Sick of understeer while autoxing..

[ChewToy]

Specs.. 95 M3, bilstein sports, h&r sports, uuc tubular sways set full soft in the front and full stiff in the rear, motorsport x brace, ACS strut brace, 17x7.5 forged bmw split 5 spokes wrapped in kumho ecsta v700's in 235x40x17's all around.

I'm getting spanked out there by lesser cars and it's getting really annoying. I know I have a lot to learn about technique in my driving style, but my first focus is to get rid of that damn understeer! My setup should produce neutral to oversteer, but in slow corner's I'm pushing pretty bad. I got the temps from the tires from a pyrometer at the last event and it showed the outside of the tires were really heating up. Looks like I need to add more camber. Any suggestions on the easiest way to do this? I don't drive the m3 that much on the street but would like to have the option here and there without ripping the tires up.
I'm running around 44-46 lbs up front and around 37 lbs in the rear. Maybe I should put more air in the rear... will that help the rear rotate around adding more oversteer?? Even at 37 lbs in the rear I'm barely scuffing up the chalk marks on the sidewalls that I placed on there before each event to monitor rollover. So my thought was to reduce the pressure to get the optimum contact patch.. but maybe I'm missing something here.

Maybe I need to rip the front sway bar completely off!? In the end I would like to reduce the push, and add more oversteer. Opinions please.

[SC87325is]

Different E36's have different front shock mounts. Some are in the center, some are offset. It is possible to find someone with different mounts then you have and switch them, giving you both more camber. A friend of mine did this on his TI, switching with a M3, and they both gained 1 degree of camber. For free!

[dngo]

Are you mainly getting understeer in slow corners only (as you said) or is the car pushing at high speed as well? What are your alignment specs?

Camber will certainly help get you more front grip, but driving style, as you mentioned, has an enormous amount to do with how you think your car handles. Any car will understeer or oversteer - it's a matter of technique. Your car setup will determine how easy it is to induce either cornering state. Is it possible that you're just going into the slow corners too hot? Are you trail braking or using trailing throttle at all to help the car rotate?

How are you handling the understeer once it happens?

[frayed]

More camber can be gained by getting a set of 96+ strut hats and mounting them on the 'wrong' sides. With one inch of lowering, I'm running -3.1/-3.2 up front. As my racer friends say, 'the bitch is hooked up.'

You may also consider some 15 mm spacers to widen track and reduce weight transfer at the front axle. Hey, works for me.

Also, in my experience with the V700's, you are running too much pressure in an attempt to even out your temp readings. Over 40, and the V700's got really greasy on me. I found 40/38 fr/rr to be a great combo (on the track, hot temps).

[John in Houston]

I replied to you on Roadkill too:

(Copied from Roadkill)

This is what I was running last weekend at the Houston SCCA Solo II event. I beleive I was the fastest BMW there and was with the BSP vettes (would have been 2nd or 3rd... I ran in Street Mod to protect my points):

1. 1998 M3 coupe
2. Bilstein sports
3. H&R Sports
4. 17 x 8.5 et 35 wheels
5. Kumho Ecsta V700s in 235x40x17
6. Tire Pressures 35/32 f/r

Stock alignment with 1/16" toe out.

Car still pushes some and will continue to until I get more camber dialed in (hopefully next weekend).

Did you check your tire wear? Were the tires rolling over any? You should see wear almost down to the stripe that runs along the top edge of the tire. If you don't, your PSI is too high (personally, I think it's way too high regardless).

Your Pyro readings aren't going to mean too much if you are pushing as hard as you say you are (push= understeer). You will be artificially inflating the outer temps as you rape the carcass across the tramac.

Can you add negative camber? Can you add some toe-out?

Are you trail-braking? Left foot braking? Are you braking in a straight line and then turning?

All of this will help.

John.

PS - as I told BJO this past weekend... you don't need no stinkin' swaybars!

