You want great handling? Look at race cars!

[Rutschpartie]

For those that dont need comfort

Go as stiff and low as you can with aftermarket coilovers and buy semislick tires (!) for smooth asphalt roads
I am not talking +30%-50% more stiffness like b6/b8 + lowering/tuning springs, I am talking (height) adjustable sport/race coilovers with +400% - 800% stiffness and lower as much as you can.
There is a reason why race cars are setup like this!!

I know some of you will think:
But the geometry, the rollcenter and bumpsteer, everything will be wrong!

That is true.
BUT superstiff springs and a low center of gravity will compensate A LOT of that if you have your static camber/toe dialed in:

Superstiff springs will reduce roll -> so you have far less dynamic toe/camber change compared to stock suspension (it just travels less during cornering).
Superlow center of gravity will reduce load transfer, "weight" is more evenly distributed to all 4 tires during cornering --> more grip!!

Also there are aftermarket parts for correcting/adjusting rollaxis/caster/camber etc. but even without those you will not believe the difference to stock.

Why should you believe me?
Don't. Try to research/understand geometry/handling with the physics behind it and experiment yourself! I am in a very small amateur race team and i have physics degree and love studying/reading about this stuff.

Also if you have too much money: replace your rubber/pu bushings with solid bearings where possible and stiffen the chassis (welding/braces/cage)

On rough roads or even gravel the above ofc is not what you want.

 

[M-Sport fan]

Yes, as your last sentence above infers, most of us are NOT driving on glass smooth, near perfect road courses, so we have to take that into consideration when slamming these cars to the ground even if we did not care about scrub radii, bump steer, roll centers, etc., or even any actual comfort at all.

Even the tarmac rally cars do not slam their ride heights down when being used on the rough Euro roads of Germany and the Central Euro Rallies.

 

[Dialcaliper]

For those that dont need comfort

Go as stiff and low as you can with aftermarket coilovers and buy semislick tires (!) for smooth asphalt roads
I am not talking +30%-50% more stiffness like b6/b8 + lowering/tuning springs, I am talking (height) adjustable sport/race coilovers with +400% - 800% stiffness and lower as much as you can.
There is a reason why race cars are setup like this!!

I know some of you will think:
But the geometry, the rollcenter and bumpsteer, everything will be wrong!

That is true.
BUT superstiff springs and a low center of gravity will compensate A LOT of that if you have your static camber/toe dialed in:

Superstiff springs will reduce roll -> so you have far less dynamic toe/camber change compared to stock suspension (it just travels less during cornering).
Superlow center of gravity will reduce load transfer, "weight" is more evenly distributed to all 4 tires during cornering --> more grip!!

Also there are aftermarket parts for correcting/adjusting rollaxis/caster/camber etc. but even without those you will not believe the difference to stock.

Why should you believe me?
Don't. Try to research/understand geometry/handling with the physics behind it and experiment yourself! I am in a very small amateur race team and i have physics degree and love studying/reading about this stuff.

Also if you have too much money: replace your rubber/pu bushings with solid bearings where possible and stiffen the chassis (welding/braces/cage)

On rough roads or even gravel the above ofc is not what you want.

Don’t mean to start an argument, but since this post is already meant to be inflammatory, let’s go - this is not right at all…for a non-aero car.

Super stiff suspension setups are not about mechanical grip, they’re about keeping ride height consistent and level in order to optimize for downforce. For an aero setup, you’re actually sacrificing some “mechanical” (aka tire/suspension) grip, because the gain in traction from downforce makes up for it and more.

Second, springs on a well set-up car are not for controlling roll, they’re for ride frequency to maximize mechanical grip. It’s the job of anti-roll bars to control body roll and front/rear roll stiffness to tune for understeer/oversteer, as they are far and away more effective for doing that.

Maximum mechanical grip for most road surfaces means a suspension frequency (vehicle body/spring) of 2.0-2.5 Hz.

