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Another lost traction on freeway thread

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accel

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@accel, the situation might have been aggravated by an undetectable road condition and/or road properties. You get a little wheel spin going then it starts stepping out on you.

For instance, down here on very humid days sometimes composite pavement type roads will lose their bite and feel greasy. Fine at normal conditions but can surprise you if you start to put any power down. The road outside the plant here is like that. On hot dry days it's sticky but if it's really cold (which compromises the tires) or it's very humid I'll get a little wiggle on the turn out the driveway.

Road conditions are always an x factor anyways, I've run down a road on a perfectly dry day then hit a wet section because of landscape sprinkler, I've also had a step out on an intersection that had a brick section in it, grip on brick is garbage in all conditions. So you gotta watch out for all the variable not just speed.
yes, a number of things went bad:

- reducing radius as I already stated.

- as radius starts reduction, the road actually also goes downhill.

- at the spot where the rear lost traction the pavement switches from asphalt to concrete.

As I saw above coming, I became very gentle with throttle. So those who thought I was recklessly mashing the pedal were wrong.

statistically, - too many things went unexpectedly unexpected.

I am not trying to find an excuse for myself though.

I still believe that the actual "straw" for me personally in that particular situation was overestimation of available traction.

I did not expect rear tires to degrade that much.

I removed both rears from the car for inspection. They are pretty worn (right more that the left one), but still did not reach indicators.

So, again, beware and maintain recommended pressure.
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GTP

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I monitor tread wear across the tire. I run 28psi cold on 275 tires. Autocross can really roll your tires. You'd need camber change and monitor temps across tire to get it dialed in.

But to your story... The combo of a little too much steer angle and throttle is a bad one. Add unfamiliar curve, impatience, and worn tires and there you have it.

Whenever this happens and I lift the throttle the car snaps straight with almost no fishtail. This is in Normal mode .. you know, for the street.

Glad you and your car were unscathed!
 
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accel

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I monitor tread wear across the tire. I run 28psi cold on 275 tires.
Should it be 32psi? Are you maintaining 28 at street or autox?

By the way, as I'm setting my tire pressure with trusted mechanical gauge to 32psi, onboard tpms shows it as 35-36psi.

What's everyone's experience? Is TPMS pretty precise or approximate?
 
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GTP

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It all depends. If the track is abrasive it will grind your tires. Overinflate to keep the shoulders from chunking even though traction may not be optimum.

Keep in mind that a road course will heat your wheels tires and brakes more than autocross and therefore the temps will rise naturally.

You can buy a cheap thermocouple probe for use with a DVM. When the temp (voltage) is similar across the tread then you have ideal camber and inflation.

My TPMS happens to closely match measured pressure. I suggest a rotary style gauge.
 

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My GT broke loose when I stepped on it and stepped out to pass all in one... The wth = I lost traction on the painted lines. No worry but, that's how easy it is to do in this car.
By the way, I agree that some of comments posted are critical beyond what I expected to see. Who hasn't passed a slower car when there wasn't much extra room left?
 
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It all depends. If the track is abrasive it will grind your tires. Overinflate to keep the shoulders from chunking even though traction may not be optimum.

Keep in mind that a road course will heat your wheels tires and brakes more than autocross and therefore the temps will rise naturally.

You can buy a cheap thermocouple probe for use with a DVM. When the temp (voltage) is similar across the tread then you have ideal camber and inflation.

My TPMS happens to closely match measured pressure. I suggest a rotary style gauge.
Found this topic, I guess I should trust my mechanical pressure gauge as tpms gives different readings to some.

https://www.mustang6g.com/forums/threads/tpms-pressure-vs-accurate-gauge.54963/#post-1668602
 
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accel

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These cars are, in fact, a bit unstable.
I've driven MR2t at autoX and that car made me think toyota was very brave to release that car to general public. I only could finish without loosing it on my third run. Once I got a feel of the car it was a blast to drive.

Mustang is fairly stable compared to that car. But I think it is a good idea to bring it to autoX once in a while.
 

FranzVonHoffer

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I've driven MR2t at autoX and that car made me think toyota was very brave to release that car to general public. I only could finish without loosing it on my third run. Once I got a feel of the car it was a blast to drive.

Mustang is fairly stable compared to that car. But I think it is a good idea to bring it to autoX once in a while.
That 2nd gen Toyota MR2 was so famously unstable Car and Driver did a side bar on it after they wrecked one. Generally the first mod owners would do was to upgrade to a staggered wheel and tire setup. Even then it was hairy. I dated a girl with one but I never got enough wheel time to get used to it.
 

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IRS movement is the big culprit on the S550's instability in certain situations. It's not the spring / damper rates or factory roll couple setup nor the tires. The IRS creates a lag / rubber band effect in stock form. That's why MotorTrend noted that hanging the tail out without it letting go was extremely razor edge compared to the Alpha based Camaro. First week I had mine I nearly wrecked it in the winter due to road salt. I never once had an issue with my Ecoboost Mustang, but I locked out the IRS the first month of having it before the engine was even broken in so I never experienced the IRS bushing deflection issues.

With the GT I decided to go slower on changes and be more careful to avoid making changes I'd undo, so I drove it stock for a while to see what it could do, it's issues / weaknesses etc. Anyway, I was merging onto the highway on a curved on-ramp. I waited until I was past the curve and going straight then gave it 50~60% throttle. But due to the excessive road salt (no snow, just tons of salt dust) rear end stepped out quickly to the left, very quickly and surprised me. I corrected, but the rear end very suddenly would snapped back, it wasn't predictable like I was used to with my Ecoboost S550 that had a locked IRS.

