This may well be the problem, I’m going to try again today with a couple of slippery plates that are free to move in all directions. Thanks, I’ll report back …
It moves in an arc!
Brilliant! ( and something that would have never occurred to me).
I use a pair of vinyl floor tiles under each tire with some lubricant between them.
Years ago, I was using the Dunlop portable alignment set. It would go over the wire wheel knock offs and give castor readings. However, there was no alignment process to make sure it was straight with the axle. Take it off and put it back and you would get a different reading. I now use a Snap on Set where you have to rotate the wheel to make sure the mounting plate does not change to assure it is straight out or in alignment with the axle. I also have a pair of proper ball bearing alignment plates. This gives consistent readings on castor. From the looks of your setup, I do not see where you can verify if it is straight or if it compensates for any wheel run out. This might be your problem of inconsistency.
I’ve used the Longacre castor and camber gauge - part no 52-78260 for many years. It’s advantage on an E Type is that it’s relatively cheap (150 bucks) and very simple to use… It has a circular magnetic base that goes onto the end of the hub - you just have to remove the spinner. This allows you to measure with out worrying about wheel run out - so you can do this after setting and driving around to settle the suspension, and can then see what your running setting is.
Nice. I’ve got a different version of that. It reads the same as what the shop did when they did the alignment so I guess it’s accurate.
I’d really like to know how exactly to check the toe in. Camber and castor I can do with repeatable results. Toe, I’ve never been able to do.
My dad made up spinners with a magnetic plate on them: you’re welcome to them, for shipping!
John - parts list - 2 pieces of aluminum or steel angle 1-11/2" by 29" long with a slot cut in one side 1 inch from each end. 2 pieces of 4x4 fence post (31/2" by 31/2" finished) 12 inches long. 2 tape measures that are identical (Tape measures can have surprising variance between them). Put the wood blocks on the floor beside bottom of each wheel, and center the angle over it. The blocks purpose is to raise the angle above the tire bulge. Drop a tape end in each slot each side and measure the distance to the slot on the other side. You will probably need a helper to hold the side opposite you.
Lets suppose that the front reads 60 1/4 inches and the rear 60. You have 1/4 inch toe out. You will need to move the tie rod ends in a certain amount either one side or both sides. The amount you have to move them is 1/4 of the measured discrepancy or 1/16".on one tie rod, or if you are going to move both 1/32" each. Why 1/4? Well because the back moves out equally to the front moving in it’s always 1/2 the distance. You need to half that again because the end of the steering arm is one half (approx) of the radius of the tire, meaning a 1/32" movement of the tie rod results in the front of tire moving 1/16" in. .
To do this accurately - back off the nut behind the tie rod end and move it away from the tie rod 1/32" measured with a feeler gauge. rotate the arm to tighten the nut against the tie rod end… If you have too much toe in the opposite is done. Loosen the nut to finger tight against the tie rod end and rotate the steering arm out of the tie rod end measuring the distance of the nut with a feeler gauge.
My example will give you zero toe in - if you want some small toe in adjust my numbers to get it, always being aware of the rule of 1/4.
The tapes will pass cleanly under my car on the 4 x 4 blocks, but I don’t have the aluminum vertical pieces by the torsion bars. You may have to adjust the the height of the blocks to clear this - just remember you have to be high enough that the angle doesn’t rock on the tire bulge.
This all presupposes that your wheels are straight. If they are not you may have to make multiple measurements and work with the average.
Thanks Paul. What did your dad attach to them.
Thanks Terry. That’s a keeper. I’ve printed it out for my library of maintenance tips.
Edit: After reading the instructions I do have a few questions.
Looking at the picture I made below I understand each angle is to be 29" long with a slot cut in each end. Is the slot like “A” or “B” in my picture? That question drives the other question shown in my picture. How far apart are the two tape measures on each angle.
And just for my understanding, I know the length of the angle drives the measurements , but how did you arrive at 29".
Which is what I use. Glossy magazine under each front wheel.
FWIW I did a simple run through on how I do it on the other site.
http://forum.etypeuk.com/viewtopic.php?f=3&t=14168&p=116037&hilit=camber+castor#p115191
We had an elaborate (pre-electronics) alignment rack, with slide ramps, circles, and a magnetic hub tool, to measure caster (not castor!) and toe: we did so many Jags, he made the k pickoffs to fit them, with the magnetic plate machined to fit them.
Thanks Andrew. When I try to write about this I get hung up in describing how to set camber, when you need to lift the car off the ground to relieve the load on the top wishbone, before you remove it from the frame to add or remove shims. That part is easy, but you then have camber lock when you set the car down and getting rid of that involves a drive around the block. Incidentally castor is 1/2 of the camber change on wheel rotation through the 20 –25 degrees. I know this because the degree markings for castor on my gauge, which also measures camber, but has a separate dial for the castor are 1/2 as wide as the degree markings for the camber. I used to know why in theory it’s 1/2 as well but I’ve forgotten it. Maybe it will come back – maybe not.
pardon me gentleman for such a basic question, but is the is the following method valid to set caster within factory acceptable tolerance on our Jags ?
" Caster angle must be measured with the axle loaded, as in wheels on the ground or at normal height on jackstands.
You should use a square on the floor against the upper ball joint, then measure from the square to the center of both ball joints. Subtract the upper and lower measurement gives you the distance between a true perpendicular line. If you measure the vertical distance between the ball joints, then use trigonometry you can compute the angle "
After consideration I think I know the answer. Tire diameter, right?
Tony,. That’s correct if incomplete.
Caster is the side view inclination of the steering axis (from vertical). So only the fore/aft difference, and vertical difference between the ball joints, form 2 sides of a triangle.
Turns out hard to measure the centers of assembled joints esp. in loaded condition. So with special equipment, camber angle is measured at 2 different steer angles to calculate.
Think you meant to say “caster”.
No,. My point is that it is difficult and possibly inaccurate to measure caster directly (esp. in a repair shop paid by the job). So the difference in camber at different steering angles is used to calculate the caster angle.
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Tony I think that your method could be valid in theory, but would be very difficult to do accurately.