[frayed]

John, by reducing the amount of body roll with sways, doesn't the car take a 'set' better/faster?

Just curious.

I remember a post from Bob Tunnell on the subject way back when. He too stated that the stock sways work just fine for auto-x.

Thanks.

[John in Houston]

What you really want to do is work with spring rates / tire pressures / alignment.

Sway bars are a bandaid approach. They also tend to move you into different classes.

FWIW, I feel (as do others who have driven my car) that the H&R sports need WAY more spring rate to be effective in an auto-x situation. The race springs may be closer, but they sacrifice ride height. Race springs with sport height might be the solution.

Actually, the E30 race springs that Turner sells (custom) would work better... if only they made them for an E36 application.

Coil-overs give you the best of both as a spring swap is easy and the rates are plentiful. That's why most racers run them. I run coil-overs at all 4 corners on the Mustang. I can swap springs in 30 minutes!

[BJO]

john: hey man, the sways may be a band aid approach, but since i run the soft H&R sports, they help out. i was able to get the car to rotate better with them. granted, i was still slower than you, but that's all driver i was getting decent times and was close to Bob, and better than donovan. like you told me, you can pilot the m3 better since you used to drive the mustang.

chewtoy: you are running the v700's with too high pressure up front. try dropping them to 37 and the rears to 35. works pretty well. the e36 m3 will always push in slow corners. the only way thru it is go in slower.

[LateApex]

Hard to comment without actually seeing the courses and riding with you, but try these:

Alter driving style- Use more trail-braking and lower your corner entry speeds. Do you turn-in under moderate braking. Remember, a tire's total available traction increases with loading (until it peaks, then drops out). M3s have tremendous brakes, even stock --use them! Coming out of tighter turns (120 deg+), "roll" onto the throttle to avoid throttle-on-understeer.

Get a good race/street alignment- You can use the factory camber bolts (easiest), or swap hats (not as easy) or put camber plates on the car (even less easy). But getting a race camber of -3.5 to -3.0 should help there. The factory camber bolts (I have these on my car) will get you to -2.0, which is as far negative as I will go for combined auto-x and street use.

From there, you can play with spring/dampner rates and so on, but that's been covered already.

BTW, my Victorracer V700s had a sweet spot of right at 40 psi at my local venue. Dunno if the new Ecstas are similar in that regard, but FWIW, I think you may be too high. (I echo other peoples comments on that)

Good luck,

-Apex

[Jim O.]

Before I jump on the driving style bandwagon, how much autocrossing and track experience do you have? Also, where exactly in the corner are you getting the understeer? At turn-in, mid-corner, or at corner exit? What are your alignment settings?

Answers to these questions will make it easier to figure out what to do.

Other comments...I agree with everyone else that your tire pressures may be too high. I'm using the Victoracers, not the Ecstas, and am running the fronts in the mid-thirties, and the rears in the twenties.

When you say "...spanked by lesser cars...", what are these cars, how well set up are they, and how good are the drivers? If the driver is really good, you may need to face the reality that you aren't going to catch up no matter what you do to your car. Find yourself a better benchmark to compare your progress to. Have you had any of the local hotshoes drive your car? Might be worthwhile, just to see what your car can really do.

About trail braking - I've seen a lot of people trail-brake way too much, which is a slow way to autox. I like to brake hard in a straight line, feather the brakes as I turn in, and when the front wheels first bite and start to turn, transition over to the gas and start rolling on the throttle before the car reaches the apex of the turn. Since I don't left-foot brake, by the time I've moved my foot from the brake to the gas, I'm pretty much ready to start unwinding the wheel while I'm feeding in the throttle. Of course, I've set the car up to work this way - your car set up may not allow you to drive this way...

Jim

[ChewToy]

Thanks for all the input guys. I really do appreciate them. To answer some questions and to add to my original post...
I have found that running under 40lbs or so of pressure up front is causing the tire to rollover (on 17x7.5's), so I added a few more lbs to try and save the sidewalls. I'm thinking that I need to raise the rear pressures, it may help it rotate = oversteer.

