New springs cause oversteer for a few. Why?

#1

So I’ve been trying to come up with a theory that fits the symptom that a fraction of folks, not me personally, are experiencing with the new springs. So how about this theory?:

The old rear springs didn’t allow much travel before becoming coilbound. Therefore the rear sway didn’t play much because you’ve gotta have wheel travel for torque to get put on the sway.

With the new springs, the rear has much more freedom to compress, and the new springs aren’t that much stiffer than the old, call it 14%, IIRC. Therefore more rear wheel travel is certainly possible with the new springs. More rear travel would mean more torque on the rear sway which would remove rear traction and cause oversteer.

That doesn’t explain why this is an issue for only “some” cars. Heck, near as I can tell, there’s as many cars that have reacted to the new springs by creating oversteer. So clearly our cars are not as similar as some (me included) imagined.

But at least we now have suspension. As opposed to bound up springs in the rear, and riding the bumpstops all the way thru the turn in the front. You fast guys were able to use your magic to cope with that, but the rest of us struggled.

So, you buy this theory? Some are experiencing oversteer now because the additional available rear wheel travel is causing rear sways to work harder than before?

#2

It’s critical that we understand under what circumstances that the oversteer happens otherwise “why” will be obfuscated by “opinion”. As the crew chief or driver-coach at this point your job is to carefully elicit at this point specifically where the oversteer is happening in the 4 phases of the corner:

  1. Braking
  2. Brake release/initial turn-in
  3. Mid-turn (near apex & max-throttle application)
  4. Corner exit.

Also keep in the back of your mind that I get understeer when I throw the car into a turn too fast and oversteer when I’m clumsy on the steering wheel during turn in.

  1. So if you get oversteer under braking then the car is basically too soft front and too stiff rear and probably has some nasty alignment and/or braking problems.

  2. Oversteer at brake release/initial turn in is more problematic to resolve. First task as the driver is to slow down the steering and throttle inputs to smooth out the cars’ response to them. The next thing to do is understand whether the road surface is bumpy or there is a particularly large curb that the driver is running over. Keep in mind that this part of the turn should be “steady state” and unwanted movement in the cars’ attitude would indicate driver issues, or road issues. - My advice is that if everything is correct - raise the car a 1/2 turn on the rear height adjustment. That being said I did soften the rear bar in my car this week to calm down the initial response to turn in. {rationale: I was having to be too smooth with the steering wheel and missing a few apexes because I was over compensating for the an over-enthusiastic rear end.}

  3. If you’re getting oversteer at the mid-turn/apex/max-throttle input phase, then I’d look at the rear ride height almost without hesitation. Again as long as the driver and car are in control, then unwanted movement is likely due to road surface and/or ride height issues. As a point to consider, It might be indicative of mechanical issues (like a crazy alignment or a loose something-or-other), but there’s no way to know unless the driver is “getting it right” too. Note that the rear sway bar isn’t the major player in the handling equation at this point in the turn, it’s really down to springs and shocks. So the solution should be in most cases spring/ride height related. As long as everything else checks out of course.

  4. Crazy driver. :wink:

#3

Hmm, interesting theory, but I’m not sure I agree. If our old springs were bound up in any kind of roll situation, that would mean you would essentially have a wheel rate of infinity which would not be conducive to a stable rear end. Also, if you look at any pictures of us on the old setup you’ll see plenty of rear roll accompanying the roll up front.

It is odd that some people are having issues though. I’m running full soft on my rear SE30 bar just as I had with the old springs. I was considering trying out some tricks with a softer rear bar, but the springs seemed to have improved what I was trying to chase down and I’m pretty happy with my car the way it is right now.

#4

I am one of those that was getting fairly severe oversteer. All this relates to CMP, FWIW. I did a bunch of testing Friday. My oversteer occurred mid-corner in higher speed corners. As soon as I would try to get on throttle (at or near apex) the back end would step out. I could hold the slide and drift through the corner, but I was pretty sure that it did not produce the fastest possible lap times. I tried many variations to solve this issue. Started with disconnecting rear bar. It helped, but I still had too much mid-corner oversteer. Next I lowered the rear springs 1-2 turns and put a spare tire in the trunk. This solved the oversteer issue, but created severe push in the low speed corners.

Next few iterations were on a wettish track. Reset ride height to where it started. Removed front bar in addition to rear. It was not great. Car felt unstable. Though I do think a smaller front bar may be a good wet setup. Next I removed the spare tire ballast and changed tire pressures - 5 psi lower in rear. Car felt well balanced. I also fiddled with wheel spacers, but I couldn’t tell that it made any difference.

I ran the no rear bar, no rear ballast, back to slight rake, softer rear tire pressure setup Sat/Sun. Car felt great and I got my first ever pole position - though a few fast guys were not in attendance :wink:

#5

Last week-end we had two instances of people having failures with the rear adjusters. My best guess is that suspension binding might be a problem now that our suspension has space to move.

