GT350R Front Toe Track Alignment - In or Out?

[oldbmwfan]

I'm personally not specialist but find this link VERY usefull to understand the basics:
http://racetrackdriving.com/car-setup/track-alignment/

"On a road course front toe primarily affects eagerness of the car to turn and mid-corner understeer/oversteer balance. A car with front toe out will initiate direction changes more easily than a car with front toe in. A car with significant front toe out will feel "darty": a small movement of the steering wheel will be sufficient to get the car to rotate. A car with positive front toe will tend to track straight even in the presence of minor steering wheel movement, which is why street cars often have a bit of positive front toe aligned into them.

The above discussion assumes a car going straight, with equal weight on left and right tires. When the car is in the middle of a corner, and the weight is transfered to the outside tires, front toe has the opposite effect on handling: front toe out produces understeer and a car that resists mid corner direction changes, while front toe in makes the car darty mid corner and may even cause oversteer under power in front wheel drive cars."

I believe that to be true also (toe out helps with initial direction change, but comes at the expense of cornering and straight-line stability and increased tire wear). I have used a smidge of toe out in an E36 BMW track car to reduce understeer at corner entry. Narrow enough tires on that car where scrub wasn't much of a factor, and I'm talking 1/16" total toe out (1/32" per side). I have my GT350R set for very slight total toe in up-front and it works well. 1:26.0 at Grattan on worn-out tires in better hands than mine.

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[BillyJRacing]

I'm personally not specialist but find this link VERY usefull to understand the basics:
http://racetrackdriving.com/car-setup/track-alignment/

"On a road course front toe primarily affects eagerness of the car to turn and mid-corner understeer/oversteer balance. A car with front toe out will initiate direction changes more easily than a car with front toe in. A car with significant front toe out will feel "darty": a small movement of the steering wheel will be sufficient to get the car to rotate. A car with positive front toe will tend to track straight even in the presence of minor steering wheel movement, which is why street cars often have a bit of positive front toe aligned into them.

The above discussion assumes a car going straight, with equal weight on left and right tires. When the car is in the middle of a corner, and the weight is transfered to the outside tires, front toe has the opposite effect on handling: front toe out produces understeer and a car that resists mid corner direction changes, while front toe in makes the car darty mid corner and may even cause oversteer under power in front wheel drive cars."

That's a common misconception that I too believed for years.

There are a ton of variables from car to car, from the tires, to the suspension geometry, steering geometry, steering ratio, weight distribution, etc... But generally for the FRONT of a car:

Toe-IN improves turn-in response and sharpness; and reduces front grip slightly mid-corner.
Toe-OUT makes the steering less responsive on-center and at turn-in; but improves front grip slightly mid-corner.

*The outside, loaded tire contributes the most to steering response and grip.

With toe-in; the outside tire is already pre-loaded and has a slip angle pointing IN to the given corner. As you turn-in, that outer tire already has a slip angle in the tread and is already generating a side force. As the tire gets loaded more, it has more grip to change the direction of the car. The inside tire goes from pointing away from the corner to straight, then into the corner, but is less loaded. Toe-in also slightly reduces steering ackermann slightly which can often reduce front grip mid-corner slightly, pending the bumpsteer of of your car.

Toe-out means the outside tire is pointing in the wrong direction from the corner. When you turn-in, the outside tire (which has the most authority) has to go from pointing the wrong direction, to pointing straight, to then point into the corner, generate a slip angle across the tread of the tire to then generate a side force that changes the direction of the front of the car. This takes time and steering angle and leads to a less responsive and numb steering feel at turn-in. The inside tire is already pointing in the correct direction and will be more responsive, but as its the unloaded tire, it has far less authority on the response of the front end. This also increases steering ackermann which can often improve front grip mid-corner which is often a more important trade-off for a car with less than ideal weight distribution and needs more front grip.

Billy

 

[honeybadger]

I believe that to be true also (toe out helps with initial direction change, but comes at the expense of cornering and straight-line stability and increased tire wear). I have used a smidge of toe out in an E36 BMW track car to reduce understeer at corner entry. Narrow enough tires on that car where scrub wasn't much of a factor, and I'm talking 1/16" total toe out (1/32" per side). I have my GT350R set for very slight total toe in up-front and it works well. 1:26.0 at Grattan on worn-out tires in better hands than mine.