I've autocrossed for 3 seasons in the m3, this is my first season on R compounds. I've raced off and on in different cars for 5 or so years, but what does that really mean? Doesn't mean a whole lot,.. seat time seat time seat time is the key and you don't get a whole lot racing. I've been to a few test and tune days to get in as much seat time as possible, but it's never enough. I've read many books on the techniques of autocrossing and I feel I have a good understanding of things to look at. However understanding and doing are two different things, and I find myself over driving quite a bit.

I'm experiencing the push at turn in, mid-corner and at the exit. I guess I need to give it up more before the turn :b When I start to oversteer I ease out of the throttle to try and get the front to bite, I have found that adding more throttle does not make the rear rotate around :\ it just causes the front tires to understeer more :b

I think I'll need to get another alignment from someone who is more performance oriented. I wonder if -2 will be good for a track/sometimes street car.

Still looking for answers... *sigh*

Btw: I got beat by some civics on hoosiers... whooooserdaddddy :b

[ChewToy]

I made an error.. I meant to say understeer, not oversteer in the paragraph below... duh.

I'm experiencing the push at turn in, mid-corner and at the exit. I guess I need to give it up more before the turn :b When I start to UNDERSTEER I ease out of the throttle to try and get the front to bite, I have found that adding more throttle does not make the rear rotate around :\ it just causes the front tires to understeer more :b

I need more camber up front.. looking for cheap and easy solutions. I have heard about getting some 96+ strut hats and mounting them on the car on the wrong side?? Will this really work? What can I expect from doing this? Tia.

[John in Houston]

Originally posted by BJO
john: hey man, the sways may be a band aid approach, but since i run the soft H&R sports, they help out. i was able to get the car to rotate better with them. granted, i was still slower than you, but that's all driver

Yeah, yeah, yeah.... just poking fun at you (and about 1000 others ).

50 more HP and you would have really seen fast! The car just wouldn't accelerate hard enough coming out of the turns! I REALLY miss my mustang

Really, if you aren't running coil-overs, and are stuck with the lame-assed H&R sports spring rates, then maybe (just maybe) a sway bar will help. I'm still trying to find some higher rate springs without going to coil-overs.

But watching your car vs. mine, there really wasn't much difference in the amount of roll. Both cars appeared 'too soft'... but no more so than the other. Even Bob's car was moving around too much (same setup as yours I believe).

While watching you, you were pretty smooth through the course... but needed to be a little more agressive. You should have ridden through with me at least once. Most of my runs (except the 3rd... damn ASC!) were pretty consistent (for once). I was going to see if you wanted me to ride with you... but I was one sweaty mofo!

Chew... seat time is important. Braking in a straight line is important. Don't be afraid to come screaming up on a turn and just nail the brakes (*braking should be done in a straight line whenever possible!). ABS is a wonderful thing. You have excellent brakes. Use them!

Aggression is good... but if you are going to be aggressive, you have to commit 100%. You can't go 'kinda' agressive and go into turns too hot... or you'll push. Too slow and the Hyundais are kickin' your butt!

I think you'll get the hang of it... just keep working at it (and drop those damn tire pressures!!!!).

[Jim O.]

Originally posted by ChewToy
I'm experiencing the push at turn in, mid-corner and at the exit. I guess I need to give it up more before the turn :b

Hmmmm...my handy-dandy copy of Carroll Smith's "Engineer in Your Pocket" (anyone who wants to muck around with the handling of their car should own a copy of this!) says:

Corner entry understeer: car won't point in and gets progressively worse:
- Driver braking too hard, too late
- Excessive front tire pressure
- Relatively narrow front track width
- Excessive front roll stiffness (spring or bar)
- Relative lack of front download (excessive rear download)
- Incorrectly adjusted packers or bump rubbers (car rolls onto packers)
- Insufficient front toe (in or out)
- Insufficient Ackerman effect in steering geometry
- Front roll center too high or too low
- Insufficient front damper bump force
- Excessive dynamic positive camber on laden (outside) tire

Rather than screw around with alignment, camber plates, etc., I'd start with the easy stuff - brake earlier, and lower your front tire pressures.

