible which was set up with softer springs, but I've driven other convertibles (even the Chrysler Sebring rental) that didn't dive and wallow around the road like a mid 80's Cadillac. I am hopeful that the IRS will allow tighter handling in the convertibles than the live axle did. If not I at least have the performance pack as an option to hopefully tighten things up a bit.
7/14/14, 10:01 AM
#30
Cobra Member
Sorry. I should have said solid axle. Live was stuck in my head. Twist beam is still considered solid even though it's slightly better.
7/14/14, 10:06 AM
#31
Cobra Member
One of the things Car and Driver mentioned in one of the articles on the new Mustang is how the IRS allowed them to tune out a lot of the dive and squat. One of the reasons I got rid of my 2005 Mustang is that when I hit the brakes the front end would dive like barge cresting a big wave. It felt so similar to my grand parents Buick that I had to get out of it. Now granted I had a V6 convertible which was set up with softer springs, but I've driven other convertibles (even the Chrysler Sebring rental) that didn't dive and wallow around the road like a mid 80's Cadillac. I am hopeful that the IRS will allow tighter handling in the convertibles than the live axle did. If not I at least have the performance pack as an option to hopefully tighten things up a bit.
The irs uses struts in the rear as opposed to shocks. That alone makes a huge difference for dive and squat. Of course ford makes it sound magical that the irs fixes this. And indirectly it does due to allowing for struts. But for the most part. This issue can be eliminated regardless of having a solid axle or irs.
Last edited by typesredline; 7/14/14 at 10:08 AM.
7/14/14, 10:53 AM
#32
I wouldn't say fixed but it is less noticeable because of the stiffer suspension which affects ride quality depending your sensitivity level. With IRS you can have your cake and eat it too.
7/14/14, 11:03 AM
#33
This has less to do with the axle and more to do with fords suspension choices. When people swap the springs, shocks, and struts, the dive and squat disappear. The irs uses struts in the rear as opposed to shocks. That alone makes a huge difference for dive and squat. Of course ford makes it sound magical that the irs fixes this. And indirectly it does due to allowing for struts. But for the most part. This issue can be eliminated regardless of having a solid axle or irs.
Last edited by newpony; 7/14/14 at 11:04 AM.
7/14/14, 11:25 AM
#34
Mach 1 Member
Even though the IRS can weight more, one of the primary reasons that’s of less significance is where the weight is: sprung verses unsprung weight. IRS has much less unsprung weight making each "corner" of the car capable of reacting quicker keeping the tire in contact with the road.
It's also worth keep in mind that just because the 2015 is supposed to weigh more doesn't that mean all, or for that matter any, of the weight gain came from the addition of IRS. Straight axles are very heavy assemblies.
John
7/14/14, 01:04 PM
#35
Post *****
Join Date: December 14, 2007
Location: State of Jefferson Mountains USA
Posts: 20,005
Likes: 0
Received 4 Likes
on
4 Posts
Most of the FWD crowd will let off the accelerator at the wrong time and now they have made the rear end even lighter.
Just like on snow and ice, giving it some throttle helps you regain traction and forward momentum. Letting off completely and you see your **** swinging by. 
Same principle applies on pavement. Sadly, too many don't learn but just make crybaby posts that the first 50 years of Mustang sucked because of no IRS.
Many are going to learn that IRS is not the magic bullet that replaces skill and knowledge of the handling characteristics of your machine.
Last edited by cdynaco; 7/14/14 at 01:05 PM.
7/14/14, 01:24 PM
#36
Cobra Member
While excessive dive in the early S197 GT's may have been reminiscent of 70/80's boatish, by the 08 Bullitt, Ford was tweaking suspension. However if you lower and tighten up too much you lose the benefit of weight transfer. Which is a function of SRA traction and handling both at the strip and on two lane twisties. You have to let the suspension work or you wind up like the whiners 'omg my rear end skipped on a pebble!'. Most of the FWD crowd will let off the accelerator at the wrong time and now they have made the rear end even lighter. Just like on snow and ice, giving it some throttle helps you regain traction and forward momentum. Letting off completely and you see your **** swinging by. Same principle applies on pavement. Sadly, too many don't learn but just make crybaby posts that the first 50 years of Mustang sucked because of no IRS. Many are going to learn that IRS is not the magic bullet that replaces skill and knowledge of the handling characteristics of your machine.
Most of the FWD crowd will let off the accelerator at the wrong time and now they have made the rear end even lighter. Just like on snow and ice, giving it some throttle helps you regain traction and forward momentum. Letting off completely and you see your **** swinging by. Same principle applies on pavement. Sadly, too many don't learn but just make crybaby posts that the first 50 years of Mustang sucked because of no IRS. Many are going to learn that IRS is not the magic bullet that replaces skill and knowledge of the handling characteristics of your machine.Well said!
