Yes, very true. Unfortunately, t is impossible to cover every potential detail with the limited amount of time we all have for replies. I certainly neglected limitations imposed by rules, leaving tire psi as one viable alternative. And, like I wrote, I'm playing with 35 front and 37 rear = 37 front hot and 39 rear hot...a tad harsh, but see there's this really really fast sweeper...I would prefer the back end to stay in the back.

 

I have definately noticed a difference in the handling of my car since I had the suspension upgraded. I am having an alignment done today to work out any inadequacies, and I hoping to track sometime soon. Off the throttle is better than the break peddle.

 

I don't agree to that being a universal truth. With good aftermarket brakes, I can stay on throttle until just before a turn, squeeze the brakes hard, and be on throttle at the apex, and regain time on others.

I did that this weekend with Samurai Will in his S. I caught him over and over again in the mountain twisties, because I could hold on to my speed longer. It's faster to deplete speed than to gain it.

 

Who ever said that it is a universal truth. We are all speaking relatively

 

There is absolutely no such thing as a universal truth.

 

This is an interesting topic as I was about to bring it up myself. Ahamos just desribed exactly what's happening.

I've noticed any throttle changes while turning really upsets the balance of the car. The super touchy steering is tough to get used to coming out of my Mustang. And don't even think about changing gears in a turn, and going back to WOT right away. Taking your foot off the gas unloads the rear, Then changing gears with one hand while trying to control your new found oversteer with the left hand gets tricky, as you go back into the throttle and grab the wheel again. This car requires a little skill, that's for sure.

this car definitely takes a little more finess and smoothness in taking turns. Taking turns on a track is an ideal situation but when you're manueuvering through traffic in a bend, and need to let up on the pedal, or pick up speed, it upsets it again. You just have to be careful and mindful of what it's going to do.

I wonder if the short wheelbase plays a factor?

 

Changing gears in the middle of a turn is basically just bad driving

Short wheelbases combined with typical FWD weight distributions do seem to make lift-throttle oversteer worse. My 85 CRX Si (best car ever) had the most wicked lift throttle oversteer I've ever seen. I think I spun that car at least one run of every autocross I ever drove it.

And so speaking of chaning gears while turning, and my CRX, I was at an autocross once on my first run where I was going through a wicked fast set of offsets, and redlined 2nd. So while going through the offset (turning slightly), I lifted to shift. The car was backwards before I could get my hand off the steering wheel and onto the shift ****. In subsequent runs, I short-shifted into 3rd while I was still going straight Worked much better

 

By the way - sorry to bring us back to air psi - if you add heavier rear springs and a larger rear bar you may want to experiment with higher rear tire psi. Heaverier rear spring rates (relative to the front) and larger rear sway bars are designed to transfer weight rearward. In fact, a larger rear bar, relative to stock, will transfer weight to the outside rear wheel and remove it from the inside rear wheel.

You may find that although grip increases with more psi under some of the above conditions, break-away may occur a tad more abruptly. So, depending upon you driving venue, you may decide to give up a little grip for rotation that is a bit more accessible.

 

Interesting thread. On the track using R888 or D01J,we run 28psi front and 26psi rear.(cold) Front may increase 10-11 psi & rear 4-5psi when fully hot. This keeps the rear end real settled and very safe.Ok on a tight circuit a little more in the back is ok. Running 36psi (cold) in the rear is way too much for circuit,-this is a '4up and a boot of luggage pressure'. Its not cool to say you like understeer ,everyone thinks they want/need oversteer. Very high rear tyre pressures & fat rear anti-roll bars are usually not the best thing . 9-10 people that have an 'off' have it due to oversteer not understeer!
Yes look long and look high. Never hold the steering wheel rigid through the corner ,a slow (2 rocks per second approx) &gentle zig-zagging of the s/wheel say 15 degrees left&right of the desired turn makes it almost impossible for either end of the car to step out,the line can be held almost perfectly even full on the gas .Particularly in the wet you will slaughter everthing else on the track if you do this.

 

A complicated subject for sure since there are so many different tires run in some many different venues. However, reducing tire psi in a rear tire after installing heavier rear springs and a larger rear bar may indeed be counter productive. I agree, too much air in the rear, under the above scenerio, will cause a snap oversteering condition...as will too little air.

I would expect the cold psi of a race tire run in race conditions at a max of say 200 mph to be quite different from a high performance street tire run in a 'track day' event.

 

I've always understood that increasing stiffness in the rear relative to the front (either by sway bar, tire pressure) will increase oversteer and vise/versa. When I raced shifter karts, tire pressure was pretty much all we had to play with and that is how we achieve balance. Does this not apply to cars? You're confusing me

 

I agree with the above 2 statements. MSFITOY, I think you are correct, this has always been my experieince, especially with front drive cars. Soft up front/stiff in back = rotation.

