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Vague Steering mid Corner

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S550 with MCS coilovers 500/750 springs gt350 front bar, lowered maybe an inch below stock, not a lot. Spherical bearing tension links and rlca’s. 305 NT01’s. Custom splitter and 9lives rear wing.

The car has good natural and aero balance for my driving style.

I’ve always felt the steering response/precision has been lacking. But especially in low to mid speed corners the mid corner response is awful. Not understeer but just very vague response to inputs. I thought maybe the tires are the culprit but switched them out for my street set which are quite stretched and no improvement.

roll center correction is supposed to help so I have some steeda arms going on. But I’ve also read that a number of places that the EPAS is to blame. I am wondering if this is it as I’ve got most all rubber removed from the suspension and springs stiff enough. Unlike the s197 we don’t have a 302R rack we can swap in s550’s.

I know some people run stiffer front springs and I’ve considered but don’t want to give up any mechanical grip if I can avoid it.

Anyone felt the same about their GT steering and been able to correct it?
 
1,246
1,243
In the V6L
S550 with MCS coilovers 500/750 springs gt350 front bar, lowered maybe an inch below stock, not a lot. Spherical bearing tension links and rlca’s. 305 NT01’s. Custom splitter and 9lives rear wing.

The car has good natural and aero balance for my driving style.

I’ve always felt the steering response/precision has been lacking. But especially in low to mid speed corners the mid corner response is awful. Not understeer but just very vague response to inputs. I thought maybe the tires are the culprit but switched them out for my street set which are quite stretched and no improvement.

roll center correction is supposed to help so I have some steeda arms going on. But I’ve also read that a number of places that the EPAS is to blame. I am wondering if this is it as I’ve got most all rubber removed from the suspension and springs stiff enough. Unlike the s197 we don’t have a 302R rack we can swap in s550’s.

I know some people run stiffer front springs and I’ve considered but don’t want to give up any mechanical grip if I can avoid it.

Anyone felt the same about their GT steering and been able to correct it?
Well, I don't have this problem on my car, but I've seen this movie on other cars I've owned in the past. It's possible that EPAS is to blame, but I'm mystified by how that could be, unless it's mounted on a soft rubber subframe or something. A steering rack is all gears - no internal slop - so it's hard to see how the steering is actually vague. If the steering is over-boosted, it might feel soft, but it should still work (says the guy who had the EPAS wobble in his 2011 GT).

If I was in your situation, I'd refine the heck out of my shock adjustments first. Now, mid-corner, they aren't particularly influential because the suspension isn't moving much. But it's good to have those sorted first.

Then I'd look at spring rates. I'd be tempted to try softer front springs. The spring setup is hard to work out from your post - if the rear has true coil-over-shock springs, then your rear wheel rate is probably similar to the GT350 which has 960 pound springs in the spring pockets with a motion ratio of around 50% yielding a wheel rate around 500. With 750's sitting further out, it's probably 500-ish as well. My point is that, compared to a GT350, your rear suspension spring rate's not massively different. The front's another story.

The GT350 has 250-ish pound springs up front. Your front rate is double that. It isn't balanced the same as a GT350 and it doesn't handle the same either. Frankly, I'd be tempted to try a pair of 400's and see how it changes things. It'll change the balance, for sure, but softer means more mechanical grip, so it might be worth a try.
 
501
550
Exp. Type
W2W Racing
Exp. Level
20+ Years
Snowy North
Are you rolling free when you feel this, or transitioning...ending the braking phase OR just tipping into the gas?

Neutral wheel OR opening/closing it?

Same feeling irrespective of fuel load?
 
Well, I don't have this problem on my car, but I've seen this movie on other cars I've owned in the past. It's possible that EPAS is to blame, but I'm mystified by how that could be, unless it's mounted on a soft rubber subframe or something. A steering rack is all gears - no internal slop - so it's hard to see how the steering is actually vague. If the steering is over-boosted, it might feel soft, but it should still work (says the guy who had the EPAS wobble in his 2011 GT).

If I was in your situation, I'd refine the heck out of my shock adjustments first. Now, mid-corner, they aren't particularly influential because the suspension isn't moving much. But it's good to have those sorted first.

Then I'd look at spring rates. I'd be tempted to try softer front springs. The spring setup is hard to work out from your post - if the rear has true coil-over-shock springs, then your rear wheel rate is probably similar to the GT350 which has 960 pound springs in the spring pockets with a motion ratio of around 50% yielding a wheel rate around 500. With 750's sitting further out, it's probably 500-ish as well. My point is that, compared to a GT350, your rear suspension spring rate's not massively different. The front's another story.

The GT350 has 250-ish pound springs up front. Your front rate is double that. It isn't balanced the same as a GT350 and it doesn't handle the same either. Frankly, I'd be tempted to try a pair of 400's and see how it changes things. It'll change the balance, for sure, but softer means more mechanical grip, so it might be worth a try.
Thanks. Yes the epas is bolted to the subframe, no bushings. So in theory it should not be a culprit for the vague feeling but it is electrically controlled which does affect the feel. But I suppose feel/feedback is different than precision. Hmmm.

yes front rate is much higher than gt350 but with coilovers these rates are fairly basic starting point. I’ll give it a further think though.


Are you rolling free when you feel this, or transitioning...ending the braking phase OR just tipping into the gas?

Neutral wheel OR opening/closing it?

Same feeling irrespective of fuel load?

I need you spend a bit more time quantifying when exactly it happens so thanks for the questions. More for me to consider so much can try and narrow it down.

so far I’ve noticed it when free coasting and when on maintenance throttle. Precision is better when braking. And my particular gripe is when closing the wheel it doesn’t turn in with the wheel straight away nor linearly. Which when I describe it sounds like minor understeer but it doesn’t feel quite that way.

two other questions:

do strut tower bars on these cars help? I have the firewall brace but no STB.

Do aftermarket sway bars help turn in relative to gt350 bars? I’m happy with the balance but if bars would help with turn in/precision I’d grab a set.
 
so far I’ve noticed it when free coasting and when on maintenance throttle. Precision is better when braking. And my particular gripe is when closing the wheel it doesn’t turn in with the wheel straight away nor linearly. Which when I describe it sounds like minor understeer but it doesn’t feel quite that way.

re reading this it sounds like I’m expecting the car to turn when there’s little weight up front, maybe under conditions where I shouldn’t be expecting precise steering?
 
501
550
Exp. Type
W2W Racing
Exp. Level
20+ Years
Snowy North
so far I’ve noticed it when free coasting and when on maintenance throttle. Precision is better when braking. And my particular gripe is when closing the wheel it doesn’t turn in with the wheel straight away nor linearly. Which when I describe it sounds like minor understeer but it doesn’t feel quite that way.

two other questions:

do strut tower bars on these cars help? I have the firewall brace but no STB.

Do aftermarket sway bars help turn in relative to gt350 bars? I’m happy with the balance but if bars would help with turn in/precision I’d grab a set.

Weight transfer management sounds good...so I'm with @JAJ. Bit too much front spring...not getting into the track when you're at nearly static weight distribution.

Perhaps try a slightly longer 400#-ish spring...bit more compliance/bite @ static w/o impacting (significantly) ride height/braking precision. Little impact on aero since you're prolly front neutral with 400 or 500.

Bars: 35-37mm front on hard ought to compensate nicely for reduced spring rate when turning into slow/medium corners, loaded. Will help a lot in downhill entries. You've got a lot of rear spring, so going to a heavier front bar likely wouldn't scew-up front grip/feel/precision center-off (manageable with small front rebound changes).

Just thoughts...YMMV...:cool:.
 

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