For most road surfaces this means front spring rates in the 300-350 lb/in range and rear springs in the 225-300 lb/in range. On rougher roads and tracks, the bottom of that range, and smoother roads/tracks, the higher end.

On a mechanical grip car, yes, low is sometimes better, but only to the point it improves suspension geometry and roll center. Our car and many other cars with Mapherson struts and compact (aka compromised) suspension packaging, the front axle is already low to the point where as the car is lowered, roll center drops faster than center of gravity. Aka, for the same suspension setup, lowering the front actually makes body roll slightly worse. Roll center adjusters can help, but only by the 0.5” or so that they lower the control arm at the knuckle.

Cars with double wishbone/multilink can often be lowered a bit more than that, but you still want lower control arms below horizontal.

More important is getting the roll center in the right range for steering and tire feedback. For a FWD car, front roughly 2-4” above ground, rear 4-10” with positive rake (rear higher than front). The rear axle roll center doesn’t change a lot with a torsion beam, so rear can go low. For the front on the other hand, 2-4” is between stock height, and about 0.5”. With fine tuning, you may end up below that.

So, slam your car if you want to look “cool” struggling over speed bumps and dragging sparks, and take solace in the fact that most people don’t know the difference, but will still peg you as a poser.

There are other specific reasons for stiffer suspension setups where racing is more about resonsiveness and chassis control with abrupt inputs, and not about maximum grip or fastest racing line. Examples are wheel-to-wheel racing in packs of cars, or tarmac rally, gymkhana and drifting where control in a slide is more important.

 

[pixelzombie]

I use Raceland coilovers on my daily driver, and the improved handling makes my drive more enjoyable. The ride is pretty much the same as the stock setup which surprised me.

 

[Rutschpartie]

Sure we can disuss @Dialcaliper Maybe we get some insights:

"Super stiff suspension setups are not about mechanical grip"
I think I never wrote that, i just wrote that it reduces roll

"springs on a well set-up car are not for controlling roll"
Ofc they also control roll, remember that your rollbars will do nothing for squat and dive

"For most road surfaces this means front spring rates in the 300-350 lb/in range"
This I don't believe/experienced, i also could not find any explanation in literature for this 2-2.5kHz and from my experience with non aero cars in national racing much stiffer rates are used on all cars, and they have some experience and test their stuff, I am also pretty sure it highly depends on the track/surface

"On a mechanical grip car, yes, low is sometimes better, but only to the point it improves suspension geometry and roll center"
I disagree: lowering GC is THE game changer to reduce overall load transfer and it is the one most important tool to increase grip over all 4 tires, body roll and load transfer are 2 very different things, not 100% sure if you are aware of that, but like i wrote, you can easily correct your roll center
A"bad/low" static roll center will not automatically result in drastically more camber/toe change compared to stock if you are stiff enough, and rolling itself will not automatically reduce grip. With mcpherson if your arms are not corrected they will reduce camber on compression but not to a amount that will take away the GC benefit, also toe/ackermann% >> camber (i think experienced race engineers/drivers will confirm)

"So, slam your car if you want to look “cool” struggling over speed bumps and dragging sparks, and take solace in the fact that most people don’t know the difference, but will still peg you as a poser." Ofc only lower it to a point where you can still use it on the streets without breaking it if it is a street car...I thought this is common sense...

There are good examples you can google of non-aero fiestas in amateur racing series where you can see that all of them are superstiff/slammed cars. Two of them are Ford Fiesta Sprint Cup in the Netherlands and the Spanish Pura Pasion Fiesta Cup. See attached picture, copyright RR2 Motorsport

 

[jeffreylyon]

Ironically, that photograph appears to show a Fiesta in the middle of a left-hander with a wad of weight transferred to the outside wheels under a compliant suspension. I'd guess close to 40mm of difference between the front-left and -right corners. I'd also guess that team has lowered no farther than a level LCA to avoid positive camber.

Fortunately, we don't have to do too much research and experimentation to come to a pretty good outcome; there is a massive body of work that describes suspension best-practices.

