Your thoughts on IRS

[Garfy]

Perhaps I'm a few minutes behind, but the difference between the current IRS and the 03-04 Cobra IRS is night-and-day different, I mean, 15+ years development changes things an awful lot. The 10R80 is 15+ years better than the AOD-E, just as the GT500's TVS R2650 is better than the 03-04's (h)Eaton M112.

Let's not forget that the current 2020 GT with the 10-speed auto is faster than a 2007 Shelby GT500 that has a bigger engine and supercharger on the 1/4 mile. (That's what 13 years of tech improvements will do.)

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[TeeLew]

Perhaps I'm a few minutes behind, but the difference between the current IRS and the 03-04 Cobra IRS is night-and-day different

It's almost exactly the same. I'm sure there are subtle differences, but the geometry appears to be identical.

 

[edco]

.... As for handling on cornering and such, unless you drive it harder, you won't notice a difference (if you drive it so your "insurance driving app" doesn't dock you for hard accel, braking, turns, etc. then you won't notice a difference).

It is a good thing I don't have a smart phone with an insurance app. Pictured is the top handling mod made to the solid axle GT. Stock seats are comfortable but they don't cut it in a turn. Most drivers brake when they lean or slide in the seat. This is why the 911 trailing me does not see my brake lights in hard turns and he has to show off his turbos to get back in trail out of a corner.

The S550. The IRS is just better. I am OK with the stock seat, but a shell seat would allow higher G.

 

[Red65]

If you want to feel the REAL difference between an IRS and SRA car, hit some small potholes while going through a corner. SRA cars unsettle like crazy in those instances. Obviously, there's more benefits than just simply that, but that's an easily felt difference on the street. Bottom line though, I'm not sure how you wouldn't feel the difference in every day driving unless you really just don't do any spirited driving at all. The later S197 cars had a lot of suspension improvements in the SRA department, and it should be distinguished that the SRA in your 1st gen mustang and the SRA in the 5th gen are VERY VERY different.

Personally, I own both a 2017 GT and a 1965 Coupe, and there is absolutely no contest. You can make SRA handle well on a road course; the American Iron series, nascar, etc have show us this much. But SRA will always be inherently bad on rough and uneven surfaces.

 

[dman]

If you want to feel the REAL difference between an IRS and SRA car, hit some small potholes while going through a corner. SRA cars unsettle like crazy in those instances. Obviously, there's more benefits than just simply that, but that's an easily felt difference on the street. Bottom line though, I'm not sure how you wouldn't feel the difference in every day driving unless you really just don't do any spirited driving at all. The later S197 cars had a lot of suspension improvements in the SRA department, and it should be distinguished that the SRA in your 1st gen mustang and the SRA in the 5th gen are VERY VERY different.

Personally, I own both a 2017 GT and a 1965 Coupe, and there is absolutely no contest. You can make SRA handle well on a road course; the American Iron series, nascar, etc have show us this much. But SRA will always be inherently bad on rough and uneven surfaces.

Willow Springs says...the pothole up at 4 is your turn-in marker for 5. cost money to repave tracks
and...buy tires

 

[PaddyPrix]

It's almost exactly the same. I'm sure there are subtle differences, but the geometry appears to be identical.

Owning both, the "new edge" Cobras were more a parts bin setup that just checked a box. As you and I are just people on the internet, objectively, I know of a well known American Iron Champ who swapped in a current generation IRS into their 99, which would seem odd, as they had quite some time and probably plenty of opportunities to swap in a 99-04 Cobra IRS rear in. They might look the same, but I'd hazard a guess that the earlier model was fraught with geometry issues.

