Bad push need help

#1

I finally got my new car on the track this weekend. I have a bad push. Can anyone help with tricks to setup the suspension?
My car:
89 325is
Front
3.4 and 3.2 neg camber in the front.
1/8 toe out.
Rear
I think it is 2.6 and 2.7 neg camber
0 toe

14" stock rims with RA1. No strut braces. Do I need them? I have not touched the swaybars. They are set as they came out of the box. I still have the factory spring rubbers. I plan to remove the fronts. Some people told me they are running the sway bars full loose and some are running tight. I was also told I have to much front camber.

#2

For RA1’s your camber is fine. Try tightening your rear sway by 1cm or so. That will reduce traction to your rear because your inside rear tire will lift more and it will add traction to your front because your front sway won’t have to do so much to reduce the car’s roll. That is to say, you are moving your “center of roll resistance” rearward.

Also get on a scale and measure corner balance. If you’re highly motivated, unfasten a front and rear swaybar connector when you weigh yourself. If corner balance is hosed up add or remove spring pads to adjust.

I don’t recall off the top of my head how much corner imbalance is ok, so someone else needs to chime in. With that caveat 3% off fix it. 2% off, maybe fix it. Or something like that.

A front strut brace is probably worth doing but the difference is likely to be subtle.

Consider also driving style. I came to this from a 911, and they don’t have to worry about understeer much. As a result I had to learn different ways to be slow.

#3

rsafreno wrote:

The good thing is the front is not adjustable, so you can’t screw that up. :laugh:

Do you have video we can see? That might shed some light on it. Where on the track is the car pushing (or more specifically, on entry, mid-corner, or exit)? If your answer is “everywhere,” the cure is probably the nut behind the wheel (e.g. braking hard, jumping off the pedal shifting weight rearward, then wrenching the wheel and mashing the gas = bad push).

It might be a combination of tire pressure, soft rear bar (links closest to the open end of the U), and technique. Invariably, a push begets more push because you feel the car NOT turning and add more steering input. By the end of the session you are convinced that the car is f*cked, but really you have just greased up the tires by exceeding their happy slip angle.

I find trail braking to help a lot in the pushy corners at Road Atlanta (1 and 6 for me).

IMHO, YMMV, WTFDIK, etc.

Steve D.

PS - Before you go the spring pad-corner balance route, make sure the car is set up as raced. If the spare tire is out, put it back in to change the front/rear distribution.

#4

PS - I’m on thin ice with this theory, but do you guys/gals think 1/8" too much toe? Any toe in/out will exascerbate greased up tires because they don’t get to cool down on the straights. I use toe out to cure a push on entry, but try to keep it straight otherwise since I am already like 11 hp down on Robinson. I don’t need my tires fighting each other. :laugh:

#5

I went thru an alignment obsession a while back and did lots of reading and asked folks lots of questions. What consensus existed was for front toe “a smidgen out”. I would interpret that as 1/16 to 1/8th.

For adjusting handling, see also:

http://spda-online.ca/modules/tinycontent/

#6

I’d concur with both. 1/8" sounds like a bit much toe. Tighten the rear bar.

Steve,

WTF does YMMV mean? I get IMHO and WTFDIK. I don’t get YMMV.

#7

donstevens wrote:

[quote]
WTF does YMMV mean? I get IMHO and WTFDIK. I don’t get YMMV.[/quote]
your mileage (results) may vary

#8

Thank you guys,
Turn in for turns is ok. After turn in the push starts. I tried tapping the brakes, moving the steering wheel, lifting and getting back on the throttle. Nothing seems to work.
Braking into the turn will get the rear to rotate some then application of the throttle starts the push. I can even spin the car on the last lap 2 turns before the finish while setting up for a pass attempt on the final turn :lol: .
I do not have any video. The right side net prevents me from getting the camera going. I am owner, crew chief, pit crew, and driver. I will try to tighten the nut behind the wheel :laugh: .
1/8 total toe out was the recommended setting.
I also come from a different car PRO7. Understeer was never an issue. It was always major oversteer. During my last race I greased up the tires half way through. I was driving hard like a PRO7. Almost forgot I also tried reducing front pressures by 2lbs.
I will try the rear sway bar and removing both front spring rubbers. Next event will be same track reverse direction so I am not shure how things will be.
Any other suggestions or secrets will be appreciated.

