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Interesting/Annoying Traction Behavior

Bluemustang

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So I noticed a weird traction issue recently with my Mustang. Say I am stepping away briskly from a full stop, making a hard left turn (90 degree turn), I am getting this grip-slip-grip action going on. Like wheel hop. I am trying to test the limit basically and let it slide a bit or hold the edge of traction. But, I'm not getting a constant slip angle. It's not hooking or slipping essentially. I don't really recall noticing this behavior before - I guess it is possible.

Car has full suspension and IRS upgrades (cradle lockout, vertical links, RLCA bearing, toe-knuckle bearing, camber arms). Car also has a swapped Torsen diff.

Recent changes were Ohlins coilovers and OEM shock mounts. I had to ditch the Steeda rear shock mounts because they didn't fit.

Car currently has Michelin PS A/S4 tires. 30/29 psi cold.

Any thoughts on what this is? My initial thought was, it's the OEM shock mounts allowing the shock to bounce. Or too much rebound damping on the rear shocks, possibly tires are too cold or too low tire pressure?

It's possible the inside tire is becoming unloaded? 🤔
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LowPSI

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I'm curious if any of the nannies are acting up. I'd recommend unplugging the dyno/nanny plug and seeing the problem persisits. Low hanging fruit that's easy to eliminate.

When I tried inducing oversteer/dial in slip angle on a skid pad it was damn near impossible to get the car to react correctly until I popped the hood to kill the nannies (even fully off with the TC/Stability killed in the cab).
 
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Bluemustang

Bluemustang

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I'm curious if any of the nannies are acting up. I'd recommend unplugging the dyno/nanny plug and seeing the problem persisits. Low hanging fruit that's easy to eliminate.

When I tried inducing oversteer/dial in slip angle on a skid pad it was damn near impossible to get the car to react correctly until I popped the hood to kill the nannies (even fully off with the TC/Stability killed in the cab).
It's possible. Actually how do I do that out of curiosity? Does that disable ABS as well?

Tbh I've never noticed the nannies act up. Usually I turn TC/ESC off and I can get her loose. Maybe I've never pushed it far enough to get this to happen.
 

LowPSI

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This guy is unbelievablely obnoxious but it's the best quick video I could find showing where the plug is:



Abs will not be impacted. It will throw a couple lights on the dash until the plug is plugged back in. It will completely disable all traction and stability control so be ready for all driver.

The nannies in this car are more intrusive/behind the scenes than most imo.
 
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Bluemustang

Bluemustang

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This guy is unbelievablely obnoxious but it's the best quick video I could find showing where the plug is:



Abs will not be impacted. It will throw a couple lights on the dash until the plug is plugged back in. It will completely disable all traction and stability control so be ready for all driver.

The nannies in this car are more intrusive/behind the scenes than most imo.
Thank you, kind sir 🙏 That is great to know. Leave it to Ford to keep you on the leash with the nannies. Lol
 

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MinDseTz

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What surface is this on? You said you changed the suspension and this started? Did you align it? If so what was prior setup vs now?

TC cuts are very noticeable, advancetrac is less noticeable and can modulates brakes based on yaw rate.
 
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Bluemustang

Bluemustang

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What surface is this on? You said you changed the suspension and this started? Did you align it? If so what was prior setup vs now?

TC cuts are very noticeable, advancetrac is less noticeable and can modulates brakes based on yaw rate.
Street surface. Yes, I believe so. Yep it is aligned to my specs - similar to the prior alignment specs. Previous setup was BMR SP083 and FP Track dampers. The new coilovers have a wide damping adjustment range. Right now I have them set to a very stiff Street setting, according to the Ohlins manual. 10 clicks and 12 front and rear (from full stiff setting) I am still experimenting with the damping.

The only other change was the OEM shock mounts. I just needed them to mount the shocks bc the Steeda ones didn't fit the new dampers. I have another solution I've yet to install with a spherical bearing.

I plan to troubleshoot this by eliminating potential culprits. I'm just looking for ideas.

This has happened a few times, shortly after take-off. So it's very low speed <10mph. It may be induced by a subtle bump in the street. I need to do more testing to confirm. Take-off in a straight line there is no wheel-hop. The tires just spin.
 

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I noticed the inside rear tire would always spin during a hard turn from a stop, this was in my PP2. Can't remember if my PP1 did it or not, but we moved to a different neighborhood so the roads are different. My Mach does it too from time to time, I always attributed it to the Torsen.
 

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So I noticed a weird traction issue recently with my Mustang. Say I am stepping away briskly from a full stop, making a hard left turn (90 degree turn), I am getting this grip-slip-grip action going on. Like wheel hop. I am trying to test the limit basically and let it slide a bit or hold the edge of traction. But, I'm not getting a constant slip angle. It's not hooking or slipping essentially. I don't really recall noticing this behavior before - I guess it is possible.

...Car also has a swapped Torsen diff
You're feeling the locking in the diff. Really tight corners where you accelerate (which tightens the diff up) will produce rear tire scrub across the axle and give it a little hop as you go to throttle.

If you're going a little faster and actually have tick of slip angle in the car when you go to throttle, it'll be smoother and you'll barely feel it. You can only really feel it in that scenario you're talking about where you're hustling it a little, but still fully gripped up.
 
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Bluemustang

Bluemustang

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You're feeling the locking in the diff. Really tight corners where you accelerate (which tightens the diff up) will produce rear tire scrub across the axle and give it a little hop as you go to throttle.

If you're going a little faster and actually have tick of slip angle in the car when you go to throttle, it'll be smoother and you'll barely feel it. You can only really feel it in that scenario you're talking about where you're hustling it a little, but still fully gripped up.
Ahh, there ya go. I thought about it last night actually, because I've heard the Torsen is known to have some odd behavior like this at low speed. I only notice it in the situation I was describing, where I'm at a stop and try to get on it and induce steering angle. Wheel straight it won't do it. Wheels just spin, a little shift off the back end to the right and then she hooks up and goes.
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