I run bar at mid adjustment( second hole on a UUC bar), lowered as much as I can and have stock bushings everywhere. I haven’t had any instance where I can blame the bar for oversteering. I Actually want to try more aggressive setting.

Another aspect to consider is maybe people run too much camber up front for the new springs. I am maxed at 3.25deg given that my shock towers haven’t aged yet, but i have seen some guys run 4 on the new springs. If you are not careful at corner entry I can see the rear unhooking.

#6

My camber is 3.5 in front and about 3 in rear.

#7

You also have to consider that driving style could be an issue. I’ve codriven cars with other people before where one of us thought the car was pushy, and the other thought it was loose. Someone with quicker hand or foot movements is often more likely to get oversteer. Everyone is going to have to relearn to drive the car, but it’ll be a steeper learning curve for some people.

#8

It’s interesting. It definitely is the harder of the 4 scenarios to get right. But a turn like that is a great indication of the “natural” balance is a car in terms of grip. If the front end is gripping more than the front your results would be manifested in the manner in which you describe. The fact that in “maintenance” throttle the car is neutral but adding throttle creates oversteer would indicate that your rear grip is actually quite badly out of whack.

OK I just saw your rear camber that you posted. I’m inclined to think you have too much rear camber. The rear bar near soft as you can get should stabilize the car. The rear bar would not involved in the equation at this point, it’s almost along for the ride. Not quite - but the emphasis should be on spring/shock and yeah - tire. If there was a bump and you hit that at the same time as the throttle, you’d get that effect, but as it was consistent lap-to-lap, then I’m looking squarely at the rear camber and suggesting a 2.2 negative would be my first step.

The fact that all this re-jigging is trying to accomplish ultimately is the maximum use of the tire.

#9

Let’s talk about lowering the rear to improve handling. That’s interesting. One thing you need to do is ensure that you have a rake from back to front. I have about 1 inch of rake from rear to front. If I raise the front I raise the rear in kind.

Ultimately with the new springs I look for 3.1 to 3.4-ish negative camber in the front (does not need to be the same from side to side) and about 2.0 to 2.4 negative rear. Toe should be a touch in, in the rear, and a touch neutral or out in the front.

Ultimately you’d want the front end to be between 5 inches to as much as 6 inches high off the ground measured at the “lollypop” bushing mount. The rear would need to be between 1/2 and 1 inch raked… But this is where advice for one car can get problematic when looking at another car. Some E30’s are definitely able to run lower than others. And some need less to no rake at all.

I would sort out the presentation of the tire to the road before I start replacing parts. Get the car square and start again.

#10

And in consideration of the camber plate issues Shawn and Ranger have outlined on Facebook I suspect all this time the root cause of this disparity is due to the camber plates. But also consider that Ground Control’s Koni shock solution actually cuts several inches out of the strut tube to permit a lower ride height.

#11

I feel like I need to clarify why you need less camber now compared to when you ran the H&R “Race” springs. A car that rolls a lot, needs a lot of camber to help the tires. Once the car is able to get a flatter stance while turning, the camber can start to become counter productive. Where 3.0 was good in the rear before, you now have much stiffer rates and the roll is not nearly as bad, therefore you need to dial that out to ensure that the tire is again square to the road surface, therefore increasing grip.

#12

You should have seen my face when I read “4 degrees” I probably looked like someone pooped on my desk. :smiley:

3.25 with the new springs is just fine.

#13

Sure, but the problems with the old suspension need to be kept in mind for this conversation. Our front was sitting on the bumps on every turn. Our rear was probably bound up pretty often.

Lets say that with the old springs our car should have rolled 5deg at turn X. But instead it rolled only 4deg because of the bump stops. So now we put on significantly stiffer front springs, and somewhat stiffer rear springs and turn X makes our car roll 4deg now. Add to that, the driver plays with his front ride height a bit and now the car can only roll 3.5deg before the outside front corner pins itself on the bumpstop.

In the absence of bumpstops, sure the car would ride flatter with the newer springs. But we can’t say for sure it’s flatter now just because we can now get off the front bumpstops. What we can say it that the spring curve is more flat. So it certainly takes more g’s to get the car to roll. If one raises the front up enough, at some point the stouter front springs will keep the car off of the bumpstops well before that would have happened with the old wimpy springs, given the same lateral g’s. But we don’t yet know the interplay of all that yet.

Sure, if your front is the same height as before, you’ve got 2mm more bump travel then you used to. The thickness of the old spring hats is the difference and they are ~2.4mm thick. I measured the heck out of all of this. So it would take 40-47% more lat g’s to get you to roll on to your bumpstops. Actually a hair more because of the 2.4mm. Therefore the car will feel much stiffer in roll and you’ll smile all the way thru the fast sweeper. Ride height being equal, you’ll spend much less time on your bumpstops. But you may still end up on them, and therefore the actual amount of roll of the car may be the same before and after the change of springs. We just don’t know.

#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!!