7/14/14, 01:31 PM
#38
Mach 1 Member
Join Date: November 26, 2012
Location: South Carolina
Posts: 1,056
Likes: 0
Received 0 Likes
on
0 Posts
While excessive dive in the early S197 GT's may have been reminiscent of 70/80's boatish, by the 08 Bullitt, Ford was tweaking suspension. However if you lower and tighten up too much you lose the benefit of weight transfer. Which is a function of SRA traction and handling both at the strip and on two lane twisties. You have to let the suspension work or you wind up like the whiners 'omg my rear end skipped on a pebble!'. Most of the FWD crowd will let off the accelerator at the wrong time and now they have made the rear end even lighter. Just like on snow and ice, giving it some throttle helps you regain traction and forward momentum. Letting off completely and you see your **** swinging by. Same principle applies on pavement. Sadly, too many don't learn but just make crybaby posts that the first 50 years of Mustang sucked because of no IRS. Many are going to learn that IRS is not the magic bullet that replaces skill and knowledge of the handling characteristics of your machine.
Most of the FWD crowd will let off the accelerator at the wrong time and now they have made the rear end even lighter. Just like on snow and ice, giving it some throttle helps you regain traction and forward momentum. Letting off completely and you see your **** swinging by. Same principle applies on pavement. Sadly, too many don't learn but just make crybaby posts that the first 50 years of Mustang sucked because of no IRS. Many are going to learn that IRS is not the magic bullet that replaces skill and knowledge of the handling characteristics of your machine.
7/14/14, 02:33 PM
#39
Join Date: January 30, 2004
Location: DMV
Posts: 2,980
Likes: 0
Received 0 Likes
on
0 Posts
You certainly can control the heavy inertia of a live axle, but that then requires very stiff springs, shocks and bushings which lead to a much greater degradation in ride quality and poor road compliance than an equivalently sporty IRS design. Of course, that would have little negative effect on rather smooth roads and tracks, but in daily driving in the broader real world, that would be a noticeable compromise. A live axle simply will exact more compromises of either ride or handling, in a narrower envelope, than a comparable IRS design.
While the FWD Fiesta does have a "live axle," depending on how you wish to define it, it obviously is not a drive axle with the intendant heavy architecture and componentry, thus is actual quite light in terms of unsprung and overall weight, being basically along for the ride. It is somewhat of a price-imposed design for the next rung up Focus ST does have an IRS design. In any case though, a non-driven FWD's lightweight "live axle" would exact less of a negative compromise than that of a very heavy RWD live axle on a powerful car like a Mustang.
In sum: it is the axle's unsprung weight that is perhaps the most critical factor hear rather than the overall suspension system weight, much like how a few ounces of weight can be far more important in an engine's valve train than say, a bit more meat on the block casting.
7/14/14, 02:40 PM
#40
Join Date: January 30, 2004
Location: DMV
Posts: 2,980
Likes: 0
Received 0 Likes
on
0 Posts
While excessive dive in the early S197 GT's may have been reminiscent of 70/80's boatish, by the 08 Bullitt, Ford was tweaking suspension. However if you lower and tighten up too much you lose the benefit of weight transfer. Which is a function of SRA traction and handling both at the strip and on two lane twisties. You have to let the suspension work or you wind up like the whiners 'omg my rear end skipped on a pebble!'.
Most of the FWD crowd will let off the accelerator at the wrong time and now they have made the rear end even lighter. Just like on snow and ice, giving it some throttle helps you regain traction and forward momentum. Letting off completely and you see your **** swinging by. Same principle applies on pavement.
Sadly, too many don't learn but just make crybaby posts that the first 50 years of Mustang sucked because of no IRS.
Many are going to learn that IRS is not the magic bullet that replaces skill and knowledge of the handling characteristics of your machine.
Most of the FWD crowd will let off the accelerator at the wrong time and now they have made the rear end even lighter.
Just like on snow and ice, giving it some throttle helps you regain traction and forward momentum. Letting off completely and you see your **** swinging by. Same principle applies on pavement. Sadly, too many don't learn but just make crybaby posts that the first 50 years of Mustang sucked because of no IRS.
Many are going to learn that IRS is not the magic bullet that replaces skill and knowledge of the handling characteristics of your machine.
Of course, if drag racing, a good bit of rear weight transfer and squat is actually a good thing.
IRS certainly won't obviate the laws of physics nor stupidity, though it might cover up the latter just a touch better. The most important handling component lies between one's ears.