An Easy Way to Set Rear Wheel Alignment

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Tirpitz
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An Easy Way to Set Rear Wheel Alignment

Post by Tirpitz » Wed Aug 22, 2012 4:59 pm

Most of you probably know that you can't rely on the marks on the swingarm to accurately set the rear wheel alignment and will have read a variety of ways to correctly line it up from bits of string to planks of wood to lazer levels. All of these constitute a fair amount of buggering around and have variable accuracy. Here's a quick and easy way to get your rear wheel 'square' in the swingarm using a vernier caliper.

1. With the axle nut slackened off but just finger tight (to hold the alloy adjuster blocks steady) ensure that the chain adjuster bolts are firmly touching the adjuster blocks. This ensures that both blocks are pushing against the axle.

2. With a vernier caliper measure the distance between the front edge of the adjuster blocks and the rear of the swingarm, as in the photo below
001.JPG
3. Adjust as necessary so they are the same.

Don't be fooled into thinking that any inaccuracy in the marks will be insignificant. I aligned my wheel using a ruler on the marks to set both sides the same yet when I checked with a vernier caliper there was almost 2mm difference in alignment. Once set with a vernier the two sides were visibly slightly different by comparison with the marks. 2mm is significant and will affect handling (worse the faster you go) and final drive wear and noise. If you have vernier calipers this is a quick and easy job to do. Just to be sure you might want to measure across the two adjuster blocks to make sure they are the same size but I'd be surprised if they are significantly different, mine were identical.
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cargo
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Re: An Easy Way to Set the Wheel Alignment

Post by cargo » Wed Aug 22, 2012 5:08 pm

sadly you are assuming that the adjuster blocks are the same and that each side of the swing arm is the same.

the whole point of wheel alinement is that the wheels are in line with each other NOT that the rear wheel is square in the swing arm having said that if the wheels are in alinement then the rear will also be square in the swing arm but that does NOT mean that the measurment on each side is the same.

Having said all that your method is prob close enough for most.................I like to check mine with a straight edge not every time but now and then.

When adjusting I count flats on the adjuster bolts

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Re: An Easy Way to Set Rear Wheel Alignment

Post by Tirpitz » Wed Aug 22, 2012 5:26 pm

I do say that people might want to measure both adjuster blocks to check that they are the same, so that's that base covered.

I get your point about alignment but I think it's another way to achieve the same thing. My method gets the rear wheel square in the swingarm. The only way that the rear wheel can be dead square in the swingarm but still not aligned with the front is if the swingarm / frame etc is twisted out of line. Adjusting the rear wheel out of square in the swingarm to compensate for one of these problems and get it aligned with the front wheel is not going to help, if the bike is in that sort of state the fundamental problems need sorting, not working around. So, assuming the bike is in good order this method is another way to achieve the same thing.

Look at it another way, if you align with a straight edge and don't use verniers to square up the wheel in the swingarm then you will miss the fact that although correctly aligned with the front the wheel is sitting skew in the swingarm. Both methods have pitfalls.
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Re: An Easy Way to Set Rear Wheel Alignment

Post by cargo » Thu Aug 23, 2012 12:09 am

Again you are assuming that all swing arms are straight and square.................they are not

True wheel alinement can only be achieved by actually alining the wheels

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Re: An Easy Way to Set Rear Wheel Alignment

Post by Tirpitz » Thu Aug 23, 2012 10:53 pm

Ok fair enough, I accept your point.

How do you align your wheels? I've read a variety of methods and to be honest some of them seem to be an enormous amount of mucking about. What is the easiest way?

Once the rear wheel is aligned with the front it should then be possible to measure the distance between the adjuster block and the rear of the swingarm on each side with a vernier as I describe above. You will then have a baseline figure for future use giving you the difference between each side when correctly aligned. This could be used in future when adjusting the chain to maintain alignment without going through the alignment process all over again. Yes?
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Re: An Easy Way to Set Rear Wheel Alignment

Post by cargo » Thu Aug 23, 2012 11:23 pm

yes you are correct

I use a bit of straight ally box section stuff

However once it is set up I adjust by counting the flats on the adjuster bolts. Seems to work well and my 250 guru uses the same method on the 250 I'm riding this week

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Re: An Easy Way to Set Rear Wheel Alignment

Post by Tirpitz » Fri Aug 24, 2012 12:49 pm

Thanks. Yes, I've always used the 'counting flats' method myself when doing chain adjustments.

Right, I've done a wheel alignment the proper way. I didn't have any reliably straight metal or timber to use as an edge so used the string method with fine cotton thread. Amazingly it was already spot on, so I appear to have the world's truest swingarm :smt004

For anyone following this thread in future, Cargo is correct in that you cannot assume the swingarm has been manufactured perfectly true and equal. I'm lucky. So do a traditional wheel alignment first, then you can measure the difference between the measurements in my photo above on each side. The difference between the two readings (if any) is the amount by which your swingarm has been made unequal. If you always maintain this difference the wheels will remain aligned.
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Re: An Easy Way to Set Rear Wheel Alignment

Post by Tirpitz » Sun Sep 02, 2012 8:02 pm

I've just taken the bike out for a 150 mile scratch round the roads of North Yorkshire towards Helmsley and I'm pretty amazed by the results of the wheel alignment. TBH I was very skeptical that it would make any difference, as I thought the handling was good already. What a mistake :smt018 This is with the alignment being just 2mm out remember. The benefits I felt today were -

1. Less drive train noise ( whining)

2. Much easier to crack on the gas through the corner without getting chain snatch, much smoother transmission take-up

3. Less head shake with power on on bumpy roads

4. It seems to turn in quicker. A couple of times I had a tightened ringpiece moment when I found the bike turning in too quickly on higher speed corners and the apex was almost 'clipped' literally shocking

It's a bit of a cliche to say that you can spend as much money on performance mods as you like but if the bike doesn't handle they'll make jack toad difference in anything other than a straight line. This little exercise re-inforces this mantra. Line yer wheels up - you know it makes sense :smt002
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