Help with oversteer

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Help with oversteer

Postby Areddi » February 13th, 2012, 9:32 am

So the rear sway bar went on yesterday, and I went from some spirited driving when I got home from Lee's. I was amazed at how much more planted the car feels now that I have both bars installed(both FM).

What surprised me was the amount of oversteer that I experience now when cornering. I wont say that it is unmanageable, just different than stock by a considerable amount.

My question pertains to general handling, but mainly to autocross as I start to prep for the spring. Is oversteer something which you want to avoid in our cars at all costs, or is it more something you want to learn to use to your advantage(i.e. drifting but not in a silly way)?
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Re: Help with oversteer

Postby basedriver » February 13th, 2012, 10:09 am

From my rc car days, it seemed to me that the stiffer end of the car would always slide first. Applied this she I put my FM sways on the Miata stiffer in front, softer in the rear, seems well balanced for me. I can now swap oversteer / understeer with the throttle.

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Re: Help with oversteer

Postby djarum69 » February 13th, 2012, 3:05 pm

Yes, give it some time. There are things you can do like lifting in a corner and being too abrupt with power while exiting a turn that will get you in trouble in a tail happy car, but those are also things you need to learn to control. Once you break the bad habits that we all tend to have, then you'll know if you need to soften the rear bar. You can go a lot faster in a car that will rotate.
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Re: Help with oversteer

Postby stpete » February 13th, 2012, 3:38 pm

Question is where did you set the rear bar. I find the car is pretty fun to drive with the rear bar stiff, but is almost uncontrollable in the rain. I have a full FM 2.5 with shocks set full stiff. You can also play around with the rear shocks until you find a point where they don't bottom out except in extreme cases and leave the sway on stiff. That's how I survive rain now. I keep the thing full stiff on dry days at the track and soften the rear shocks when it rains. Helps, but still a little too tail happy in the rain. If I know it's going to rain, I'll change the rear sway setting. If I forget and leave the shocks soft in the dry, I'm very likely to spin as catching a slide causes the car to fling itself into a tank slapper. If it's a daily driver, including bad weather, I'd keep the rear sway as soft as possible. I may even recommend getting something a little smaller.
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Re: Help with oversteer

Postby Areddi » February 13th, 2012, 4:05 pm

Currently I am on the recommended setting from FM of outer-most of the two holes on the front bar, and middle of the three holes on the rear bar. It feels good, and I can tell that once I get some practice in it will be fine.

I guess the main point kind of ties in with what Ben said of whether or not it is worth it try to always avoid understeer, or learn to harness it.
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Re: Help with oversteer

Postby Gunny » February 13th, 2012, 4:49 pm

I agree with driving it a while to get the feel of the new setup. Once you have a better feel for how the new bars are working there are several things you can try besides more front bar or less rear bar.

To get rid of some of the oversteer:

Lower front tire pressure or increase rear tire pressure.
More positive front camber or more negative rear camber.
Stiffer front springs or softer rear springs.
Take the Porsche route, narrower front tires and fatter rear.
Add more weight up front (ie: empty the trunk).

Or change the settings on the bars.

Whatever you do, only make one change at a time.
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Re: Help with oversteer

Postby jdf » February 13th, 2012, 5:12 pm

A further possibility is you may now have more effective spring rate in the rear than the shocks can effectively damp. If your shocks are adjustable, kick 'em up a notch or two in the back before you do anything else; at least that's something you can try for free.
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Re: Help with oversteer

Postby Aure » February 15th, 2012, 10:41 am

Gunny wrote:To get rid of some of the oversteer:

Lower front tire pressure or increase rear tire pressure.
More positive front camber or more negative rear camber.
Stiffer front springs or softer rear springs.
Take the Porsche route, narrower front tires and fatter rear.
Add more weight up front (ie: empty the trunk).

Or change the settings on the bars.


I've been told by knowledgeable people that staged wheels are not worth it on a Miata. I can see why, considering the cost and the trouble.

