Last weekend while at a autox event I notice that my Mini was Oversteering really bad. The last few events last year I didn't have this problem but I was on small tracks. The track I was at last weekend was more open for speed I guess you would say. Anyway I setup the Koni coilovers the same as last year which was half way in back and full firm in the fronts. The rear sway bar is set the same as last year which is on the lowest setting or the back hole on the alta sway bar.

Why would my mini be oversteering to the point of losing control. When I say oversteering the back end just losses grip all together.

Any Ideas?

 

How is your alignment set up? Which tires and what pressures? What was the temperature at the track?

 

I haven't done anything to the alignement. So I guess Factory. The tires are Kumho Ecsta AST. At the end of the year last year I was also using Kumho Ecsta but they were not the AST. I don't remember the model. Tire pressure was 38 all the way around. The temp at the track was 40 samething with a little rain on the track.
But there was a Mini cooper in Hstock and a Mini cooper s in G stock and I talk to them and they were fine out on the track. I mean I watch them and they look great out there. I watch my videos and I was all over the place with the back end. Anyway I don't think it was the Temp or the little bit of rain. I don't think. .

I guess it could be the tires. Anyway what do you think?

 

Kumho AST's are not great autocross tires. They are all season tires. Maybe they are finally worn out? Maybe they just don't have the grip of the other Kumho's you ran? (712's? SPT's? MX's? )

Realize that if your car oversteers at all, it will get worse on a faster course. It's very common to change the car when you go from slow/tight/small lots to big/open/high speed lots. You're lucky you have the adjustablity to do it.

I would also check the condition of your tires. Maybe they've gotten hard?

Front shocks blown/leaking? Front sway bar linkage broken?

Rear sway bar lube is gone/shot and needs to be re-lubed? Unhook the linkage and make sure it moves freely.

Maybe you backed into a curb to hard or your rear toe plate bolts wern't tight so they slipped? Dunno.... But those are the things I'd check.

 

Another possibility given the low ambient temps is changing tire pressures. The front tires warm up much faster than the rears when it is cold out. That can lead to a much greater difference in tire pressures front to rear if you weren't adjusting after each run.

The situation gets even more dramatic when running R compounds.

Scott
90SM

 

Duh! (I always forget the simple solutions!). I agree with Scott. Sorry I didn't think of it.

 

Thanks for the info. I'm going with worn out tires. Today I basic took the back end apart and checked for problems. Everything check out good. Maybe before the next run I can get some new tires.

Again thanks for the help.

 

One last thought on this subject. I also had developed a real bad oversteer problem on track last year. I figured out I was simply drive better, had more confidence on the track and was going faster than the previous year. New tires made a difference but two other adjustments were just as important; first, adjustable camber plates up front (set to -2 deg.) helped to settle the car in the corners, and secondly I adjusted my driving style to brake harder coming into the curve and accelerate out of the apex instead of sliding into the curve. Both my lap times and tire ware improved considerably. Good luck next time out!


DJDport

 

Was this alarming tendancy to spin present equally on all runs? Or was it worse for the first one, and then progressively less?

Did you use the "hand pyrometer" to see what temperatures you had at the tires for the front and back axles at any point during the day?

Did you measure your tire pressures during the day? What effect did running the car have on them?

How long was the wait between runs? How many runs did you get?

My experience under similiar conditions is that I can get 20-30 degrees in the front tires in the first 100 feet of the course, which makes the car truly exciting until some heat also appears on the rear tires. This was worst when I ran Hoosiers, but still very true for the 'Kook RS2s I run now. I have also found that I have to give up a lot on the first run, but not too much, because only with some generous slip angles at the back can I EVER get any heat back there.

Last week's Evo was run at 39 degrees, and the car was damned near undriveable for the first two runs. This past Sunday was 70 degrees and sunny, and a track temp of 80. The rear tires were at 100 degrees after the first run, and oversteer was not an issue.

 

I didn't read all the posts, but, if I am experiencing oversteer it is because of the following, keep in mind, these are the non-obvious things other than tire pressure, alignment, shock settings, swaybar setting's etc.............

#1 Cold temps
#2 1st heat runs - only because there is less grip, so, see #3. :-)
#3 lower grip surface - if you are on concrete, rotation is much more difficult to obtain. In the rain/wet, you would expect to experience more rotatio/oversteer.
#4 either all or rear tires are older - basically that means less grip for the rear
#5 higher speed transitions create more oversteer than slow speed transitions typically

thats all the not so obvious elements that I can think of right now

 

So as a follow up question (and as a new FWD racer).....when it's cold outside do you let the car come to you? Or do you adjust the tire pressures/shocks after the first run?

