You have the standard all-season M+S 16" runflats, right? Not the performance ones? Replacing them with performance tires will surely help.

Increasing the rear tire pressure will give you some oversteer and might even things out. You don't want to drop the fronts much or they'll get soggy and your corner handling will suffer.

I'm not a suspension tuner but my gut feeling is that better front springs would help you, not a stiffer rear bar.

Harry

 

Here check this article out, it has some advice for improving the handling for autocrossing. http://www.minicooperonline.com/modules.php?op=modload&name=AutoX&file=index

If you don't feel like reading the whole thing...Cliff's Notes: Bring the "toe" out in your rear wheels.

 

Here check this article out, it has some advice for improving the handling for autocrossing. http://www.minicooperonline.com/modules.php?op=modload&name=AutoX&file=index

If you don't feel like reading the whole thing...Cliff's Notes: Bring the "toe" out in your rear wheels.

Thanks Lucky.

 

the rule of thumb is to increase traction in the front to promote oversteer or reduce understeer; you also don't want to reduce traction, so:

reducing roll stiffness in the front and increasing it in the rear will reduce understeer.

changing camber, tire pressure may reduce adhesion from the optimum.

check out Fred Puhn "How to Make Your Car Handle", that I paraphrased.

 

Decreasing Understeer

jmardy,

If you want to decrease understeer you should try pumping the front tires up a couple of pound, and lowering the pressure in the rear a couple of pound.

Make your adjustments in say 5psi increments doing 1 end at a time. Work slowly until you get what your looking for. Just don't over or under inflate the tires. Usually a 5 to 10 psi difference should loosen you up.

Increasing the pressure will lower the slip angle on the tire giving better bite. Lowering the pressure does just the opposite, increasing the slip angle lowering bite.

Hope this will help.

 

I'll give that a try.
Thanks.

 

Re: Decreasing Understeer

jmardy,

If you want to decrease understeer you should try pumping the front tires up a couple of pound, and lowering the pressure in the rear a couple of pound.

Make your adjustments in say 5psi increments doing 1 end at a time. Work slowly until you get what your looking for. Just don't over or under inflate the tires. Usually a 5 to 10 psi difference should loosen you up.

Increasing the pressure will lower the slip angle on the tire giving better bite. Lowering the pressure does just the opposite, increasing the slip angle lowering bite.

Hope this will help.

I'm not an expert but I'm not following this. From the little I do know, slip angle has something to do with which way the tires are travelling compared to the wheels. I agree that lowering pressure should increase slip angle but I'm thinking that "bite" (traction?) is the other way around? From my drag racing days, lowering tire pressure should yield more traction (bite?) so I would think you'd want to raise the rear tire pressure to induce oversteer.


--
Cheese

 

generally adhesion is improved by raising tire pressure over the recommended highway settings, say from 34 lbs to 38 or 40. after running at the track, you would lower the prressure back for a less bumpy ride home and to promote better wear during generally moderate driving conditions.

Puhn's view is that you want to find the pressure that gives best adhesion (skidpad test) and stick(!) to it, controlling understeer by controlling roll stiffness, not by reducing adhesion at the rear from the optimum.

 

Go for the extreme!

Get a set of super-sticky semi-slick Yokohamas. Appalling wear rate, lethal in the wet but amazing dry grip. Had a set on my Civic VTi.

 

here is another tid-bit to correct for understeer.

during understeer, the front wheel slip angle is too great, so the tire slips instead of rolling. to correct, you need to turn the steering wheel less, which is counter-intuitive. so if you want to turn right, for example, and the car is plowing along too much to the left, TURN LEFT more to reduce the slip angle and regain traction of the front wheels.

 

I tried AutoX for the first time a few weeks ago. It seemed to me that reducing understeer would be a good idea. I have been throwing it around in parking lots experimenting with left-foot braking. I know it used to work on my Mini 30 years ago. So far I am able to get to neutral feeling steer but I cant make it oversteer. I wonder if the ABS is getting in the way.

Does anyone know how to disable it?

 

here is another tid-bit to correct for understeer.

during understeer, the front wheel slip angle is too great, so the tire slips instead of rolling. to correct, you need to turn the steering wheel less, which is counter-intuitive. so if you want to turn right, for example, and the car is plowing along too much to the left, TURN LEFT more to reduce the slip angle and regain traction of the front wheels.

Maybe I shouldnt believe everything I read but I read that "slip angle" has nothing to do with slipping. It has to do with tire traveling in a difference path then the wheel. Which is right?


--
Cheese

 

Maybe I shouldnt believe everything I read but I read that "slip angle" has nothing to do with slipping. It has to do with tire traveling in a difference path then the wheel. Which is right?


--
Cheese

That sounds to me like what jlm is saying.
As I understand it (please correct if wrong).
Let's say your car is turning at a 30 degree angle, if you have 100% traction, your wheels are at the same angle. If you are understeering, your wheels are turned to -let's say- 35%. The slip angle would be 5%.

I actually tried what jlm suggested on the way in this morning. Same long right hand uphill turn, same gear same speed, felt the front end start to snowplow, turned the wheel toward straight and got some traction back.

