Reaper19

Okay, I finished up all my suspension work and started checking my rear then front alignment with the string and level method. This has probably been asked before, but just want to clarify.

When checking the measurements from the tire/rim to the string when checking the toe, my understanding was to measure from tire to the "Center of the string". Is that correct when taking the measurements? Or should you measure the distance "between" the string and tire?


Thanks

69autoXr

It doesn't matter, just be consistent in your method.

Reaper19

Thanks, the front toe specs for my 1981 are 1/32 of an inch toe-in on each side. Just wanted to clarify if I should be measuring the from tire to string or from tire to center of string.

zwede

You should measure from the edge of the rim to the string, front and rear. You then multiply so you get the toe for the diameter of the tire.

Example:
A 15" rim will be about 16" diameter at the lip.
Let's say you measure 2.00" to the string front, 1.90" rear.
You take your delta, 0.10", and multiply with the ratio between your measurement and the tire diameter.
0.10 * (27/16) = 0.17" (or just shy of 3/16"). This is your toe.

You do this because the toe spec is for the thread of the tire, or 27" diameter for stock tires.

And, of course, if you have trim rings they need to be removed before measuring.

zwede

Here's a pic of me doing the string method on my other car:

Barry's70LT1

Don't forget to first check for a bent wheel, not all wheels run true. Your alignment will be off.

CanadaGrant

I was always under the impression that toe is the measured difference between the front and rear rim edge or lip and not the front and rear of the tire so no multiple is needed for tire size. Applying or adding in an adjustment for tires would show a larger toe in measurement that what you actually have.

Reaper19

Great information guys. Thanks

These are a couple you-tube videos that point in a good direction I reviewed. The gentleman does mention measuring "from the tire to string", also? Little confusing, I guess a good way to verify is measure the rim then cross reference the tire to see if both read 1/32 toe-in.

zwede

In the olden days toe was measured by spinning the wheel while holding chalk to the middle of the thread. Then put the car down and measure difference between chalk line front and rear. So that's where the spec comes from.

Of course cars soon became low enough to where you couldn't get a toe gauge up far enough to measure but the spec stuck for a while.

These days toe is speced in degrees which makes it less ambiguous.

It's not speced at the rim. Notice that cars that had 14" standard rims with 15" optional (like 2nd gen Camaros, etc) had the same toe spec regardless of rim size.

CanadaGrant

I have a 4 or 5 different years of C3 Corvette Chassis Service Manuals here and all list total toe in fractions of an inch and how it is measured. The below quote is from page 3-5 of my 1969 chassis service manual but they all state the same:
"It is the difference of the distance measured between the extreme front and the distance measured between the extreme rear of both front wheels."

Since toe is listed in inches at a specific measuring point and not degrees in the service manual it seems to me that modifying the measuring points to the outside front and rear of the tire would throw off (reduce) the listed toe settings by more than a little bit.

zwede

I think you're misunderstanding the term "wheel", a wheel includes the tire. So "It is the difference of the distance measured between the extreme front and the distance measured between the extreme rear of both front wheels." means a distance of 27" with stock wheels.

CanadaGrant

I think you are correct. I checked and Speed Direct lists a C3 with 1/8" total toe at .290 degrees.
If I measured it at rim lip which on a 15" wheel is about 16" lip to lip, then 1/8" toe would give me .448 degree toe in. Way too much so that isn't right...
If I measure it at the 27" tire measurement then 1/8" toe works out to .265 degrees which is almost the same as Speed Direct lists and even closer with a 26" tire (.275 degrees) so it looks like you are right.
I'm not only slow, I do poor work too....

Convert Toe Inches To Degrees
https://robrobinette.com/ConvertToeInchesToDegrees.htm

zwede

No worries, I was confused about the whole thing too. Took a while googling before I got it right. And we're not the only ones, there's a reason the industry switched to degrees.

cagotzmann

The string method is very difficult to get a good alignment where the tires last a long time. Good thing most of us drive only a few thousand miles a year. I use laser levels for my toe alignment. Much more accurate and easy to setup.

zwede

I'll have to disagree with you. The string method, when done right, is extremely accurate. Your method looks perfectly fine also.

cagotzmann

Extremely Accurate Could be but this is how I see it.

Using Strings:

Using 15" Wheel so the measuring span ~ 16" The human eye / measurement ability is ~ 1/32" so over a 16" distance this calculate
to 0.1119 degrees per wheel. To set 1/32" total toe you need to measure 0.0829 degree's total toe. 0.1119 degree's ~ = 1/16" total toe.

To improve using the same string method you need to increase the distance of the measuring points.

When I use the laser method the process measures over a 2764mm (108.8")

using the same ability to measure 1/32" difference you now get.

0.01645 degree's / wheel less than 1/64" total toe.

Now that fact the suspension doesn't hold 100% it may not matter. If you want max tire life due to high mileage driving I would not use string alignment by calculations it's not accurate enough by process.

The car will drive great but the tire won't last the full life they should.

Its a good thing we need to replace most corvette tires due to age before the thread is worn.

zwede

You can see how I measure in the pic. I gently touch the rim while watching the string. If the string moves I add 0.1mm and do it again until the string stays still. I can repeat my measurement within 0.1mm easily.

Big2Bird

I'm okay with either way.
I don't fly it to the moon, I just back it out the driveway and take it cross country.
In a pinch I have even clamped a 2x4 to each tire and eyeballed it to get to an alignment shop.

slofut

Hey, do you have a full pic of your car with the minilites?