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Fighting understeer in high speed corners

shogun32

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what's so bad about reducing rear camber? There should be JUST ENOUGH, and no more IMO. Now front camber, you can't have enough (well, ok you can...)
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honeybadger

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what's so bad about reducing rear camber? There should be JUST ENOUGH, and no more IMO. Now front camber, you can't have enough (well, ok you can...)
I think you might be taking my reply a little too seriously. My use of GIFs are my way of conveying strong sarcasm.

On a more serious note, I took Billy's feedback about camber to going backwards from where I had adjusted it to, not going less from where I started. I only run -1.9 typically. Slicks really don't like less than that.

Edit: Just to add more clarification around why I mentioned camber in the follow-up - as has been said, having too much camber in the rear is another way of making the rear feel a bit looser. I knew going in it wasn't the fix, but I wanted to see what it felt like in the context of this scenario and then report back. More of an experiment. My current camber of -1.9 was landed on by using a pyrometer and going through a few sets of tires to verify proper wear.
 
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ShatterPoints

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what's so bad about reducing rear camber? There should be JUST ENOUGH, and no more IMO. Now front camber, you can't have enough (well, ok you can...)
Yup, you typically don't want a lot of rear camber in a rwd car. The suspension geometry in the rear does allow camber gain so you likely are running more dynamic camber than you think.
 

Norm Peterson

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what's so bad about reducing rear camber? There should be JUST ENOUGH, and no more IMO. Now front camber, you can't have enough (well, ok you can...)
I'm afraid I don't know how to take that .gif either - even after explanation it's still not clear. (I'd expect it from Terry Fair, though).


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Norm Peterson

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Sheesh...serious crowd today.
Not by direct intention, anyway. Couple of weeks from today I'll be 74 y/o retired engineer, and such visuals as icons, smileys, memes, and gifs don't always come across as intended. That's on me, I suppose . . .


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Norm Peterson

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FWIW, I understand BillyJ's reluctance to go too deep into providing detailed solutions to individual issues.


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honeybadger

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Not by direct intention, anyway. Couple of weeks from today I'll be 74 y/o retired engineer, and such visuals as icons, smileys, memes, and gifs don't always come across as intended. That's on me, I suppose . . .


Norm
No worries. Apparently my particular type of sarcasm and chicanery isn't universally appreciated. Who knew!

On a serious note, all is good!

FWIW, I understand BillyJ's reluctance to go too deep into providing detailed solutions to individual issues.


Norm
Yep. This is why I didn't ask him specifically. That's a can of worms that's pretty wild to open.
 
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honeybadger

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So I had a chance to swap in some BMR handling springs in the rear that upped the spring rate a good bit. Made a pretty clear difference. Best line through the carousel yet. Car was super predictable under heavy acceleration load while in sweepers and was much more balanced when I got on throttle at apex. This should be good enough to hold me over until I can put a proper coilover set on (which it desperately needs).

Here's the previous carousel line:



Here's the new one that I had been trying to take, but the car would understeer:



Notice how the car doesn't push to track out so much at the exit of 18, so it's easier to get back across the track for T19, which I added a couple more MPH to at apex
 

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shogun32

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So I had a chance to swap in some BMR handling springs in the rear that upped the spring rate a good bit. Made a pretty clear difference. Best line through the carousel yet. Car was super
why not Steeda dual-rate rears?
 

ShatterPoints

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why not Steeda dual-rate rears?
For race applications you want a predictable linear rate. If you are valving shocks to match it is important so you do not have wild swings in damping rates as you engage spring coils between rates. Aside from that with dual rate springs you could still get yourself into trouble if you're not ready for the changes in spring rate at corner entry/ exit.
 

NightmareMoon

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For race applications you want a predictable linear rate. If you are valving shocks to match it is important so you do not have wild swings in damping rates as you engage spring coils between rates. Aside from that with dual rate springs you could still get yourself into trouble if you're not ready for the changes in spring rate at corner entry/ exit.
Good in theory, but in actual driving, the dual rate rears are perfectly predictable. With or without the dual rate or stiff (650ftlb) linear front springs, with and w/o aero, with cheap and expensive dampers, and with 8 or 9 different codrivers, only one of whom had anything but praise for the car setup. That one guy had issue with the rear axle setup and he was relatively inexperienced to RWD (only a little corvette seat time).

So, IDK about easily getting into trouble because of damping issues with the dual rates. That sounds like fake news to me.
 

ShatterPoints

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Good in theory, but in actual driving, the dual rate rears are perfectly predictable. With or without the dual rate or stiff (650ftlb) linear front springs, with and w/o aero, with cheap and expensive dampers, and with 8 or 9 different codrivers, only one of whom had anything but praise for the car setup. That one guy had issue with the rear axle setup and he was relatively inexperienced to RWD (only a little corvette seat time).

So, IDK about easily getting into trouble because of damping issues with the dual rates. That sounds like fake news to me.
What was the spring length vs ride height? How many coils were engaged at the car's static ride height with fuel and driver? A large majority of people use dual rate springs but actually by preload or by actual spring rate will engage all of the initial rate coils and then operate in the next stage of the spring rate (basically making it linear anyway). Also cheap vs expensive damper doesn't mean anything either with regards to what damping they can generate. Your value in shocks mainly comes with the service interval of parts, followed by time spent on building a damper curve.

m6.JPG


if look, "system spring rate" is included in the critical damping calculation. So if that number changes by a large amount the damper wont be able to "dampen" both rates well. So you would end up making compromise after compromise with the setup until you either had the lap times to feel good, or the driver confidence in order to aspire for wanted lap times.
 

shogun32

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The steeda dual-rates the car sits (static) with a little over 1/4" of travel left in the 800lb/in rate before it engages the higher. The motion-ratio of the spring is 0.5 so that means somewhere close to 1" of wheel travel is needed to engage the higher rate.

Edited for correct ratio.
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