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earl1412
Senior Member

101 Posts

Posted - 11/07/2016 :  06:33:59 AM  Show Profile  Reply with Quote
This may be nothing, but has anyone that's having rear inner tire cupping/ stairstepping find that the actual camber is off? I am having issues with 2 birds (2015MY) with Hendrickson rear axles with air ride. Both units show negative camber driverside of 0.04 degrees (OK) and passengerside negative camber of 0.44 to 0.46 degrees.(bent?)
Am I grasping at straws or do you think there is an issue here? I have 4 other buses that have similar mileage, but are wearing fine.
I asked my bird rep for any info on the numbers, and was told there isn't any available. I understand that these units operate mostly in turns, but there was good tread left on the outers (13/32"avg) and most of the inner tires with about 2" messed up with 31,000- 36,000 miles on them.
Thank you for your help,
earl

jeeptjken
Senior Member

147 Posts

Posted - 11/08/2016 :  03:45:48 AM  Show Profile  Reply with Quote
your not alone 5 of my 2015 birds are doing the same thing but all on the passenger side all 5 had to have drive tires at 20,000 miles

How did you get the gosinta in the whatchamacallit
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krmvcs
Advanced Member

362 Posts

Posted - 11/08/2016 :  07:26:05 AM  Show Profile  Reply with Quote
a couple years ago i got a few new Thomas HDX's with what i think is the same rear suspension as your BB. FROM THE FACTORY...the wheel seals were leaking and the rear wheel bearing adjustment, well, wasnt adjusted. id guess they were at about .010-.015. and the eccentric bushing came loose and changed the thrust angle. after replacing the stemco seals with nationals, i ended up taking the time to measure and adjust everything. no problems 60k-80k miles later. i didnt see the kind of wear that youre talking about but all this work was done at about 3000 miles. moral of the story, dont assume anything was done absolutely perfectly until youve measured and inspected it yourself.

-Ken-
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BigPapa
Advanced Member

215 Posts

Posted - 11/08/2016 :  07:33:00 AM  Show Profile  Visit BigPapa's Homepage  Reply with Quote
May not be related, but we had a customer that had a Dodge Cab & Chassis dump truck that they continually overloaded and it had tweaked the rear axle tubes in the differential enough to cause the rear tires to wear and it caused hub bearings to wear prematurely. He ended up buying a new axle and welding the tubes in the chunk.
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torque
Advanced Member

Canada
358 Posts

Posted - 11/08/2016 :  1:21:43 PM  Show Profile  Reply with Quote
We have a few BB and a few IC's like that. Tire guy say problem is with assembly of axles, not square when welds made. All about quantity not quality.
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earl1412
Senior Member

101 Posts

Posted - 11/08/2016 :  1:45:19 PM  Show Profile  Reply with Quote
Well, thank you for all of your input. I don't feel alone in thinking something is amiss with quality control
I have to chalk it up to the nature of the game.
Take care,
earl
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57fan
Senior Member

United States
148 Posts

Posted - 11/09/2016 :  8:48:34 PM  Show Profile  Reply with Quote
What and how are you measuring the Camber with? Camber is non adjustable on a Large school bus as far as I have ever seen. We have all wheel alignments on our buses and have found some that have the rear axle so far out of alignment that they had to add 3/4" shims on one side or the other. (crab walking mostly IC buses). You can change Caster by shimming the axle housing at the spring perch but not always easy to do. We have a mobile alignment company do the work.

We have had cupping issues on rear tires when I first started working at my current employer. We have since began to rotate rear tires every 10K miles and have a different tread pattern and the problem has gone away. I think the fact that tires were only rotated when they wore out was the main issue. Tires will often wear differently form outer to inner tire due to the crown in the road and the fact that School buses make lots of starts, stops and turns.

Lead, Follow or get out of the way! Thomas Paine
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Fastback
Top Member

1500 Posts

Posted - 11/10/2016 :  04:53:20 AM  Show Profile  Reply with Quote
Has anyone checked the wheel bearing adjustment on the rear axles that the tires are cupping and/or the camber has been determined to be off?

