Hey guys I have a 2003 MINI Cooper with these susension mods:

1. H-sport spings
2. Koni yellows
3. H-sport lower rear control arms
4. Powerflex front control arm bushings
5. HandR 18mm rear sway bar
6. OMP lower front strut brace

I am thinking about changing my alignment settings from this:

Front Camber: passenger: -0.3 driver -0.5
Front Toe: 1/16 toe out
Rear Camber: -1.4
Rear Toe: 1/16 toe in

I want to change my alignment settings for these reasons:

1. better turn-in
2. more oversteer
3. even better straight line stablity

I am thinking about getting camber plates but I think I have a lot of mods already. What do you guys think I should change my alignment to and are camber plates really needed for a 400 mile plus driven car a week?
THANKS!!

 

If you want more oversteer, try playing with tire pressure a bit. More pressure in the rear and less in front will help.

Another option is a stiffer rear sway bar. I put the 19mm H-Sport bar set to the stiffest setting and I love the way my car rotates. One of my bets friends who is that guy who always has the best most expensive stuff who is a major car junkie (he's had highly modded Z32 (300zxTT), M3, and currently a supercharged G35)) actually asked me if the car was RWD!!!

Anyway, camber plates and adjustable rear arms are the two major items I haven't added yet to my ride, and I can feel by the way the front tires act right now that camber plates will be a huge advantage.

I'm also told that camber plates are the one mod, if you had to choose only one, to do to your mini's suspension. I'm starting to agree, though I haven't done them yet.

 

Camber plates.

 

Yeah.. camber plates. My car has plenty of throttle oversteer, to the point where it's frankly too much on very fast autocross courses. My tire pressures are now dead even front-to-back. (I'm not pumping up the rears to reduce traction back there.) The Koni Yellows have helped immensely.

I don't believe increased camber helps initial turn in. (It will increase traction in turns.) Your toe-out up front already looks pretty aggressive. More camber also won't help straight line stability. If you're looking for more stability, adding camber plates would probably allow you to dial back some of that toe out for an easier to live with alignment.

Better minds will probably chime in though.

 

Ooh. Methinks there is some questionable advice on tire pressures in this thread. Within the proper range, increasing pressure in the rear will reduce oversteer.

 

Without camber plates you'll have to remove the rear camber. 2.5 in the rear will INCREASE rear end grip in proportion to the front wheels having zero. Also, toe in will give better INITIAL turn in, whereas toe out will perform better during mid to exit. There are a lot of variables in suspension set up, as well as circumstances, that can throw all rules out the window, but generally speaking, increasing the rear pressure (beyond a certain point) will reduce rear end grip.

 

Huh. I experimented with decreasing rear pressure on a track day and got more oversteer as I went down. I've read the same thing in a bunch of places, like...

http://www.tirerack.com/tires/tirete....jsp?techid=58
http://www.rogerkrausracing.com/Tech...verunder.shtml

???

 

Obviously there is a sweet spot as far as pressure is concerned. Anything lower OR higher will decrease traction. Sidewall construction has a sizeable part to play as well. Increasing the front pressure will reduce understeer for about two laps, then it will flip flop. Depends on how much heat you're putting in to the tires.

 

2x what flow said. I've tended to pump my rears higher for more neutral handling @ autox, but either way works. The biggest PITA is finding that 'sweet spot'!

 

Hey guys I have a 18mm HandR rear sway now. If I go up to something like a 22mm Alta rear sway, will I see Improvments in turn-in and oversteer. Right now the 18mm only has two settings(stiff and hard) Also I im trying to keep my tire pressures under 35 psi cold. If I dont the car starts to get twitchy as I drive it more.

 

Lower rear pressure is typically - traditionally - used to create a little more neutrality in front wheel drive handling. When a the rear wheels are toed in ever so slightly, and, rear tire pressure is a hair lower, the rear tires will build slip angles in sinc with the front tires. This is vital on a road course and on the street. AutoXing is a different animal; the forces acting on the car are not nearly as high as they are on a road course so the car needs more help rotating.

