1LE Rear Tire Size

[Billy10mm]

Originally Posted by JusticePete

A car driven at 8/10ths with understeer is in my opinion going to be slower and more dangerous than a well mannered neutral to mild oversteer bias driven at 6/10ths. That is exactly what you see in a SS to 1LE comparison. People flog the SS to get around a course and people drive the course in the 1LE.

This makes no sense. A car driven at 8/10ths, by definition of the fraction, hasn't exceeded the limits of cornering adhesion - in other words, it isn't pushing or rotating. The car is following the direction of the tires. Same thing for the car at 6/10ths.

The problem is when you are at 11/10ths. When the driver has entered the corner too hot or in the wrong line. If the car begins to push, the driver gets scared and lifts. If the car he's driving is understeering, the lift puts more weight on the front tires which makes them scrub/understeer more, or if he's lucky, the extra weight gives them some traction and they turn in. Either way, the driver is now scrubbing speed very quickly and the the car is still heading relatively in the same direction he wants.

If the driver is in a perfectly neutral or oversteering car during the same situation, when he lifts, the car will begin to rotate. Now he's screwed. He will panic when this happens and likely do all the wrong things. I don't think I've ever met a driver who instinctively handled oversteer properly - it's not as simple as "steering into the skid" as most crap drivers-ed courses would have you believe.

Please describe the scenario you are trying to explain, as I can't grasp how any oversteering situation is better for a relatively new driver than any understeering situation.

[Billy10mm]

Originally Posted by Norm Peterson

Sure does . . . but anybody who thinks that's what they're doing on the street at 0.3, maybe 0.35 lat-g is kidding themselves.


Norm

+1

I've got a co-worker who keeps insisting that he prefers cars that will "wiggle their rear-ends a bit" at the limit so he can steer them with the throttle. Has never been on a track and no desire to go. Has quick cars with decent rubber and still expects me to believe that he's at the limit on the street. He's delusional.

Given modern tires, even all-seasons, the limiting factor on the street is line-of-sight. There are VERY few corners you can see all the way around and actually attack at 8/10ths or above, especially on a 1G+ capable car like the 1LE.

Took said guy for a quick spin in my 1LE when I got it and he braced himself so hard when I didn't brake for a ~50mph right-hander, I thought he broke the door handle.

[Spoolin]

Originally Posted by X25

They might also be doing trail-braking; works great in some cases :P

Originally Posted by Norm Peterson

Sure does . . . but anybody who thinks that's what they're doing on the street at 0.3, maybe 0.35 lat-g is kidding themselves.


Norm

I've only recently learned trail braking while at the track and I'm addicted to it and do it way too much. I know it's more of an pro driver's technique but ever since I learned to rotate the rear with the brakes I've been doing all the time(on the track), even on corners where I shouldn't be doing it.

On the street I don't dare do it, I am not confident with trail braking when the tires aren't up to temp and the road surface is unpredictable. I'll keep those shenanigans to the race track.

[JusticePete]

Originally Posted by Billy10mm

This makes no sense. A car driven at 8/10ths, by definition of the fraction, hasn't exceeded the limits of cornering adhesion - in other words, it isn't pushing or rotating. The car is following the direction of the tires. Same thing for the car at 6/10ths.

The problem is when you are at 11/10ths. When the driver has entered the corner too hot or in the wrong line. If the car begins to push, the driver gets scared and lifts. If the car he's driving is understeering, the lift puts more weight on the front tires which makes them scrub/understeer more, or if he's lucky, the extra weight gives them some traction and they turn in. Either way, the driver is now scrubbing speed very quickly and the the car is still heading relatively in the same direction he wants.

If the driver is in a perfectly neutral or oversteering car during the same situation, when he lifts, the car will begin to rotate. Now he's screwed. He will panic when this happens and likely do all the wrong things. I don't think I've ever met a driver who instinctively handled oversteer properly - it's not as simple as "steering into the skid" as most crap drivers-ed courses would have you believe.

Please describe the scenario you are trying to explain, as I can't grasp how any oversteering situation is better for a relatively new driver than any understeering situation.

You are speaking in absolutes, I am speaking in increments. A car doesn't move from controlled to out of control at 7ths. It begins to under or oversteer. Loss of control that is difficult to correct occurs at 11/10ths. Anyone that has driven an SS and a 1LE would not define the more neutral 1LE as dangerous. The same I true for the even more aggressive setup in the Z/28.

