I don't know why its so hard to find this answer or if it really matters, but when doing your own four wheel alignment using the string method, where do you take the toe readings, at the rim lip, tire sidewall or at the tread using some sort of toe plates?

I've always thought that toe is measured at tread diameter but in all the videos I've seen, the guys are measuring at the rim lip. The rim is about half the diameter of the tire so my thinking is that if you measure at the rim for say 1/16" toe in then you are really around 1/8" at the tread... Not sure if I'm over thinking this or not. What do you all say?

 

I use toe plates - makes it very easy to check toe and they aren't that expensive.

https://www.longacreracing.com/produ...-Magnets-(pair)

 

I am picking up what you are laying down. Very puzzling to me why this never seems to come up. How big is your triangle???

The distance measurement spec is technically flawed because the farther you are away from the center of the wheel, the bigger the toe "measurement" will be for any given setting.

Toe specified in angle degrees would be much more precise. Maybe its just not that important?

 

I run my strings forward. Taking a measurement just in front of the car. Then a second measurement 3 feet in front of the first measurement.
the specs for these cars are zero toe or just a fuzz toe out.
using a measurement 3 feet apart can get you darn close to that.

 

Measured at the tire tread so basically the tire diameter
M

 

It is the difference from front to back......you could run strings a mile away in both directions and the difference would still be 1/8".

Jebby

 

This is how I do alignments, doesn't matter what tires you have. (measure in degree's) and convert to inches via a calculator based on tire size.

My DIY Alignment method - CorvetteForum - Chevrolet Corvette Forum Discussion

Convert Toe Degrees to Inches (robrobinette.com)

 

The rims are usually straighter than the sidewalls, so there are less errors.
But you can use the sidewalls, and still get good results, as long as you are careful to miss any raised letters, and be up off the ground high enough to miss the tire bulge.
The measurement itself is based on the tread, so the tire diameter.
The way to get good accurate measurements at home is to use two 4 foot aluminum square beams from Home Depot and measure the toe-in at twice the tire's diameter. Keep them roughly 3" off the ground, then slide 2 tape measures under the car.
Then cut the numbers in half, 1/16" on your tape measure becomes 1/32" toe-in.

I double-checked this against the rim method, it was just as accurate, requires less equipment and is much faster to setup.

I gave up on the string method 30 years ago, far too time consuming.

 

IMHO, KISS. In my case, tires will probably age out before they wear out.


This is an old photo. I currently have 17" TT

 

Now that's what I'm talking about.!

Now just spread the two tapes until they are 4 ft apart. It's much more accurate.
Then cut your 1/16" measurement in half to 1/32"

I like your "turntable" also! LOL
I use 1/8" floor tiles for leveling anyway, and then add some layers of aluminum foil and wax paper to reduce the turning friction.

 

that is what I use

 

The standard convention is to measure at the rim. The wheel will typically be more consistent and have less variations than the tire sidewall. The most common of those is to have Toe based off of an 18" wheel diameter but that varies by car. If you're after a specific specification then it may state the diameter it's based on. If it's in degrees or arc-minutes you can convert it to inches or mm based on the wheel diameter. Toe Plates locate off of the sidewall and induce error. The most cost effective way to do it is with strings and a ruler/scale to the rim. Strings also ensure the steer ahead and thrust angle (front and rear wheels aligned with each other) are maintained. As long as you have a repeatable and accurate method, it should work out just fine.

-Colton

 

Thanks guys, you are all very helpful and its good to know that toe is in fact still measured at the tire diameter. It makes sense that taking readings on the rim could be more accurate than on the side wall but the best seems to be when using the 4 foot bar method so I'll give that a shot. I wish I didn't have to use this string method because it sure is a pain to set up but since I've had both ends apart, I want to make sure it tracks properly too.

 

 

For the front, I followed this last week when I finished up my Borgenson upgrade. My steering wheel was way off. Worked perfectly.

 

Need to use an alignment machine. Measuring with tape measures tells you total toe in/out but not what each wheel's toe is. For sake of discussion, you get 1/4" in. Now is each wheel 1/8" in? One wheel 1/4" in the other zero? One toed out, the other toed in to read 1/4" in?

 

...you can if you use a string or laser to line things up based on the centerline of the car first.

 

No need to use a $50k alignment machine. All they offer is speed, and some level of protection from lower skilled mechanics.
Once I saw Rick Mears Indy car aligned with strings trackside. 1/32" was accurate enough for him at 200 mph, and to win.
I have been doing all my own alignments, for 40 years, on my whole fleet, with tape measures, straight edges and levels.
But it does require more knowledge & skill.
The hardest part is making some of the adjustments on some cars without out a lift! LOL Easier for a shop then.
I have occasionally used an alignment shop, for various reasons, but usually double check their toe-in settings later.
I have made them re-do it at least 30% of the time, because they were off. Those guys will believe the fancy machine, even when they set it up wrong, because they were in a hurry. Hurry causes mistakes.
The four foot tape measure method is easily as accurate as the machines, I have checked multiple times. And more accurate than a guy in a hurry.

 

Step 1
If you set the thurst angle ~ 0.1 degree then measure total toe. Then you will have very accurate toe readings for each. This requires 2 steps vs the machine which you can do in 1 step.