Why yes, the ORIGinal CHARGER is a Fastback

Edited by - Fastback on 11/10/2016 05:11:50 AM
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torque
Advanced Member

Canada
358 Posts

Posted - 11/10/2016 :  05:25:17 AM  Show Profile  Reply with Quote
We checked in the beginning but always found bearing adjustment to be OK. Then we suspected the tires and that is when our tire salesman mention it has been a problem on some vehicles due to the axles not being welded true when manufactured.
And have since noticed, the problem does follow the same buses.
But yes, you should check bearing adjustment, if recaps make sure the tires are the same outer diameter. If you are having a problem, don't assume, check all possible causes.
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BJ Henderson
Advanced Member

USA
280 Posts

Posted - 11/13/2016 :  4:46:38 PM  Show Profile  Send BJ Henderson an AOL message  Reply with Quote
What about the thrust alignment on the front to rear axles?

CMTT,CMAT,CMBT
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earl1412
Senior Member

101 Posts

Posted - 11/16/2016 :  08:41:56 AM  Show Profile  Reply with Quote
quote:
Originally posted by Fastback

Has anyone checked the wheel bearing adjustment on the rear axles that the tires are cupping and/or the camber has been determined to be off?


Yes, and I have found that on the two units I am having issues with, the opposite side is loose.
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earl1412
Senior Member

101 Posts

Posted - 11/16/2016 :  08:48:56 AM  Show Profile  Reply with Quote
quote:
Originally posted by 57fan

What and how are you measuring the Camber with? Camber is non adjustable on a Large school bus as far as I have ever seen. We have all wheel alignments on our buses and have found some that have the rear axle so far out of alignment that they had to add 3/4" shims on one side or the other. (crab walking mostly IC buses). You can change Caster by shimming the axle housing at the spring perch but not always easy to do. We have a mobile alignment company do the work.

We have had cupping issues on rear tires when I first started working at my current employer. We have since began to rotate rear tires every 10K miles and have a different tread pattern and the problem has gone away. I think the fact that tires were only rotated when they wore out was the main issue. Tires will often wear differently form outer to inner tire due to the crown in the road and the fact that School buses make lots of starts, stops and turns.


We have a local truck shop that is using a less than 1 year old system, so I am at their mercy as for the precision.
Unfortunately, I am by myself with 33 buses, and can only do what I can in regards to rotating tires. They only last 30,000 miles or so, which is about 2 years of use here.
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earl1412
Senior Member

101 Posts

Posted - 11/16/2016 :  09:09:12 AM  Show Profile  Reply with Quote
quote:
Originally posted by BJ Henderson

What about the thrust alignment on the front to rear axles?


On the bus that's the most out on chamber, when we received it in 2014, it had a thrust angle of 0.05 deg, with rear axle right side camber of -0.2deg.
When it was in last month the figures were: thrust 0.02deg, rear axle right -0.46deg camber.
I just am wondering if this is common for rear axles to degrade like this? Someday, I will pull the wheels/axle shafts and check into the bearings, but as this is a pretty new unit still under warranty, I will put it lower on the list of things to worry about
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BJ Henderson
Advanced Member

USA
280 Posts

Posted - 11/19/2016 :  12:39:49 AM  Show Profile  Send BJ Henderson an AOL message  Reply with Quote
You have a bushing problem where it connects to the suspension, something is causing this camber problem, if not the axle tubes bent. If the camber problem is most extreme on the right, then I would look at bushings, where it connects to the frame, the axle. The lean angle while going down the road is more pronounced on the right side, as we all know.

I have as of yet to see an axle come wrong off the assembly line, but I have enough sense to know
I haven't seen it all!

CMTT,CMAT,CMBT
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Tb4020
Senior Member

United States
82 Posts

Posted - 11/26/2016 :  06:16:20 AM  Show Profile  Reply with Quote
Might be a dumb question but, are you running on pavement or gravel? We have the same issue with inside rear dual wear but on everything. Following them down the narrow roads with high crowns you can sometimes see daylight under the outside wheels. I always tried to switch the inners and outers when doing brake work or saving the outs till I had a set of four for spares and lesser used units michelins seemed to be the worst. The tires all were open shouldered which were cheaper and fit our rural roads turn arounds and snowfalls the best.
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