Rear wheel alignment

[SRTie4k]

Always kind of wondered, will a rear wheel track itself straight? Just replaced the chain and sprockets on my bike, and adjusted the rear axle assembly so that they look like they're on the same hash mark on either side of the swingarm, then snugged the bolts up. Took a 30 mile ride and noticed that the right side is no longer snug against the adjuster bolt anymore. Axle nut is torqued to spec, chain slack is good, nothing is loose. Should I just snug the adjuster bolt back up to the axle block and forget it?

[Paul_E_D]

Are the marks still lined up the same on both sides? if so, sung up the adjuster bolt. It is common for the axle to twist while torqueing the axle nut, moving it out of alignment. A trick to prevent this is to put a screw driver handle uder the top run of the chain and back it into the teeth of the rear sprocket. This pulls the axle evenly against your adjusters. hold some pressure on the wheel while you torque the axle

[SRTie4k]

Is it better to use the hash marks on the swingarm for alignment, or measure the adjuster bolt lengths?

[Paul_E_D]

I would say hashmarks. I never thought of measuring the adjuster bolts. The only accurate measurement I know of is from the swingarm pivot center to the axle center. They make a special tool for that though as it's a bit tricky to do otherwise.

[SRTie4k]

I'll have to try realigning it again tonight. Thanks.

[Petorius]

I usually align it based on centering the chain on the sprocket. Spin the rear wheel and adjust until the sprocket teeth are floating between the chain plates and not sitting on one side or the other. This is probably not the best way to do it, but maybe less chain wear?

[NPDCPA]

I always try to run a piece of wire between the swingarm pivot to axle. Once you set that up and the adjusters are snug to the adjuster bolts, R&R of the rear wheel just means pushing the adjusters against the bolts, eyeballing the sprocket to chain alignment and calling it a day. I put little to no trust in the hash marks.

[Paul_E_D]

If you measure the pivot to axle once, and check the hashmarks for accuracy, then you don't need to measure anymore. Just use the hashmarks. All my bikes have been pretty accurate.

[The Snowman]

Ideally, you want the center of the axle on each side of the bike to be the same distance from the center of the swingarm pivot as the other side. Hash marks can be off.

[Stoneman]

I always used the hash marks as a guide. I then measured the axle center to the end of the swingarm. They were always pretty damned close and it never caused a problem...

[cdovego]

The hash marks are notorously not accurate, plan accordingly. There are 1,000 ways to solve the problem.

[Kurlon]

I've got a piece of aluminum bar stock from Home Despot that I carry in my chem tote. I can lay it directly on a rear sprocket to verify that the sprocket alignment matches the chain path. It's worth spinning the rear wheel after and observing how the chain rides will point out if the sprocket is slightly wobbly. I also have two zipties with short ends on it so I can quickly verify swingarm pivot to axle alignment. Fun fact, the two alignments do NOT always agree...

[reks95]

I saw a youtube video where a guy placed a used fluorescent tube on either side of the back tire. If the front is in the middle, you're good.

Saw another youtube video where a guy puts the bike on a painted stripe on the floor and rolls it. If you're still on the line, you're good.
Duct tape is kinda like paint if the floor is clean enough

An anal way of using the hashmarks is to measure it with calipers. Usually you can get the teeth in there to measure the length of the exposed bolt as a proxy. Calipers are sensitive enough to detect differences of a 1/6th of a turn in the adjusters.

[Paul_E_D]

This is a lot of trouble for lining up the rear wheel. Unless you're on a 125, it doesn't need to do superbly accurate. As far as some of these techniques, careful what you are measuring for. Motors are not usually dead nuts straight in the frame, so front to rear sprockets can look out. GP bikes are actually assembled with motor shims so that the motor goes in straight.

On bike with plenty of torque, you are wasting your time. No real power loss will be detected. And unless you are waaaay out, no handling issues will be detected either. tire flex, chassis flex, and just the way the front end works will compensate for a little misalignment.

[rolker]

This is a lot of trouble for lining up the rear wheel. Unless you're on a 125, it doesn't need to do superbly accurate. As far as some of these techniques, careful what you are measuring for. Motors are not usually dead nuts straight in the frame, so front to rear sprockets can look out. GP bikes are actually assembled with motor shims so that the motor goes in straight.

On bike with plenty of torque, you are wasting your time. No real power loss will be detected. And unless you are waaaay out, no handling issues will be detected either. tire flex, chassis flex, and just the way the front end works will compensate for a little misalignment.

What's the best way to check on a 125? Broken sprockets have been the reason for my last 2 DNFs, and I'm trying to determine if it's the sprocket that is too flimsy or another issue.

[Paul_E_D]

Are you following the shimming procedure from the manual? Or just putting whatever you had in there back in? Is your chain too loose? in your case I would try to get one of the tools that measures from pivot to axle, then verify sprocket alignment with laserbeams or something.

[rolker]

Are you following the shimming procedure from the manual?

Yes

Or just putting whatever you had in there back in?

No, I chose the shims that fit snugly in the spaces.

Is your chain too loose?

Not usually... maybe it loosened up when the sprocket went? Not sure...

in your case I would try to get one of the tools that measures from pivot to axle, then verify sprocket alignment with laserbeams or something.

Laserbeams? I thought this was supposed to be a simple bike!

[Paul_E_D]

That is simple for you!

[Jim]

The swing arm marks are notoriously inaccurate. I have an alignment tool that I keep in my toolbox.
Since I'm swapping sprockets every other week for different tracks, I use this alignment tool frequently and be rally keep the rear wheel aligned within 1mm or less.

[xrocket21]

You guys are overthinking the shit out of this. Use the hash marks or measure the bolts, jesus..... I personally use the hashmarks.

[SRTie4k]

On bike with plenty of torque, you are wasting your time. No real power loss will be detected. And unless you are waaaay out, no handling issues will be detected either. tire flex, chassis flex, and just the way the front end works will compensate for a little misalignment.

Wasn't really worried about power loss on a TL1000S. Was more worried about abnormal tire wear.

[Tunertype]

This is a lot of trouble for lining up the rear wheel. Unless you're on a 125, it doesn't need to do superbly accurate. As far as some of these techniques, careful what you are measuring for. Motors are not usually dead nuts straight in the frame, so front to rear sprockets can look out. GP bikes are actually assembled with motor shims so that the motor goes in straight.

On bike with plenty of torque, you are wasting your time. No real power loss will be detected. And unless you are waaaay out, no handling issues will be detected either. tire flex, chassis flex, and just the way the front end works will compensate for a little misalignment.

Wasn't really worried about power loss on a TL1000S. Was more worried about abnormal tire wear.

Since you only have 2 wheels I don't think it works that way with the alignment on a bike. You will track in line with the front and back wheel and a slight miss alignment will not cause any kind of wear or handling issues. The other mentioned issues of chain and probably brake/tire rubbing would be more of a concern on extreme miss alignments.

[martia]

Check out this YouTube https://youtu.be/4Dw2RZlUoUY

[Jim]

I use this alignment tool frequently and keep the rear wheel aligned within 1mm or less.

I just want to point this quote out again.
Get this alignment tool and a millimeter tape measure. Done deal.

[cdovego]

I just want to point this quote out again.
Get this alignment tool and a millimeter tape measure. Done deal.

Your front tire is flat.