Checking Frame Alignment

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I have just taken my rear mudguard of to clean and paint it and discovered that the rear wheel sits about an inch closer to the chain side, i drew a chalk line between the front and back wheel and it is 1" closer at the front compared to the back. this could just be tire width diferences i dont know but i sure do know that the wheel is sitting to one side. Is there anyway to check the frame with out dismantling the whole bike. Or could the tailsection just be bent from a small drop?

Here are some photos so you can see what i mean.
http://boganpages.burnoutworld.com/gall ... d/P1020592
http://boganpages.burnoutworld.com/gall ... d/P1020593
http://boganpages.burnoutworld.com/gall ... d/P1020594
http://boganpages.burnoutworld.com/gall ... d/P1020595
 
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I am sure the problem is not with the frame. The Commando is meant to have it's rim offset 3/16 to the right in relation to the hub (Norton Twin restoration by Roy Bacon P.231), many people unknowingly build these centrally when putting on a new rim or spokes. Additionally In the photos your wheel doesn't look as though it is adjusted evenly in the rear swing arm fork. Have you tried aligning both wheels with a long straight plank of wood?
 

Ron L

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Could be just the tailsection. These things are pretty weak. They are only designed to hold the fender and taillight. Looking at the bent brake pedal it seems that the bike took a pretty good hit from the left side at some time. I would try laying a carpenter's square across the top of the frame parallel to the plate at the end of the main frame tube. You should be able to see the bend if it is there.

From the pictures the front of the wheel appears to be centered, but the rear is not, also indicating the loop is bent.
 
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If you run a straight edge down the centre of the back bone to the rear loop then the centre of the rear loop should coincide with the centre of the backbone. In the photos the rear wheel does not look in line with this backbone.
 
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my eyes may be crooked, but it looks like the axle is further back on one side of the swingarm, or the wheel itself is not in good shape. I see nothing with the frame itself. Pictures can lie, and eyes can be deceptive, but does the wheel have a wobble in it? Measure and check wheel alignments...remember, this bike has no markings on the swingarm, like Jap stuff...you have to measure and think about what you are doing when you adjust the chain and also.....the wheel looks like it is cocked to the right on that third/#29 photo....that can happen if an iso or two is broken inside and the whole motor and drivetrain leans to one side...or the swingarm is mighty bent..... :wink:
 
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The chain is perfectly straight with the sprocket on the G/B therefore the wheel must be straight in the swing arm im guesing. The wheels are in alignment as i have checked this. The iso's may be broken not sure the bike seems to handle ok.
 
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Re: chain adjust

Once I got a Norton rear wheel aligned, my technique to keep it straight was to count flats on the axle adjusters. Always move the chain side first, and only turn it a few flats at a time, before moving the other one. As long as you turn it equal flats, it will always stay in alignment unless you change axle parts. ( ignore the flats on the lock nuts )
 
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Black/gold,

Would it be possible to post another couple of photos? One from above, centered with the main backbone and including the triple clamp, backbone and rear loop and one from the side at the level of the backbone, including the whole backbone? No tank or seat, please. These might help with a further analysis.

The main backbone is the centerline of the frame and must be straight. It is relatively thin wall tubing and can get bent in a crash.

The rear loop appears out of alignmnt. It may just be the rear loop that is bent to the right but it should align with the backbone.

The engine cradle in a Commando is offset in the frame slightly and the swingarm is assymetrical to move the wheel back from this offset into alignment. As previously noted, both rims are also offset from the centerlines of the hubs. What you want is for the front and rear rims/tires to be in alignment with one another. This can be checked with a straightedge or straight board placed between the front and rear tires, both sides.

The first thing to look at though is whether your backbone is straight.
 
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