Something you can consider is to add a LSD, if you currently use an open differential. It also makes cornering much stronger.

And well, a little oversteer can only add to the fun!
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Re: Help with oversteer

Postby Areddi » February 15th, 2012, 11:35 am

I'm with you on it being fun!

I have the Torsen unit in my 01'.
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Re: Help with oversteer

Postby prostwest » February 15th, 2012, 2:41 pm

Porsche has two things that a Miata will never have. A world-record rear weight bias, and a surfeit of power. That is why they need wider rears and we don't.

Be a better driver first. That goes for all of us. If you try to dial out driver-centric tail happiness with setup, you are very likely to induce a miserable push in the car.

Balance is speed dependent.

Adding more grip to one end of the car does not raise cornering speed, it just increases the amount of unused traction circle at that end while the other end is sliding ever more frustratingly.

Cars rotate a lot at low speed because torque is multiplied most in lower gears.

Cars with negative camber need to roll onto the outside tires' contact patch for max grip. In the rain, less initial grip is available to allow this roll, and the tires ride on the inside edges more. Stiffening sways exacerbates this issue.

I love oversteer, but it is not fast, except for extremely tight hairpins and for Aliens.
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Re: Help with oversteer

Postby Areddi » February 15th, 2012, 2:53 pm

Becoming a better driver is top on my list!
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Re: Help with oversteer

Postby mj71 » February 15th, 2012, 6:54 pm

prostwest wrote:Be a better driver first. That goes for all of us.

Amen. Besides track-day tire pressures, I've not changed a single setting on my Spec suspension since I first had it setup almost five years ago. I continue to get quicker each year. Is it optimal, probably not. Is it good enough, absolutely. K.I.S.S.
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Re: Help with oversteer

Postby Gunny » February 17th, 2012, 4:22 pm

prostwest wrote:Porsche has two things that a Miata will never have. A world-record rear weight bias, and a surfeit of power. That is why they need wider rears and we don't.

Be a better driver first. That goes for all of us. If you try to dial out driver-centric tail happiness with setup, you are very likely to induce a miserable push in the car.

Balance is speed dependent.

Adding more grip to one end of the car does not raise cornering speed, it just increases the amount of unused traction circle at that end while the other end is sliding ever more frustratingly.

Cars rotate a lot at low speed because torque is multiplied most in lower gears.

Cars with negative camber need to roll onto the outside tires' contact patch for max grip. In the rain, less initial grip is available to allow this roll, and the tires ride on the inside edges more. Stiffening sways exacerbates this issue.

I love oversteer, but it is not fast, except for extremely tight hairpins and for Aliens.




Agreed, the other options were just meant to point out that there is more than one way to correct that particular problem.

When you finally get your car near to perfect a small tweak in one of the other areas may finally be all that was needed.

Now that a couple of tenths make the difference between up front and mid pack, take help where you can find it.
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Re: Help with oversteer

Postby Areddi » June 8th, 2012, 11:00 am

So after having done a fair amount of autocrossing thus far, I feel like the limitations that I have for carrying more power through the corners is definitely the oversteer if I go too fast. I am considering changing my rear bar to the outermost setting, i.e. softening it.

Correct me if I have it backwards: This should decrease the oversteer correct?
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Re: Help with oversteer

Postby bill_keksz » June 8th, 2012, 11:06 am

Yep.
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Re: Help with oversteer

Postby Gunny » June 8th, 2012, 12:42 pm

Yes, less rear bar will help with oversteer.
Holes at the end of the bar are softer.
Try the position change and see how much help it provides.
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Re: Help with oversteer

Postby prostwest » June 8th, 2012, 12:54 pm

You've got it right.