Increasing rear tire pressure will cause the tire to build smaller slip angles making for an edgier experience. Also, the tire is, relatively speaking, riding along its center section in this case.

So both will help the oversteer case, but the way the car feels is very different...and the way it breaks loose will also be very different. Smaller slip angles generally yield less break-away warning - the tire saturates very quickly. This is relative too.

Do not mix AutoX set-ups with road course set-ups. Each is very specific; an autoX set up will be very dangerous on most road courses and will not yield good times. A road course set-up will feel lethargic on an autoX course and will not yield good times.

 

Hey Meb I tried 35 cold the front and 30 cold for the rear before. The car had good turn-in with some rotation but the car got more twitchy as I drove it. I tried 34 cold front 33 cold rear. The car was more stable in a straight line, but it had less tun-in and the car was more netural. I tried 32 cold front and 35 cold rear and car was pretty stable in a straight line but it seems like the car wants to understeer at the limit. I am ALWAYS ADJUSTING tire pressure because the car might feel good one day on that setting and the next day feel bad. I NEED HELP WITH THIS! THANKS!

 

camber plates. more negative camber in back then you have in front will give you crazy amounts of understeer. At least it did on my car. try running -2 up front and -1.5 or -1.25 in back.

 

This is complicated by tire type and outside temps. Somtimes, front tire pressure grows more than the rear...so you need to take a look at your hot temps too. You my find that although the rear tires temps grew by 3 deg, the fronts grew by 5 deg for example - the ratio has changed. In any event, I maintaine equal tire pressure front to rear in my mini at all times - 34-35psi cold. you can use alignments to alter a stock setup by asking the tech to adjust a hair toe in up front while all else is stock. Some techs will use very conservative toe settings up front - more toe in. This was done with my very first alignment and I drove the car back and asked the tech to re-do the front toe. This will help a lot with repsect to the mini.

If you add front camber plates, you have to start over...and no more than 2 degrees neg up front, anywhere. This car cannot really use more when you consider braking and accelerating. I used just under 2 deg neg camber up front, slight toe in, Rear - 1.5 deg rear camber and stock toe in. The mini is pretty friendly with repsect to toe changes despite aggressive lowering. By contrats, I have a 99 Honda civic Si with a double wishbone setup that is freaky sensitive to any thing. It has a very aggressive rear camber curve and if the car is lowered too much, the rear tires become exponentially neg with each degree of lean...and then break loose.

Keep it simple and leave your tire psi alone at 35 psi cold. You'll be fine for anywhere but the track. Add front camber plates and stickier tires and your car will be transformed...if you have a bigger rear bar, you'll want to back-off any aggressive settings after adding front plates.

Understeer at the limit is your friend, by the way. Also, building a G-machine that is touchy at the limit is not fun, nor fast. It might give you bragging rights, but a car that is accessible anywhere - easy to drive fast - is just plain faster. That IS a bragging right.

The mini is a very accessible car in stock form. too many of us have removed this wonderful trait in the name of oversteer. Go play at Watkins glen or at Lime Rock or your favorite venue and see how unhappy oversteer is. The mini can be a wicked accomplice; a little more control and a little more grip is all the car needs. I find the high speed balance in stock form perfect! PM me any time!

 

i just want to add that mebs advice has transformed my car into a solid handling car which is very easy to drive. So much so that my woman has autoX'd it with great results.

 

another vote here for camber plates and adjustable lower rear control arms. i couldn't get through a track event w/ one set of tires without camber plates. i now have -2.5* front camber and -1.5* rear camber. i have over 18k miles on my street tires (bfg kdw2's) without excessive inner tire wear. others have warned of excessive wear w/ these settings on the street, but i'm thrilled w/ the miles i've obtained.

 

Yes Meb, I live in VA where the weather is always changing. One week it will be warmer and the next colder. i guess this is why I am changing the pressure so much?

 

You guys think this is a good idea? Alta 22mm rear sway with Alta adjustable rear end links?

end links: http://www.jscspeed.com/mini/suspens...V2endlinks.htm

rear sway: http://www.jscspeed.com/mini/suspension/amp_swaybar.htm

 

Maybe my understanding of car physics is not complete, but is it possible to increase both oversteer AND straight line handling?

