Toe-in measurements

[Kent mosby]

I am doing my alignment again tonight. It looks like my camber is off a bit. I have the Fast trak alignment setup. My question is, where are the toe-in measurements taken. If they are at the wheel you would get one measurement. If at the end of a 4 foot level, you would get another number (exaggerated example). Are you measuring across the tire or rim(with the Fast trak extensions)? At what height from the ground?
I watched the video instructions and it says a close to the tire as possible but at what height from the ground?

I hope that I am clear at what I am asking. Another way to look at it.
At 12 inches, 1 degree angle is .209 inches.
At 24 inches, 1 degree angle is .418 inches.

So,,, The higher you go on the tire, the longer the distance is and the greater the measurement would be for the same "angle" toe-in" I understand toe-in is measured as distance not angle, but it is relevant.

 

[toolmanmike]

It's nearly impossible on a car but the front and rear toe measurement should be as close to perpendicular with the shop floor as possible. (half way up on the front and the rear of the tire) That's why proper alignment machines are the way to go. A little off makes a big difference. And, old school measured toe fractionally. Now days with the computerized machines, it is measured in degrees.

 

[Kent mosby]

It's nearly impossible on a car but the front and rear toe measurement should be as close to perpendicular with the shop floor as possible. (half way up on the front and the rear of the tire) That's why proper alignment machines are the way to go. A little off makes a big difference. And, old school measured toe fractionally. Now days with the computerized machines, it is measured in degrees.

So If I am using the Skosh chart as a reference, The 1/16 toe -in is measured at 26 or 27 inches across (width of tire)? Correct? I can use Fasttrax extensions and measure at 26 inches across.

Does that sound correct?

 

[rklein383]

Toe in is measured relative to the tire diameter. If you choose to measure toe in with long rods, like they do on the track at NASCAR, you would have to adjust the difference based on the length of the rod. So 1/16 difference between the front of the tire and the rear of the tire would be more like 3/8 (wild guess) of an inch if you took measurements three feet to either side of the tire. Rod

 

[rklein383]

PS, a few inches off on tire diameter will have essentially no impact to what you need.

 

[toolmanmike]

So If I am using the Skosh chart as a reference, The 1/16 toe -in is measured at 26 or 27 inches across (width of tire)? Correct? I can use Fasttrax extensions and measure at 26 inches across.View attachment 1715546140
Does that sound correct?

The photo doesn't show the rear of the gauge but I would imagine the toe extension is the same as the front. The gauge head locates off the rim and tire so as long as the toe extensions are the same length. (they should be) just measure the backside and then the front and it will measure the toe either in or out and then adjust accordingly. Pay attention to your steering wheel centering. That's something you will have to mess with. The computerized machines will do that for you.

 

[kursplat]

i usually draw a verticle chalk line in the center of the tires, front and back and mesure off those. i got a set of toe plates recently and haven't tried them yet, but hoping it will make it a little easier

 

[kursplat]

so it looks like the toe adapter for the fasttrax is extentions that stick out past the tire to run the tape messure against?

 

[Kent mosby]

so it looks like the toe adapter for the fasttrax is extentions that stick out past the tire to run the tape messure against?

yes, that is correct. but they can be straight out or angled next to the tire. I will measure the tire diameter and use that for the distance to measure on the device

 

[kursplat]

...but they can be straight out or angled next to the tire.

since that's mounted on the rim i would just keep the arms straight and have the tape measure against the face of the tire. i'd measure from the rim to the edge of the bracket, front and back, to make sure it's mounted perpendicular to the rim. then if you had zero toe, the measurement front or back of the tire, should be the same

 

[supertruck]

Get a set of toe plates as used in racing. Simple to use. Worked for me at the track for many years and I'll use them again as I get my Sport project ready to go to a good shop for a professional alignment.

 

[rklein383]

I have these plates from Tenhulzen but they essentially do the same thing yours do.

 

[Kent mosby]

I completed the alignment today. My scamp is set up for the strip right now. I was able to set the camber at -.25 both sides, caster +2.5 and 3.0 with essentially 0 toe-in. When I took it for a test drive, it seems to be able to wander a bit. It does not track much. Is this to be expected from that setup?

