Ideas on checking rear wheel alignment?

[Vulcan Bill]

This came up in another thread and I thought I would throw it out there in an attempt to get some ideas. Occasionally I get the overwhelming feeling my '05 1600 is not tracking straight. It feels like the rear end is pushing slightly to the right I have even consider putting a sheet metal or aluminum spacer in between the final drive and swingarm housing connection to bump the wheel slightly CCW (looking down from the top).
The first thing to do would be to take some sort of measurement to confirm the wheel is not straight.
Anybody have any ideas on how a guy might go about doing this?

BTW...I've noticed this long before I did the Harley front wheel mod.

[dshelly]

So are you saying that you think the top of the wheel is out of alignment vetically with the bottom ? Or like the camber on a car?

[Vulcan Bill]

No. Front to back. I was giving your pole idea (different thread) some thought. I could rig up one of those easy with some 1/2 inch conduit and a piece of all thread. Next tire change I may just do dat.

[redjay]

With the handlebars in the straight ahead position get a long straight edge and hold it against the rear tire (front to back). Get another person to measure from the straight edge to the front tire. Do the same thing on the other side of the bike. Measurement should be the same.

[Vulcan Bill]

Originally Posted by Mongo PHUMC

I saw a guy do it with a string one time on a sport bike. He was very knowledgeable about suspensions so I doubt he would do it this way if it was half ass. Not sure if the vulcan would be the same- the swing arm shaft would have to be even on both sides (not offset) and there can't be anything get in the path of the string. Bear with me because I may not remember everything correctly:

He started by measuring the tread across the tire then divided by 2 to get the center line of the tire. He marked the center with a marker. He then positioned the mark so it was 90 degrees from the ground toward the rear (you could see the mark looking at the back of the bike if the fender wasn't on). He then taped a piece of string to the tire and pulled it tight to the center line of the swing arm pivot shaft. He would mark the string then pull it to the side and measure the length from the center line (this is why he used the string- he said it was easier to measure a string pulled straight out to the side then trying to measure across a rounded tread). Then repeat for the other side.

(This copied from another thread)

[cnc]

Originally Posted by Vulcan Bill

(This copied from another thread)

With regard to what you copied from the other thread. Interesting but how did he determine if the front wheel was positioned dead straight? If it was off even by a few degrees, it would make the measurement with the string useless.

A long straight edge might work but if the front and rear tires are of different widths it also may induce some error.

Maybe two straight edges, one on each side?

[redjay]

Different width tires front and back should make no difference when using a straight edge.
It is the measurement to the front tire from the straight edge you are interested in.

[cnc]

Originally Posted by redjay

Different width tires front and back should make no difference when using a straight edge.
It is the measurement to the front tire from the straight edge you are interested in.

I disagree, put the straight edge and lay it parallel to the rear tire, if the front wheel is turned even one degree from straight ahead, your reading will be off and make the rear wheel appear out of line. I'm thinking with one down each side, measurement on both sides will confirm if any misalignment is the result of the rear wheel or the front wheel slightly turned.

[vulcanscott]

I would think something more like finding two points on each side of the frame cradle around the rear mounts and measure to the center of the rear axle on each side .Should tell You if the rear wheel is tracking with Bike .Just a thought .

[ringadingh]

I'd check for sideplay in the swingarm, mine had about a 1/8" gap which I shimmed to make it stop moving back and forth.

[Vulcan Bill]

Originally Posted by cnc

With regard to what you copied from the other thread. Interesting but how did he determine if the front wheel was positioned dead straight? If it was off even by a few degrees, it would make the measurement with the string useless.

A long straight edge might work but if the front and rear tires are of different widths it also may induce some error.

Maybe two straight edges, one on each side?

I thought the same. It would be very difficult to get an accurate measurement using this technique. It might be better to have the bike up straight, use a plumb bob to make a center mark on ground centered on the middle of the radiator, then placing the straight edge against the rear tire measure to that mark from the straight edge from each side.
But how do you know the bike is perfectly straight?

[Vulcan Bill]

Originally Posted by ringadingh

I'd check for sideplay in the swingarm, mine had about a 1/8" gap which I shimmed to make it stop moving back and forth.

It has been 24K since the last swingarm service. I intend to grease the bearings again my next tire change and will check it again.

[VulcanE]

I know on Harley's (the one my friend rides anyway, an Electra Glide Classic) there is an adjustment to pivot the engine in the frame to make the bike track straight, something to do with a V-twin's centrifugal force, sorta like a gyro.
I have 2 final drives, the black one that came on the bike, and the polished aluminum one off a Classic. Which ever one I use, everything is the same as far as the feel of the bike, and the way it tracks. Both of the final drives do have "shims" that fit between the final drive and the drive shaft tube, and they are different between the two. I'm sure there is a "number" from the face of the final drive where it mates to the drive shaft tube, and the center-line of the hole the axle goes thru, and those shims make it hit that "number".
IMHO though, the only way to check what your wanting to check, would be like the method Dave mentioned, a way to measure from the center of the pivot rod, to the center of the axle on both sides, and that is assuming the pivot pin of the swing arm is perpendicular to the tracking line.

[dshelly]

For wheel alignment on a car they make digital measuring devices that attach to the wheels. Wonder if there is such a thing for motorcycles?

On my old chain drive bikes which have a bolt that runs clear through the swingarm, alignment is easy to check with the method i mentioned earlier. Not sure how you would do that on the shaft drive bikes.

[cnc]

Originally Posted by Vulcan Bill

I thought the same. It would be very difficult to get an accurate measurement using this technique. It might be better to have the bike up straight, use a plumb bob to make a center mark on ground centered on the middle of the radiator, then placing the straight edge against the rear tire measure to that mark from the straight edge from each side.
But how do you know the bike is perfectly straight?

Bill you got me thinking about this more than I should.
I'm thinking a laser level.might be useful, not the short little kind, I have one that is about 18in long. If the bike is dead upright and the front wheel were removed then this might work well. Position the bike facing a wall, actually the further back the better as any misalignment will show more the further away. Maybe 10 feet.
If you could find and mark two points under the frame that are dead center, rad and swing arm area, you could lay the straight edge of the level along this line with the laser on. Have a helper mark the exact laser spot on the wall with a marker. Draw a level line horizontally about a foot in each direction where this mark is. Next lay the level along one side of the rear tire bringing the level up or down till the laser rests on this horizontal line, again mark the spot. Next lay the level along the other side of the tire bringing the laser up or down to rest on the line, mark that spot.
You now have 3 marks along a horizontal line, measure the distance between each outer mark to the center mark and you should be able to see any mid alignment and which way to go to correct.