 

[Rutschpartie]

Ironically, that photograph appears to show a Fiesta in the middle of a left-hander with a wad of weight transferred to the outside wheels under a compliant suspension. I'd guess close to 40mm of difference between the front-left and -right corners. I'd also guess that team has lowered no farther than a level LCA to avoid positive camber.

Fortunately, we don't have to do too much research and experimentation to come to a pretty good outcome; there is a massive body of work that describes suspension best-practices.

this one is better, you can also see the massive amount of static camber the last car has dialed in, with that amount of lowering it is hard to avoid positive camber gain and have a level LCA
But again the benefit of that low GC is what you want, even with a little positive camber gain, It directly determines the overall load transfer 30% lower GC means 30% less load transfer!

"with a wad of weight transferred to the outside wheels" <- this is also one of the important points: roll is not weight transfer, only because you see a car rolling, it does not mean necessarily it transfers a lot of weight, i know it is not easy but if you are interested and read a little about it it will make sense. Ofc the amount of roll you see also depends greatly on how fast the turn is.

copyright RR2 motorsport

 

[Rutschpartie]

Yes, as your last sentence above infers, most of us are NOT driving on glass smooth, near perfect road courses, so we have to take that into consideration when slamming these cars to the ground even if we did not care about scrub radii, bump steer, roll centers, etc., or even any actual comfort at all.

Even the tarmac rally cars do not slam their ride heights down when being used on the rough Euro roads of Germany and the Central Euro Rallies.

I was rly suprised how low the WRC and national rally cars sat when i saw them on CER!

 

[jeffreylyon]

this one is better, you can also see the massive amount of static camber the last car has dialed in, with that amount of lowering it is hard to avoid positive camber gain and have a level LCA
But again the benefit of that low GC is what you want, even with a little positive camber gain, It directly determines the overall load transfer 30% lower GC means 30% less load transfer!

"with a wad of weight transferred to the outside wheels" <- this is also one of the important points: roll is not weight transfer, only because you see a car rolling, it does not mean necessarily it transfers a lot of weight, i know it is not easy but if you are interested and read a little about it it will make sense. Ofc the amount of roll you see also depends greatly on how fast the turn is.

copyright RR2 motorsport
View attachment 60954

The car in the back..., is broke. Look at the cars around it; nobody is running close to that amount of negative camber.

Weight transfer causes roll (and squat and dive). If the suspension is setup properly it can also increase total grip. F1 teams reduce anti-sway and increase negative camber at Monaco because they are down on aero-grid so they dial in more "mechanical" grip.

Try to find a copy of "How to make your car handle", published by HP Books - it's a great primer.

 

[Rutschpartie]

The car in the back..., is broke. Look at the cars around it; nobody is running close to that amount of negative camber.

Weight transfer causes roll (and squat and dive). If the suspension is setup properly it can also increase total grip. F1 teams reduce anti-sway and increase negative camber at Monaco because they are down on aero-grid so they dial in more "mechanical" grip.

Try to find a copy of "How to make your car handle", published by HP Books - it's a great primer.

Not sure that one is broken, I have seen camber like this.

Thx for the book recommendation I guess? Have you read it? I am not sure...

"If the suspension is setup properly it can also increase total grip" <-- ofc! there is no doubt about that

Reducing roll has almost no effect (but it directly relates to the dynamic geometry change) on overall load transfer which is what i was talking about when lowering GC to increase grip, this load transfer reduction is a much bigger effect than the minimal positive dynamic camber gain compared to the static camber that potentially decreases grip. But I think this is the last time i should highlight this in this thread

 

[jeffreylyon]

Yeah, I’m with you - this convo isn‘t going anywhere.

 

[gtx3076]

I like the stock ride height. Just wish it was a bit softer.

 

[Mech_Mike412]

I like the stock ride height. Just wish it was a bit softer.