This is the biggest reason I don't recommend folks running toe OUT. I've experimented a lot with toe and always found that toe OUT resulted in a darty car under braking. Here's HB pulling 1.5gs at COTA with 1/16th toe IN, 0 toe rear, and 0-3.7 front camber. Keep in mind this was lap 4 of the first session and the FIRST session since the winter refresh, so we weren't even pushing it that hard.




IME, toe makes a big difference in braking.

 

[jmn444]

I believe that to be true also (toe out helps with initial direction change, but comes at the expense of cornering and straight-line stability and increased tire wear). I have used a smidge of toe out in an E36 BMW track car to reduce understeer at corner entry. Narrow enough tires on that car where scrub wasn't much of a factor, and I'm talking 1/16" total toe out (1/32" per side). I have my GT350R set for very slight total toe in up-front and it works well. 1:26.0 at Grattan on worn-out tires in better hands than mine.

got any video of that lap? My best this weekend was a 1:27.56... i know i should be on the gas harder thru 11 and 12 but not sure where else i could improve... way better than my 1st weekend there, i think i was only running 1:33's that time but man it is fun!

 

[oldbmwfan]

got any video of that lap? My best this weekend was a 1:27.56... i know i should be on the gas harder thru 11 and 12 but not sure where else i could improve... way better than my 1st weekend there, i think i was only running 1:33's that time but man it is fun!

Sadly no. Time was recorded on the driver's Aim Solo, but I didn't have a camera in the car for those laps :-(

 

[SVTinAR]

My 17 was aligned with toe out when I bought it with 2300 miles. At the time I researched this and found that to be the recommended setting. Seems to be some variance in specs. I reset it to a slight amount of toe in with a tram gage to help tire life.

 

[jmn444]

Sadly no. Time was recorded on the driver's Aim Solo, but I didn't have a camera in the car for those laps :-(

Ha! I just figured out that Anthony must have been driving... he's a good dude!

 

[oldbmwfan]

Ha! I just figured out that Anthony must have been driving... he's a good dude!

Yep, you nailed it. I am about 2.5 seconds slower than him, but I am also the guy that makes the payments. At MO in my E36 with cage, I am "only" ~1.25-1.5s slower. He's fast.

Your 1:27.56 is very good - what tires?

Re. on gas harder thru 11/12 - that is a big one for me, over-slowing into 11 in particular. But, Anthony tried to go with no brakes at all into 11 and we had a very, very sideways moment, pitched toward the wall. Nearly had a code brown in the right seat but he gathered it up and said, ever so calmly, "turns out you do need a little brake there." Next lap was the 1:26.0, if I recall correctly. :-)

 

[jmn444]

Yep, you nailed it. I am about 2.5 seconds slower than him, but I am also the guy that makes the payments. At MO in my E36 with cage, I am "only" ~1.25-1.5s slower. He's fast.

Your 1:27.56 is very good - what tires?

Re. on gas harder thru 11/12 - that is a big one for me, over-slowing into 11 in particular. But, Anthony tried to go with no brakes at all into 11 and we had a very, very sideways moment, pitched toward the wall. Nearly had a code brown in the right seat but he gathered it up and said, ever so calmly, "turns out you do need a little brake there." Next lap was the 1:26.0, if I recall correctly. :-)

I was on RE71R's and yes risk vs reward is a tough balance there!

Mid Oh it on next weekends schedule for me, 1st time there so not expecting much other than to learn the track.

 

[oldbmwfan]

I was on RE71R's and yes risk vs reward is a tough balance there!

Mid Oh it on next weekends schedule for me, 1st time there so not expecting much other than to learn the track.

Awesome. If it rains, be super careful; that place is like greased goose shit in the wet and there are a few spots where water will run across the track. But it's beautiful, and in the dry it's got an awesome flow.

 

[jmn444]

Awesome. If it rains, be super careful; that place is like greased goose shit in the wet and there are a few spots where water will run across the track. But it's beautiful, and in the dry it's got an awesome flow.

yeah i'm not a fan of trying to go fast in the rain anyway, had a bad experience/off first time i tried so hoping it stays dry!

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