offset in the front and rear wheel alignment

[evileric]

Hi all from sunny South Africa,

It is so nice to be on the forum again. Over the December break, I gave one of my 78e's a thorough service and check. One of these checks was the swing arm alignment (which I have never done on this bike). I have done it on my other 78e and found it out from factory, and resetting it improved the straight line stability of the bike.

But when I did the check this time, I took it one step further and then measured the alignment between the front and rear wheels. I found that the front wheel runs 11mm offset to the left compared to the back wheel. This bike was never dropped or in any accidents - it is also still 100% standard. This bike runs straight and its high speed stability is good. The only reason I can think for this, is to counteract the anti-clockwise torque action of the engine around the drive shaft. I am still busy rebuilding my other 78e (the 3rd time since new), and could not compare the two.

Has anyone out there measured this before, and found the same / something else??

Best regards,
Evileric

78 E YAMAHA XS 11 (times two)
92 N SUZUKI GSXR
06 K SUZUKI GSF Bandit

[Pat Kelly]

The torque of the engine is to the front, not the side.
The only torque action from the driveline is the torque-tube (hollow tube the driveshaft is in, left arm of the swingarm) raises the swingarm pivot. I guess this raising of the left side of the swingarm could cause the bottom of the rear wheel to twist to the left. But as beefy as the swingarm is at the pivot area I kind of doubt it.
I haven't made an alignment board for my XS as I know I can't adjust it like with a chain-driven bike. I used to do this with my Honda. Get a board that is at least as long as the overall length of the bike, front of front tire to rear of rear tire. Measure the actual with of the widest part of each tire (don't go by manufacturer specs). Draw a centerline down the length of the board and mark one half the with of the front tire on one end and half the width of the rear tire on the other. Rest the board against the tires and mark where the tires touch, both front and back of each tire. Cut-out the areas to fit around the tires (and centerstand). Place it against the tires (elevated 3-4" off the ground) to check alignment. The board should touch the front and rear of both tires (4 contact spots). On a chain-drive bike the back wheel is adjustable, not so on ours.

[Mathh]

I have aligned several bikes but only when switching to different or larger wheels. As the rear swingarm of the XS can be adjusted left to right by means of the bolts under the shiny covers you can already predict that most bikes of this age have the wheels misaligned, as most of them probably have been apart once in their lives. Factory tolerances of bikes this age are HUGE. I've seen and riden V-Maxes, also the later ones, with wheel offset up to 17 mm. As a matter of fact, fitting wider wheels to the V-Max is THE solution of getting both wheels in line. To be honest I did not notice the difference.
Until a couple of years ago I have ridden my turbo for years with offset larger wheels and have found no problem whatsoever. The stock XS (well set up) is also very stable in a straight line AND in corners.
I do not know how to eliminate 11mm on a stock bike without making major mods to the frame? How are you planning on doing that?

[Pat Kelly]

Eric,
Are the wheels both straight up and down? If one is canted off-center that could cause or be an indicator of a problem.

[pggg]

Use the board trick or stringline on a flat surface with felt-tip pen, 10mm or so is pretty much insignificant really but the pivot points still have about 6mm or so of sideways adjustment, chances are it's the front end thats slightly 'out'

[50gary]

Funny, I've asked this very question when constructing my project XS650 bike. I changed the swingarm and cut the entire front half of the frame off so I wanted to know this very important answer. I called "Traxxion Dynamics" (all they do is suspensions) the answer from them (on front to rear centerline alignment) was 1/2mm that's not a typo it's .5mm. I spent a great deal of time and effort to get my chassis as near perfect as I could. once it's welded ...
I would think 11 mm to be quite a bit too much.
"GMD Computrack" does Laser measurement for not too much money, if there's one near you it may be money well spent?
Cheers, 50gary

[pggg]

A $30 lazer gizmo from hardware shops should do the same, on a chain bike if the front/rear sprockets are more than a couple of mm's out, the front sprocket starts to wear on one side, but 5mm variation between front wheel and back wheel(the width of 3 letters on this page) - isn't really an issue on a motorbike, but the closer the better of course.

[evileric]

Hi guys,

Gee, this is a interesting one. Firstly thank you for all the replies. You guys gave me some good ideas what to do to check it more accurately. Basically this is only for interest sake as the straight-line stability of the bike is good, but I did find the 11mm quite odd - hence the thread.

Sofar it seems no-one has an idea, if the bike should actually have a 'built-in' mis-alignment (to possibly counteract the torquing effect), or if the bike is indeed intended to be aligned. Has anyone measured the alignment / mis-alignment of their XS 11's, with the swingarm set in the center of the frame (as per manual)?

What I do deduct is that the general consensus seems to be that the XS 1100 (like chain driven bikes) was intended to be in-line. If so, I tend to agree, the front end are the most likely cause, as the head angle could only be out by less than a degree and it will amount to most of the 11mm over the length of the forks, with the rest made up of production tolerancing and / or other causes.

The engineering laser is a good idea, will get myself one.

Regards,
Evileric

[50gary]

I'm not buying the torque steer thing. Mototrcycles are single track vehicles and as such need the wheels in centerline with each other. If you car was out of line by that much we'd call it "dogtracking" and work to get it fixed? 11mm over a short distand of 60.8" wheelbase is a lot, again if that where extended to the length of a car wheelbase it'd be an inch or more? Having said that I'm afraid in 1978 quality control was not t the top of the list. I have not checked my 1978e but probably should. I'm not trying to beat this to death but just some thoughts here.
Cheers, 50gary

[pggg]

Ev and Gar, I did stringline a couple of XS11's, they were dead on within a mm or two 'as is'

[xschop]

dead on

I am glad someone chimed in. I was looking at this thread confused for a second (or two). I did my swingarm under the assumption the Japs got the factory alignment correct. I figured the stock xs11 rear wheel centerline is 5 5/8 inch from the left S/A pivot point....

[evileric]

Mathh

Hi guys,

Again thanks for all the input (Pat Kelly, pggg, 50gary and Mathh). It seems I would need to ponder my next move. I am currently rebuilding my other 78e and will give that one very close attention on this subject.

To change the subject, Mathh - I have come across your bike (the turbo XS) somewhere else as well. It is wicked my man! You run wider (newer) rubber on it? How did you go about fitting another rim in the back, as that is what I would like to do on my other 78e. I got a Suzuki GSXR 750J rear rim for the job. It is 4.5 inch in width. Do you think it will work?

Evileric.