this is starting to bug me, so i'm looking for advice on how to reduce it.

i have an early 2003 mcs with:
- over 100 lb. removed from the rear
- eibach lowering springs
- hotchkiss upper and lower rear control arms givind rear camber back to within stock range.

i'm in the market for coilovers (leaning toward teins, which would allow me to go with various spring rates in the back). while i'm at it, i'm up for changing other things if i can reduce this.

thanks in advance.

 

I would start with adding a little bit more negative camber in the rear to increase grip. Another option would be to go to a smaller rear sway bar, say a used bar off of a Cooper with the standard Sport Suspension (not plus).

Scott
90SM

 

^Mushier rear bar would do the trick, but a STIFFER front one would do the trick and improve everything else as well.

Well, except ride quality.

 

if you make the rears stickier to help this, you'lll increase understeer. Face it. It's a front drive car with over 60% of the weight on the front wheels. Lifting throttle oversteer is the nature of the beast!

Matt

 

Sometimes that oversteer will come in very handy.

 

I'd play with alignment and tire pressure before switching out parts (more rear toe in, more or less rear tire pressure, depending on what you're currently running), but I tend to agree with DrO, every fast FWD car that I've ever driven had a tendancy towards lift throttle oversteer. You can take the edge off it, but I think you'd end up ruining the handling of the car before you completely eliminate it.

Edit, and by the way, don't lift. That's the easiest way to stop it

 

i was going to put in my post "and don't just say don't lift..."

first try: when i get the new, lower coilovers, i'll just leave the control arms where they are and get some increased rear camber. i'd be willing to live with more understeer to reduce the trailing throttle understeer.

if you guys have any more suggestions, please post. thanks again.

 

Keep a couple of thoughts in mind; road cars require heavier damping because they are heavier. If you've removed 100lbs fromt the rear of your car, the spring rates are now more effective...100lbs is a lot! And, in addition to - the suggestion - more rear camber, try this; add more rear toe-in. Toe-in in the rear helps to build slip angles a little faster than say no toe-in. The rationale here is that the front - because it enters the turn before the back - builds slip angles first. If you give the rear tires a chance to build slip angles fatser, you may find that the car still slides, but much more progressively and with much more control. Slip angles are required for grip, essential in fact. So if you front tires are at saturation and the back end has not even begun to build slip angles, yer look'n for a spin!

All the other factors like tire compliance, spring and damping, sway bars - all mentioned above, not to mention weight, will affect how much toe-in is good. Finally, I beleive that rear toe has a much greater affect on striaght line stabilty than the front... you can try slightly more than a stock setting for rear toe...

Interestingly, I had a wild spin at LRP a month or so ago. The car snapped around like never before. I thought it was a bad rear bushing...turns out the folks who performed the alignment used my toe-in spec for toe-out:impatient

 

MINI specifications for an alignment start with a spring test to determine a specific height. They acomplish this by adding weight to your car. The rear trailing arm suspension is much more susceptible to this than the front struts. So in effect , by removing the 100 lbs in the rear, you removed some rear camber. Also by lowering the car you gained some rear camber. One thing to consider is that if your alignment shop did not have any weight in the rear at the time of alignment you probably have less rear camber than the way MINI has spec'ed it out. Also the weight in the car at time of alignment, such as fuel capacity will also have an effect. If the alignment guy will allow you to sit in the car at the time of alignment (some of us weigh 150 lbs-some of us weigh 250 lbs) you will get a more accurate reading. A good test for this is to align the car to the specs you want with you in the car and then get out and watch the specs change. When you get out you will notice less camber in the rear. Just some things to think about. What ever you do try to duplicate conditions as close as possible from one alignment to the next. Steve

 

when you lift in a turn, weight transfer goes from the back to the front! Nothing in allignement settings will ever change that.

Matt

 

...with not too much effort, a car can be designed to off throttle understeer, easier with a nose heavy car. This handling attitude dominates most car manufacturer's goals. And as Doc pointed out, the weight transfer will initiate either off throttle understeer or off throttle oversteer (FWD) depending on the type of modifications, and, corner entry speed.

