Roll bar spring rate
Roll bar spring rate
(OP)
What about the roll bar rate in relation to the springs rate? Does the rollbar rate have to always be less than the spring rate?
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RE: Roll bar spring rate
RE: Roll bar spring rate
RE: Roll bar spring rate
On a racing car with a compromised suspension design (eg macP) you might well end up with front a/r stiffer than the springs.
The best reason to do so in my experience is to stabilise the front end of a RWD car, so providing better traction for the rear end out of corners. But the tradeoff is that you'll have less effective braking into the corner. You'll also probably get more weight transfer understeer, which may or may not be an advantage.
Other reasons you might do it include that if you have a very low RCH, as racers often do, then you might want to reduce the roll gain.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Roll bar spring rate
Typically, the stiffer the suspension the quicker the lap times but make the car rather unforgiving and require far greater driver skill levels.
Rod
RE: Roll bar spring rate
Teo - whether the sta-bar rate is less than or greater than the spring rate depends on the vehicle and the philosophy behind its design. Of the four cars in my driveway, two have greater front wheel rates from the springs and one has more front wheel rate from the sta-bar even after fitting much stiffer than OE coil springs (haven't gotten around to dealing with #4 yet).
Perhaps it's better to first select the springs based on other ride considerations and then see what sort of sta-bars would be required.
Norm
RE: Roll bar spring rate
If the car has no anti:s the suspension (wheeltravel) of the car will deflect more for the same G load sideways than from acc and braking. That is becouse of the track width is less than the wheelbase. Therfore we can mount a swaybar that add as much roll stiffness as is needed to bring the roll down to the same deflection a we have in pitch. Just a rule of thumb for bar stiffness.
Goran
RE: Roll bar spring rate
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Roll bar spring rate
For my type of racing, saloon/sedan racing, as I have said before, stiffer generally yields quicker lap times on most of the smoother (virtually all) racing circuits.
Rod
RE: Roll bar spring rate
Greg
It is a bit of a Catch-22. We want to have a low center of gravity, and a low drive provides a low center of gravity. Thus, it is idea to lower the car as much as possible, and the limit is when it hits the ground. We can then have a harder sprung car that is lower, or softer which must be correspondingly higher for not hitting the ground. But having a high car that is tightly sprung becomes a loss in the CGH, as well as a soft car that is too low will be a loss in that it hits the ground the whole time. Should we adjust the springs to rideheight or rideheight to the springs?
First let me say that my theory is that we must have balance based on the choice between the stiffness of the suspension of the roll and pitch in order to benefit all suspension travel effectively. Then we look at how the track looks, how smooth or rough it is, because that is what determines how much travel is that we need. Depending on the asperities looks (and curves), we will receive different combinations of balance between the suspension and shock absorbers, which in turn affects the rideheight which must be used. Right adjusted car is using all available rideheight effectively.
It is wrong to say that a harder or softer car go faster or slower in general. We will always be a frontier where the hardness becomes too hard or softness of soft. But if we see it from a purely tiregrip situation, softer suspension gives more grip, but then the chassis movement must be dealt with on the right way, and we have a deterioration of the needed CGH.
Goran