When I start to oversteer I ease out of the throttle to try and get the front to bite, I have found that adding more throttle does not make the rear rotate around :\ it just causes the front tires to understeer more :b

At that point, it's too late. If your front end is already sliding, adding more gas won't make the back end rotate because there isn't any force for the back end to push against. Some suggestions. First of all, when the front end starts to wash out, try correcting by straightening out the wheel. That allows you to learn what sort of turning radius your car has at various speeds. Once you figure out the turning radii, you can adjust your corner entry speed to match the type of turn you want to make. Second, try giving it gas when the front is still biting, instead of after the front has lost all grip. However, remember the friction circle - if the fronts are already at 100%, and you try to get more out of them by giving more gas, or braking, or turning the wheel more, all you'll do is break them loose. You need to reduce some of the inputs before you can add more.

Jim

[BJO]

john: i have been told that i need to be more aggressive, i am getting there, just more seat time is needed. i was going to ask you for a ride,but since it was for points i didn't want to mess you up. maybe next auto-x.

[John in Houston]

Originally posted by BJO
john: i have been told that i need to be more aggressive, i am getting there, just more seat time is needed. i was going to ask you for a ride,but since it was for points i didn't want to mess you up. maybe next auto-x.

Points, shmoints... its all good. Next time just jump in the car, strap in, and then ask if you can ride. That's what most people do!

I should be at the BMW / PCA event in three weeks (Police Academy). Not sure if I'll be in the M or co-driving that red C5 Vette. We just decided to run the vette at the Divisional in Ft. Worth... so I have to get some seat time and help sort-out the suspension (it's doing some wierd loading and unloading mid-turn). Either way, you can ride (if they allow riders).

John.

[John in Houston]

Originally posted by Jim O.
- Incorrectly adjusted packers or bump rubbers (car rolls onto packers)

Before any of you sick bastards get a hold of this...PACKERS is old-school terminology for bump-stops

[LateApex]

Originally posted by ChewToy

I'm experiencing the push at turn in, mid-corner and at the exit. I guess I need to give it up more before the turn :b When I start to oversteer I ease out of the throttle to try and get the front to bite, I have found that adding more throttle does not make the rear rotate around :\ it just causes the front tires to understeer more :b

Btw: I got beat by some civics on hoosiers... whooooserdaddddy :b

Yea, adding throttle in most auto-x situations will just give you MORE understeer (in this car). All the weight just moves to the rear tires, taking download off the front tires, which is the opposite of what you want when the car is pushing. And since this is all happening at low speeds, this tendency increases.

Higher spring/bump rates in the rear will help some, if that option is open to you. (resists/slows down rearward weight transfer)

A somewhat *cheezy* way I have found helps this is to drop the rear tire pressure DRAMATICALLY. On some courses, I run 40 F/28 R -drag race style - The rear end gets pretty loose, and I can get good rotation under full throttle. Of course, this approach simply *masks* the fundamental problem --reducing total grip on one end of the car to help the OTHER end does NOT really get you what you want in the long run --which is good grip on BOTH ends. But on the plus side, this approach costs you nothing. In addition, on some courses I find it is simply faster than NOT doing it.

And hey, a CSP prepared Civic in the right hands on the right course will absolutely OWN. Nothing to be ashamed of there. Those cars have betweem 500-700 lbs on us, depending on model.

-Apex

[ChewToy]

Thanks to everyone who has chimed in on my issue Keep the good tips coming! LateApex, I too am using a very high psi in the front tires.. around 44psi -46psi, and around 36psi or so in the rears. I'm thinking about dropping the front down a bit to see if it'll hook up a little better. Sorting out these pressures is a pita! I think I might find an open parking lot this weekend and see if I can do some testing and tuning Hopefully I won't get busted.

