Ride height and track width?

[ICA]

Can someone please explain how ride height (not including ground effects) and track width effect grip?

Does a higher ride height provide more grip because you get more weight transfer?

What about track width?

Regards,

[Jersey Tom]

Load transfer = bad for grip.

Low ride height = better for just about everything.

Wider track = less load transfer for a given lateral acceleration. For a skidpad, wider is better. However there is also the consideration that narrower track allows you to take a broader line, which means for a given grip level you can carry more speed through. On really tight stuff (like slaloms in an FSAE course) this makes a difference.

[Belatti]

Load transfer = bad for grip.

Not always true. Haven´t you driven a kart in the wet?
Even in F1 ride hieght is increased for wet weather.

[ICA]

Lets say that we have a narrow front end, does this make a chassis 'sharp' or 'twichy'?

[Jersey Tom]

Not always true. Haven´t you driven a kart in the wet?
Even in F1 ride hieght is increased for wet weather.

Proof? Source? Other than maybe if they're running softer springs in general and just to offset for how much aero is gonna compress everything.

Nothing about it being wet (that I can think of) makes an axle want more load transfer for better grip. There may be other reasons, but they're going to want to keep it as low as they can get away with.

Lets say that we have a narrow front end, does this make a chassis 'sharp' or 'twichy'?

No.

[Ciro Pabón]

Not always true. Haven´t you driven a kart in the wet?
Even in F1 ride hieght is increased for wet weather.

Proof? Source? Other than maybe if they're running softer springs in general and just to offset for how much aero is gonna compress everything.

Nothing about it being wet (that I can think of) makes an axle want more load transfer for better grip. There may be other reasons, but they're going to want to keep it as low as they can get away with.

So, you havent driven a kart in the wet!

Proof, source, verse and chapter, you dear and agnostic Tom (page 15):

CRG Kart Tuning Manual

Simple: "by raising the front ride height, you effectively raise the center of gravity in the kart and will be increasing the side bite on the tire, making it grip harder. If you go too high however, the raised CG will make the kart "bicycle" or pick up its inside wheels."

I don't know why, but it happens. I imagine it happens because you have a large lever and the weight transfer to the outside wheels is larger. If anyone can put this in an equation, I'll applaud.

Actually, I'm tall for karts at 1.83 m (6 feet). Just by stretching my spine I can feel the extra grip (extra lever you get, read page 6). On the other hand, by crouching (or, better, by lowering the front ride height), you will take side bite away from the tires and allow them to slide instead of grip. This will decrease the grip in the front-end.

I assume that the extremely low weight of karts has something to do with this "effect".

Finally, I was totally adrift with "narrower track allows you to take a broader line, which means for a given grip level you can carry more speed through". Could you ellaborate? I know JerseyTom knows tons about that stuff (I have no idea of the best way to "slalom").

[Jersey Tom]

Simple: "by raising the front ride height, you effectively raise the center of gravity in the kart and will be increasing the side bite on the tire, making it grip harder. If you go too high however, the raised CG will make the kart "bicycle" or pick up its inside wheels."

Sounds like BS, to be honest.. and that guy is mixing up terminology. Not exactly a reputable source (not that there really are any).

Karts do have their own nuances particularly with the solid rear axle. There IS some benefit to increasing load transfer, particularly in the rear, to start lifting in the inside rear tire and allow the car to rotate. It will FEEL like it has more grip and it will indeed rotate better, but you're sacrificing cornering power. I bet in a fast broad sweeper the lower setup will have more grip, but in anything tight and twisty lifting tires will allow you to get the thing pointed better.

For pro road racing vehicles, anything WITHOUT a locked rear end, I can think of no reason to have the CG anything but as low as possible (within reason of bottoming out). Again in the rain with an open wheeler you will probably run some softer springs in general since you're gonna lose some speed and some downforce, but ideally you'd have the car set up to ride pretty low once aero load compreses things.

With regard to racing line... the larger radius you can take through a corner the better.

For example, suppose you had a car that was SUPER wide. As wide as the race track! In theory you'd have real great grip on a skidpad. However, the width of the thing would mean your racing line would be stuck going around the center of the track. With a narrow track width, you can take a much broader arc through the corner. It's a tradeoff.. you lose some steady-state cornering capacity but since you're traveling on a larger radius you can often carry more speed through.