Reducing trailing throttle oversteer or making it more controllable - to fit the venue or driver comfort - is something flyboy has to tinker with. If he can cause this oversteer to happen in a smooth and linear fashion, it is controllable at most levels. It's not like a 9 series Porsche whos engine sits out behind the rear axle line...the exact opposite of the mini.

...as Doc wrote, the weight will move forward. What path it takes depends on the tuner.

 

But what can one do that won't make other stuff worse? There's already understeer in the car, and since pretty much any forward weight transfer in our cars will reduce the understeer, the only way to keep it from going to oversteer is to make the normal understeer worse. Or am I missing something? Seems to me that almost anything that will be done to reduce throttle lift oversteer can't help but have the effect of making the problems with the stock set up worse....

Maybe this can be attacked from driving style, as opposed to suspension tuning. If you're lifting hard in the middle of turns, your braking too late, not enough, or both, and if you're finding that you need to lift suddenly on the street, then it's probably the case that one is overdriving for conditions.

Matt

 

Hard to know Matt...I'm an amateur at this stuff, not an angineer . My intuition tells me that the character or degree of oversteer along with the element of time - how fast - is all we can really change. The Mini is a really good car in stock fashion. I still think slightly better damping -quality - and slightly higher spring rates with the same balance along with a 19mm rear bar and a camber kit up front is all anyone needs to make this thing fly on a road course. But, I will continue to experiment with other setups...I cannot help myself.

Increasing grip up front in an effort to take advantage of the weight transfer is key in my opinion. And some understeer is not a bad thing on a road course. An autoX course is different, in my opinion.

I agree with you; the mini has come to us as a compromise, just like any other car. But it is a really good compromise.

Finally, the level of speed that can be achieved on the street in no way mimics the forces on a track. So, and in my opinion, tuning and driving style ought to walk hand in hand with some relative connection to the basic driving venue.

...for goofs and giggles, my car oversteers under power thru really fast sweepers and moves to slight understeer as I drop the throttle. But this is due to the rear toe-out condition...I much prefer the opposite and definately like a little understeer at high speeds. Keeps my enthusiasm from hurting me and my ego

 

Many years of motorcycle riding and rider training taught me to get the braking completed before the turn (finish weight transfer) and square-off the corners to minimize time spent at the limits of tire adhesion (and see more of the corner before entering); now I have to learn trail braking and smooth steering inputs driving an auto. Of the two habits, braking before the turn has been the hardest to overcome, but getting the braking over early ensures progressively increasing throttle input through the turn, decreasing the likelihood of snap-oversteer.

I’ve made suspension modifications that kind of round off the edges of each other’s characteristics and see the alignment as the moderator. I’m running -1.75 in the rear with .22 toe-in, a wimpy 18mm bar (at the stock length hole postion), and more negative camber up front with good results on the street; although unlike Steve I've added weight to the rear.

 

...1.75 in the rear...I was just thinking about trying 1.5+

 

Embrace it! A bit of oversteer can be your friend!

 

...well, at 90mph when the back end comes around and your car becomes airborn from riding over the rumble strip at said speed...and when it comes down it blows a tire right off the rim...but thankfully did not roll...oversteer wasn't my friend that day

I was driving too fast for the track temps, in reality. What sticks at 70-80 degrees doesn't at 34 degrees.

 

I run the -1.25 plates front, -1.25 rear and 0 toe all around on a JCW suspension Makes me pretty happy!

 

He didn't say anything about track driving so I assumed he was talking about street or canyon driving which is usually slower speed stuff. places where a little throttle off oversteer can help rotate the car around tighter corners. But I know what you mean, the Mini seems to get a little loose at the high speeds. But, I must admite, oversteer nibbled at me last Sunday morning. I was getting off the freeway, a downhill fast sweeping right hander the leads to a 90 degree right hander onto the surface street. Or really I would call it a downhill decreasing radius right hander. It was drizzling and the pavement looked drier then it was. I didn't have to brake till I was close to the right hander, so I healed and toed down into second gear, turned into the corner, and the rear end broke clean loose and swung around about 45 degrees. It really suprised me, but I dialed in a lot of opposite lock, got on the gas a little and rode it out like did it on purpose. And, there was a small truck in the outer lane, he was probobly going "WTF".

