Where do you measure toe-in

I replace the rack and pinion on my car and need to reset the toe-in. Where should the toe-in be measured ? I'm thinking on the wheel .

 

Center of the tire tread.

 

Here's some information I used when I set mine.

[FONT=Verdana,Arial,Times,sans-serif]You will get better more consistent results adjusting your toe in settings if you go the extra mile to eliminate variables. You must first decide which technique that you plan to use to take the measurements. Each technique offers different benefits and drawbacks. The methods discussed here will be the Toe Plate method, Toe Bar Method and Tire Scribe Method. If you understand each toe setting technique you will be assured of repeatable results.
Before you begin taking measurements you must insure that the car is race ready. Ride heights set, weight percentages correct, driver weight accounted for, bump steer set, camber and caster set, Ackerman set, air pressure set, stagger correct....you get the idea. You should also inspect the steering components and replace any that are worn or bent. Center up the steering before you begin. Center the drag link or rack so that the inner control pivots and inner tie rods are centered to each other. Tie rod lengths should be adjusted to match you lower control points if possible.
String the right side of the car to line up the right front to the right rear. By lining up the right side and starting with the right front in line with the right rear you will eliminate any Ackerman effect that is in the car. If the wheels are turned away from straight when you take your toe measurement the Ackerman effect can add toe out that will not be present when the wheels are straight ahead. Take the time to string the right side and you will get more precise results. Make sure to settle the car and roll it forward just before taking a reading. By rolling forward the caster in the car will pull the front wheels take any clearance in your suspension components all in one direction. Be sure not to let the car roll back after you have rolled it forward. By rolling the car forward each time you will get more accurate repeatable results. Be sure to roll the car back then forward after each adjustment to relieve any pressure in the tire and suspension components.
When taking toe measurements that utilize the side wall it is a good idea to spin each front tire and mark the high spots on the side wall with a piece of chalk. Jack up the car and spin the RF wheel. Hold a piece of chalk on a jack stand about 1/8" away from the sidewall. Spin the tire and see if the chalk hits anywhere on the sidewall. If the chalk does not leave a mark then move the chalk gradually closer until you get marks on the high spots. Then find the uniform spots on the side wall and orient the tire so that those points will touch the Toe bar or toe plate when the car is on the ground. Lower the car and repeat the process on the other side.
Toe Plate Method: Toe plates offer fast and easy measurement of the front end alignment. When using toe plates be sure to have the toe plates resting flat on the ground and centered on the tire. You should always be sure to have the toe plates flat against the side wall. Make sure that the plate is up against the side wall evenly on both sides. Air up the tires so that there is not a bulge at the bottom of the tire in the center due to under inflation. Go the extra mile and mark the high spots of the side wall with chalk. Use a tape measure to check the back of the tire and the front between toe plates. The toe plate method should give you a smaller number at the back of the tire if you want to have toe out. Remember that any bent wheels or imperfections in the side wall will affect your settings.
Toe Bar Method: When using a toe bar make sure that the toe bar is held in the same place on the side wall each time on both sides of the car. Make sure that the toe bar is straight up and that equal pressure is placed both front and back. Chalk the wheels and take your measurements. Measure the difference from the toe bar to the side wall on the back and on the front. To have toe out you will need to see a larger measurement on the back side of the tire. This is opposite of the toe plate and Tire Scribe measurement techniques. Any wheel run out or side wall imperfections will have an effect on your readings.
Tire Scribe Method: Start by scribing a line in each front tire. By spinning the tire and scribing a line with a tire scribe you will take out any variables to to bent wheels or side wall wobbles. Measure the front and back of the tire. A smaller number at the back side of the tire will produce toe out.
Regardless of the method used you should use care to adjust the tire rods equally so as to keep the geometry of the front end correct. Be sure to tighten all jamb nuts and other steering components as well as visually inspecting the steering system. All three methods can give you good results if you take your time and eliminate as many variables as possible.
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On a front end machine. Ken

 

Thanks Ken .....never would have thought of that .

 

I have wondered about this too. My toe-in bar pointer is about 12" off the ground but shouldnt the measure be taken at the mid point?

 

In Australia it's easy.....in boots its "toe in".....in thongs (flip flops) its obviously "toe out".

I dont understand why you would ask about something so obvious.........

 

I would think it should be at the horizontal center of the wheel . I wish some experts would chime in here .

 

Mmmm, thong toe.

 

Right. There's always something in the way to keep you from measuring 180 degrees from where you measured up front. Frame, engine etc. Just not accurate at home. You can get it close. Close enough to drive it to the alignment shop where they can do it right.

 

And that's what I'm trying to do ! So does anyone know where the fractional toe dimension ( +1/8 ) is measured ? Wheel or tire ? I thought it might be an obvious question that only I didn't know the answer to . Apparently I was wrong about that .

 

Start a poll.

I use the tire tread like Tinbender suggested.

 

http://www.jalopyjournal.com/forum/showthread.php?t=757935... One of about 10 hits when you search the subject. There is different ways of doing it, as covered by the moose above in this thread, or like MR.48chev posted in the link I posted. 48chev goes into good detail about where to measure on the tire itself.