In FSAE this is important through a slalom section. If you have a really broad car it will be awkward to navigate through and require a lot of steering input. A narrow car can snake its way through.

[modbaraban]

Even in F1 ride hieght is increased for wet weather.

Proof? Source? Other than maybe if they're running softer springs in general and just to offset for how much aero is gonna compress everything.

I clearly remember Brundle saying that wet weather tyres have slightly larger diameter hence extra ride height.

[ICA]

Why do softer springs give more grip? dont soft springs increase load transfer?

Regards,

[modbaraban]

Why do softer springs give more grip? dont soft springs increase load transfer?

Regards,

Yes, but soft springs allow riding over bumps and curbs w/o loosing grip altogether.

[fatburner]

Can someone please explain how ride height (not including ground effects) and track width effect grip?

Does a higher ride height provide more grip because you get more weight transfer?

What about track width?

Regards,

How would you define "grip"?Is it the friction factor*weight?Or just the situation,when car has a feel of more grip?Or sth. else?

I would say that decreasing ride height increases overall grip,it lowers the center of gravity and thereby decreases rolling of the chassy.If you need more grip,there are definitely more reasonable ways than raising the car.
As for racing in wet conditions in f1,they sometimes need more clearance to prevent car "swimming" on it´s floor.

Going fast isnt all about grip,or loading the outer wheels when cornering.

Combinations like making front(rear) wider(narrower) may give different changes of car`s behaviour(feel) depending also on vehicle/other setup parameters.

The go kart theory could be true,but there are always more than one answer for a question.

[Jersey Tom]

Why do softer springs give more grip? dont soft springs increase load transfer?

Regards,

Soft springs have nothing to do with steady-state load transfer. That's a function of lateral acceleration, track width, and CG height. Softening springs while keeping everything else the same WILL increase chassis roll.. but big deal.

Soft springs mean low tire load variation which generally gives more grip.

[Ciro Pabón]

Sounds like BS, to be honest.. and that guy is mixing up terminology. Not exactly a reputable source (not that there really are any).

Yes, agreed. I swear it works, but the reason? Don't know. What I know is that everybody and his dog rides with rear axle as high as possible (it has only two positions, btw) and raises the front axle in the rain (this can be graduated, unlike the rear). I do and I really like driving in the rain. I think I have an advantage because of my height. You lose a little bit of braking, but, also in the rain, you want to stomp on the brakes, another thing in karts that goes against the full-racing-car theory, btw.

For example, suppose you had a car that was SUPER wide. As wide as the race track! In theory you'd have real great grip on a skidpad. However, the width of the thing would mean your racing line would be stuck going around the center of the track. With a narrow track width, you can take a much broader arc through the corner.

OMG. I'm getting dumber by the minute. I swear I thought you both were talking about the racetrack width... damn english.

How would you define "grip"?Is it the friction factor*weight?Or just the situation,when car has a feel of more grip?Or sth. else?

Grip, I think, is the amount of lateral force a tyre can develop before sliding.

[Krispy]

So here are my thoughts relating raising the CG in a Kart to using softer springs on a race car.

With a Kart most (nearly all?) of your suspension travel is in the tyres right? By raising the CG you are increasing the lateral load transfer and thereby putting more force on the outside tyre. The tyre is effectively your spring and has its own spring constant. With more load it deflects more (the same way changing to a softer spring and the same CG would cause more deflection at the spring in a given cornering maneuver).

To people with Karting experience: Do you find that different tyre pressures are favored in the rain? Are they higher or lower than the setup you would normally use on a dry track?

[Jersey Tom]

So here are my thoughts relating raising the CG in a Kart to using softer springs on a race car.

With a Kart most (nearly all?) of your suspension travel is in the tyres right? By raising the CG you are increasing the lateral load transfer and thereby putting more force on the outside tyre. The tyre is effectively your spring and has its own spring constant. With more load it deflects more (the same way changing to a softer spring and the same CG would cause more deflection at the spring in a given cornering maneuver).

To people with Karting experience: Do you find that different tyre pressures are favored in the rain? Are they higher or lower than the setup you would normally use on a dry track?

Except the deflection isn't what matters. The spring constant is what matters in terms of lowering tire load variation, and you don't change that (much) by putting on extra load.