 

mine is not dependent on speed (has happened between 20 and 60 mph), but seems absolutely dependent on lateral g load; it ONLY happens when the car is coming from a (relative for ME) high lateral load situation.

i talked to a guy about this phenomenon on the toyota mrs; i'm wondering now ( amateur guessing more like ) if there is enough compliance in the rubber bushed rear suspension to be causing some weird toe change?

 

I believe the early model rear trailing arm bushing allows diaphragm type movement which can alter toe. To a lesser extent the H-Sport camber link poly bushings have some give also, especially if they are the early versions with high mileage. After a very unsettling high speed road obstacle avoidance maneuver I found my H-Sport bushings had badly deteriorated and there were cracks in the trailing arm bushing. When replacing my rear trailing arm brackets/bushings the cracks turned out to be minor splits in the rubber surface but the bushing could be pushed in and out with finger pressure; the new bushings were not as compliant. After replacing the trailing arm brackets/bushings and changing to solid contact joint ended control arms/links the unsettling rear end behavior went away and feed back increased (which may have helped me compensate for the behavior rather than eliminate it). I also tried poly bushing inserts but there were some side effects I didn’t care for. If you would like to try the inserts Steve, I’ll send you a set.

From the latest information you provided it sounds like the previously suggested areas of tire pressure, camber, and sway bar stiffness (what do you have now?) are the things to start experimenting with.

 

k-h,

i have the h-sport arms with the "new" version of the bushings; i think the durometer is the same, but the design is different. besides the arms and the eibach springs, everything else is stock.

if your bushings are indeed firmer than the stock h-sports, i'd consider trying them. but the first thing i'll try is a little more rear camber and a little more rear toe in.

since your describing good results with the solid joint rear control arms, i may just bite the bullet and try heim jointed arms with aircraft style rubber booties over the bushings. i'm willing to live with possibly increased ride harshness to reduce the lift throttle oversteer.

many thanks to those helping me.

 

I think replacing the current control arms would be low on the list of priorities for what you’re trying to accomplish. I also think poly bushing inserts would not address your issue either, I mentioned the inserts because it related to your question and it would be an easy way to test the changing toe theory. The inserts fit into the trailing arm bushing not the H-Sport links.



It would not be a bad idea to have a look at the front wishbone/control arm bushing. At the moment concentration is on the rear but a really bad front wishbone bushing can cause erratic behavior also. Turn the front wheel to the side, reach in and grab the wishbone near the bushing end, if it moves with only arm strength, consider replacing.
Good bushing on the left, bad on the right.


Imagine that torn bushing flopping around in this.


Forgive me if you’ve already looked at these other gloomy possibilities.

 

I have been thinking about a limited slip and how it would affect this dynamic. Only my concern was that it would decrease the oversteer too much.

This is only an idea and not theory by any means. Here's what I was thinking.

If the inside wheel spins first from too much power, then wouldn't it also apply the most engine braking force there too. So that not only would the weight transfer rotate the car, but so would the extra inside braking, Just like how someone in a wheel chair holds onto the inside wheel to whip around a corner. Now if that is true, then a limited slip would distribute the engine braking more evenly (less to the inside) and help to reduce the oversteer.

Again this is just something that has been in the back of mind while prepairing for an lsd install, but if true, may help in this case.

Also, I would like to know the exact conditions under which the oversteer is taking place. Obviously you will oversteer if you abruptly lift off the gas while in a tight turn with higher engine rpm's, but until I replaced my front control arm bushings my car was very touchy in highspeed back road switchbacks. Maybe that is what he is experiencing and not "normal" trailing throttle oversteer.

 

002,

Good thoughts, but it doesn't exactly work that way for a couple of reasons.

The inside tire spins on an open differential car because it has the least traction due to the weight transfer to the outside while cornering hard. Our engines don't produce enough compression braking to be much of a factor on dry, or even wet pavement. The reason the car oversteers when the throttle is closed mid-corner is due to weight transfer to the front of the car and the subsequent reduction in grip at the rear tires. The wheel chair analogy works for wheel chairs, tanks, and specialty cars with individual brake applications to the wheels. It doesn't apply to our MINIs or any other production car, nor nearly all race cars.

When I installed the Quaiffe in my MCS, there was no reduction (or increase) in trailing throttle oversteer.

Scott
90SM