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Off-throttle understeer ?

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119
Exp. Type
Time Attack
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Under 3 Years
Greenbrier, TN
Ok, so my latest hurdle on track with DE-DAY (my S550) Is this. When I’m either..
A. on warm ups learning a new track
OR
B. In Lap traffic where I can’t be deeper into the throttle.
If I have to lift In a corner I get some serious understeer. (All the way out to the gators understeer)
Shouldn’t lifting put more load transfer To the front and cause the opposite?
It seems to be more of an issue on fairly flat turns like 7 at Road Atlanta.
I’m still running the Eibach Sport springs and Eibach Red sway bars With Koni single adjustable yellows.
Thanks
 
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Under 3 Years
SoCal
I'm definitely no expert here but lifting in a corner should give you MORE grip in the front, typically causing oversteer. What tires and size are you using? Sounds like the car is severely under-tired.
 
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Time Attack
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Under 3 Years
SoCal
That's how I thought it worked too. I'm running 19x11 square setup with Han. RS4 and -3 camber.
Ok, now I'm equally confused...
Mid corner lift should cause oversteer with your setup. That tells me something else is going on.
Is it possible that your front tires are heat cycled out? Maybe you replaced only two tires at some point? Are the pressures all equal? Have you checked your alignment recently? Maybe things moved on you.
 
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Time Attack
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Under 3 Years
Greenbrier, TN
In a perfect world where I could just stay in the throttle life would be good!
I'm thinking maybe it's a rebound issue or something like that.
 
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SoCal
In a perfect world where I could just stay in the throttle life would be good!
I'm thinking maybe it's a rebound issue or something like that.
That could be.
Is this understeer a new development or has this been the case for as long as you've had this suspension/setup?
 
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Time Attack
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Under 3 Years
Greenbrier, TN
Ok, now I'm equally confused...
Mid corner lift should cause oversteer with your setup. That tells me something else is going on.
Is it possible that your front tires are heat cycled out? Maybe you replaced only two tires at some point? Are the pressures all equal? Have you checked your alignment recently? Maybe things moved on you.
That could be.
Is this understeer a new development or has this been the case for as long as you've had this suspension/setup?
I did check alignment. I'm running 0. maybe I should try a little toe out.
Yes. Since I went to this set up. I'm just noticing it more now that I'm getting more track time and experience. Now that you mention it, maybe It could be tire pressures? It happens worst early in the morning warm ups and when the weather is colder like at Memphis last month when the high was 50f. I've been trying to keep my hot pressures at 38 all the way around. The drivers rear always seems to get a lb. or 2 higher than the others.
 
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3,935
3,987
true, jumping out of the gas SHOULD get you looser, however, if the car is already at max front grip, and you add more weight to the front, then it can, in some really bizarre cases, under steer. I would even dare say that the car might be a bit pushy already, and then you buried it with weight when you let off.
Let the flaming begin..
 
1,021
956
In the V6L
I think either your front springs or your front bar is too stiff. When you lift, you transfer weight forward. In a corner, the outside tires are already heavily loaded. If the front setup is a little too stiff, the increased load shifting forward to the outside front tire could overwhelm the grip on that corner and send you sliding.
 
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W2W Racing
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20+ Years
Snowy North
What happens with hot fronts? Same-same?

Does onset worsen with rate at which you are adding wheel? Is it worse if you jump offf the gas.....or is this only a cold tire/ flat corner entry issue?

Finally and importantly...have you tried dragging the brake on cold tires? 911s (for example) are hard to rotate on cold fronts w/o a bit of load, esp in flat corners.

Pay for easy....get a certified instructor to drive the thing and start there.....:cool:.
 
152
119
Exp. Type
Time Attack
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Under 3 Years
Greenbrier, TN
true, jumping out of the gas SHOULD get you looser, however, if the car is already at max front grip, and you add more weight to the front, then it can, in some really bizarre cases, under steer. I would even dare say that the car might be a bit pushy already, and then you buried it with weight when you let off.
Let the flaming be
What happens with hot fronts? Same-same?

