I only have a couple hundred miles on the roadster and the front tires are wearing rather quickly! Toe in is right on the money and caster is around 11* (yeah....a bit much). I you look close it looks like the top of the tire is out and the bottom in. When I put a framing square on it, it kinda verifies that. Top of tire..... Bottom of tire..... The outside of both tires are wearing significantly while the insides don't show much wear at all. The pic doesn't really do it justice, they're actually pretty bad and they're 14's so they ain't cheap! Any solutions to this other than buying new tires every couple of months?
With that much wear on few miles, I doubt that your toe-in can be correct. How are you checking it?...hopefully not with a ruler between the tire sidewalls, or going by measuring to grooves in the tread. > The massive low miles wear is not from that amount of camber. Bank on that. Also, I can't see how far out your scrub radius is, without a straight-on pic directly right in front of the king pin area. (the imaginary centerline of the king pin needs to intersect the pavement under the tread, not along side of the tread) Not talking about you in particular, but I'm amazed of seeing so many cars on here with scrub radius completely ignored during the build.
It does have the appearance of being a toe problem. When you run your hand along the tread are there sharp edges ?
I also support the idea of it being a toe issue. Initially after the build and first 2000 miles I saw a similar wear pattern. I had too much toe in.
Camber wear is too slow a rate for that much wear in so few miles. Theoretically. Can you feel scuff on the tire rubbing your hand back and for across the tread? Is the Ackerman correct, allowing toe-out on turns? Is the wear equal right and left tire? Looking at your first pic, it looks like the scrub radius is off. Looks like the centerline of the kingpin would hit way inside the tire's tread edge. But to answer your question, camber is changed by bending the axle as needed. We had light truck tooling to do that in our shop.
From the look of pic 2 it appears to have excessive toe out. The outer edges of the treads are higher than the inners.
OK, running my hand over the tires front to back, there are sharp edges. Back to front....not so much. It's been so long, I don't remember how I set the toe in but recently I had the car in a front end shop for another reason and I thought they said my toe in was 'right on the money'. Also, I was unaware of scrub radius. Someone kindly explain and please do so as if you were speaking to a 6-year old!
Take a tape measure and measure the front and back tires. I would use the second groove in the tires as the place to measure from and to. Do this on as same a plane or parallel as possibly. Compare the numbers. If toe out the front # will be greater. If the suspension components are old I would adjust to a little bit in in the front, say a 1/16th or an 1/8th of an Inch. https://en.wikipedia.org/wiki/Scrub_radius
Not saying it is right; but I have seen excessive scrub on rods not causing that much of a wear problem. Camber looks about normal for stock axle, if you don't find the toe out of whack, wonder if the 11 degrees inclination in combination with everything else has something to do with the problem. Are all four wheels aligned square? Nothing to do with your tire problem; but are the front brake hoses rubbing where they go thru the hole in your shock/headlight mounts?
This is not a good method. You are assuming the grooves are absolutely straight. Best way to measure toe on an old solid axle car (I was told this by an old-time front end shop owner who's family ran the place for over 6 decades) is to jack the tires up, spin the tire and draw a line with a sharp marker, set the car down, roll it backwards 8 inches, then forward 8 inches (to set the loose joints into a forward-motion position), then measure between the centerlines at the front and back of the tire. Don't trust any grooves in the tire.
All 4 wheels are aligned square and the brake hoses are securely mounted with plenty of clearance inside the shock/headlight mount holes. They don't come anywhere near touching. Thanks to all for the scrub radius explanation! Using my mickey mouse/eyeball method, it looks like I have about 2" of positive scrub radius. Would that cause the tire wear issues or should I have a shop check my toe in/out?
You are probably correct, but my method is only designed to establish an apx baseline and is not a precise measure. For that i prefer a decent alignment shop.
Scribing a very accurate line is important. The tool shown has been used since the early days. It is spring loaded to allow the needle to follow low spots on the tread. You could dream something up at home to try. Start the needle at the balding side of tread, where it won't jump into a groove. Get both tires scribed, eyeball the front tires to make sure it's pointed perfectly straight ahead, then have a helper measure to each line in front and on the back of each tire. This is super accurate if your lines are done precisely. Scribing for toe setting/checking is still done today on solid axle big rigs. .
You have too much positive camber (tire out at top) then with the looks too much toe in along with caster wear from all the positive caster when you turn corners. Older ford pick ups were bad about caster wear. If you brought it to my shop and to do it right, I'd drop camber down around 1/4° positive, toe in 1/16 to 1/8 and drop caster down around 7°. If your looking for a work around your only option is to back the toe off. Toe-in wears outside, toe-out wears inside. So you would be down to around 0 toe.
Back when I did alignments on big rigs we would jack up the axle and spray aluminum paint on the center tread before scribing. It provided a nice sharp scribe line to work with. I prefer a toe gauge in place of a tape measure for simplicity and the ability to work around obstructions. I feel it’s more accurate as well.
I used to bend them all the time when I was doing truck alignments. It was all done cold, restrain the axle, used a bottle jack to do the bending, took a little trial and error. The toe is the last thing to be adjusted.
For those who are not familiar with early fords camber spec from a 40s factory shop manual is 0 +1/-.5. Most pre 37 axles have a kpi of 7 degrees which works out to a positive camber reading with factory spindles. Most 37-48 axles have closer to 8 degrees kpi but some come across the bench closer to 7. I agree that looks like a toe issue not camber. Lots of early fords running around with positive camber and not burning the tires off.
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