 

[dman]

Owning both, the "new edge" Cobras were more a parts bin setup that just checked a box. As you and I are just people on the internet, objectively, I know of a well known American Iron Champ who swapped in a current generation IRS into their 99, which would seem odd, as they had quite some time and probably plenty of opportunities to swap in a 99-04 Cobra IRS rear in. They might look the same, but I'd hazard a guess that the earlier model was fraught with geometry issues.

the early Cobra IRS was known as a parts bin build with only a few new parts using some existing elements. i had just bought a 98 Cobra and knew of the "next best thing" coming.
Was i glad i skipped that dance...wheel hop city! Ford supposedly under pressure offered a fix which i don't believe worked out to well. next, let's just detune the engine a bit and hope no one notices.
Busted...no Cobras for two years. good old American corporate denial, what else?

 

[Red65]

Owning both, the "new edge" Cobras were more a parts bin setup that just checked a box. As you and I are just people on the internet, objectively, I know of a well known American Iron Champ who swapped in a current generation IRS into their 99, which would seem odd, as they had quite some time and probably plenty of opportunities to swap in a 99-04 Cobra IRS rear in. They might look the same, but I'd hazard a guess that the earlier model was fraught with geometry issues.

The definitely had some serious geometry issues. I remember my days of browsing an older mustang forum waaaaay before I ever owned my 17', as I just had my 65 coupe at the time. There was a company that sold some adapting brackets that allowed you to put a cobra IRS into a 1st gen car. But the geometry issues had a lot of people torn between doing that swap vs just a really well set up Mike Maier SRA kit. Unsettling over rough surfaces aside, the Mike Maier stuff for 1st gens have some really good lap times to back them up.

 

[TeeLew]

the early Cobra IRS was known as a parts bin build with only a few new parts using some existing elements. i had just bought a 98 Cobra and knew of the "next best thing" coming.
Was i glad i skipped that dance...wheel hop city! Ford supposedly under pressure offered a fix which i don't believe worked out to well. next, let's just detune the engine a bit and hope no one notices.
Busted...no Cobras for two years. good old American corporate denial, what else?

I have an entire assembly in my garage. Many parts are direct swaps. Don't forget, the present suspension has some wheel hop problems, still. This is mainly a bushing issue. My guess is the early version was compounded by a limp noodle chassis. Live rear axles can have all sorts of wheel hop problems, too.

 

[dahnuguy]

I'm just wondering what those of you who have owned multiple Mustangs of different years think about the independent rear suspension? For years the big knock on Mustangs from all the car review guru's was it's old prehistoric solid rear axle. Well I've had my '19 GT for about a year and a half now, it's my third Mustang, a 1969 and a 2011. Personally I can't tell any difference between the handling of this one from the 2011. But when I look under the car I see a very complicated assembly that must have added thousands of dollars to the cost of the car and will probably need a boat load of maintenance further down the road. So what was the point of going that route? Just to shut the reviewers up. I doubt many of us will ever push these cars so close to their limit that we would notice a difference.

If you can't tell any difference at all, then it doesn't matter for you.
I prefer the feel and simplicity and rugged design of a solid axle.

I had a 79 Celica with solid axle and mild upgrades that was a lot of fun to drive.

My 65 Mustang had maybe 350HP and a Shelby suspension and was much faster in every metric than the then new Mustangs in the 80s and 90s and it would leave all the imports, with a few exceptions. It was very reliable and never needed anything. I beat on it for years and it never broke or wore out. Once I got sticky tires, and pushed it hard, the axle would walk in a hard corner.
That was interesting. I had leaf springs and they have limits. But I knew when that would happen and I could deal with it.

I had a 94 probe GT with the most amazing suspension I have ever driven. Mazda design and flawless in all conditions.

I had a 14 focus that felt similar to the probe but quicker and lighter.

I drove all these cars on the same little stretch of curvy road in my home town.

The celica and the focus were the most fun.

The Mustang blew through at much higher speed and was faster all the way, reuired less effort but was still fun.

The probe could carry more speed at every turn and seemed effortless but needed work to keep the revs up and maintain speed.

Recently I took my 2019 Bullitt down that same road.....while chatting with my son about the old days and feeling perfectly safe and not pushing anything, we slipped through the course with would have been unimaginable quickness and ease in the old days.

