Strange tyre wear - please help

Lots to think about here and some pretty good advice

I believe that most left and right chassis rails are not a mirror image
So even measuring off the chassis rails is probably as useful as measuring off the body

I would check that someone hasnt had the springs out for what ever reason and put one back the wrong way around

So measure from the center bolts to the center of the spring eye

40 mm is a fair way out so maybe worth a look

Also could measure from the center bolt on the front axle to the center bolt on the rear axle to check if a axle is bent

Paul

All Coach's & most Bus's these days Don't have a Chassis & are Monocoque Construction.
Having said That Mammoths Suggestion of the Plumb Bobs & String Lines to ensure It's all nice & Square would be a Great place to Start. In My opinion..

The 40mm can be "floating" about on the spring movement. Flat springs will shift an axle that far. Just look at the shackle and imagine it being horizontal.
The spring goes flat and the axle moves back.

Cracked spring? Flat spring? Look at gaps between rim (not tyre) and body components. Spring shackle angles or gaps between stops etc.

Also, ensure your reference points (the dots on the diagram) are the same distances from each other. You need to find independent and square reference/datum points.



Laser points help to get the reference point clear of the body work. www.aliexpress.com/item/1005004027114852.html ? allow you to mount the sight and get parallel.
(I use them to set the toe. A degree at the wheel is a measurable 2 feet at the end of the driveway.)




BTW, I spent years looking at the front of the bus measuring things trying to work out why it had a 35mm lean. Then the penny dropped. The bumper bracket was bent upwards.


Also, another thought. measure the distance between the eyes of each spring. Each end should be the same.

Plumb bob, flat concrete floor and a marker is a great start. Measuring distances between the eyes of the springs and see they match the oppositie the side.
For some reason I thought that some leaf springs are longer on one end to the other, ie centre pin not in the middle of the overall length hence making a front and back dirction of a spring. Flat springs or bad shackle bushes will cause your problem and can be seen easily when they are bad as the shackle is siting way forward or back from a normal position.

For some reason I thought that some leaf springs are longer on one end to the other, ie centre pin not in the middle of the overall length hence making a front and back dirction of a spring.

Yes, My bus front springs are. Less latteral (?) movement in the wheels/axles when the spring flattens. Akin to bump steer.

Thanks a lot guys
I'll have to clean the shed out and get her in on the concrete and do some more measuring.
When I did the last measurements I measured from the grease nipple on the spring hanger to the front of the axle.
Lots more measuring and head scratching to go. Will definitely look at getting some professional help but just not possible at the moment.
I really appreciate your thoughts and assistance
Regards
Ash

Hi PaulFH
Whose business are you referring to?
Cheers
Ash

Hi Jon_D
I'm not getting my head around what you mean.
Could you perhaps include a diagram?
Cheers
Ash

Hi Mammoth
It's a single drive
Cheers
Ash

The Truck Whisperer, Ken Dennis.
Based at Benalla, travels to other states.
Corrects power steering system faults, even in quite new trucks. Shows up in uneven steer tyre wear, wandering, tram tracking etc, and dropping off bad road edges.
Might not be your answer, but worth watching his you tube posts and listening to what the drivers say. Best wishes, Paul.