Q: “My question is what effect does stiffening the front sway bar have on a front wheel drive car. My Mini Cooper is a track-only, highly-modified over-sized go-kart and I have the ability to stiffen the aftermarket front bar, however I am curious as to what effect it will on handling. If it will make it understeer more I don’t need that. If, in theory, it will tend to make it rotate better, that would be a good thing. There is not a lot out there on how to make your FWD (front-wheel-drive) work better so I thought I would ask you.”
A: I have a Mini, too, although not modified like yours. But still a quick, fun car!
Typically, going stiffer on the front bar will increase the likelihood to understeer. And that would be the case in a FWD, RWD, or AWD car. The simple way of thinking about this is that stiffer bar will result in more load transfer to the outside tire in a corner, and take more load off the inside tire. The more load transfer, the less overall grip that axle will have. So a stiffer bar on the front – in relation to the rear – will lead to more understeer; a stiffer bar on the rear will lead towards more oversteer. From your email it seems you’re looking for less understeer and more rotation as you turn into a corner. If that’s what you’re looking for, softening the front bar should help. If you can’t soften it any more, can you stiffen the rear bar?
If you can’t make any more changes with the bars, you would then look towards the springs (softer front springs; stiffer rear springs), and/or shock adjustments (same direction).
Of course, there are always exceptions to the rules! There are times when understeer is caused by too much roll, in which case a stiffer front bar setting could help. But this is the exception to the rule, and is less likely than the typical advice I gave you above. The only way of knowing for sure is to experiment – try stiffening the bar and see how it handles.
For more advice on how to tune your car’s handling, download my free How to Tune Your Car’s Handling eBook here.
I tracked (general DE days) a R53 Mini Cooper S for some time, and found that a 19mm rear anti-roll bar dramatically dialed-out unwanted understeer while maintaining a stock front anti-roll bar. This was using H&R springs and Bilstein struts (non-coil overs). Turner has a nice write-up on that set-up, and I was VERY pleased.