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Author Topic: Rear Wheel Alignment Jig  (Read 1767 times)

rayivers

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Rear Wheel Alignment Jig
« on: September 10, 2016, 03:13:12 AM »

After a bunch of work and several revisions, I finally got my alignment jig working OK (the tubes are straight to within .002", my camera not so much):



This setup basically aligns the rear axle with the LH stub-axle swingarm pivot, performing what's generally referred to as a 'thrust angle' alignment (drive axle perpendicular to vehicle centerline).  No, it's not equivalent to a 3-axis frame alignment jig - not even close ! - but on my bikes at least, it's much more accurate than the swingarm hash marks.

It's pretty simple; one 10mm-O.D., 610mm (24") long tube each into the rear axle and swingarm-pivot centers, with two adjustable yokes that ride along these tubes to ensure they're parallel.  Yoke adjustment is done by rotating the center hex rod, which has LH and RH threads into the inner yoke ends.  The rear tube has a brass adaptor to fit the axle hole, while the front fits into the swingarm pivot as-is.  To use it on the chain bike, I loosen the axle nut, lift the bike, insert the tubes, then adjust the yokes to fit the tube-center distance and slide it back and forth until I'm happy with the tubes' alignment (usually 2 or 3 passes).  I then tighten up the axle nut most of the way, re-check the tubes, turn the axle adjuster(s) until they contact the axle sliders equally, then lower the bike and tighten the nut up fully. The belt bike is more difficult; the belt tension means the tube alignment must be done using the axle adjusters, not simply by hand using the tubes (OTOH, it doesn't have to be done very often). I do it during belt / chain adjustments, it adds about 5 minutes (chain) or 10-15 min. (belt) to the process.

It's interesting how my Zeros steer after being aligned with this jig.  Before the alignment, they were what I thought of as 'normal', with one direction having slightly easier steering than the other and a tendency to wander just a little.  Afterwards, the bikes held a straight line better and also had what felt like a slight 'power steering' effect, where my steering input caused the front wheel to move (or feel like it was moving) to the new line with what seemed like additional assistance.  This effect was completely symmetrical, and faded out on the 'MX' after several chain adjustments - until I realigned it yesterday morning and the feeling returned.  It was fairly subtle and only really noticeable on the street; in the dirt the main difference was much less difficulty staying centered in ruts without the tires 'climbing the walls', which was the main reason I started this PITA project to begin with. :)  It's amazing how precise the steering is now - I even find myself using the narrow raised areas between ruts (@ 4" to 10" wide) which I avoided like the plague before.

If you don't have knobby tires, are certain your front and rear wheels share the same centerline, have a way to hold your front wheel absolutely straight, and know your tire edges/rims are true, there are plenty of string / straightedge / laser methods online that will give you some kind of result with far less effort than this.  The ones I tried didn't work for me at all.

Here's the final combined diagram - it uses various scales, but each individual item is proportionate:



I got my metal (316 stainless tube & hex rod, 360 brass tube) from onlinemetals.com; they're expensive, but they sell in small quantities and can cut to order if needed.  The two #82055062 yokes were from mscdirect.com (their larger #84258219 yokes will also work). The yoke extension tube is JB Welded to the outer side of the yoke arm, with the rod thru it & the yoke to keep it aligned while it hardens.  I had two made up, but the jig works fine with just one (on the forward yoke).

Ray

« Last Edit: November 07, 2016, 01:26:59 AM by rayivers »
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BrianTRice@gmail.com

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Re: Rear Wheel Alignment Jig
« Reply #1 on: September 10, 2016, 04:18:12 AM »

Nice! I'm switching from the DSR OEM tires soon to 90/10 tires and hopefully can make the alignment this good soon after.

I ride on some fairly rough highways and do notice when the tires climb ruts inappropriately...
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MrDude_1

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Re: Rear Wheel Alignment Jig
« Reply #2 on: September 10, 2016, 08:08:56 AM »



If you don't have knobby tires, are certain your front and rear wheels share the same centerline, have a way to hold your front wheel absolutely straight, and know your tire edges/rims are true, there are plenty of string / straightedge / laser methods online that will give you some kind of result with far less effort than this.  The ones I tried didn't work for me at all.


even with knobby tires, you can do it with a piece of string...
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rayivers

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Re: Rear Wheel Alignment Jig
« Reply #3 on: September 10, 2016, 03:48:34 PM »

Quote
even with knobby tires, you can do it with a piece of string...

Absolutely - with results that vary every time, and are hardly worth the effort.