Add a front strut bar and it will ride much better

 

[M-Sport fan]

I was rly suprised how low the WRC and national rally cars sat when i saw them on CER!

Yes, given how rough/broken much of that pavement along those stage routes really is on that event.

But they are nowhere near as slammed as the WEC cars, or even the DTM rides (or whatever they are calling the German touring car series nowadays) are competing on their billiard table top smooth road courses!

 

[jeffreylyon]

But they are nowhere near as slammed as the WEC cars, or even the DTM rides (or whatever they are calling the German touring car series nowadays) are competing on their billiard table top smooth road courses!

But those cars aren't really slammed - they're engineered to that ride height by world-class mechanical engineers. A world's of difference than someone radically dropping the ride height of a strut car, having to increase corner and anti-sway stiffness to offset the increased roll due to the buggered roll-center, and fool themselves or their driver into believing that the car is super twitchy cuz..., race car!!

 

[M-Sport fan]

I like the stock ride height. Just wish it was a bit softer.

I like the factory ride height, but just wish that it was a good bit higher in spring rate (with relative, matched, compression/rebound damping of course ).

 

[M-Sport fan]

But those cars aren't really slammed - they're engineered to that ride height by world-class mechanical engineers. A world's of difference than someone radically dropping the ride height of a strut car, having to increase corner and anti-sway stiffness to offset the increased roll due to the buggered roll-center, and fool themselves or their driver into believing that the car is super twitchy cuz..., race car!!

YES, I know that, but I was using the 'wrong' term because that is the vernacular that most everyone who is not into the correct methods of suspension engineering knows/uses to describe EVERY ride which is lowered.

 

[Dialcaliper]

Not sure that one is broken, I have seen camber like this.

Thx for the book recommendation I guess? Have you read it? I am not sure...

"If the suspension is setup properly it can also increase total grip" <-- ofc! there is no doubt about that

Reducing roll has almost no effect (but it directly relates to the dynamic geometry change) on load transfer which is what i was talking about when lowering GC to increase grip, this load transfer reduction is a much bigger effect than the minimal positive dynamic camber gain compared to the static camber that potentially decreases grip. But I think this is the last time i should highlight this in this thread

First of all, look up Milliken and Milliken, “Race Car Vehicle Dynamics”. It’s a great light read. Ironically, the first third of the book is about tires.

Second, roll center is just as important as CG in determining load transfer. What actually matters is not one or the other independently, but the distance between them - specifically how far above the roll center your CG is. That lever arm is literally what determines the vertical load transfer on the tires at a given lateral g-load.

If you lower the car an inch and the roll center drops two inches, you’ve just increased the moment arm by an inch, not decreased it, which means increased load transfer and increased roll.

Squat and dive are important, but they are not the same as roll, and can be dealt with partially by anti-squat/anti-dive geometry in the suspension.

Body roll itself is only bad in the case where your camber gain in the suspension is crap, as in the case of Macpherson struts. But the load transfer that occurs with it is bad because tires have decreasing effective friction at higher loads (less maximum lateral force generated for a given vertical force)

I think I addressed the case of wheel to wheel racing, but unless you are actually doing so, the stiff rates used there are not advantageous.

And pretty much every high end race league (DTM, WEC, WTAC, F1, Etc Etc - even WRC) uses significant amounts of aero downforce, which leads to totally different design constraints on the suspension.

In any case, do what you think is cool. More power to you. Just don’t mislead others with “advice” that you appear to have no actual grasp of, except “because racecar!!!”

 

[Rutschpartie]

First of all, look up Milliken and Milliken, “Race Car Vehicle Dynamics”. It’s a great light read. Ironically, the first third of the book is about tires.

Second, roll center is just as important as CG in determining load transfer. What actually matters is not one or the other independently, but the distance between them - specifically how far above the roll center your CG is. That lever arm is literally what determines the vertical load transfer on the tires at a given lateral g-load.

If you lower the car an inch and the roll center drops two inches, you’ve just increased the moment arm by an inch, not decreased it, which means increased load transfer and increased roll.

