Alignment Toe Question

[JIM THEO]

Originally Posted by gpvecchi

I think here in Italy we measure toe at the rim edge, can you please tell me what 1/16 of inch is with 17" rims? I have total rear toe in of 1,6 mm... Thanks!

1/16 of inch is 25.2mm/16=1.575mm, when 1mm toe for 17" rims is about 7' this means 1/16 is 1.575x7'=11' toe!
I think I am the only one that uses toe out (1mm) front and parallel rear wheels for DD in our very slippery roads...

[jamal]

You might want to check your math on that one.

1/16 over 17" is more like 0.2º of toe.

other thing is a cambered tire creates a thrust force in that direction so it may be a good idea to have a small amount of toe out with a lot of camber. If you have in the ballpark of 1.5-2 degrees of negative camber that would be an alright amount of tie.

[JIM THEO]

https://robrobinette.com/ConvertToeInchesToDegrees.htm
If you set toe in inches 0.0625 (1/16) and tire diameter to 17" (24.6") then the result is 0.072...where am I wrong?

[jamal]

Originally Posted by JIM THEO

tire diameter to 17" (24.6")

Well, which is it?

And .07 is not 7 degrees- It's .07 degrees.

Also 7' is not the right symbol for degrees assuming that is what you meant. With regard to angles that is the symbol for a "minute," which is 1/60th of a degree. To get a degree symbol (º) type alt+167

[JIM THEO]

Originally Posted by jamal

Well, which is it?

And .07 is not 7 degrees- It's .07 degrees.

Also 7' is not the right symbol for degrees assuming that is what you meant. With regard to angles that is the symbol for a "minute," which is 1/60th of a degree. To get a degree symbol (º) type alt+167

I mean minutes not degrees as alignment machines read minutes or mm locally, but I am really confused now, how much is then 1/16" to minutes or mm?

[ZDan]

Units for alignment can be confusing...
' in this context is arc-minutes, not feet.
1 arc-minute = 1/60 = 0.0167°

1/16 inch toe-in at 17in. is (1/16")/17" = 0.0037 radians = 0.21° = 12.6' (arc-minutes)
1/16 in. toe-in at 25 in. is (1/16")/25" = 0.0025 radians = 0.14° = 8.6' (arc-minutes)

Personally I wouldn't want more than 0.1° toe-in, and preferably closer to zero...

[JIM THEO]

Originally Posted by ZDan

Units for alignment can be confusing...
' in this context is arc-minutes, not feet.
1 arc-minute = 1/60 = 0.0167°

1/16 inch toe-in at 17in. is (1/16")/17" = 0.0037 radians = 0.21° = 12.6' (arc-minutes)
1/16 in. toe-in at 25 in. is (1/16")/25" = 0.0025 radians = 0.14° = 8.6' (arc-minutes)

Personally I wouldn't want more than 0.1° toe-in, and preferably closer to zero...

I run zero toe rear and 1mm toe out per wheel front with -1.4 degrees camber all around for DD but I believe a pyrometer is a "must" have for those that use their cars on track.

[jamal]

I like to just use degrees and decimals at each corner, seems that's how most printouts I've see are. Then you don't have to worry about that whole how big is the wheel thing. And not that it makes much of a difference but the points you're measuring on a rim are going to be farther apart than the wheel size by like a whole inch.

Other thing I rarely see mentioned is the effect of camber thrust. Leaning a tire over creates a side force that wants to pull the tire in that direction. Some books indicate in the ballpark of the equivalent of 0.1 degree of toe per degree of camber. So, maybe it's a good idea to have a little toe out with a good amount of negative camber to make the tires roll straighter and reduce scrubbing and the tires both trying to turn in. On the other hand compliance in the suspension and steering might generate some toe out from tire drag. And also toe out will make scrubbing on the inside tire worse in a corner.

[cjd]

And here I am worrying about hundredths of a degree while people can't even sort out how many degrees of toe they even have!

I currently have 0.02° toe out up front, 0.05° toe in rear... Basically zero...

Originally Posted by JIM THEO

1/16 of inch is 25.2mm/16=1.575mm, when 1mm toe for 17" rims is about 7' this means 1/16 is 1.575x7'=11' toe!
I think I am the only one that uses toe out (1mm) front and parallel rear wheels for DD in our very slippery roads...

Small correction... An inch is ~25.4mm

[JIM THEO]

Originally Posted by cjd

And here I am worrying about hundredths of a degree while people can't even sort out how many degrees of toe they even have!

I currently have 0.02° toe out up front, 0.05° toe in rear... Basically zero...



Small correction... An inch is ~25.4mm

We live in different parts of the world, it doesn't mean people don't know how many degrees toe have but how to convert from one system to other, they have minutes or mm, so simple!
By the way how many mm toe you have?

[churchx]

Don't most dyno rigs allow selecting different measure units for toe, whichever seem more convenient? I don't get much all the fuss about converting.

[JIM THEO]

Alignment machines may be allow it, their operators don't know very often how to do it if you know what I mean...

[cjd]

Originally Posted by JIM THEO

We live in different parts of the world, it doesn't mean people don't know how many degrees toe have but how to convert from one system to other, they have minutes or mm, so simple!
By the way how many mm toe you have?

I don't figure you need to care about inches very often. lucky you. Just wanted to note in case government contractors building satellites decided to use your post as a reference...



No idea how many mm toe I have, because it's a useless conversion for the way I do alignments. About that much. Might be 0.5mm toe in rear, 0.2mm toe out front (using the tire) if I didn't mess up the math. Which is interesting, because that means on this car each hundredth of a degree of toe might be just about one tenth of a millimeter of toe.


I've been told my alignment setup has about 4x the resolution of the best laser alignment setups... It also can take 10x as long to do a proper alignment... partly because of cramped quarters in my garage...

[JIM THEO]

Originally Posted by cjd

I don't figure you need to care about inches very often. lucky you. Just wanted to note in case government contractors building satellites decided to use your post as a reference...



No idea how many mm toe I have, because it's a useless conversion for the way I do alignments. About that much. Might be 0.5mm toe in rear, 0.2mm toe out front (using the tire) if I didn't mess up the math. Which is interesting, because that means on this car each hundredth of a degree of toe might be just about one tenth of a millimeter of toe.


I've been told my alignment setup has about 4x the resolution of the best laser alignment setups... It also can take 10x as long to do a proper alignment... partly because of cramped quarters in my garage...

And here I am worrying about some minutes while people can't even sort out how many mm of toe they even have!