So why does my S650 GT not handle as well as my S550 GT?

[Upacurb]

@Upacurb .....there are a quite number of authoritative videos wherein the differences in the S550 and S650 are concerned. One of the most informative is a lengthy one from Ford.

Well Ford is not going to say the new Mustang is worse than or the same as the old one....they would never sell more cars that way : )

You really need to drive all the different cars to understand the differences .....videos really dont cut it ....

I now have a lot of seat time (hours) in

S550 GT PP1 A10 (put 40K miles on)
S550 GT350R (put 7K miles on)
S550 GT350
S550 GT500 w/ handling pack

and a little seat time (say 15 minutes...but did get to throw them into some corners) in

S650 GT PP1 A10
S550 GT500 CFTP
S550 Mach 1 Handling Pack 6M
S650 Dark Horse Handling Pack 6M
S550 EcoBoost PP A10

Conclusion - There is no bad variation of the S550 or S650- they are all fun cars in different ways....in fact its amazing how different some different variations can feel .....

In fact the 2 that I though felt most similar in feel were the S550 GT500 and S650 Dark Horse while the 350R feels the most different from all of them.....

I think the difference in feel is what is throwing the OP off - both S550 and S650 GTs are capable cars but definitely feel different ... some like blonds some like brunettes : )

Sponsored

 

[Upacurb]

FYI

I am a convertible owner.

The convertible is about 180 lbs heavier than the fastback, and has a slightly more neutral front/rear weight ratio as most of the additional weight is over the rear axle. They will flex more than a fastback even with the rear subframe added.

The vert will typically have a slightly smaller sway bar than the same car in a fastback to reduce the possibility of oversteer.

You may like the feel of the vert because of the above factors. With similar alignments, I believe the fastback will outcorner my vert as it came from the factory.

CVCashmere

Agree- less weight and the weight for the convertible top mechanism is higher up - so from a physics point of view (not to mention the stiffer body) the coupe should outhandle the convertible.....that being said on a warm summer night convertible>coupe

 

[robvas]

@MAT1955

What BMR had to say about those braces (which rust out like yours did and most people ended up just throwing them in the trash so they didn't have to take them off to work on the rear of the car):

I do not have the engineering or "scientific" data to back up my thoughts on this.

But, I have always had a very hard time accepting that the OE braces do much of anything.

1: They are not very strong.

2: They are bolted on via weak hardware.

3: Where they attach to, the sump/tire well is a very weak area.

4: If torsional rigidity is the purpose - I fail to see how they are effective when they span from the outboard subframe area and mount inboard close together. When we design a chassis stiffening part, especially for something like this particular part, we would want it to spread wide and triangulate together. When you mount a "brace" to an area of the car you want more rigid, why would you mount the two individual pieces so close together?

As you will see in the picture above of the aftermarket braces - look how narrow. Would the chassis not easily be able to "roll" or "pivot" around those "braces"?

A lot like those useless bolt-in subframes some SN95 cars had.

 

[Old School1]

FYI

I am a convertible owner.

The convertible is about 180 lbs heavier than the fastback, and has a slightly more neutral front/rear weight ratio as most of the additional weight is over the rear axle. They will flex more than a fastback even with the rear subframe added.

The vert will typically have a slightly smaller sway bar than the same car in a fastback to reduce the possibility of oversteer.

You may like the feel of the vert because of the above factors. With similar alignments, I believe the fastback will outcorner my vert as it came from the factory.

CVCashmere

What exactly is the rear subframe? Obviously to stiffen the chassis but is this tubular?

 

[robvas]

What exactly is the rear subframe? Obviously to stiffen the chassis but is this tubular?

It's the stamped piece above the IRS in this picture. It bolts into the cars body. The aftermarket makes stiffer bushing and braces to tie it into the body better.

 

[Old School1]

It's the stamped piece above the IRS in this picture. It bolts into the cars body. The aftermarket makes stiffer bushing and braces to tie it into the body better.

Appreciate the picture, thank you.

 

[Flyingtexan]

Let me first be clear: I really like my 2024 GT coupe a lot. A whole lot. And overall it’s a nice handling street car. But try hard as I may to ignore it, the fact is that when both are pushed a bit into a corner my 2020 GT convertible is just flat out a better handling car. The term “better handling” is subjective of course but I mean that the ‘20 easily goes into a corner faster, deeper and flatter than the ‘24. It’s not my imagination. And there’s nothing mechanically wrong with the ‘24. It’s completely up to snuff. The ‘20 has 5,000 miles and the ‘24 has 1,000.