A driver needs to learn there car and there limits.They need to learn car control. Sooner or later they have to make the transition.

[Billy10mm]

Originally Posted by JusticePete

You are speaking in absolutes, I am speaking in increments. A car doesn't move from controlled to out of control at 7ths. It begins to under or oversteer. Loss of control that is difficult to correct occurs at 11/10ths. Anyone that has driven an SS and a 1LE would not define the more neutral 1LE as dangerous. The same I true for the even more aggressive setup in the Z/28.

A driver needs to learn there car and there limits.They need to learn car control. Sooner or later they have to make the transition.

And until then you would have them drive cars that have a greater tendency to oversteer rather than cars that have a lesser tendency to oversteer?

And you are correct, no car moves from controlled to out of control at 7/10ths because at 7/10ths .... there is no slip angle whatsoever. Slip angle doesn't START until 10/10ths. 10/10ths might be different speeds for different people. If you nail the correct line at 72mph you might hover right at 10/10ths whereas I could early-apex the same corner at 68mph in the exact same car and find myself pushing as I try to scrub off speed to get back on the line. You went to 10/10ths, I went to 11/10ths, but I was slower.

I'll ask it again ... you believe that understeer is LESS SAFE than oversteer to someone who is relatively new to the racetrack (let's say, less than 1K track miles)?

[JusticePete]

I believe a novice driver should drive within their limits and they learn more faster in well balanced car. If a pure novice buys a performance car and takes advantage of the mfg's driving school they do not learn in a slower less balanced car. They go on track in what they bought.

If they don't respect the instructor, track or vehicle under over doesn't matter.

[X25]

Originally Posted by JusticePete

I believe a novice driver should drive within their limits and they learn more faster in well balanced car. If a pure novice buys a performance car and takes advantage of the mfg's driving school they do not learn in a slower less balanced car. They go on track in what they bought.

If they don't respect the instructor, track or vehicle under over doesn't matter.

I recommend the Miata to 'learn'. It helped me overcome my fears I've developed in many years of driving high HP cars

[Norm Peterson]

Actually, there is slip angle at any level of lateral acceleration, and the front slip angle(s) and rear slip angle(s) are generally not going to be the same.

It's once you're operating above where the slip angles are nonlinear that US/OS becomes noticeable. Especially when one end of the car is forced to operate further up into the nonlinear portion sooner than the other end of the car.

But yes, as long as lateral g's are relatively low, they won't differ by much and everything will still feel completely stuck down even though there may be 2° or 3° of slip angle being developed at all four corners (right in that 0.3-ish lat-g neighborhood).

Slip angle plots for the better tires that are fitted to the 1LE or that people choose to upgrade to for open track use lie somewhere between the green and red lines on the thumbnail pic. They'll stay linear longer than the street tire shown, but not as far as the F1 tire, and the curve will nose over a little faster than the green line. Imagine how tricky a car might feel if its tires behaved like the blue line . . .


BTW, don't take these curves as numerical gospel; they're just something I grabbed for illustration purposes here.


Norm

[Norm Peterson]

Originally Posted by Billy10mm

+1

I've got a co-worker who keeps insisting that he prefers cars that will "wiggle their rear-ends a bit" at the limit so he can steer them with the throttle. Has never been on a track and no desire to go. Has quick cars with decent rubber and still expects me to believe that he's at the limit on the street. He's delusional.

Given modern tires, even all-seasons, the limiting factor on the street is line-of-sight. There are VERY few corners you can see all the way around and actually attack at 8/10ths or above, especially on a 1G+ capable car like the 1LE.

Heh heh.

Some years ago - several years before getting the Mustang in '08 actually - I'd been instrumenting the lateral acceleration of another car I had at the time (really crude "instrumentation"), and when there was other traffic around I happened to notice how hard they tended to take corners. Even when you could see adequately far around the turn, most traffic stayed below 0.2g, maybe 0.3g. A few got up into the 0.4g range. At 0.5g there might have been one car in a thousand keeping pace. It didn't seem to make a whole lot of difference what the other cars were, that's just where people (around here anyway) were comfortable.


Norm

[chuyito92]

[QUOTE=So Cal Camaro;6630155]Here you go

You have 305-35-20 on back? What do you have on front?

[chuyito92]

Originally Posted by So Cal Camaro

Here you go

You have 305-35-20 on back? What do you have on front?