"bambam" pampers his car? Now I've heard everything

Enjoy your day, man. Later.

 

Well I'm glad that everyone, except Jeffs, believes in the freedom to ask a question...in or out of his personal context. I love threads like this.

Kenchan, yes, slow speed corners and a bit off camber as well. Not my first time behind the wheel, but I was and am surprised by this, repeatable character...perhaps an alignment is due.

 

Geezz.. lighten up people. He was asking a simple question about the cars handling characteristics. Since I am awaiting on my MCS, I want to read and learn everything I can about the cars handling.
I do enjoy Hwy on-ramps and clover leafs taken at speed. The occasional redlight blast to 60 and those smooth right handers on my favorite back road.
Thats why I buy these types of cars. I get it on when the conditions are favorable and traffic allows. I dont drive like an idiot but I do enjoy a sensible sprint when the road conditions allow it.
Still much safer than someone on the cell phone driving slow but not paying attention.

 

I'm right with you mikem53. When your MCS arrives (and you make it through the break-in period) let's hook up and play tag

 

I think our former semi driving friend, bambam, is experiencing a connection to the road he has not had before. The MINI is, as we all know, a great handling car with exceptional "turn-in" for a front-driver. It also has a very short wheel-base. These two combine to make the car much more "twitchy", i.e. responsive to input. Someone mentioned looking where you want to go. That is the key to getting there. (Also in life, but I digress!)

Bambam, enjoy your new connection to the road and as a poster said look where you want to go and be smooth.

Enjoy!

Dave
June gloom in San Diego
2003 DS/B MCS

 

eMINI... sounds good! My MCS arrives in port on July 1st. So it won't belong.
I also got the DS/B...with the 17" web spoke wheels.... I am in south Charlotte on Providence south of I485.

 

Spoken like a true "person who has never autocrossed"

I think it's insane to buy a car like a mini and never get the thing on a closed course. Autocross doesn't hurt your car - you're spending like 5 minutes the whole day at full throttle, and doing some corners, and that's about it.

 

I have an 05 MCS w/LSD. Have about 2300 mi on the clock.

My first impression of the car is that is like every other car out there, built to understeer, however if prodded enough will turn a bit better than most. I felt there was a surprising bit of body roll in stock trim. This is largely due to spring rates and the stock sway bars, to make the car comfy for the masses.

The MINI has very limited suspension travel, if you are turning hard enough you may have reached the bump stops. If this happens in the rear the car will tend to go into an oversteer situation relatively quickly. I kinda doubt you are doing this on the street with street tires.

If this type of handling concerns you, I would lessen the rear pressures, if it still concerns you, replace the rear sway bar with a non S one. I believe thay are a bit smaller and will make the car understeer more than it does.
Another consideration, are you making any other inputs to the car other than steering? Are you in a constant radius turn or are you adding more steering when you begin to notice the oversteer? Are you braking or lifting off the throttle? These movements can all affect the handling of the car. Lifting off the throttle in a turn in a front driver will result in "lift throttle oversteer" - which basically means the weight that was once on the rear or loaded side of the vehicle is shifted forward which lightens the rear (reduces grip) and moves that weight to the front (increasing grip) causing the car to rotate or oversteer. Which is not always a bad thing :-)

 

Actually, reducing the rear tire pressure will cause the backend to come'round a tad quicker. More rear psi will help to keep the backend a bit more stable.

 

Compared to what? Maybe not as short as you really think. Bigger then an AC Cobra I know.

 

A semi, perhaps.

 

Yea thats right, I bought a Mini Cooper to pamper it Theres a fine line between driving hard and beating it to death.

I'm going to have to look into the autocross thing. I did do the BMW driving experience where they take you out on a track set up in a parking lot. I almost matched the instructors time and would have with a few more laps of practice.

 

Our autocrosses are 6 runs of about 50 seconds, 10 events a year. That's 50 minutes a year. I don't consider that "beating" the car. The experience is invaluable. You not only learn what the car can do, you learn what you can do. It's made me a much better driver on the road as well, not that I'm that good anyway.

 

Are you sure about this? This hasn't been my experience. My last day at Buttonwillow, I had about 2 psi less in the rears than the front, and it was more stable than when I had equal pressure all around...

 

If you plot "grip" of a tire versus pressure, you'll get some kind of an upside down parabola sort of curve. In other words, there is some pressure where the grip is highest, and going above or below that pressure will decrease grip.