Both cars are equipped the same. They’re both non-PP premium GTs with the A10/3.15s and both have the slightly upgraded 19x8.5 wheels with the 255/40 19” tires. To add insult to injury, the better handling ‘20 vert is rolling on the PZeros that everyone loves to hate and the ‘24 coupe has the Conti Pro Contacts. Pressure is correctly set.

The ONLY variable I can see is that the ‘20 GT being a convertible has the strut tower brace and the ‘24 does not. If I thought the STB made this big a difference I’d slap one on the ‘24 immediately but generally nobody thinks this matters much.

Any thoughts as to what the variable might be would be appreciated. It’s making me a little crazy.

Don't you just hate it when you take the time to write a fairly lengthy thread and no one takes the time to actually read it? For all of those who went on a rant about why a STB is a must for the Convertible, be a reader, his has one. So y'all win the thread highjack award.

Now my two cents....so many variables. Alignment, tire condition and age, road conditions, etc. Some convertibles in Mustang history got a stiffer chassis via more pinch welds in the body seams, specifically in the seam running parallel to the sub-frame, but I'm not sure about the 2020 but it would be worth investigating.

 

[young at heart]

Don't you just hate it when you take the time to write a fairly lengthy thread and no one takes the time to actually read it? For all of those who went on a rant about why a STB is a must for the Convertible, be a reader, his has one. So y'all win the thread highjack award.

Now my two cents....so many variables. Alignment, tire condition and age, road conditions, etc. Some convertibles in Mustang history got a stiffer chassis via more pinch welds in the body seams, specifically in the seam running parallel to the sub-frame, but I'm not sure about the 2020 but it would be worth investigating.

Flyingtexan, you sure hit the nail on the head here! But it’s kinda one of those “welcome to the world of internet forums“ things and I’ve come to expect it I guess. Having said that if you sift through the chaff there have been more than a few reasoned and thoughtful responses to my OP and I do appreciate them.

You‘re correct about the variables. Trying to eliminate as many as possible has been my lifelong approach to problem solving. But it’s like playing whack-a-mole; you can’t get ‘em all!

I honestly never thought about the pinch welds thing. Anything is possible. This has always just been one of those cars that got built on a good day. It does most everything right. Even the engine- the ol’ butt dyno would bet money it pulls as strong as my lighter 3.55/3.73 higher hp coupes. These are reasons why it’d probably be my last car to go away if I had an emergency. But the real reason has red hair and blue eyes and would likely see that I went away with it, so there’s that.

 

[Flyingtexan]

Got to keep them (her) happy, the important thing is you have options. Making your 24 handle is so simple, lots of options in the after market world. The STB keeps the front end geometry stable, that can't hurt. Anytime you can stiffen up the front end, the truss made by the lower K frame and completed by the addition of the strut tower brace, the better the car will feel and handle. Don't listen to the "stb's are useless crowd if that were the case why do all the Road race competition cars have them? And the factory performance optioned cars have them?

 

[Snakebyte]

Here's a pic of the convertible bracing installed on a S550.

Actually, is a link to even better pics for those interested.
https://mustangforums.com/articles/l-a-auto-show-flips-over-flipped-mustang-gt-convertible/

 

[robvas]

Don't listen to the "stb's are useless crowd if that were the case why do all the Road race competition cars have them? And the factory performance optioned cars have them?

Nobody has still answered why there isn't one on the Dark Horse R.

And what about this Mustang GT4 $250k race car?

 

[young at heart]

Nobody has still answered why there isn't one on the Dark Horse R.

And what about this Mustang GT4 $250k race car?

Not trying to be argumentative nor the contrarian here because frankly I have no real idea.

But I do try to employ logic, which would lead me to think the chassis are stiff enough without needing additional bracing.

 

[Snakebyte]

Nobody has still answered why there isn't one on the Dark Horse R.

And what about this Mustang GT4 $250k race car?

Great question!!!!! Those strut towers for one thing are anything but stock. There's definitely some beefing up of that structure and they don't reply on spot welds. Of course the underside K-member is probably far from stock as well to handle race conditions.

 

[robvas]

Great question!!!!! Those strut towers for one thing are anything but stock. There's definitely some beefing up of that structure and they don't reply on spot welds. Of course the underside K-member is probably far from stock as well to handle race conditions.

Probably has a roll cage too.

He said "all the Road race competition cars have them"

But the point was the strut tower brace doesn't make the vert > the coupe

 

[Sofa King]

You could try a tire swap, and an alignment... see what that does.

Sponsored