Has anyone successfully swapped strut hats from a 96+ m3 to a 95 M3 with good results? How much camber did it come out to? Is it obvious how to install them on the "wrong side?" How long did it take to do this? Thanks guys.

[autox320]

I've swapped out my front strut mounts on my 328is with 96' M3 mounts.

When put on the right way ( thier labled LEFT and RIGHT), you only get about a degree. When swapped opposite you get about -3 degrees. The down fall of the plates from the 96'+ M3's is the added castor which is good for street driving but in autocross it causes slower turn in.

Cheap way is tire pressure and "crash bolts" to get about -1.5-2.0 deg camber for a couple bucks.

Expensive way is adjustable castor&camber plates.

[ChewToy]

Where can I get these "crash bolts?" I don't really know much about them, or how to use them. Any input appreciated. Tia.

[frayed]

Originally posted by autox320
I've swapped out my front strut mounts on my 328is with 96' M3 mounts.

When put on the right way ( thier labled LEFT and RIGHT), you only get about a degree. When swapped opposite you get about -3 degrees. The down fall of the plates from the 96'+ M3's is the added castor which is good for street driving but in autocross it causes slower turn in.

Cheap way is tire pressure and "crash bolts" to get about -1.5-2.0 deg camber for a couple bucks.

Expensive way is adjustable castor&camber plates.

Couple of notes here. You can always reduce caster in a 95 by using centered front c/a bushings, or using offset bushings and turning the mounting holes inboard. For auto-x, you may want to do the latter if you can swing it in your wheel well. You will lose some high speed stability however. I recommend the poly RTRS bushings from bimmerworld.com. Note though that you will lose a bit of ride quality, but not much.

Crash bolts are an OEM BMW part. The issue with them is they have a reputation for slipping, since essentially they are a smaller bolt that allows free play b/t the kingin and the strut, enough so you can add or subtract 1/2 degree of camber. Another drawback is that you lose precious tire/strut clearance (same with shims). I used shims for a while, then killed them in favor of swapping plates.

[Bry]

Shouldn't you run higher pressure in the front, to allow the back end to break out sooner, and have the front more grippy?

[trumperZ06]

Good thread here Guys... lots of good info.........

1. lower your tire pressure 38/36 to start.... about 2 lbs more on front vs. back.
2. Is your car lowered??? If not , get the C/G down... as low as practicle
3. Camber... 2 to 2.5 degrees...

Auto-cross is fast reactions... brake in straight line before... turn in and "roll on throttle" as early as possible... Slow in/ Fast out.

Good Luck.... and have fun.

[ChewToy]

After a few events and a driving school... I've made some good improvements... most of which has been in the seat. Looking back... I have been overdriving, and going to fast in the slow sections. I've learned to give it up EARLIER and get on the gas EARLIER, and give it up in the slow sections. I've realized there isn't any time to be made up in the slow sections, just time to loose. I have found that with my bilstein sports, h&r sports, and uuc tubular sways (full stiff rear and full soft front), that running 42 lbs up front and 39 lbs in the rear gives me a setup I like. I would like the rear to step out a bit more while on throttle though. Input?? I'm thinking I should raise the rear tire pressure for that, but from the chalk marks, the tire isn't rolling over at all at 39 lbs, if anything I may need to drop the rear to make use of it's full contact patch!?! If I add more, it may bow the center out too much. The front at 42 lbs manages to rollover a bit, but I'm sure it has to do with my hard cornering. BTW I'm running 235x40 kumho ecsta v700's on forged bmw wheels in 17x7.5 all around. I'm still wondering what I can do add a little more rotation in the rear. I'm reluctant to add more air in the rear. What I really need is camber plates.... *sigh* Suggestions on where to get them?
Anyway.. I'm open for tips Thanks for reading and sorry about the long post.