Adding my 2 cents because I've gone down the suspension rabbit hole a bit
timmy201 wrote:
With a classic mini, normally a sway bar is added to the back end, and the stiffer effective suspension reduces the rear grip, in turn reducing the amount of understeer.
Yes, if you consider the rear axle in isolation you lose grip, the rear arb does however contribute to limiting roll for the whole car not just the rear axle, the mini has skewed roll (rear roll centre lower than the front) which means the rear has an outsized effect on roll. Limiting this means the weight distribution can be more even at the front and you get an overall gain in grip.
Phil 850 wrote:
I just reread the “Suspension” chapter of David Vizards, How To Modify Your Mini.
His recommendation is to maximise the grip of the front suspension first (you will need adjustable suspension components to do this) and if this does not reduce understeer enough, then perhaps fit a rear anti roll bar.
I agree, it seems much more productive to add grip to the front before taking it from the rear, the mini was setup to understeer from the factory so reversing some of these seem a good place to start. Negative camber bottom arms (fixed or adjustable) and adjustable caster / tie bars, maybe lowering a bit and roll centre adjusting lower ball joints then if required start on the rear.
FNQ wrote:
the action of either reducing front understeer or actually increasing oversteer by letting the rear hang a bit is exacerbated in the wet.. In just about every case I know in a wet race setting - teams either loosen up the rear sway bar or disconnect it due to the much higher probability of doing a pirouette ( losing the back) There is practically zero warning . No idea of whether spirited road driving in wet conditions would trigger that scenario - but i thought it worth a shout out.
Absolutely this is the reason the mini and most OEMs set their cars up to understeer, the layperson will automatically react by easing off the throttle or braking which is a response for understeer that won't get you into worse trouble. Note power oversteer and oversteer are different (or so it's been explained to me) a rwd which kicks out the rear under power can still understeer at a corner.
By adding grip to the front incrementally to sort understeer you can stop once the balance is where you want it.
Other ideas to limit understeer / promote oversteer:
- The other approach that worked for me was to add rear hydro bumpstops to a rubber cone car, I added them primarily because it made it 'feel' better coming into a corner but it also would help control roll.
- Caster can also be used to create dynamic camber at the front, that is when you turn the wheels, which sounds useful but camber also adds steering weight and the mini doesn't have power steering...
- The factory settings for toe on the rear favoured toe in, setting this to straight could also help limit understeer. Toe out at the rear promotes oversteer and is not recommended for a road car or most race cars AFAIK.
- Just as negative camber (more grip) in the front promotes oversteer or less understeer, positive camber (less grip) in rear can promote oversteer.
- Another more left field way might be to put wider 165? tyres on the front and narrower 145? on the rear. Sounds whacky but it would be a cheap experiment to see if you like more oversteer.
A question I've wondered... when you see a race mini or similar with it's rear inside wheel dangling in the air are these always cars with rear anti roll bars fitted? There's a massive amount of droop travel on a mini so I can't see them running out of droop so to my mind it has to be ARB related.
