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front end alignment question

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5 months 2 weeks ago - 5 months 2 weeks ago #250387 by jon_d
A question for the brains trust.

The bus,  72 Bedford NJM  (SB5) beem axle has started wearing out the drivers front tyre - inside edge.  It's worn a significant amount of the edge and into the next row of tread.

There  was a little bit of wheel bearing play and the bearing has since been replaced. However the tyre is still wearing.
The wear has occurred in the last 600 ks.
The only thing I can spot is that the driver side body is about 1/2 inch lower. (ie a little spring sag)  Previously, the tyres have traveled 30,000ks with no wear.

From a visual perspective, everthing looks ok.  And I'm a bit puzzled.  Track straight.

Any ideas?    I'm wondering what are the symptoms of a 'failed' king pin and whether the king pin is stuffed.

thanks jd
 
Last edit: 5 months 2 weeks ago by jon_d.

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  • Swishy
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  • If U don't like my Driving .... well then get off the footpath ...... LOL
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5 months 2 weeks ago #250388 by Swishy
Replied by Swishy on topic front end alignment question
Here U go
try this on for size

LOL

 

Hope eye steerd U in the right direction

cya

OF ALL THE THINGS EYE MISS ................. EYE MISS MY MIND THE MOST

There's more WORTH in KENWORTH
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5 months 2 weeks ago - 5 months 2 weeks ago #250392 by 77louie400
King pin or bent axle would be my guess. Bent axle vertical no big problem a bloke came to my shed with a big Ute full of stuff and fixed it, bent horizontal no bloody idea probably the same although that bloke would be 100 years old now.
Like the bloke who came to my shed and fixed all the bottle jacks he would be 115 he was pretty old 35 years ago and that was all them years ago when there were blokes around that could fix stuff.
Last edit: 5 months 2 weeks ago by 77louie400.
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5 months 2 weeks ago - 5 months 2 weeks ago #250393 by V8Ian
Replied by V8Ian on topic front end alignment question
As the fellows above have already said, toe, bearings, king pins or the least likely (hopefully) bent axle.
Also bear in mind, once a wear pattern has started, it's all but impossible to prevent further uneven wear. 
Last edit: 5 months 2 weeks ago by V8Ian.
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5 months 2 weeks ago #250407 by Morris
Replied by Morris on topic front end alignment question
I am not a mechanic but over lunch today, I happened to be reading a VACC (Victorian Automobile Chamber of Commerce) newsletter from 1978 and came across an article about tyre wear.  It said the same as the previous writer said (it is a pain that we can no longer see the previous comment) Once a wear pattern has started it is almost impossible to correct it, even when you have corrected the fault that caused it.

I have my shoulder to the wheel,
my nose to the grindstone,
I've put my best foot forward,
I've put my back into it,
I'm gritting my teeth,

Now I find I can't do any work in this position!
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5 months 2 weeks ago - 5 months 2 weeks ago #250414 by jon_d
Replied by jon_d on topic front end alignment question
Thanks,

I'll going to have to find a flat empty car park and start doing some measurements.

The tyre's b$ggered.  Probably taken most of the inside edge off.   Michellin XZY too.
Last edit: 5 months 2 weeks ago by jon_d.

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5 months 2 weeks ago - 5 months 2 weeks ago #250419 by 77louie400
Another thing you need to keep in mind is the right hand spring pack was often set lower in the 70's and 80's to compensate for the large camber in the country roads, it made keeping it in line on the road a lot easier when most of the rural road had big cambers, not that it would make any difference to you Tyre wear but would be the reason for the right side being lower partially if it was a country school bus, things that were quite normal 40 years ago seem quite odd now on our pretty much wide flat roads were your Tyre is a meter of the edge.
Last edit: 5 months 2 weeks ago by 77louie400.
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5 months 2 weeks ago #250423 by jon_d
Replied by jon_d on topic front end alignment question
Thanks,   the spring packs were replaced about 2+ years ago.
I was aware of the camber allowance.

I can't quite get my head around this logic;   however,....

being a beam axle with king pins;  if the beam is straight and the king pins are good,   then,   (and assuming a flat surface)  isn't  the wheel camber controlled by the king pin angle?

And, the spring height and body position is irrelevant?  ie, the body height or angle has no mechanical bearing on the wheel camber.

Have I got that right?

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5 months 2 weeks ago #250426 by V8Ian
Replied by V8Ian on topic front end alignment question
There is supposed to be no discernible camber or castor movement in the kingpins, any camber adjustment is made by controlled bending of the axle, whilst castor is adjusted with wedges between the axle and spring.

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5 months 2 weeks ago #250429 by 77louie400
I agree with both posts, the setting of the spring packs for road camber firstly felt better on the road and probably steered better but nothing else other than stopping the steering pull to the low side maybe, with power steering we forget the 100 tricks to get the mongrels to feel like they were good to drive.
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