2016 GT suspension recommendations

[GreenS550]

Be aware that wider tires do not necessarily make for better handling. Often you will lose some of the nimbleness. One of the reasons staggered setups are from the factory is so the front tires being narrower have quicker steering response.
Lower will make the car flatter around curves but at a comfort cost and you will also have to be careful parking with a curb in front.
Much research has been done and the number one factor in good handling are the tires.

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[Norm Peterson]

Lower will make the car flatter around curves

Not exactly. Particularly with MacStrut suspensions, the geometric roll center drops much faster than the amount of lowering. Meaning that the sprung mass roll moment increases even while the total amount of lateral load transfer decreases. So even if only one end of the car is strut-suspended, lowering alone is going to give you more roll.

Any lessening of cornering coming from installing lowering springs is coming from the lowering springs having stiffer rates than the OE springs, stiffer enough to more than compensate for the falling roll center effect.

Much research has been done and the number one factor in good handling are the tires.

Mostly agree here. The unofficial autocross/track day mantra goes something like "seat time, tires/wheels, everything else".

I suspect staggered wheel/tire setups are done more to help guarantee limit understeer and to possibly make life easier for the stability control system. Wider front tires do tend to make the handling feel subjectively 'heavier', but that's not quite the same thing as "less nimble".


Norm

 

[GreenS550]

I respectfully have a different opinion.

All things equal, a lower car makes for better handling. Through a curve, the momentum needed decreases as the car is lower and will impart lateral forces more directly on the tires. Hence the need for good tires.
Narrower front tires not only gives nimbler steering, but also better gas mileage.

The CB005 will help in reducing wheel hop as well.

 

[Brian@BMVK]

I respectfully have a different opinion.

All things equal, a lower car makes for better handling. Through a curve, the momentum needed decreases as the car is lower and will impart lateral forces more directly on the tires. Hence the need for good tires.
Narrower front tires not only gives nimbler steering, but also better gas mileage.

The CB005 will help in reducing wheel hop as well.

Except that's not how it works. Lowering a car doesn't leave everything else equal, and lowering too much without a revised geometry is not better. The roll couple actually increases more than the CG lowers. It's nice to have an opinion, but this stuff isn't based on opinion at all.

 

[GreenS550]

Lowering a car doesn't leave everything else equal, and lowering too much without a revised geometry is not better.

My comments "all things being equal" meant to refer to modifications appropriate to lowering. I have lowered 6 Mustangs using many different combinations. With appropriate mods, lowering almost always gives better handling.
My opinion is my experience. And, if it was an EXACT science, one suspension setup would always be used. Ford is constantly changing the Mustang suspension.

FWIW, I am not a fan of lowering unless one wants a lower ride quality, more NVH, etc.

 

[Norm Peterson]

I respectfully have a different opinion.

All things equal, a lower car makes for better handling. Through a curve, the momentum needed decreases as the car is lower and will impart lateral forces more directly on the tires. Hence the need for good tires.
Narrower front tires not only gives nimbler steering, but also better gas mileage.

I'm not arguing with the fact that better handling is possible from lowering. Mostly that the handling improvement does not come from the lowering itself. It's as important to get the reason right as it is to form the right conclusion.

All things equal (I'm assuming you mean 'all other things equal' when discussing the matter of lowering an existing car like we are here), your lowered car absolutely will roll more. And this isn't just theory.

I'm not sure why you're bringing momentum into the discussion, but OK, I'll roll with that. The truth is that when you lower the car, and the geo-RC's drop faster than the lowering, you have less lateral load transfer happening immediately (this being the load transfer through the RCs which does not produce any roll). But you make up for that with increased load transfer going through the springs/bars/dampers, which takes time. And with those things held constant, you're going to have more momentum in roll, not less.

Lateral forces develop at the tires. That's what gets the whole business of cornering started. The car's sprung mass responds to that, directly through the geo-RCs and less directly/less immediately through the suspension.


Norm

 

[Norm Peterson]

My comments "all things being equal" meant to refer to modifications appropriate to lowering. I have lowered 6 Mustangs using many different combinations. With appropriate mods, lowering almost always gives better handling.
My opinion is my experience. And, if it was an EXACT science, one suspension setup would always be used. Ford is constantly changing the Mustang suspension.

FWIW, I am not a fan of lowering unless one wants a lower ride quality, more NVH, etc.

Your improved handling has primarily been due to the lowering springs being stiffer. It's not possible to look at a lowered car and see the stiffness of its springs being any different from OE, but you have to get to the point where you understand that visual appearance isn't telling you anywhere near the whole story. It can't.

This isn't the only vehicle topic where people want to believe that what they can see tells them everything about what's going on.


Norm

 

[GreenS550]

Stiffer springs lowered vs stiffer springs not lowered, depending how stiff, other mods, etc. of course will give better handling.
Say what you want, but take a look at any perfomance/handling car. They are lower for a reason. Simple physics.