Squat and dive are important, but they are not the same as roll, and can be dealt with partially by anti-squat/anti-dive geometry in the suspension.

Body roll itself is only bad in the case where your camber gain in the suspension is crap, as in the case of Macpherson struts. But the load transfer that occurs with it is bad because tires have decreasing effective friction at higher loads (less maximum lateral force generated for a given vertical force)

I think I addressed the case of wheel to wheel racing, but unless you are actually doing so, the stiff rates used there are not advantageous.

And pretty much every high end race league (DTM, WEC, WTAC, F1, Etc Etc - even WRC) uses significant amounts of aero downforce, which leads to totally different design constraints on the suspension.

In any case, do what you think is cool. More power to you. Just don’t mislead others with “advice” that you appear to have no actual grasp of, except “because racecar!!!”

The Milliken book i would rly like to read once in my life and i think there is a reason that the first third is about tires: they are the most important thing on a race car.

"Second, roll center is just as important as CG in determining load transfer." it is what many people think but I think it is not entirely true: Look at the simplified definition of overall lateral load transfer (it is independent of roll center!), all of this is actually from the book you recommend, it is also well described here:

https://racingcardynamics.com/weight-transfer/



dW = W*Ay*h/t

dW = load transfer
W = weight
Ay = lateral acceleration
h = GC height
t = track width

one of the reasons for this is that the lever arm for that fromula above is NOT the distance between roll center and CG you describe (but it in reality it has some influence, see below), but the height of the GC h! It rly means, lower your CG by 50% -> decrease load transfer by 50%

You are right that roll center has an effect on load transfer, but I think more in a sense that you can balance the load transfer over the axles (this is also how race teams use anti-roll bars to set axle roll stiffness):
"when we increase front roll centre height, the lateral weight transfer decreases on the rear axle while increasing on the front. Conversely, if you increase rear roll centre height, lateral load transfer increases on the rear axle and decreases on the front axle"

To reduce overall load transfer of the car (this you want to increase overall grip) you should to lower CG!

But it is a little more complicated than the above formula, there are 3 components and if you look at the complete derivation roll center height has some effect on load transfer.
This considered, load transfer for a single axle NOT the overall load transfer(it is directly derived in the article linked above with an explanation of the parameters):





"In any case, do what you think is cool. More power to you. Just don’t mislead others with “advice” that you appear to have no actual grasp of, except “because racecar!!!”"
Yes! I 100% agree but I think I laid out a lot more arguments in this thread than just "because raceacar" - although I do not understand why this should be a bad thing, race engineering + competitive race cars are the thing you should look at/study if you want handling (wait, is that what the title says?). You yourself recommend the book "Race Car Vehicle Dynamics"

 

[Dialcaliper]

The Milliken book i would rly like to read once in my life and i think there is a reason that the first third is about tires: they are the most important thing on a race car.

"Second, roll center is just as important as CG in determining load transfer." it is what many people think but I think it is not entirely true: Look at the simplified definition of overall lateral load transfer (independent of roll center), all of this is actually from the book you recommend, it is also well described here:

https://racingcardynamics.com/weight-transfer/

dW = W*Ay*h/t

dW = load transfer
W = weight
Ay = lateral acceleration
h = GC height
t = track width

one of the reasons for this is that the lever arm for that fromula above is NOT the distance between roll center and CG you describe (but it in reality it has some influence, see below), but the height of the GC h! It rly means, lower your CG by 50% -> decrease load transfer by 50%

You are right that roll center has a effect on load transfer, but I think more in a sense that you can balance the load transfer over the axles (this is also how race teams use anti-roll bars to set axle roll stiffness):
"when we increase front roll centre height, the lateral weight transfer decreases on the rear axle while increasing on the front. Conversely, if you increase rear roll centre height, lateral load transfer increases on the rear axle and decreases on the front axle"

To reduce overall load transfer of the car (this you want to increase overall grip) you have to lower CG!