 

[72bluNblu]

I completed the alignment today. My scamp is set up for the strip right now. I was able to set the camber at -.25 both sides, caster +2.5 and 3.0 with essentially 0 toe-in. When I took it for a test drive, it seems to be able to wander a bit. It does not track much. Is this to be expected from that setup?

Toe-in is prescribed for a reason. That reason being that when you’re rolling down the road the force of the spinning tires tends to pull out on the steering linkage. That pulls any play in the steering linkage out and allows the tires to toe out some. Which is why a standard alignment calls for a little toe-in, so counter play in the linkage. How much depends on the steering components, these cars usually call for 1/16” to 1/8”. 1/8” seems like a lot, but if the linkage and tie rod ends aren’t super tight it adds up quick.

Now, you set your toe to 0, so, rolling down the road you probably have a small amount of toe out. And that can lead to wandering.

If your goal is drag racing, you ideally want zero toe when you’re going down the track. But, depending on how much play is in your steering system, you may need to have a small amount of toe-in with your static alignment to be at zero when you’re rolling. The tie rod ends on these cars generally have some play, so some toe in will probably help. With heims or a rack and pinion you could run closer to zero on the static. It doesn’t matter as long as you set the toe right for your car.

The rest of your numbers are fine. Your positive caster is ok, more positive caster would also help with the wandering. But +2.5* and 3 isn’t bad at all, that’s pretty much the max for stock UCA’s with offset bushings.

 

[turbofreek]

Toe-in is prescribed for a reason. That reason being that when you’re rolling down the road the force of the spinning tires tends to pull out on the steering linkage. That pulls any play in the steering linkage out and allows the tires to toe out some. Which is why a standard alignment calls for a little toe-in, so counter play in the linkage. How much depends on the steering components, these cars usually call for 1/16” to 1/8”. 1/8” seems like a lot, but if the linkage and tie rod ends aren’t super tight it adds up quick.

Now, you set your toe to 0, so, rolling down the road you probably have a small amount of toe out. And that can lead to wandering.

If your goal is drag racing, you ideally want zero toe when you’re going down the track. But, depending on how much play is in your steering system, you may need to have a small amount of toe-in with your static alignment to be at zero when you’re rolling. The tie rod ends on these cars generally have some play, so some toe in will probably help. With heims or a rack and pinion you could run closer to zero on the static. It doesn’t matter as long as you set the toe right for your car.

The rest of your numbers are fine. Your positive caster is ok, more positive caster would also help with the wandering. But +2.5* and 3 isn’t bad at all, that’s pretty much the max for stock UCA’s with offset bushings.

positive caster added by qa1 upper control arms. do they have add cast in them?
i have the qa1 non adjustable uppers and custom heim end lowers with coiloverz. i need to adjust caster and camber before i do toe adjustments on the rack n pinion. any pointers?
my dr side is damn nesr perfect but pass side wheel cambers pretty hard. never done an alignment but willing to do it. 1500+rwhp car fwiw

 

[72bluNblu]

positive caster added by qa1 upper control arms. do they have add cast in them?
i have the qa1 non adjustable uppers and custom heim end lowers with coiloverz. i need to adjust caster and camber before i do toe adjustments on the rack n pinion. any pointers?
my dr side is damn nesr perfect but pass side wheel cambers pretty hard. never done an alignment but willing to do it. 1500+rwhp car fwiw

Yes, the QA1 upper control arms have additional caster built in compared to the factory control arms.

Your suspension sounds decidedly custom though, so what you get out of all that I don’t know. Normally you use the eccentric bolts that hold the UCA’s on to adjust caster and camber. A rough setting is usually setting the adjustment so that the front arm of the UCA is as long as possible, while the rear arm is made as short as possible. That maximizes positive caster.

Hopefully you aren’t using the stock spindles with the steering arms turned forward for your rack and pinion. Otherwise you’ll have Ackerman and other geometry issues.