A little guide to rear wheel alignment

[Ola]

Adjusting the chain, changing the rear wheel or other work entails wheel alignment. The common tip is usually to just sight with your eye but if your bike is like mine that is pretty much impossible. First off, the rear wheel is wider so it obscures the front. And looking to alternating sides might help you spot a huge misalignment, but it's not going to be very accurate.

But worry not, aligning properly is easy, rewarding and fun for the whole family. You need:

1. A centrestand, pit stand or other way of setting the bike upright.
2. A piece of string, 15-20 feet long. Only thing I found at the hardware store was expensive mason's string but it was excellent.
3. Two slightly heavy but easily movable things, i.e. anchors. Axle stands are perfect, a big bottle of water would work too.
4. Duct tape or similar.
5. A tape measure or caliper - but your eyeball is what will do most of the measuring!

Keep in mind you need to be able to stretch that string between the wheels, some centrestands interfere with that.

There's two parts to the process: Checking the alignment and adjusting the alignment. Checking is actually a bit trickier than adjusting, you'll see why.

This is how we set it up:



The string in blue goes in one piece from anchor to anchor around the rear wheel. Duct tape the loop to your rear wheel, making sure that it's at an height where the string can reach the front wheel uninterrupted and that it's tied to your anchors at the same height.

Now you get to play the back and forth game. To figure out how the wheel is aligned we want to make each side of the string loop run perfectly parallel to the rear wheel and then extend this line forward, exaggerating the angle which makes it easier to compare to the front wheel.

Pull each line taut by moving its anchor, the mason's string was excellent for this, thin and strong. The string is already taut against the rear lip of the rear wheel due to the loop. What you now want to do is make it barely touch the front lip but not so taut that it bends. Thusly:



It takes a bit of walking back and forth, moving the anchor a tiny bit, pulling and pushing a little on the string and so on. You can check that the lines are parallel by measuring the distance between them. It should be equal to the width of the rear wheel, so get a good measurement on that.

[Ola]

A bit of fiddling and you'll suddenly get a very clear picture of the situation.



This was adjusted as best I could by the swingarm markings and eyesight. The actual markings on the swingarm were good, but the notches on the moving bits were wide and scraped up, so it wasn't easy to say where the actual line was. Adjusted as best I could - but not very good then as we can see.

The front wheel needs to point straight of course, just set it as best you can by eye. Once you stare down the strings it doesn't have to be super straight as you are sighting against its centre point and not against its angle.

Now we move on to the adjusting but. What you do is simply move the anchors until the lines are as straight as possible and that the distance between them is equal to the rear wheel width.

Like so:




Then walk back to the rear end. You will now see that the string isn't parallel with the wheel anymore, one line will be slightly too loose and one will be too taught, like the ones with the red Xes above.



Now you can simply tune the adjustment screws until the wheel lines up with the string. It's very easy to do by eye and suddenly you realize how little movement on the screw is needed to alter the angle quite a bit. I was just using fingers and it was almost like trying to get that radio station tuned perfectly. Keep in mind that this adjustment (or your clumsiness) alters chain tension, so you might need to readjust that and then readjust alignment again.

Once you are happy, check your swingarm markings for accuracy. You can now make new marks with a center punch or something so you know you have accurate readings.

I found my bike tracking truer, but there's still an unresolved issue. It wants to lean left a bit when I let go of the bars. I think my forks might be sitting slightly askew in the tree, I'll give that a try some other time.

[toolman]

good method for setting up the rear weel alighnment . i have been doing the same thing for years and it works great. thanks for sharing it with all us gsers
.....toolman

[TeamDar]

That is a good method. There is a much easier method. This is borrowed from the talented chassis builder, Puppet's web site.

"The best way I have found to align the rear wheel is to snap a chalk line on the ground about 30 ft. long. Walk the bike along keeping the front wheel on the line, at the end check the rear wheel to see if it's centered on your line. If it's not, adjust your rear wheel and do it again. Mark the axle blocks and measure from this point."

Thanks Puppet,
Sounds like a plan. Dar

[81gs1100]

chain...

An easy way I have done it is to get it as close as you can and while the rear tire is off the ground spin the wheel forward and then inspect the chain and how it lays on the sprocket. You should be able to see light on both sides of the sprocket through the chain.

| (=) | good

|(=) | bad

| (=)| also bad

it is so much easier then draging a clothesline out and fiddling around for an hour setting everything up.