Went to correct and it suddenly snapped back the other way. Then the car went into an oscillation left, right, left right until I was able to dampen it out and get it straight. At the limits of traction it was very hard to control because of that lag between the front and rear. It wasn't predictable like my old MX-5 was or the modified Ecoboost Mustang I had prior (same year), I could hang the tail out on purpose all day long with either of those cars and always control it precisely. The stock PP GT, not so much. Now, with the IRS locked out, it doesn't do that. The front and rear are in sync and I can hang the rear end out with ease and with predictability. Even if it starts to step out, it's easy to bring back inline. There's no lag, it doesn't suddenly snap as it starts to grab pavement again like it did stock.

I highly suggest locking out the IRS on any GT. Every GT, weather base model, premium and especially PP, benefits greatly from a stable IRS and I cannot detect any difference in NHV before or after the BMR kits. Maybe with a meter you could read a dB or two more noise, but nothing a normal person could discern before or after. Also FP toe links help a lot with traction and add another level of predictability. Toe deflection also plays a small part, but in terms of that lag it's all in the IRS bushing deflection which is frighteningly high. Had Ford used the spherical bearings in the outer ends of the toe links and stiffer IRS bushings (either higher durometer, or solid bushings), the car would have handled quite a bit better stock with no other changes! But, they gotta fulfill those ridiculous NHV requirements....at all costs...
 

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what is this whole irs lockout thing?

do not remember anything like this @ bmw forums while I was having one.

From my experience I can tell - I had BMW with sport pack (staggered) @ autocross on tires that were close to their end of life, rears worn more than front, but more even that my gt pp front/rear wear ratio.

The car was oversteering.

I replaced tires with exact same and attended another bmw autox event. No matter how hard I tried, I could not loose rear end. Felt like fwd. That bmw did not have as much horsepower as gt had of course.

GT PP - autox on oem pirelli tires that were 1 year old (very modest wear). Autox is not the place where you'd drift, so I was just trying to learn new to me car and be reasonably fast. I remember how enjoyable the car was. It would understeer if you exceeded speed for the turn, but if I stayed within traction limits, rear end was very predictable, stable, allowed for power oversteer, would never just go out in sweepers even if I applied brakes, etc.

It didn't occur to me the incident like in the beginning of this thread could happen to the car at slower/safer than autox overall situation just under one year later.

On both staggered cars I observed a change of the over/understeer balance through the span of tire life. It is actually a complete swing of balance

I am going to go to square 275 @ 19x10 everywhere. I believe if I will be able to rotate tires for even wear then overall car balance will be much stabler going from new to the end of life tire condition.

My only concern would be steering feel with 275 in front.

Staggered needs just way more tire care/attention, like much earlier/preventative tire replacement which I do not want to justify. It's like throwing a sweet fruit in the trash before I finished it.
 

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what is this whole irs lockout thing?

do not remember anything like this @ bmw forums while I was having one.
Steeda have a IRS Stop the Hop pack. And BMR had IRS Credle Lock Kit both options adress an issue with the IRS Diff bushings where Ford used rubber bushings for the Diff and this had a lot of play. This causes Wheel Hop and Wheel Hop causes oversteer.

A great review of the Steeda stop the hop kit could be found here:

https://motoiq.com/tested-steeda-anti-wheel-hop-package/

I hope this helps.
 

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what is this whole irs lockout thing?

do not remember anything like this @ bmw forums while I was having one.

From my experience I can tell - I had BMW with sport pack (staggered) @ autocross on tires that were close to their end of life, rears worn more than front, but more even that my gt pp front/rear wear ratio.

The car was oversteering.

I replaced tires with exact same and attended another bmw autox event. No matter how hard I tried, I could not loose rear end. Felt like fwd. That bmw did not have as much horsepower as gt had of course.

GT PP - autox on oem pirelli tires that were 1 year old (very modest wear). Autox is not the place where you'd drift, so I was just trying to learn new to me car and be reasonably fast. I remember how enjoyable the car was. It would understeer if you exceeded speed for the turn, but if I stayed within traction limits, rear end was very predictable, stable, allowed for power oversteer, would never just go out in sweepers even if I applied brakes, etc.

It didn't occur to me the incident like in the beginning of this thread could happen to the car at slower/safer than autox overall situation just under one year later.

On both staggered cars I observed a change of the over/understeer balance through the span of tire life. It is actually a complete swing of balance

I am going to go to square 275 @ 19x10 everywhere. I believe if I will be able to rotate tires for even wear then overall car balance will be much stabler going from new to the end of life tire condition.

My only concern would be steering feel with 275 in front.

Staggered needs just way more tire care/attention, like much earlier/preventative tire replacement which I do not want to justify. It's like throwing a sweet fruit in the trash before I finished it.

OEM Pirelli tires suck on most public road surfaces because of the weight of our cars and the stiffness of the pp suspension.
275 square will not take any steering feeling away, and will give more traction in the front, the back will still slip....how much depends on how sticky the tire is.
 

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also check your tire pressures. with rears being so wide it makes sense to keep the pressure exactly as recommended.

overinflation may reduce traction.

i checked this section of forum as to what tire pressures are good for autoX, track and most people suggest to keep it exactly to recommended.
When you say over-inflation, what kind of pressures are you running?
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