 

[Brian@BMVK]

And, if it was an EXACT science, one suspension setup would always be used. Ford is constantly changing the Mustang suspension.

It is. It is fully modeled & tested and there is no guessing on this at the OEM level.

Ford chooses their performance targets and attribute targets and designs to it. There are compromises everywhere. The best handling car rides poorly. The most responsive component design has additional NVH. A car with lowering has reduced ground clearance, which violates their targets for approach, break-over angles in addition to static clearance. Every specification: spring rates, damper curves, swaybar rates, ride heights, material choice, all are what Ford chose to be a best fit to the targets they chose, or a compromise for the targets they couldn't hit.

When you lower a car, most of the typical lowering springs also come with higher spring rates to account for the change in roll couple. Those rates can and often do negate the additional roll that would be present without an increase.

 

[GreenS550]

I think you are making my point. I never meant to imply lowering without necessary components to compliment the lowered geometry.
I know the physics are exact, I get that. But many different methods are used by many manufacturers to achieve good handling.
Actually the term "good handling" is quite vague. Which opens up the whole concept and involves many "opinions".

 

[Brian@BMVK]

Actually the term "good handling" is quite vague. Which opens up the whole concept and involves many "opinions".

It is highly quantifiable, but yes, it is based on an expert's (or several experts) opinion, and then is analyzed and turned into objective measures. Yaw rate, yaw moments, roll rates on either axle, lat-g rate with steering input, skidpad g, etc, etc.

 

[Norm Peterson]

Stiffer springs lowered vs stiffer springs not lowered, depending how stiff, other mods, etc. of course will give better handling.
Say what you want, but take a look at any perfomance/handling car. They are lower for a reason. Simple physics.

Yes, lowering the car does lower the amount of lateral load transfer, and yes that means that total lateral grip goes up. But once again, there's more to it.

Your car's outside tire grip - in terms of friction coefficient - certainly does gain. But have you stopped to realize that having less load transfer away from the inside tires means that you've actually penalized their coefficient of friction a bit?

So the net increase (what the car actually gets to use) is less than that gained by the outside tires. And most likely less than what the amount of lowering suggests. I actually have a rough idea what the magnitude might be. Roughly, a 2" drop in the CG means about a 10% change in lateral load transfer. Tire mu can be estimated as a power function of vertical load, somewhere between 0.7 and 0.9 for the outside tires and I think a somewhat lower number for the inside tires. Long story short, lowering the CG by 10% does not buy you 10% more grip. Less than 5% grip improvement, probably closer to 3% from a fairly serious amount of lowering would be my guess.

Lowering only really gets critical when you're at the point of lifting both inside tires and rolling the car over due to tire grip.


Norm

 

[HourlyB]

Your Blizzaks' grip may improve slightly with driving. I've consistently noticed tire grip to be a bit 'off' in the first few drives after taking them out of storage and swapping, that recovers a bit. On both ends of the cold season.


Norm

Gotcha, I'll be sure to keep a eye on them. My alignment also seems to be off, even though I just had it done at Sullivan. Car wants to pull to the right constantly.

Yep.

I ended up going with the BMR Cradle Bushing lockout.

 

[HourlyB]

Yes, lowering the car does lower the amount of lateral load transfer, and yes that means that total lateral grip goes up. But once again, there's more to it.

Your car's outside tire grip - in terms of friction coefficient - certainly does gain. But have you stopped to realize that having less load transfer away from the inside tires means that you've actually penalized their coefficient of friction a bit?

So the net increase (what the car actually gets to use) is less than that gained by the outside tires. And most likely less than what the amount of lowering suggests. I actually have a rough idea what the magnitude might be. Roughly, a 2" drop in the CG means about a 10% change in lateral load transfer. Tire mu can be estimated as a power function of vertical load, somewhere between 0.7 and 0.9 for the outside tires and I think a somewhat lower number for the inside tires. Long story short, lowering the CG by 10% does not buy you 10% more grip. Less than 5% grip improvement, probably closer to 3% from a fairly serious amount of lowering would be my guess.

Lowering only really gets critical when you're at the point of lifting both inside tires and rolling the car over due to tire grip.


Norm

This became very sciency extremely fast. But yeah, car set-up is not really like Forza or Gran Turismo where you just go for the farthest option and things are better.

I think the best anecdote is "Oh boy I just got a lightened flywheel installed! Where's my A/C and what's that knocking noise?"

Right now the set up I have works great for what I wanted. (albeit I do have the pulling right issue, but I'm pretty sure that's more to do with something in the alignment then the set-up)

 

[Brian@BMVK]

Gotcha, I'll be sure to keep a eye on them. My alignment also seems to be off, even though I just had it done at Sullivan. Car wants to pull to the right constantly.

I ended up going with the BMR Cradle Bushing lockout.

The thrust angle at the back is significant enough to feel in regular driving, as is the difference in L and R front camber. The total rear toe is pretty decent but it's not the same. While you're in there get the front toe back to zero or at least the same on both sides.

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