2 things it's not showing, neg camber or excess toe. If it were camber, it would wear across the tire not just the 2 inside treads. It's not toe, if it were toe you would have feathering across all the treads not just the the 2 inner treads. Sure you can bump up camber and it might seem to help some but it's not going to cure it. More masking it then curing it. I agree with above, tire scrub. See a lot of it with the tire and wheel combos set out side the ball joint/ king pin inclination. And as stated above you need to check your angles. Btw you can feel toe, run your hand against the face of the tire, if you feel feathering across each tread then your feeling toe, it's called knife edging on each tread and your pics show no knife edging.
The reason it is not wearing across the tire, only that second rib, is because of how bias tires wear...we discussed that already. If the camber is right, it will wear that second rib on both sides of the tire, if it's off, like his is, it will wear only one of them.
That is true on a radial tire and the amount of excess camber will usually put it's wear on one section of the tire. The Bias tires usually carry the weight on the second ribs and that rib wears even when the outside one doesn't wear that bad unless the camber is way to hell and gone off.. On the OP's car that the tire is on the neg camber is just enough to cause that rib to wear more than it's mate on the other side of the tire. The one I showed earlier that I have out here had even wear on both ribs and no sign of toe in or out wear. Just normal bias front tire wear on a tire that probably went a couple thousand miles past when it should have been rotated.
Won't this give you a bit of a false reading due to the bottom bulge being a bit wider because of the vehicle weight being on the tire? Assuming there is "really" 0º camber, the bulge at the bottom would tend to suggest some negative camber. Better to have the level cross the bulges at 1:00 and 7:00, and then again at 11:00 and 5:00, with the wheels pointed straight ahead.
You need 5 to 6 Deg of caster and 1/8 in toe in with a fwd motion load on the front end, eg park it down hill, could be this or sloppy kingpins. If the car has been towed with a chain on the front axle it could be bent, that'll cause it too.
Pist-n-Broke got it right in post #12...it is scrub radius.. at the least... most people have no clue when they build an ''axle car"...then add disc brakes that always shoves the imaginary line of the king pin that "should" be under the center of the tire contact...to a point inboard of the tire. it can't help but "scrub" the tires at turns! It would be hard to find a good looking front wheel "offset" that could fix that scrub radius issue on our types of visual wants when building a hotrod. another important thing is what he said about more things need to be checked other than "toe/caster/camber"....meaning Ackerman. Look in the damn charts for wheel alignment for "toe OUT at turns" !! ...Yes, you set toe to be "in" at dead center, but most people are clueless about the fact that it quickly turns to "toe OUT" as you begin to turn. Note that toe out at turns IS checking Ackermann. ...as well as comparing both sides during an alignment to see if one arm is bent for whatever reason like a crash. If the Ackermann is not correct for the wheelbase , you also will then "scrub" the tires in a turn. So, if your scrub radius is off, AND the Ackermann is off, then what can you expect for unusual bias wear? (Yes, bias "rib-type treads" like the tread style shown, do wear differently than a same size radial will show with the same build screw ups.
I checked the camber with better equipment than I had, and it’s 1.2 deg and 1.4 deg negative. Which puts it at 2.2 deg ang 2.4 deg from 1deg positive. I hadn’t really paid a lot of attention to the camber, and took for granted that a new axle would be correct. Going to replace the cast Super Bell with a forged axle this winter. It’s not severe enough to put any urgency on it since it took 14,000 miles to make a noticeable wear pattern.
I wonder if exact ackerman ( toe out when turning) is not extremely critical. Didn't 55_57 T birds use the same steer arms etc. as a 54 Ford full size passenger car? The pass cars had a longer wheelbase. Also 57_ 58 cars had 2 different wheelbases yet used the same steer arms. Did early Corvettes use complete front suspension from 53 54 ( again longer wheelbase) pass cars? I will appreciate some input on this. Greg
Short word No..I will look later but all I've read in technical manuals is that the Ackerman lines should intersect at the centerline of the vehicle at or near the centerline of the rear axle differential. Diagrams I have seen show a bit ahead..I think the ideal intersection point also includes castor, camber, and scrub.
I have a roadster that had very similar wear on bias ply front tires. As a result of front axle bottoming hard on a rough road I had between 1 & 2 degrees negative camber, 1/8 toe in at spindle height, 8 degrees caster. I bent the dropped axle to set the caster at 1/2 degree positive on left & right, replaced the tires. Tire wear looks perfect now. Incidentally with 8 degrees caster the front wheels need to be exactly straight ahead, maybe lined up with the rears, when setting camber. Otherwise you will get a false reading. Scrub radius does not cause this. Greg
I can tell by the grease cap on your rotor that they are volare or I like to call them 1975 dodge charger rotors, or raybestos 7032R so, IF you measure up from the king pin centre then out to the wheel face you will have exactly 5 inches your king pin to king pin being 46 gives you a 56'' wheel mount face to wheel mount face - not track If you lay the chevy version rotor that fits this disc brake kit, known as the 70-77 chevy rotor, or as I like to call it a 1975 monte-carlo rotor or a raybestos 5214R - if you lay them flat side by side and put a ruler across the wheel mounting face, the 5214R is 10mm or 3/8'' shallower than the 7032R so in a 46'' wide axle the wmf <> becomes 55 1/4 --------------------------------------------------------------- If you fit the so-cal finned caliper brake kit to your car, the distance from the top king pin centre over to the wheel mounting face is 4 inches, you come over a smidgers more than an inch per side. you will be 54'' your wear pattern might simply move outwards one inch per side if it is scrubbing. but you have quite a tall tyre, I am guessing 26 inches tall, on full lock it will hit the hair-pin. I bet just by half an inch, so you fit a 47'' wide axle, the so cal brakes, your wheel mounting face becomes 47 plus 8 55'' you are half an inch narrower than where you started! PLUS now your steering arms are farther outboard a half inch each side, your Ackermann triangle bisection point is farther rearward, which may change it for the better. fyi a so-cal finned kit on a stock 40 ford axle gives you exactly 57 1/4 inches on the wheel faces, alsmost exactly the same as the 57 1/4'' ford 8''
Had the exact same wear pattern on the front tires on my model A (I think I ran Firestone 6.70-15 up front). My theory was that there was some play in the steering/front suspension that made the wheels go from toe in to toe out when I was driving. The car drove fine both in low, and high speed, and when I measured everything static i seemed OK. I sold the car before I could verify this though.
I had Pos-a-traction tyres on the rear of my F100 that exhibited wear not unlike the one in the OP pictures. Front ones did the same but with the rears it can't have been alignment.
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