Let me ask one thing- think back to the showcase turn: a big, constant radius sweeper. If you have slowed enough by corner entry to have the car neutral before you get to the apex cone, and smoothly apply throttle right at the apex cone (give or take) does the rear come around on you there? So much that you end up sawing corrections into the wheel, or just enough that you have to modulate pedal to control yaw a bit? That, IMHO, might be your litmus test for changing handling balance toward oversteer.

Consider stiffening the front instead of loosening the rear, if you decide to change. Miatas are camber-sensitive, so more roll stiffness overall tends to help overall grip.
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Re: Help with oversteer

Postby Areddi » June 8th, 2012, 2:41 pm

prostwest wrote:If you have slowed enough[/i] by corner entry to have the car neutral before you get to the apex cone, and smoothly apply throttle right at the apex cone (give or take) does the rear come around on you there? So much that you end up sawing corrections into the wheel, or just enough that you have to modulate pedal to control yaw a bit?


I would say the latter is where I find myself the majority of the time. I suppose my intent would be to try to carry more throttle through the entire turn. I do not find myself encountering understeer very often since I have a good feeling for transferring the weight. The problem I run into is that moment when the weight shifts to the back and I apply the throttle I feel like the back end doesn't stick enough to have the amount of throttle I want.

Obviously I do not have the best or most expensive tires, so I want to try to mold my driving around those moments. I feel like a softer back would not be as likely to slide, and therefore I may be able to put some more power into the corner at that point. Is this the right idea?

Also, tightening the front bar is an option. I am having trouble wrapping my head around what that will do when I go into a corner since I transfer the weight. Maybe you can help me understand.

Also, I have been running a fairly aggressive tire pressure in all 4 wheels, something around 36-37 lbs. Would it be better to lower the rear to keep the grip higher, but keep the front higher for sidewall stiffness? Am I in the right zone already?
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Re: Help with oversteer

Postby prostwest » June 9th, 2012, 4:19 pm

I think you're on the right track. I tend to be skeptical to the point of cynicism, so forgive me if I sound like like I don't trust your feedback (I rarely trust my own).

There are myriad ways to set up a Miata, but the resultant handling characteristics are finite. You really have to try hard if you want to screw it up.

Driver technique, OTOH, has infinite nuance of imperfection. Trust me, I've explored hundreds of ways to drive badly, yet haven't scratched the surface of mediocrity.

So, some more points:

If the car is predictable enough that you can get on the throttle without playing catch-and-release, you may still have some technique adjustments to try. How about this: take a tighter line in the first half of the corner. If, at the apex, your arc is wider than will carry you to your desired exit point, the application of throttle might just tighten the line right where you need to be. Perhaps only the slightest modulation, or, even better, decrease of steering lock, will get the car tracking right where you want it.

I will concede, this is the stuff off bench-racing, and perhaps a purely academic exercise. I expound theory from my cerebral cortex and drive from the seat of my pants, and rarely, despite what you may have heard about me, do the two juxtapose.

So, from the setup side, I give you stock class, where only front bar changes are allowed. Despite the common denominator of out-of-the-showroom-C-OEM-A understeer, the stiffest possible front bar is generally considered the go-to setup. While this would normally be eschewed, the overall grip dividend from more roll stiffness outweighs the balance concerns. Again, the camber sensitivity of the Miata is minimized by roll stiffness. Now this is from my experience in Stock class where R-Comps endow more lateral grip than a full slate of ST legal suspension mods. YMMMFV,Y.

I'm confident that if Mox has 5 minutes to add to the discussion, he can shoot huge holes in both my technique and setup musings. By way of excuse, I have been out for a while now. Also, I just got back from the Greek festival. OPA!
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Re: Help with oversteer

Postby Claff » June 9th, 2012, 4:57 pm

prostwest wrote: How about this: take a tighter line in the first half of the corner. If, at the apex, your arc is wider than will carry you to your desired exit point, the application of throttle might just tighten the line right where you need to be. Perhaps only the slightest modulation, or, even better, decrease of steering lock, will get the car tracking right where you want it.