The problem is there isn't one unique curve for a specific tire, there are other factors like camber, surface, etc. So it's more of an art than a science.

But the bottom line is, running either "low" or "high" pressures in the rear can cause oversteer For autocross, I like to run the rears about 10psi lower than the fronts, depending on things like weather. That gives me good rotation without making the car impossible to drive.

On the street I run them closer together, but I don't drive very "aggressively" on the street, so I am just trying to make sure they wear nicely.

 

hhmmmm... we have differing opinions. I have always jacked up the rear to get street tires to slide. R compounds seem to be brand dependant.

 

But the bottom line is, running either "low" or "high" pressures in the rear can cause oversteer For autocross, I like to run the rears about 10psi lower than the fronts, depending on things like weather. That gives me good rotation without making the car impossible to drive. - Yup! But! Low psi oversteer is caused by larger slip angles and side wall deformation. High psi oversteer is caused by too little tire contacting the road. A low psi tire will also warn you of a slide a tad earlier than one with too much psi...the latter may not actually give you any warning at all.




Absolutely positive! Increasing the psi in the front vs back will aid front end grip. Increasing psi in the rear will aid back end grip. Essentially, more psi will keep the sidewalls from deforming. So less deformation or distortion up front means more deformation in the rear and less grip. Read another way, the tire with more psi will have smaller slip angles, which means more grip, to a point, afterwhich too much psi causes a lack of optimal tire contact. One of the reasons low profile tires corner better than high profile tires is due to their smaller slip angles. Also, some current thinking suggests not playing with tire psi at all; the idea that every tire posseses an optimal handling characteristic at a given psi level says, set suspension balance up so that you can achieve that optimum level of adhesion without resorting to removing psi and therefore potential grip.


Obviously more psi works within limits as too much psi will cause the tire to ride at the center of the tread leaving very little between the tire and the road. Ah, as an aside, adding a bit more tire psi causing the tire to crown a tad is a trick for racing in heavy rain; less tire contact reduces hydroplaning. However, this can cause handling problems so you must take the course into consideration. Long straights, good. Lots of turns, bad.

 

tire pressure thing, I agree with meb. It's been this way at least on
the streets for me.

more rotation, lessen rear tire pressure, increase front.
less rotation, lessen front tire pressure, increase rear.

Difference of 5lbs.

It has to do with the structural stability of the sidewalls.

 

I think it also depends what pressure you're starting with. If the tires are initially inflated to below optimum, then the below is true. If the tires are initially inflated to above optimum, then I believe the opposite is true. Am I looking at that correctly?

 

Well, you must also become aware of what your cold and hot tire temp relationships are for your racing/street venue. For my daily commute I can expect a 2psi gain from any (35-37psi cold) baseline psi. With temps hovering around 100 degrees lately, I've found a 3psi gain.

The operating tire temp. also depends upon alignment specs as well sustained high speeds. Aggressive neg camber settings may cause a tire exhibit uneven operating temps across the tread and elevated temps at slower speeds.

You may find that 35psi cold at a track event yields 40psi operating temps. Whereas the same baseline will only change 2psi in normal driving. You just have to play with what works for your set-up.

The delection at the flat spot on the tire - the part that touches the ground - is in part what causes some of the heat build up in a tire. The frequency og this deflection obviously increases with speed. This is why it is important to correctly infalte tires so that the amount of deflection, and, frequncy of deflection do not cause temps to elevate and cause a tire failure. Kind of like bending a hanger; bend it fast and at extreme angles and heats up rather quickly and breaks.

I run 35psi front and 37 psi rear - cold.

 

I think that this is definately the best way to do it, but often you're limited in the adjustability of the suspension - and the fact that the ideal setup will change from day to day - so you're often stuck to playing with tire pressures at least a little bit. In the case of my car, which is set up for stock class autocross, tire pressure is just about the only variable I have to work with.

... which is actually fine with me, just finding good tire pressures is hard enough If I had 10 other things I could adjust, I'd never get the car right

 

Awesome info thanks

 

I think that eMINI hit the nail on the head. You need to look further ahead of the car. This will help to smooth out your entry and set the arch of the curve.

It has nothing to do with "setting" the suspension, not at the speeds that you are talking about. If you were pushing the limits of the car and the tires, then that is different. But, you insist that you are not speeding or driving too fast for the conditions.

 

Do you have an LSD?

 

Read up, and practice in a safe place:

http://phors.locost7.info/contents.htm

With the Mini, it is "Fast in, Faster Out"

Dave.