Rather than simply dumping on this system, try describing your alignment method, the bike(s) you did it on, and the results.

Ray
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Kocho

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Re: Rear Wheel Alignment Jig
« Reply #4 on: September 10, 2016, 05:24:16 PM »

Wouldn't simply marking the center of the tire and the swig arm and aligning them visually achieve the same?

Wouldn't the rods bend if you use them with these pulleys as far away from the bike as you show in the photo? You need to maintain tension on the rods to counter the belt tension effect, which I expect will cause bending...
« Last Edit: September 10, 2016, 05:26:37 PM by Kocho »
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rayivers

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Re: Rear Wheel Alignment Jig
« Reply #5 on: September 10, 2016, 06:13:15 PM »

Quote
Wouldn't simply marking the center of the tire and the swig arm and aligning them visually achieve the same?

Try actually doing these things yourself, accurately.  My setup is accurate & repeatable to < 2mm at the front axle.  If accuracy isn't needed, the swingarm axle-alignment marks are fine.


Quote
Wouldn't the rods bend if you use them with these pulleys as far away from the bike as you show in the photo? You need to maintain tension on the rods to counter the belt tension effect, which I expect will cause bending...

If used properly, the tubes won't bend at all, except a tiny bit down from gravity.  If used improperly, there's no limit to the damage that can be done. :)

From my original post:

"the belt tension means the tube alignment must be done using the axle adjusters, not simply by hand using the tubes". 

With belt tension present the tubes must be approximately aligned by eye (using the axle adjusters) without the yokes on, then the yokes used to check their alignment, then repeat as necessary - as mentioned, it's a lot more work than with the chain, where simply sliding on the yokes aligns the tubes & rear axle.

Ray
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Fred

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Re: Rear Wheel Alignment Jig
« Reply #6 on: September 10, 2016, 08:05:49 PM »

I simply line up the front and rear edges of the rear tyre by eye. I turn the front wheel to line up the front and rear edges of the front tyre. Then I compare the visual gap between front and rear on each side. Easier done than described. Perfect results - even for the race track. Zero cost.
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rayivers

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Re: Rear Wheel Alignment Jig
« Reply #7 on: September 10, 2016, 08:42:16 PM »

Quote
Perfect results - even for the race track.

You ought to pass these tips on to all the factory MX / SX / GNCC / road-race teams - they'll be happy to know they no longer need those hi-tech alignment setups they wasted all that money on. :)

Ray
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ctrlburn

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Re: Rear Wheel Alignment Jig
« Reply #8 on: September 11, 2016, 01:15:51 AM »

"New" mine felt like one side of the bike was heavier than the other.
I do like the rods "amplification of error" function.

I didn't find the alignment notches very useful, and even measuring in from the swingarm had a cantered result.

I tried aligning the overall track - front to back. With my shop lighting, my old eyes (and bifocals) one tire or the other is blurry. I tried shooting a laser parallel to the bike, and measuring out a fixed distance... good for "checking" but not for "adjusting" because the whole rig needed to be reset each time.

I 'aligned' by setting the rear wheel in the air and spinning, then adjusted by watching the belt track on the rear pulley. So my rear tire is aligned to the motor and not specifically to the frame or front wheel.

From the thread I am reading there are three targets for alignment?
  • Rear Tire aligned within frame
  • Rear Tire aligned with front tire
  • Rear Tire aligned with motor
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MrDude_1

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Re: Rear Wheel Alignment Jig
« Reply #9 on: September 11, 2016, 02:40:05 AM »

Quote
even with knobby tires, you can do it with a piece of string...

Absolutely - with results that vary every time, and are hardly worth the effort.

Rather than simply dumping on this system, try describing your alignment method, the bike(s) you did it on, and the results.

Ray

I wrote more than that, but I suppose I lost it when I snagged the quote.
I think its a neat tool, and suggested drilling/tapping the yolks for set screws. making them more solid will let you keep them aligned easier... but still one tweak of an adjuster with it in there can bend it.

I dont think this is more accurate than stringing your bike, simply because of the lengths involved.
as to how to do that, there are better how-to articles than I can make.

http://www.motorcyclistonline.com/simple-motorcycle-wheel-alignment

It is 100% repeatable if you're doing it correctly. the middle is the middle.
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Fred

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Re: Rear Wheel Alignment Jig
« Reply #10 on: September 11, 2016, 05:07:32 AM »

Quote
Perfect results - even for the race track.