But it is a little more complicated than the above formula, there are 3 components and if you look at the complete derivation roll center height has some effect on load transfer.
This considered, load transfer for an axle is (it is directly derived in the article linked above with an explanation of the parameters):

View attachment 60957



"In any case, do what you think is cool. More power to you. Just don’t mislead others with “advice” that you appear to have no actual grasp of, except “because racecar!!!”"
Yes! I 100% agree but I think I laid out a lot more arguments in this thread than just "because raceacar"

Milliken is a great book, but dense (that article is largely lifted from it), and no offense, but it appears you’ve read about a 1/4 way through the article and gotten bored and confused.

First, the straight up CG vs Track width “total lateral load transfer” is a simplified model that ignores suspension geometry and while it still has an effect on load transfer, it has little actual effect on when it comes to chassis setup. The more complex model gets broken down later in the article.

This is an artifact of simplifying from Milliken, which spends several chapters on multiple simple models of a vehicle, starting with a single wheel, then a two wheel bicycle, then a four wheel rigid vehicle, and finally a model that includes suspension geometry. It also derives cg and roll center as mathematical concepts, initially ignoring (but acknowledging later) that in an actual car at the final
chassis setup stage, cg and roll center cannot be changed independently.

The reason for this is that the initial assumptions are based around actually designing a suspension system from scratch, where cg and front+rear roll centers can be defined separately.

In the end, the roll component that is insignificant is from roll angle and the effect from gravity due to the CG being offset laterally from roll center. This establishes that “extreme body roll” in itself has very little effect on load transfer.

With suspension taken into account, The only portion of the car that behaves as you are assuming is the unsprung mass (wheels, tires and outer control arms/shocks/struts) which is a small component of the vehicle mass.

What’s described later is that in fact the “direct” or “kinematic” load transfer at each axle is defined by the distance from cg to roll axis, where roll axis is the line between front and rear roll centers.

The “it’s complicated” part comes in is that in moving roll center and cg at one end of the car by raising and lowering that axle has a compound effect on both axles of the car, the angle of the roll axis and that stiffness of one axle has an effect on load transfer at the other. It’s from this effect that we change understeer/oversteer dynamics.

In the end, on a street car that is past the design stage and has predetermined CG and suspension geometry, the total load transfer cannot be changed much at all, and changing CG height alone is fairly irrelevant when it comes to “tuning” the suspension.

Instead, some knobs we have to turn in a non-aero car are:

1) Ride frequency which determines the ability of the tires to follow the road. This is primarily influenced by spring rates, and the optimum 2.0-2.5 Hz target mentioned previously is an empirically derived figure that comes from typical road surface feature sizes for a typical car sized mass (1000-2000kg). Frequency ratio also affects pitching vs heaving (aka flat ride) behavior over bumps which influences vehicle stability and controllability.

2) Relative front to rear roll stiffness ratio, which affect understeer/oversteer dynamics. When ride frequency is optimized, anti-sway bars have a much higher (2-3x) effect on roll stiffness, and so tuning this behavior is best done with sway bars.

3) Increasing roll stiffness (which has little effect on total load transfer) on a Mac-strut car, geometry has poor camber compensation with roll, so this points towards higher roll stiffness to maintain tire geometry. Not as important on a double-wishbone car, which can allow more body roll.

4) Higher roll stiffness can help with dynamic stability, as large amounts of body roll mean a slower response time to steering inputs

5) There’s an opposite influence - high roll stiffness from anti-sway bars means your suspension is less independent, and results in deviation from optimum ride frequency when it comes to one-wheel bumps, and so this means we want the least roll stiffness we can get away with and still accomplish #4 (vehicle stability and response)

And of course this all goes completely out the window with heavy underbody aero, as then we care more about keeping the front splitter and rear diffuser level and maintain the most consistent ride height (as total downforce changes as the aero gets closer and farther from the ground, from changes in airflow). Aero cars want stiffer setups.