Corner weight distribution question.

[Bluemustang]

It might be time for some IRS bracing.

The only time I've experienced something that could be described anywhere near like what you have noted was when I took a tire pressure staggering test sequence to a truly foolish level, where the tail was loose under both leading throttle and trailing throttle. In that case, it was rear tire pressures too low. In your case, maybe you're running the rear tires at too high of a cold pressure, or perhaps they're gaining an unusual amount of pressure for some reason. Not enough rim width for the tire size could be at play here as well. Street tires aren't built like cantilever race tires to get around class restrictions on wheel width.


Norm

Actually, I think this might be it Norm. I second.

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[Norm Peterson]

Its not a grip issue. The tires are pretty good for A/S.

Agreed, they aren't as terrible as some seem to think (I think that's what's on the Maxima in my sig). But they aren't PS A/S 3+ either.


Norm

 

[Bluemustang]

I think what Norm said - subframe movement. The car can start to behave erratically near the limit if the subframe is allowed to deflect like it can in stock configuration.

 

[K4fxd]

I've got steeda stop the hop kit.

Interesting day. We bolted the slicks on and I did a warm up lap, the car felt pretty good. I then did a fast lap. Or so I thought. I blew the brakes on the 4th corner, went into the scrub.

Not enough to get a feel for the car.

Replaced the rotors, pads and fluid and put the all seasons back on. The car felt squirrely again. So we added pressure till it felt stable. Then adjusted till my lap times fell off. These tires like 35 cold.

So it was the tires.

I think when I finish off these tires I'll try the Pilot Sport 3+ A/S

Anyway the car feels much better.

 

[Norm Peterson]

Replaced the rotors, pads and fluid and put the all seasons back on. The car felt squirrely again. So we added pressure till it felt stable. Then adjusted till my lap times fell off. These tires like 35 cold.

So it was the tires.

What size tires? And what wheel width(s)? This hasn't been mentioned yet, and there are at least three possibilities just with Ford's OE fitments.


Norm

 

[K4fxd]

These are the stock base tire size 235 50 18 on stock rims.

I'm not looking to set any track records, in fact it will probably never see a track again. The brakes suck. I just want a stable predictable car.

Seriously thinking of trading for a M series.

 

[Norm Peterson]

These are the stock base tire size 235 50 18 on stock rims.

Thanks . . . there's probably some general correlation between car weight and wheel width, vs use, and 8" wide wheels on a 3700-ish weight car (around 475 lbs/inch of wheel width) isn't too much better than what you'd find on a mildly sporty family sedan. PP1 wheel widths (9" / 9.5", 425/400 lb/in) are only starting to get a little serious. I've seen (and made) similar comparisons between car weight and power vs tire measurements.

I'm not looking to set any track records, in fact it will probably never see a track again. The brakes suck. I just want a stable predictable car.

Just a pad upgrade should go a long way here, assuming that you can live with some dust and a little noise.


Norm

 

[Bluemustang]

The base GT brakes should never see a race track under any circumstances.

 

[TeeLew]

Seriously thinking of trading for a M series.

You sent the car off in the 4th corner. That's on you.

 

[TeeLew]

The base GT brakes should never see a race track under any circumstances.

Nonsense. They're likely to overheat if pushed because the cooling is on the wrong side of the hat, but these brakes are plenty big enough to have reasonable performance for the majority of people who want to run a couple laps and then park to B.S. for a while. They just don't take extended punishment like brakes meant for track duty.

 

[Brian@BMVK]

These are the stock base tire size 235 50 18 on stock rims.

I'm not looking to set any track records, in fact it will probably never see a track again. The brakes suck. I just want a stable predictable car.

Seriously thinking of trading for a M series.

Those tires are the #1 reason for your ails. That size tire has no business on a Mustang and inspires zero confidence.

What is the rest of your setup?

The base GT brakes are not competent for longer sessions, but it can be fixed. The whole thing can be fixed and can be extremely competent, but you need to approach it holistically.

 

[Bluemustang]

Nonsense. They're likely to overheat if pushed because the cooling is on the wrong side of the hat, but these brakes are plenty big enough to have reasonable performance for the majority of people who want to run a couple laps and then park to B.S. for a while. They just don't take extended punishment like brakes meant for track duty.

I've heard feedback from a few fast drivers who have blown through and gone off track after one lap. Just saying.
I agree the calipers and pads are powerful enough, but there's no way to get any cooling to the front brakes. Granted quite a few people have used the Base GT brakes and been fine, but for safety reasons I don't recommend it. Brakes are not a thing you want failing on you. However, if you replace the front rotor with a proper vented one and put in decent brake fluid it should be pretty competent.

 

[TeeLew]

I've heard feedback from a few fast drivers who have blown through and gone off track after one lap. Just saying.
I agree the calipers and pads are powerful enough, but there's no way to get any cooling to the front brakes. Granted quite a few people have used the Base GT brakes and been fine, but for safety reasons I don't recommend it. Brakes are not a thing you want failing on you. However, if you replace the front rotor with a proper vented one and put in decent brake fluid it should be pretty competent.

Completely agree on cooling, but that's not the brakes 'failing'...that's *fading*. You can't blame the brakes if you pitch it off the track after 3 corners. That's not a car problem, that's a driver problem. Buying an M 2,3,4,5,6,7,8,9 whatever doesn't fix it.

 

[Dana Pants]

The base GT brakes should never see a race track under any circumstances.

Or all season tires or wheels.

 

[Bluemustang]

Completely agree on cooling, but that's not the brakes 'failing'...that's *fading*. You can't blame the brakes if you pitch it off the track after 3 corners. That's not a car problem, that's a driver problem. Buying an M 2,3,4,5,6,7,8,9 whatever doesn't fix it.

Agree with you on the first part but disagree on the second part. If the brakes are fading that quickly that's a brake problem IMO. Track driving is very abusive and using parts that can handle that abuse is important, especially if you hope to put down any fast times.

Agree, a BMW M series won't solve it. This sounds like a driver problem. Running 235 wide A/S tires on a race track is a tell tale sign of not understanding the machine.

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