You ought to pass these tips on to all the factory MX / SX / GNCC / road-race teams - they'll be happy to know they no longer need those hi-tech alignment setups they wasted all that money on. :)

Ray
No need to get shitty about it. You did ask, after all. I didn't rag on your technique, I explained mine and the bikes it was used on (plenty of road bikes, home built supermotos and my 250 race bike over three years of reasonably successful racing).

If I didn't describe my technique well, it's much like the string technique but without any string!
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rayivers

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Re: Rear Wheel Alignment Jig
« Reply #11 on: September 11, 2016, 06:35:27 AM »

Quote
You did ask, after all.

Yes, I did.  It was intended specifically for MrDude, but I can see how it might not have seemed that way - my bad.

Regarding my jig - I didn't make it out of boredom or linonophobia :) but because every other alignment method I tried (string, chalk snap-string on the garage floor [yuk], straightedge [with & without side extension bolts], swingarm side clearance - couldn't really get laser to work) either was unusable with side knobs or indicated I had 'perfect' alignment - yet every time I encountered ruts the bike did its very best to throw me off, sometimes violently. :(  Since my alignment was 'perfect' (sarcasm) I then wasted a bunch of time and money looking at other stuff that just wasn't the problem & finally worked my way back to alignment, which turned out to be the real issue after all.  Now I fly through the ruts like the outdoor-MX guys (in slow motion).

Here's a variation on the same alignment-jig theme, the Tiger Wheel Gauge.  I need a one-sided solution, but if you have easy access to both swingarm-pivot centers this should work a lot like mine does.

Ray
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rayivers

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Re: Rear Wheel Alignment Jig
« Reply #12 on: September 11, 2016, 09:34:04 PM »


Quote
"New" mine felt like one side of the bike was heavier than the other.

This could be a wheel-offset and/or weight distribution issue, although if the rear wheel is angled the bike will always want to 'fall' easier to the opposite side which could give it a heavier feel there.  IMO a bike with this situation will never feel right or corner symmetrically.

Quote
I do like the rods "amplification of error" function.

I tried to get as close as possible to a 1:2 tube-to-wheelbase ratio, giving jig error x 2 at the front axle.  With perfect jig components / frame / forks / etc. this error would be < .010" / .25mm at the front axle, but realistically it's more like 2mm or less.

Quote
I didn't find the alignment notches very useful, and even measuring in from the swingarm had a cantered result.

Mine are way out too - the 'MX' by about .4 division, the FX by .2 division.  Doesn't sound like much, right?  Well, according to my numbers this works out to @ 12.6mm misalignment at the front axle for the FX, double that (25mm) for the 'MX'.  After the jig alignment and the front wheel was free of side loading, I really felt a change for the better; also, the bike's tendency to veer once the front wheel left the ground (which I'd always taken for granted as part of the 'wheelie experience') vanished, which was a minor epiphany.

Quote
I tried aligning the overall track

Even though this seems like the right way to go about aligning a motorcycle, I no longer believe it is (if I ever did).  I now think the correct way is to align the rear wheel so it pushes the mass of the motorcycle straight ahead of it, leaving the front wheel to do only what it was designed to; steer, corner, and brake. Of your three choices, this is closest to 'rear tire aligned within frame', but I'd call it 'drive axle set perpendicular to motorcycle centerline'.

As far as the belt goes, if it was working OK before, proper rear-wheel alignment should only make it work better.  Any belt alignment needed would best be done with the sprockets, not the wheel.

Quick note: visual and string alignment methods do NOT generate a number, only an anecdote ("looks pretty good!"  "Man, that's close!!").  That's not even close to close enough for me. :)  Normal street riding - where surfaces are mainly flat and even, and traction usually ample - is much less demanding of alignment than the mostly-dirt riding I do, where one finds out real quick whether the bike is natively stable & straight-tracking, or being held in check by duelling tire contact patches either side of an imaginary centerline.

Ray
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MajorMajor

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Re: Rear Wheel Alignment Jig
« Reply #13 on: September 12, 2016, 08:09:20 PM »

Anyone know if the 2016 FXS and FX use the same brake pads?
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Re: Rear Wheel Alignment Jig
« Reply #14 on: September 12, 2016, 08:58:42 PM »

Anyone know if the 2016 FXS and FX use the same brake pads?

We've tracked brake pad shapes on a wiki manual. Please double check pad shape, but FXS and FX should be identical:
http://zeromanual.com/index.php/Unofficial_Service_Manual#Compatibility

Also, please find a relevant thread next time to comment on. The forum can be searched modestly well.
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