Kind of the same idea as turning into the spin, but somehow it seems so much more natural with a rear wheel drive car...
Fun stuff

 

glad it worked! the idea is to get traction on the steering wheels so as to retain steering; if the wheels are turned beyond the usable maximum slip angle, the tires plow and don't steer and you get understeer.

 

understeer

I know this is an old thread and you have probably solved this to your satisfaction by now but no one suggested my solution which is real simple----put your foot on the gas!!I am not trying to be a wise guy and I too have driven rear drive cars since selling my 77 Saab 99 in 83. On my first blast through the mountains a few months ago I too was a little put off by the understeer at first but I found that in almost every case a little extra throttle (not always flooring it!!) made the car track very well around corners. This is with the crummy 16" all season run flats with about 32lbs of pressure all around. Now the line through the turn is a bit different than my Boxter S and while the total grip might not equal it either, the fun factor was at least equal.

 

SLIP ANGLES
Slip angle is a term used to describe a particular type of flex in tires. Even though the name uses the word "slip," this characteristic has nothing to do with slipping or skidding. Slip angle is a measurement of how much the tire's contact patch has tw isted (steered) in relation to the wheel. A good way to demonstrate this characteristic is to stand beside your car and turn the steering wheel. If you watch the left front wheel, you will see that it steers a few degrees before the tire's contact patch starts to turn. It is not uncommon for this slip angle to be as large as 6 to 10 degrees on the race track.

This characteristics is important, because as long as the tires have traction, the car tries to go where the tires are pointed. So, even though the wheels may not be steering, the tires can be steering due to the slip angle.



From http://www.auto-ware.com/setup/slp_hndl.htm

I agree with some of what is said, but I dont think we're talking about slip angle... anyone?

--
Cheese

 

"slip angle: the difference in degrees, between the direction a tire is pointed and the direction it is travelling." p. 159
"Technically, understeer is the condition in which the slip angle at the front of the car is greater than at the rear of the car. Understeering happens when the rear tires are maintaining traction and the front tires are not.

The solution when you are in the middle of understeer is to correct the slip angle of the front tires and get some weight on the front of the car.

Sometimes steering corrctions are all you need. Turn the steering wheel...back toward center. This immediately gets the slip angle back to a range where the tires can be effective."
Henry Watts, Secrets of solo Racing pp.38ff.

get this book.

 

I think you guys are talking about things that occour at the absolute limit of tire adhesion that can be experienced regularly on the race track or autocross course and sometimes at slower speeds in the rain, certainly in those situations getting on the gas is the worst thing you could do. I thought the original poster was talking about the understeering feeling that you get in spririted road driving which is usually well below the absolute limit of adhesion, in which case a little extra throttle helps pull the car around the turn and gets rid of a lot of that plowing sensation.

 

Understeer is understeer, DONT ACCELERATE

regardless whether it's 'sporty' driving or autocrossing. The Mini suffers greatly from power on understeer.

So, IMHO:

1. add more tire pressure up front, less in back to get better front traction (said elsewhere) and increase the 'stickiness' of your tires

2. add more weight upfront (not allowed in stock competition ax OTHER than the addition of tow hooks...but it DOES add weight, which effects acceleration) to gain more traction. So it's not a very good solution

3. sway bar changes and adjustable shocks, negative camber...MAKE: read a book, these are 'nominal the better' design characteristics that require experimentation to optimize and is as individual as the driver style 9although there are general presciptions), but there's lot's of room here to tweak...in H stock though, you are limited in what you can change. OR BUY: You can spend thousands with a lot of different suspension gurus to tweak your optimum autocross stock acceptable suspension system, and if you do, why would you share that with competitors?

4. Lift OFF the throttle, DONT ADD throttle, that's why you are understeering...adding throttle to steady state understeer will only get you into more trouble

5. steer slightly and briefly away from the apex (mentioned elsewhere as it allows the slip angle to 'catch up' with your speed), this isn't a dramatic adjustment in most situations, just a little adjustment

6. Control your speed into the turn so that you aren't understeering coming out of it... (hell, this one's the toughest for me)

7. Add limited slip differential, but that's also not allowed in Stock class autcrossing.

8. Upgrade to the SS+, that's allowed.

There's others here who are hot shoes in the AX nationals and regionals that know and have more than my RV dinghy Mini that I use to AX (SS, Mini lightweights with Yoko A520's and the Wife's damn moonroof, also towing bracket welded up front)...but this works enough for me to finish generally in the top three of most local ax's behind all those hot shoes if they are present.

AXAugs

 

the idea with getting on the gas is partially right. If you brake early and maintain the same speed going thru the turn, as to avoid shifting the weight of the car in two directions (sideways when steering, and back and forth when accelerating or breaking) you will achieve better traction.

 

well of course

if you brake early you will probably get on the gas again in order to smoothly transition through the corner, that's not what I'm refering to...

if you are already experiencing understeer, adding more throttle without correcting your steering is NOT going to decrease understeer as some previous posters suggested, it will only give you more push.

Physically impossible to recover from active pushing by accelerating (I'm talking the Mini here) unless you also correct for the mismatch in slip angle by turning away from the apex.

ElastomerAugs