#9

there’s this new thing called google that makes finding out answers to just about any question like this pretty easy …

donstevens wrote:

[quote]

WTF does YMMV mean? I get IMHO and WTFDIK. I don’t get YMMV.[/quote]

#10

if it is possible, compare data acquisition of you driving with another car/driver. It could just be that you’re trying to go too fast through the corner
bruce

rsafreno wrote:

[quote]Thank you guys,
Turn in for turns is ok. After turn in the push starts. I tried tapping the brakes, moving the steering wheel, lifting and getting back on the throttle. Nothing seems to work.
Braking into the turn will get the rear to rotate some then application of the throttle starts the push. I can even spin the car on the last lap 2 turns before the finish while setting up for a pass attempt on the final turn :lol: .
I do not have any video. The right side net prevents me from getting the camera going. I am owner, crew chief, pit crew, and driver. I will try to tighten the nut behind the wheel :laugh: .
1/8 total toe out was the recommended setting.
I also come from a different car PRO7. Understeer was never an issue. It was always major oversteer. During my last race I greased up the tires half way through. I was driving hard like a PRO7. Almost forgot I also tried reducing front pressures by 2lbs.
I will try the rear sway bar and removing both front spring rubbers. Next event will be same track reverse direction so I am not shure how things will be.
Any other suggestions or secrets will be appreciated.[/quote]

#11

rsafreno wrote:

Another thing to check is whether you have preload in the front bar that is causing it to be stiffer than the already-too-stiff single setting we have. With the end links adjusted right and the suspension weighted, you can slide the bolts out of the bar/link connection with very little resistance. If you can’t, just turn the barrel adjusters. You can feel when you hit the sweet spot of no preload.

Does the push happen in both directions?

One of my many weaknesses is that I tend to blame the driver before I look for problems with the equipment. That kept me from making a cross adjustment at Miller until Friday. Probably should have tried that earlier in the week. :blush: The car turned left much better after we de-wedged it.

Steve D.

#12

Another simple and often forgotten top secret adjustment is Rubber donut filling pressure. Try 2 lbs less in front OR 2 lbs more in rear to start. Then add the other. Easy, simple, cost effective, often solves the issue. Think about how you are changing the size of the footprint front to rear.

You will have lots of different turns to try it on at BW in October.

Good Book for this is “The Racing and High-Performance Tire” by Paul Haney.

#13

Did you ever figure this out?

If not, have you been talking to anyone outside of this forum?

#14

I moved the rear adjuster at Sears Point. I did not notice the same push however it was a different track. I have only run 2 weekends and do not know when I will have the money to run again. I need to find a real job.
I have not talked to anyone outside of this forum.
I need seat time and playing a little with the settings (sway bar, air pressure).
Rich

#15

You might want to check the subframe bushings. If they are really bad you can get unwanted geometry changes in the either end of the car.

Also without hard bushings, don’t try to overdrive the car into the 1st part of the turns, the cars’ front suspension will not support very hard braking & simultaneous turn (trail braking) without all the peices under the car working together. YMMV

#16

Do you have the M series offset bushings. Are your tyres new, if not, how many heat cycles. Tyre pressures too high, you are not driving an autocross.
Like most drivers, do you turn in too early. Brake too deep, harsh and hard. Over driving the car. You don’t have 650HP to help rotate the car.

We need more information but even if I had more information I would need to sit in the passenger seat and…then:woohoo: we’ll all know.

Markus K.M. BoschB)

#17

I have the hard rear subframe bushings. I also have the offset eyeball bushings. Turn in is ok. It is the rest of the corner. The tires were brand new shaved tires. 0 heat cycles. I have to start playing with tire pressures. What pressures are some of you running? Initial settings and immediate off track pressures.
Right now I am not braking hard enough or late enough. I use to run a 1st gen RX7. Big braking difference!
Overdriving is a possibility. I can still spin a car with a bad push :lol:

#18

sent PM…

#19

What is PM?

#20

rsafreno wrote:

Private Message - see that PM box under you name/avatar? people can click it and send you a message. When you log in to the site there will be a notification message that you have a PM to read.
bruce