 

Keeping everything else the same? We adjust pressures down, to allow heat to build in the tire quicker (sidewall flex)... For our setups and tires, about 3 -4 psi lower all around does the trick. If it's cool and wet, we dial back the shocks a bit, too.

 

Qustions I need to answer. Ok here we go!!

Was this alarming tendancy to spin present equally on all runs? Yes I ended up off the track on the first run.
Or was it worse for the first one, and then progressively less? The last run I couldn't turn in time and hit a cone plus point cone right at the end gate. That was almost really bad.

Did you use the "hand pyrometer" to see what temperatures you had at the tires for the front and back axles at any point during the day? No I used the temperatures reading from the MINI.

Did you measure your tire pressures during the day? nope I know I should have.
What effect did running the car have on them? don't know.

How long was the wait between runs? about 10 mins.
How many runs did you get? 4 runs.

Here is what I think. And what I'm going to do. First I do push the Car very very hard this year. All last year I was learning to get faster.
But I believe the problem was the Tires. I had a Mini Group run this last weekend and everybody had to point out my tires. But I had no problem on the run but I didn't push the car as hard.

Again thanks for the help. I must bet the WRX's.

 

New Question! Ok was was talking with the guy from Alta here at the Dragon. I asked them what each setting is on the Bar. I beleive they told me the hole closest to the front of the car is the Softest which is not what I was thinking. I have it on the very back hole closest to the back of the car.

Is the back hole not the Softest setting?

 

Yes, the hole farthest is the softest. (Think of it like this: it allows the bar to twist the most.) Alta better re-educate whoever the hell that was.

 

Thanks for the Answer. Today in the rain at the dragon I had the back Shocks at half and Fronts at half . Also new Toyo Tires and all is good on the setup.

 

Yes, use the hole closer to your rear bumper like this-

It's still plenty stiff compared to stock.

Most of the time you will do best with the rear bar on softest setting.
It is possible to set it too firm but it can depend on your other upgrades and driving skill/style.

For autocross I'm using softest setting on my rear swaybar so that I lift my rear wheels less and use more of my tires (4 tires work better than 3 for weight distribution and traction).

 

There is a test & tune on june 2nd that I will be setting my swaybar to the stiffer settings to see how it works. But I've been able to get the car completely neutral feeling by playing with tire pressures (36/26 give or take depending on conditions). And my friend was able to spin the car out. Still, should be fun.

--> softest on 22mm alta.

 

Thanks again for the great info Minihune. My Alta Sway bar has three holes but I do have it in the back hole closest to the back bumper. I know some people that have theirs on the middle but they don't have the koni's so I guess they need it on the middle one.

Anyway next weekend we will see what happens at the Auto X event.

 

Don't forget, on a sway bar with 2 adjustment holes, there's actually THREE settings.

Front holes = soft
Rear holes = stiff
Left on front hole and right on rear hole = medium

Actually 4 settings.

Dissconnect one side of sway bar = softest setting of all

 

Today I had a AutoX event. The car Handle much better. I had the Front Koni's set at half, Backs at half. Tire Pressure was 38. Rear sway set in the Back holes closest to the back of the car.
Same setup as I had at the Dragon. The oversteering today was much less than before but there was still some there.

I have the 22mm Alta Bar. Is that to much for the MINI?

I think I saw where someone else has the same idea in their head. Would the Stock sway bar be better?

 

Since you have adjustable Konis, try stiffening the fronts about 1/4 to 3/4 turn (counterclockwise to stiffen them).

By playing slightly with the front Konis, you can get where you want with maybe only a very slight rear tire pressure adjustment as the tires/course heats up.

To reduce oversteer, make the front Konis stiffer, or the rears softer.

The swaybar should be fine as is, at least for now.

On the other hand, being able to induce rotation by steering with the throttle can be dialed out if you make the front too stiff.

But that's related to your personal comfort zone.

Higher speed sweepers on cold days with old tires probably only means the fronts got a smidgeon of heat in them and the rears got none.

Test 'n Tune days are perfect for getting the f/r balance dialed in.

 

Just so you know, I went to the stock rear bar and it's now driving like I think that it should. If you have the ability, I'd swap in the stock rear bar for an event and see how it does. You can always go back.