New springs cause oversteer for a few. Why?

#14

Recall that the only thing changed in the spring test car was the springs. Camber and sways weren’t touched. In the months before our springs finally arrived, I contacted a half dozen E30 racers to get insights as to how our stouter springs might behave and what we might need to do differently. Without exception, everyone I talked seem to be doing pretty mainstream SpecE30 stuff. There were zero surprises re. camber #'s and sway bars. That led me to conclude that our SpecE30 mainstream camber and sways were going to be fine.

That’s why I was very surprised to hear that a few cars started oversteering.

#15

The best empirical analysis here is photography. If you compare how my car looked at Blackhawk in 2014 during the SE30 race compared to 4 weeks ago, the difference is incredible. It’s as though my car doesn’t roll at all any more.

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#16

And that’s now on Hoo hoo’s instead of RR’s

#17

I was also thinking about studying old pics.

I’d sure like to spend some time getting tire temps too. Maybe I can do it in Sept at Roebling.

#18

I have better.

Try to guess who has the new vs old?

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#19

Also, I am running as much rear camber as I can get away by lowering the rear without adjusters.
Worked very well last week-end.

#20

I’d be cheating, I know Steve and NFMD too well!!

#21

Well… I actually don’t know what Neil runs. You still have Ed and I to guess.

#22

You are the white car? And good job beating up on Steve :grin:

I can’t tell, is that Star Mazda???

#23

Yup white car!

T18.

Thanks, but it was his own fault.

#24

@Ranger send me an email offline after the weekend.

#25

I’d be interested in whether the cars having oversteer problems are early or late models. I must have gotten the setup wrong with the new springs and my car was undriveable due to oversteer even with the rear bar disconnected. I have an early model.

#26

Late model

#27

I was expecting all the cars to see a decrease in understeer (transition to oversteer), based on the new springs adding a lot more roll stiffness in the rear than the front. The fact that it’s only affecting SOME, and in apparently dramatic fashion, is interesting, and could point to something else.
Has anyone MEASURED the spring rates of the cars that now have oversteer vs ones that didn’t find a change in handling balance?
For anyone discussing coil-bind, I would expect to find snap-oversteer when suddenly bottoming out.
The consideration of the front having previously been utilizing the bump-stops is interesting, I would expect those cars to have had severe understeer, though, especially when hitting mid-corner bumps. In any case, if the car is now NOT using those bump stops, then the increase in the rear spring rate vs the front may be even more dramatic than the spring rate changes alone had indicated.
I would suggest looking at ride heights as a potential common theme. If the rear roll center is too high, or had too much rake, it could create oversteer. If too low, it could be getting into the bump stops, possibly.

#28

Anthony or others,
What are the best measurement points to determine rake?

#29

New springs added a lot more roll stiffness in front then rear. 40-47% more stiff in the front, depending on who’s #'s one uses for H&R Race. 14% more stiff in the rear.

#30

When I switched to these springs I had oversteer, I reset my camber, ride height and sway bar settings to essentially “zero them out” and soften my rear bar settings. It’s pointless chasing this until people with issues have done this.

#31

I still think the mindset of lower is better is wrong. I think you need to raise the car in order to let our suspension do what it was designed to do. But I really have no other basis for that other than looking at how things work back there and applying some simple logic…which probably means I am wrong.

#32

That synchs with what the Aussies have been telling us. They said “don’t go low”.

#33

My understeer problem was solved by using a 16mm rear bar on its softest setting. I was running with no rear bar and got push. The OEM rear bar is to thin and the typical Suspension Techniques 19mm rear bar it to much for these cars.