My son was not impressed and thought it was a simple easy road.
He barely noticed we were even doing anything. He kept asking when the tricky part was I kept telling him about on the way over.

I should have done it with a focus first to illustrate the difference.

The S550 mustang is so much more than can be used on public roads, it is ridiculous.
BMWs are the same way.
Inside it feels like a no effort Sunday drive as you blast through a mountain pass at double the the posted limit.

The focus requires more effort and driver input just go the speed limit on a curvy road.
That driver engagement is where the "fun" comes from.

If I want to get there quick and easy, I take the Bullitt.

If I want to work and adjust and put some effort in, I get in a solid axle V8 car with manual.

 

[dahnuguy]

The only issue I have with IRS is that weird insane thing that happens when a lot of power is put down too quickly and the car launches hard to the right and points you at the the ditch.

A 4 cyl rental car did this to me.
I corrected and recovered, but for someone inexperienced or not expecting that, it would have been a wreck.

My Bullitt hasn't done this yet, but I don't push the car to the limit either. Public roads will not support the limit of this car.

 

[TeeLew]

Public roads will not support the limit of this car.

It's funny you say this. I autocross my car and have done a lot of suspension work. I've kinda gotten to the point where if I make a change, I really can't evaluate it for handling on public roads. To do so, I have to be going faster than I feel is reasonable. I might feel the same change no problem on course, but I'm just not comfortable pushing fast enough on city streets for it to be a beneficial read. It's not MY car that makes me feel uncomfortable. It's all the others.

 

[dahnuguy]

It's funny you say this. I autocross my car and have done a lot of suspension work. I've kinda gotten to the point where if I make a change, I really can't evaluate it for handling on public roads. To do so, I have to be going faster than I feel is reasonable. I might feel the same change no problem on course, but I'm just not comfortable pushing fast enough on city streets for it to be a beneficial read. It's not MY car that makes me feel uncomfortable. It's all the others.

I have seen enough gravel in turns and potholes and weird dips and patches and on coming traffic across the line to make me wary of going too fast.

Blind corners, uneven , poorly maintained surfaces, limited line of sight and unaware drivers all around just add to the uncertainty.

There are no corner judges with flags or course cautions and no EMT track side when you are driving around the mountain.

When I was young, I didn't care. I literally did not care if I lived or died. I was over 100 everyday just going to work and over 140 frequently, sometimes in traffic, blind corners, whatever.
I was close to death on a daily basis. I pushed every car I drove to the limit and held it there. Thresh hold braking at every stop, max acceleration at every start. Ran from every blue light like it was a game, and usually won. Reckless abandon has the edge until it all ends.
I was so lucky so many times.

Yes I collected lots of tickets for everything you can think of.

Pushing modern sports cars to their limit is much harder to do now. The limit is so much higher and the roads are still the same.

I can have fun driving efficiently and spirited without being reckless now.
I enjoy the feeling of the machine working and being part of it.
I don't need the adrenaline or the shadow of death hovering over my shoulder anymore.
I guess that's growth, maturity, wisdom, or just getting old.

I doubt I will ever get close to the limit of a new Mustang on any public road.

There are too many variables, it is just reckless and inconsiderate and irresponsible to even try.

I am looking at joining SCCA or similar club and do some track days.
I doubt I will exceed the Mustang on the track either. I doubt I will survive my next wreck.
But it will be fun and safe to get closer to the edge.

 

[MikeHTally]

It only effects ride, handling, cornering and stability. But if you drive mostly smooth straight roads you probably won't notice much difference.

And ever since I discovered girls, I've appreciated curves over straight lines.

 

[MikeHTally]

"... Pushing modern sports cars to their limit is much harder to do now. The limit is so much higher and the roads are still the same."

Hear, hear! Who's is faster? It'll take 130+ to find that out. NOT a great idea.

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