Does onset worsen with rate at which you are adding wheel? Is it worse if you jump offf the gas.....or is this only a cold tire/ flat corner entry issue?

Finally and importantly...have you tried dragging the brake on cold tires? 911s (for example) are hard to rotate on cold fronts w/o a bit of load, esp in flat corners.

Pay for easy....get a certified instructor to drive the thing and start there.....:cool:.
This only happens on right hand turns, especially if they are fairly flat. And only when I jump off the gas. If I have a clear path and can get back on throttle it hooks right back up.
 
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This only happens on right hand turns, especially if they are fairly flat. And only when I jump off the gas. If I have a clear path and can get back on throttle it hooks right back up.
they wouldn't happen to be decreasing radius or off camber would they?
 
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IMO, set the car up at an alignment that favors both right and left hand turns, then do that driver thing for turns that are off camber or decreasing radius. Mustangs are easily over driven, sometimes you have to take the bull by the tail and face the situation that maybe your car will not go through a particular corner as well as you'd hope.
 
152
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Exp. Type
Time Attack
Exp. Level
Under 3 Years
Greenbrier, TN
Have you tried slightly tapping the brakes to transfer more weight to the front...thereby increasing front grip
Have you tried slightly tapping the brakes to transfer more weight to the front...thereby increasing front grip?
No. I may give that a try. I get what BS1 is saying too. I’m not too eager to change things since the car is good everywhere else. And it doesn’t do this in the left hand turns at all.
 
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One thing about this chart, is that this is correct in most cases, however.. especially with tire pressures, once you go too far in one direction, (like underpressuring the front tires to aid in oversteer, and they now become water balloons because you went too far) so you can get too much of a good thing, the only possible exception would be the sway bars, where bigger is almost always "flatter"
 
74
93
Exp. Type
HPDE
Exp. Level
Under 3 Years
Michigan
As far as I understand it, @blacksheep-1 is exactly correct.

There's a good video on YouTube by a guy named Andre Marziali called Physics of Racing. It's about 90 minutes long but there's some very good information in there. Explanations for the 'why' to the things you hear.

The SN95 is like a 56/44 weight split in general. Yours is likely better, but let's say more than 50% is on the front wheels, static. In a 3000# car, that's ~840# on each front tire and 660# on each rear. [You can find coefficient of friction tables for tires I've heard.] Under braking or deceleration, how much weight transfers to the front tires? Say it's 8%.[?] Now you've got 960# on the front and 540 on the rears. And, how much more on the outside front tire now that you're attempting to change direction? Probably well over 1000#. You can quickly see how a good portion of the weight transfer ends up on your LF tire and is overwhelming it's traction abilities.

My first time at GingerMan, my instructor thought I was turning in late because I was overdriving the car so bad that I missed every apex. I raced dirt bikes when I was a kid, so I understood braking into a corner. But, I was attempting to trail brake an already nose heavy car with not enough tire under it to support the speeds and weight transfer. He tried to tell me that getting off the brakes and back on the gas would help and I thought he was nuts. But, turns out, as I later discovered, he was correct. When I decided to listen to him understeer almost went entirely away (as long as I didn't overcook the entry) and my corner speeds were much faster, because by getting back on the gas I balanced out the car. Thus, unloading the outside front tire.

What's your alignment like? What springs? Sway bars? Have you corner balanced the car? If it's happening in turning one way and not the other I would assume it's inconsistency's in alignment settings R-L or a balance issue.

And, if you think about it, it happens on right handers, and you're on the left side of the car. So it's likely heavier and more likely to overload the LF tire in a right hander, especially when you let off and cause weight to shift forward, because that's the tire attempting to do the brunt of the work.

Sorry for the long winded post, I've had a lot of coffee this morning...hope it helps.
 
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