Alignment

[birdarchitect26]

I bought a bus in spring and have been converting it. Test drives fine except someone noticed while following that the bus drives caddywompus to the road lane. That got me looking and sure enough, the drive and tag axle are a different offsets to the chassis. See pics.

Anyone have an idea as to what this means? I don't really feel it while driving but I'm sure a long term wear issue is at hand.

Thanks,
J

[Oonrahnjay]

     Not my area of expertise, but the drive axle is dual wheel/tire on each side and the tag is single wheel/tire.  That makes the offset look different so you can't tell much by that.  But alignment between the two axles and also the steer wheel/tires is critical -- if it drives cattywhompus, something is wrong and you gotta get it fixed.

[bevans6]

What kind of bus is it?  Looks MCI'ish but I don't recognize the model with the conversion.  It looks like it has two sets of duals on the rear.


Brian

[luvrbus]

With the side radiator and duals on the tag it is a MCI 7 combo

[TomC]

Yes the tandems look like they are offset to the left. That is controlled by the cross strut typically on top of the axle. Maybe to short or to long. It is offset enough that I doubt you could shim. You'd probably have to get new cross struts made. But more importantly-how are they aligned with each other then aligned in relationship to the steers? Side to side isn't really that important. Good Luck, TomC

[birdarchitect26]

So the Bus is an MC7, has upgraded tag axle to duals, so 10 tires.

I have read that there is a rear alignment. I suppose you would adjust the cross-member the center. I have no idea. I was hoping someone would chime in with experience.

The bus seems to drive just fine, just doesn't drive straight in the lane, I'm sure that causes unneeded wear and might grab a curb on occasion. I'll have to buy some new tires and see what the show suggests. Maybe they have knowledge I don't, I'm sure they know more that I

[bevans6]

MCI rear suspensions that I know about, MC-8,9 and 5C, all have a four link drive axle and independent tag axles (if they have tags).  The four link has two top radius arms angle at around 45 degrees and locate on top of the differential.  They locate the drive axle both front and rear, and side to side.  The lower radius arms locate the axle front to rear.  None are adjustable at all, they do have rubber/urethane bushings.  The tags are on swing arms, adjustable for toe only as far as I can see.  So while a complete alignment checks the rear axle, and probably sets the toe on the tags, it can't adjust the side to side alignment of the axles with respect to the body.  If you have one side sticking out farther than the other side, I wonder if the brake drums are the same, and if the wheels are the same offset and width?  If I wanted to go further, my next step would be to pull the drive axle wheels off both sides and measure from the center of the rear axle between the radius arm mounts to the body on both sides, probably should be equal within 1/2".

[luvrbus]

That bus has the same rear setup as the 4501 GM Scenicruiser maybe those guys know how to align one 

[Jim Eh.]

For a quick (albeit not 100% accurate) check is to place a long straight edge along the outsides of the drive tires on each side halfway up. If they are aligned parallel to each other the amount of offset should be identical from side to side (just a mirror image from one another) meaning all the gaps from the straight edge to the tires should be identical. This is only a starting point and a check to see if the two rear axles are running parallel. It does not tell you if the axles are running 90 degrees to the center of the steer axle tho.

[Bus Lurker]

Bevans6 may be on to something regarding the radius arms which are also known as radius rods.  There are threads at the end or the rods/arms with a clamp holding them.  It could be the threads on the rods/arms have stripped or the clamps have loosened thus affecting the alignment. That could cause the "sidewinding."   

[chessie4905]

You could give Luke a call. Last time I was there, he had a Sceni-cruiser in his shop.

[kyle4501]

Nice looking coach!  And, yes it has a Scenicruiser drive train - engine to axles to radiator & fan drive.
Brian is right on about checking the axles - I'd measure to the hub to start before the trouble of removing wheels.
Inspect the rubber bushings - they are the most likely reason things aren't in the proper location.

If the rubber bushings are worn out -- they are difficult to get - IF you can even find them.

Probably having some made out of polyurethane is your best solution.
There used to be some places that would cast replacement bushings in place. Maybe you can find one of those places.

(I sent you an email - hopefully you will be able to open the .xps file)

[Emcemv]

Interesting thread.  I also have a MC7 Combo, it's a 73. The previous owner had the same problem.  The fix was actually some very long threaded rods and brackets used to pull the trailing axle in line. I was not involved in the fix so don't really have all the details and the PO is now passed away. I could possibly take some photos.

Interesting that 2 combos have this problem, wonder if anyone else has seen it. ?

[birdarchitect26]

Good morning,

Thanks for the replies fellas!

Kyle, I got your email, much appreciated! I'll be going through those radius rods as my next adventure! I have access to a decent shop, so maybe I'll make up some bushings using some high cycle poly.

Emcemv, I think you are on to a point I haven't heard before. This gives me some motive to crawl under there and try to find these threaded rods, that has to be one hell of an ACME thread. That also makes a lot of sense! The wheels seem to otherwise be the same offset. They also seem to see pushed out the same distance and the passenger side is inset, so the entire rear seems to be pushed driver side.

In lieu of this exiting new info, I will get under there and post up some more pictures explaining what I have found!

[Emcemv]

The fix I have with the threaded rods and brackets is not OEM, it was added by the PO to correct the problem.  If I remember correctly, it caused a tire wear problem as well on the trailing axle.

Bruce