 

The bottom line is that there is more than one way to skin a cat. I like moderate to heavy oversteer without "snap". With the rear bar set on the stiffest setting, -2.5 front/-1.9 rear camber, 1/8" toe out front/0 toe rear and 205 15" Victoracers with 42# front/36# rear I get a decent amount of oversteer that is very controllable (not to say that I've never spun on an autocross course ). The key is experimentation in a safe setting to see what setup fits your car and driving style the best.

 

Exactly! Suspension settings will determine how accessible oversteer is. When I write accessible, I mean to say you determine when to employ it, it shouldn't come as a surprise. Tire psi can be used to fine tune any characteristic. You can add more psi to the front tires of a front drive car and this will cause the front to bite harder, essentially adding a bit more oversteer. The same is true if you remove psi from the rear tires; this will still leave the front biting harder than the rears, but this was accomplished by removing psi from the rear, not adding psi to the front. The realtionship remains the same front to rear, although total psi is different for either scenerio.

Lets isolate the rear tires for a moment. As I wrote above, oversteer can be achieved in two different ways with horrible results at the extremes. Say we have 37 psi front and 39 psi rear - operating temps on high performance street tires. This will add to rear end stability in really fast sweepers - 100mph +. This will also cause a tad more understeer in slow speed cornering - barely perceptible but there nonetheless. If the psi in the rear tire is raised to say 45, you can indeed expect the backend to become very loose and probably without much warning; there will be zero sidewall flex or tire screeching and the tire may suddenly lose grip.

Now, lets say we have 37 psi front and 35 psi rear. This scenerio will more than likely yield very controlable slow speed oversteer and high speed instability in the fast sweeper mentioned above - instability is a very relative term here. If the psi in the rear tire was reduced to say 29 psi the back end would become very loose and unstable but would probably give you a fair amount of warning as the sidewall flexed.

You do have to experiment. I sometimes raise issues not meant to be taken in black and white terms, rather, to trigger thinking; you know, maybe 2psi more in the rear with the 22mm bar and 400lb/in springs is a good idea for fast sweepers. Or perhaps you've decided to add a bit of tow-in in the rear to stabilize the back end. You simply have to think about what you are asking the car to do...and heavy rear springs relative to the front along with big rear bars is designed to transfer weight to the outside rear tire - the bar will remove weight from the inside rear tire - making that outside rear tire a very important piece of equipment should it flex too much or lose grip without warning. That's all I'm suggesting, nothing more.

We are fighting physics; this is a nose heavy, front wheel drive car. The techniques available to us simply make the 'Mini package' less stable. The Mini will never have the feel of a 50/50 weight distribution...that kind of set-up does not need to be leveraged so much to handle well, really well.

 

Thanks Meb for the info. I'm sure you've already posted, but what are your favorite cold tire setting and suspension combination? How much would the pressure rise during street driving as opposed to track?:smile:

 

Okay, now you're testing me. I've not been on the track with this car yet...in a month or two...still putting a package together.

I have Kumho 712 205/45/17 on forged BBS wheels, stock 2005 MCS suspension with 26,000 miles - feeling very soft by the way. The fronts are set at 35 cold and the rears at set at 37 cold. I have two extremely fast triple digit sweepers on my way to work. My personal limitation is protecting my backside while going thru these turns. At an even 35/35, the back end gets a hair nervous. Operating temps usually hover around 37 front 39 rear for an average 80mph commute.

EDIT - OOPS! I'm playing with 36/36 now, very sorry forgot in all my enthusiasm. Not bad...

 

Those are good numbers for comparison. I'm running HSport springs with Konis set at slightly greater than 1/3 stiff front and 1/2 rear. My cold pressures (Kumos Ecsta MX 215/40-17) are set at 35 front/rear. My 22mm rear sway are set at 1/2. On 80mph sweepers, mine starts to get a little unstable in the rear. At low speeds like around boulevard turns, she understeers a bit. Curiously, prior to the Konis, she would pivot around such tight turns like on rails. I'm wondering if I should tighten up the front Konis or increase front pressure or increase rear bar stiffness. Any thoughts?

 

The quick answer is turn the rear Koni 1/4 - 1/2 a turn from full hard and the front half way between full soft and full hard for starters. I think the HSports are too soft up front by the way. Yes this can cause lots of dive under heavy braking, but, the Koni set at full hard for this soft spring makes the front end very lazy with respect to the back. Meaning, soft springs mated to too strong a damper will usually result in a lazy response from that combo. I'm sort of surprised by the lack of rotation given the difference in spring weights. You may actually be feeling that the front end is not as responsive BECAUSE the dampers are stronger than stock. Too strong a spring for a damper causes the opposite; the spring never settles down.

...I don't know what your other settings are - tow, camber, etc so the above suggestions are outside of that knowledge.

 

Clarifying the psi thing; to a point, adding psi reduces slip angles and removing psi increases slip angles. Smaller slip angles means more grip, in a relative world.