It seems to me that increasing one of these will decrease the other.

 

Chili, the bar on the stiffest setting is great....

Yucca, yes, it is possible to increase both oversteer and straight-line handling....leaving out high-speed aero considerations, you can get a 1980's Porsche (like a Turbo with the bungee trailing arm bushings), and have a car that has just a hint of final corner understeer which abruptly changes to oversteer if you get into a corner too hot and try to save your life by backing out of the throttle. Increase oversteer by shutting down the throttle and you'll be off the road backwards, which is fun to watch but not to do....straight-line handling is a cinch....just a bit of toe (in) will provide that. Straight line INstability is caused by (1) improperly adjusted suspension, (2) a body/frame that is not square, or (3) altering the relationship between the center of pressure and the center of mass.

Cheers!

Stephen.

 

Thanks for that explanation Stephen.

Love learning new stuff!

 

What is the center of pressure?

 

could the OP please state his/her objective for handling upgrades? it is agreed that what works for the street is different than what would be required for A/X or a road course.

meb: you start with a comment about tire type and ambient temps. with what tire/ambient temps do your subsequent recommendations apply? with my setup, i start w/ 32 lbs. front and rear (cold) and end up w/ 41 lbs front and rear. i'm running hoosier R6's 225/40/17. maybe it is driving style....an element too often overlooked. tire temps after a run indicate that i might be running too much camber. (i.e. inside temps are slightly higher than outside temps). however, when my tires are corded, the outsides wear first. i don't understand this phenomenom. fyi my alignment specs are -2.5* front camber, 1/16 toe out, -1.5 rear camber, zero toe. adding the alta PSRS definitely helped straight line stability while not negatively effecting turn in.

i really like the way that my car handles on the track and any subsequent changes will be very small. seat time is very important in being able to evaluate suspension changes. get on the track as often as you can afford!

 

how about you just replace those h-sports for linear rate springs?

 

Since this was not in the racing forum I assumed we were writing about high performance street fare...? But a fair question since your tires are a dedicated track extreme; tires come in many varieties!

Re your tire wear problem...all too often changes are made without following the thread of physics. Intantaneous centers - front and rear - determine camber compensation curves - the literal curve the wheel moves thru. For example, my BBS wheels have a 38mm offset and when I added a 5mm spacer to the rear, I had to add more neg camber because the instant centers are really far way - the greater offset moved the instant center farther away creating a less aggressive camber curve...the tire would not compensate for camber as well during a turn. Conversely, if offset changes are made up front, and a Mac Strut loses camber as it compresses, these might actually cause the front tire to become positive much sooner - too much compensation - than in stock form despite some added neg camber. Unfortunately, changing wheel offset will alter the instant center, but so will changing camber; instant centers determine role center location and migration as well. I might expect this with wheels that have a numerically high offset - 45-50mm. Tire width plays a role here too; a tire can be so wide it lifts the inner portion of the tire off the ground during cornering. The tire would have to be quite stiff in compliance...

Increasing front track will definately help your tires perform more work. The added leverage is really quite nice. But again, this changes instant centers and therefore role centers etc...

Re the corded vs heat...the inner portion of the tire will heat up more with that much neg camber and toe out while running on a straight...toe out literally drags a tire along the road. Braking efficiency is also reduced with more than 2 deg neg camber and toe out; you need more brake pedal for a given stopping action and this adds more heat to tires via the brake system, but this action also comprsses the tire into the pavement leveraging those tire regions with the greatest mechanical contact - defined by neg camber and toe out - the inside portion of the tire. When cornering however, you may be point-loading the outside portion of the tire. This places all of the load on the outside for a brief, but brutal, moment. When the tire points straight ahead again, the outer portion has time to cool off while the inner portion is gaining heat again. Just a theory...and if you take a cool down lap or two, the outside will definately cool while the inside remains warm-er.

The Alta and the Power flex control arm bushings are a must for anyone tracking extensively. I used the powerflex for quite a while. The folks at Texas speedworks use both...barely any difference between the two in operation.

I don't know enough about your car to make another suggestion