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Use center of tread, measure back of front tires. Then measure front, should be about 1/8" less, this with steering wheel centered. Should get close enough to drive to shop.

 

Yes, center of tire, front and back, at axle height.

 

Toe-in is measured at the center of the tread at the horizontal center line of the front spindle.

One easy tool is a length of 1/2" electrical conduit a foot longer than the treadwidth, couple of hose clamps and a couple of pieces of welding rod.

Jack up the front, spin the tires and scribe a line in the approximate center of each tread. Back on the garage floor, bounce the suspension a couple of times to settle, roll forward. Put the conduit behind the front tires, bend the end of a piece of welding rod 90-degrees and clamp one piece of rod so the end is at the spindle height and touching the scribed line. Repeat same on other side.

Move the conduit and rods to the front without disturbing the pointers. Lay it against the front of the tires and the toe in/out will be immediately visible. Adjust tie rods to get 1/16"-1/8" toe-in (front lines 1/16"-1/8" closer together than rear), go front-rear-front with your tool a couple of times to verify and you'll be as close as an alignment shop will get it.

jack vines

 

String line from the rear wheels

 

Here's my one man secret with minimally sized equipment. First as others have said, use both horizontal and vertical CL of your front tires. Then use a plumb bob so that way I can place a mark on the floor. It's surprising how well the tape measure behaves this way as compared to trying to keep it suspended horizontally in the air and trying to read the damn thing at both ends at the same time .

 

I use this Manbee toe in guage from the 30's-40's, it measures at 11" from the ground, notice it registers from the inside sidewall on one side,to the outside of the other. After any adjustments I always roll the car backwards a minimum of 20', then roll it forward the 20' and check it again.

 

O.K. Just to throw something out there for discussion , I've always used the "center of tread" . So when the FE shop hooks up their fixture to the wheel w/ the fancy laser machine , are they measuring toe at the wheel or is there compensation built into the machine to compensate for tire diameter ??
dave

 

My machine actually measures toe in degrees. It isn't measuring inches at the tread. But degrees of rotation. If the tire size is known then you could convert to inches


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They are measuring on a compensated for run out plane off the wheel rim. With the wheels in the straight ahead position the difference in track from wheel center to rim edge will not measurably effect the reading.

Whats most important when using inches is the diameter of the 2 measurements.

Here is a chart I made for converting from different diameters.

 

Hoop , you're way ahead of me on the chart , sorry , but is there a more graphic [pictures , drawing] explaining what the chart is telling us . [guess it finally happened... I've gotten too old to worry about looking stupid !!!!]
dave

 

Here ya go, two ways of looking at it sonny....

3/16 Toe at 22 inches front to back is equal to 5/16 at 36 inches.

If you have to measure below the center because the frame is in the way this chart could help you compensate.

If you have the spec in degrees then 1/2 degree at 29 inches is 1/8 inch or 2 1/6.

 

I took 2 pieces of 1/2 by 1/2 wood about 6 ft long. Put a point on either end, and made black marker marks in the middle.

Once I was sure I had the wheels straight and equal, I then lined the outter edges with the center forward tread. I compared front of the tire center tread to the read of the front tire center treat until I got it right where I wanted it..... I then took it to a buddys shop, put it on his Front end machine, and it was dead nuts on....

 

OOOO. K. Now I get it .. thanks hoop [ been a long tine since anyone called me "sonny"

dave

 

I don't have any fancy tools, but I made up a tool years ago to check. I go from sidewall to sidewall on the tires inside. I have a piece of 1/2" EMT tubing that I welded a rod on one end that is about 10" long to contact the inside on one end. Then the other end I welded a rod to a piece of pipe that slides over the 1/2" EMT and has a setscrew to tighten it. I simply slip it under the car and check width at axle center line on the tire, then move it to 180 degrees and check again. Adjust until the front side has the toe in I want.
I've gotten where I don't bother having it double checked at an alignment place on straight axle cars, as they make either no adjustment, or very slight adjustment after my setting.

 

Just kiddin, I feel young!!!

 

The way I was taught 35-40 years ago was to chalk and scribe the tire as described in post #25.
Then use a plumb bob as in post #18 to mark the floor. Hold the string for the plumb bob on the scribed line on the tire at spindle height.
Mark the floor in front and back of each front tire. It's helpful to place pieces of masking or duct tape on the floor so you can make your plumb lines on the tape rather than the concrete. It's a lot easier to see the lines on the tape than the floor.
Use a tape measure to measure between each set of marks.
You can adjust the toe very accurately using this method.

 

Ok, I have plenty to go on now. I plan on having the front end aligned but the guy I use ( and trust ) shuts his shop down for the month of July. So I'm trying to get the toe at a point where it won't ruin the tires if I drive it a little before I get it aligned. What I've done is to use the tire tread centerline and set the total toe at about 1/8 inch positive . It took a while because it was trial and error in the sense that after each adjustment I set the car down , rolled it back and forth a bit then rechecked. I fell pretty confident that its at a point where I won't ruin the tires. But then ...they're only tires >

Thanks to all for the help .