What does a "race" suspension really do? 3

[1Sick6]

Hi, pretty sure this is my first post, but i've been reading on here for a few years - great forum!

Ok, I've read tons about the details of suspension design (ie roll rates, roll stiffness, roll couple %...) but as I took a step back and was trying to explain the big picture to someone, I realized I don't really know what's going on haha.

Basically, my question is what is the goal of a "race" suspension?

From what I've absorbed (through both good and lots of bad info) the two goals are:
- to keep as much of the tire in contact with the ground for the greatest amount of time possible.
- to limit "weight transfer" in order to get the most out of the tires.

I realize there are tons of other factors that go into the design, but I'm just trying to figure out the basic goals that are directly related to how fast a car can go around a corner. Am I missing any?

The first goal makes sense so long as you stick to the convention that more tire on the ground = more grip (something that my physics teachers try to challenge but I'll keep ignoring them for now)

The second goal also makes sense, but its what i've got the most questions about. If load transfer is only related to mass, CG height, and track width - how do things like ARB's and stiffer springs result in more grip? How does the "all evil" body roll hurt performance? The same load is being transferred through the springs (and ARB's), they're just not compressing right?

My only thought on it is that as the body rolls, the CG is shifted slightly to the outside of the turn giving us *some* weight transfer (we actually get to use "weight" for once). The part i struggle with is: how much does this really affect things?

Also, I hear people talking about "balancing" the car with ARB's. Saying that "a stiffer bar will reduce load transfer at that end of the car." Then they get into roll couples and then appears all kinds of facts about car behavior due to one end of the car resisting roll more than the other. Where does that come from?

Sorry this ended up so long,but if nothing else I already better understand whats going on by typing/thinking this out. Thanks for the help!

-matt

 

[GregLocock]

No. Not if nobody else is doing it and you have the best driver and the best engine and the best reliability.

Otherwise...yes.

Also bear in mind that in a non aero car suspension tuning for a particular circuit can really only get you about 2 seconds a lap, assuming that your initial settings were generic and reasonable, and that you are running the right tire temperatures. The latter being rather important. For instance I am told that FSAE cars often run with rather strange static toe and camber in order to get their tires to heat up as quickly as possible, because in their events they don't have enough time to get heat into the tire.


Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[1Sick6]

For instance I am told that FSAE cars often run with rather strange static toe and camber in order to get their tires to heat up as quickly as possible, because in their events they don't have enough time to get heat into the tire.

I was on a young FSAE team for a bit, and while we were by no means a representation of a team that had all the answers, we did not use any crazy camber/toe but instead choose a smaller/narrower tire in hopes of getting more heat into them. However, they ended up seeming overheated by the end of the endurance competition (20min). I think this also had to due with our compound change as well, the previous year we were running hoosiers, they were about an inch and a half wider but never really got up to temp in the short events at competition.

 

[hemipanter]

And if this is not enough we could expand the suspension discussion by including downforce...
Goran

 

[1Sick6]

naw, I was just wondering about non-aero setups. Mainly just trying to figure out what the real objective is when modifying a suspension to handle better. IE: With mass, cg height, and track width all constant on a vehicle, what changes how fast it can corner.

 

[hemipanter]

It is a distorted view to imagine the shock absorber calibration is "objective", it is very much "relative". However, there is a rough rule for how it should be, but then it is up to the team to understand how to make nice customization of the current circumstances.

I have changed the Mr. on a car on several occasions and not even Ohlins can say which set of damper valve system should be used. We set the damper up in a rough guess at these occations and then I have to go ahead with testings and clarify my wishes.

Now we should not (on a general level) dramatize the importance of shock absorber settings, if we buy a quality adjustable dampers for the purpose so you can drive very quickly, what I am talking about is the "icing on the cake".
Goran