This sounds backwards. From my understanding, if you're tracking out too wide for proper corner exit, adding throttle will cause the nose to push further, unless you're adding power to the tune of breaking the rear tires loose and kicking the rear out (causing a need for corrective action and/or heating up the rears). I've been taught that a too-wide arc should be addressed by lifting off the throttle, which transfers weight to the front tires which should grip better. Whether I've actually done this on-course is questionable since I have little evidence of my brain processing on that level while driving.

There is also a very good chance that I've completely misunderstood the hypothetical situation you've presented.
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Re: Help with oversteer

Postby REDFUN » June 9th, 2012, 8:43 pm

Alex,

PSI 36-37 is very high IMHO. Only because 26Psi is recommended for the 99. With that kind a pressure you may not have the full foot print of your tires. When going into a curve the one tire rolls over using more of the side tread. The opposite side try's to hold on while the weight shifts and the tire begins to lift off the road. So with the extra air the opposite tire is running more just on the center of the tread and not the full tread.

Also I nice alignment from Ed York with about 2 1/2 % negative camber out back helps to keep those back tires planted on the road. Ed will give you a text book explanation about toe, caster and camber. Then he will ask you what you want or what kind of driving you will be doing. He pulls the car in and does the job with you in it to compensate for the weight of the driver. After that he marks the alignment bolt settings with white paint so you can check them once in a while.
I think you got the new springs it might be time for some shocks :dunno:

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Re: Help with oversteer

Postby Areddi » June 10th, 2012, 9:15 am

Never ended up getting the springs, still on the stock stuff at the moment. It is on the list though.

I ended up switching to the softer setting yesterday morning. I took a spirited drive around some local spots, and I can definitely feel the rear is not as stiff. I'm running out in Winchester next weekend, and they gave us a discount for buying two spots in the lineup, so I'll have 12 runs. I think I am going to leave it soft and do my 6 morning runs that way, and if it feels slow I'll bring my tools and switch to the middle setting again, so I'll know for SCCA the next week.

As for tire pressure, I may look at lowering it. Alignment could be cool, if Ed York a club member?

Also I sort of have the same thought as Alan. If I am swinging wide, I would tend to cut back on the throttle to pull the car back in. Unless of course I felt like I could effectively kick the back and drift. Am I thinking about it wrong?
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Re: Help with oversteer

Postby REDFUN » June 10th, 2012, 3:10 pm

Sorry about that it's Ed York at


York Automotive
300 S Main St, Mount Airy, MD 21771
(301) 831-7337


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Re: Help with oversteer

Postby Claff » June 10th, 2012, 11:46 pm

I'm envious of you big 1.8L drivers (make that drivers of big 1.8Ls). Us 1.6L drivers don't entertain thoughts of jumping on the gas to try and break the rear loose. If I try that all I'm left with is broken dreams.
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Re: Help with oversteer

Postby NicholasJay » June 11th, 2012, 8:36 am

Claff wrote:I'm envious of you big 1.8L drivers (make that drivers of big 1.8Ls). Us 1.6L drivers don't entertain thoughts of jumping on the gas to try and break the rear loose. If I try that all I'm left with is broken dreams.


Put your rear sway bar back and get tail happy again.
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Re: Help with oversteer

Postby Areddi » June 11th, 2012, 10:24 am

Claff wrote:I'm envious of you big 1.8L drivers (make that drivers of big 1.8Ls). Us 1.6L drivers don't entertain thoughts of jumping on the gas to try and break the rear loose. If I try that all I'm left with is broken dreams.


That made me chuckle for so many reasons :mrgreen:
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Re: Help with oversteer

Postby prostwest » June 11th, 2012, 11:09 am

Alan, you're right: that jibes with my experience. If I'm not careful exiting the showcase I'll push right out onto I495. But if, as he contends, he is fighting power-on oversteer, then the early apex line would put that tendency to his advantage. Now if he tries it and finds the understeer he has been missing, then that would be informative.
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