Different methods of wheel alignment

[salty_monk]

So far I've seen the string method & Matchless's variation using a laser level.

Anyone got any other methods worth looking at?

Dan

 

[cavehamster]

I used a variation on the laser method for mine, but others have very strong opinions about it, so.. hehe

http://www.thegsresources.com/_forum/showpost.php?p=1085289&postcount=50

I tried the string method the other day, but found it harder to juggle all the variables.

Good luck!

 

[Steve]

The string method works a bit better if you can somehow balance the bike without using the centerstand to give you more room to work.

This method can also benefit from not using the centerstand:
Instead of using string, go to Lowe's, Home Depot, wherever, see if you can find two 1x2s that are 8' long and STRAIGHT.
Clamp them as high as you can on the rear tire, you can easily see how they align on the front tire.
You can also use angle iron or angle aluminum, but I was trying to keep the cost down.

.

 

[posplayr]

Let me preface this by saying I just went through this exercise and evaluated various approaches from an systems engineering perspective (as a paid professional with about 30 years doing this sort of thing). In addition I can say, I was somewhat amused by the string method as it appeared "Mickey mouse" to say the least. So after having evaluated the various alternatives :

• laser methods (with and without special attachments
• String Methods
• Methods with tires mounted on wheels
• Wheel mounts alone

Here is a summary of my observations/conclusions.

The first thing to consider is what wheel alignment accuracy are we trying to achieve and then we can perhaps determine what measurement accuracy we will need to achieve the required alignment accuracy. Stated another way, we need to recognize that it is difficult to determine where the center of your tires are and therefore there is a limit to how well you need to know this in the first place.

The various Suzuki manuals quote runnout numbers of approximately 1.0 mm for their factory cast wheels , but a cast wheel that is relatively straight should be close to +/-0.2mm of maximum runout. You can verify this pretty easily with a dial indicator but the wheel runout for a straight wheel is much better than the tire. So the best form of frame alignment would be to use the wheels as reference points and project lines from the rear wheel to the front wheel using either the wheel lip or other point on the rim. An adequate form of tire alignment maybe to just use the tire as that is in fact what runs on the road. Bottom line for overall alignment accuracy is and as has been discussed before alignment to 1mm over 6 foot is a noble goal but even that is not necessary and for a bias ply, high profile tire on a GS 2-5 mm may be unnoticeable I have seen much worse and be tolerable.

If you can account for wheel run out then you may be able to achieve sub 1mm accuracy as measured over the length of the bike; however most methods using straight edges use the sidewall of the tire as reference. Sidewall run out can be significant and is much worse for a high profile tire. For example a 130/90-17 will be worse that a low profile 180/55-17 which will follow the rim much better as there is simply less rubber between the rim and when a straight edge will leave the side wall.

At least one commercial product I reviewed used a special clamping device that was able to reference repeatably off of the rim without using the tire sidewall. Of course it also used a laser which I will discuss later.

As far as straight edges, I built one out of oriented strand board glued together with a long section of aluminum angle iron screwed to it. I used this during my frame alignment activities . I calibrated the straight edge to about 1mm in 6 foot. (using the string method).

While a laser is more straight than a string (strings bend with gravity along the vertical ), the laser is diffuse and at 6 foot the tolerance is at best 1-2 mm of uncertainty as to where the center (or other reference is of the laser). On the other hand with a string, I'm sure I was able to any errors well below 1mm because I could very accurately determine the string departure from the rear wheel as well as accurately measure the string relative wheel (I would estimate the tolerance to be no worse than +/-0.2 mm per side). Therefore the maximum error is approx +/-0.3mm total.

This is achieved using a thin string and monitoring how the string vibrates as it comes in contact with the sidewall. In contrast my straight edge I built was about 1mm and very difficult to determine when it was aligned with the rear tire which could cause much larger error.

My conclusion from all this was that:

• for a low profile radial rear tire, the tire side wall provided a good reference to project forward to the front tire.
• A string at 6 foot is easier to use in determining it's relation ship to the rear tire than a diffuse laser (+/- 1 to 2mm for a laser v.s. +/- 0.2mm for a string).
• 1mm alignment accuracy is all that is needed
• A string alignment is easy to achieve the stated 1mm; by using a string bounce technique along the side wall.
• The laser you have to struggle to figure out it's distance from the rear tire or to get an offset from a reference point on the front wheel/tire.

Summary:
You maybe able to buy something that costs more, but if executed correctly I doubt you can do any better than an thin string toward achieving sub 1mm measurement accuracy.

Pos

 

[Nessism]

Let me preface this by saying I just went through this exercise and evaluated various approaches from an systems engineering perspective (as a paid professional with about 30 years doing this sort of thing). In addition I can say, I was somewhat amused by the string method as it appeared "Mickey mouse" to say the least.

(skip to summary)

Summary:
You maybe able to buy something that costs more, but if executed correctly I doubt you can do any better than an thin string toward achieving sub 1mm measurement accuracy.

Pos

I agree with Jim, the string method is easy and it works.

 

[Footy.]

I agree with Jim, the string method is easy and it works.

I have just fitted a new rear tire to my GS750E, and have used the string method. I really went to town and took every measurement i could to ensure a really accurate alignment.

Now here's my tip.

Once i was sure of the alignment, i used my vernier caliper depth function to measure from each wheel adjuster bolt head face, to the adjuster body. My brake side measurment was 35 Thou (english) more than the chain side.

I can now ensure very accurate wheel alignment every time the chain needs adjusting, or the wheel comes out, just by making sure the brake side adjusting bolt head measures 35 Thou out more than the other.

Footy.

 

[Baatfam]

What I find interesting is we use none of those for the drag bike....of course the swing arm is fixed, so maybe that is part of the deal...

A lot of the guys and us, use a home made tool that measures the distance from the center of the pivot bolt to the center of the rear axle...
That way the wheel is straight in relationship to the rear fork...

Of course from there we tweak it a little to achieve a straight launch under power...

My question than becomes....will this work well on a street bike?
Because that is what I use and it seems fine.

Can't wait for an answer...off to the track in a couple...check back tonight....

 

[posplayr]

What I find interesting is we use none of those for the drag bike....of course the swing arm is fixed, so maybe that is part of the deal...

A lot of the guys and us, use a home made tool that measures the distance from the center of the pivot bolt to the center of the rear axle...
That way the wheel is straight in relationship to the rear fork...

Of course from there we tweak it a little to achieve a straight launch under power...

My question than becomes....will this work well on a street bike?
Because that is what I use and it seems fine.

Can't wait for an answer...off to the track in a couple...check back tonight....

I Would like to see that device, but from your description " pivot center to axle center" not sure if you mean axial center or mid point. Regardless, this doesnt take into acount any other issues such as frame tweek. Without knowing much more, a dragster is not so worried about front wheel alignment but rather drive wheel alignment in the frame.

The laser and string methods are directly measuring one wheel with respect to the other for both alignment (parallel) and being on center (no lateral offset).

 

[posplayr]

I have just fitted a new rear tire to my GS750E, and have used the string method. I really went to town and took every measurement i could to ensure a really accurate alignment.

Now here's my tip.

Once i was sure of the alignment, i used my vernier caliper depth function to measure from each wheel adjuster bolt head face, to the adjuster body. My brake side measurment was 35 Thou (english) more than the chain side.

I can now ensure very accurate wheel alignment every time the chain needs adjusting, or the wheel comes out, just by making sure the brake side adjusting bolt head measures 35 Thou out more than the other.

Footy.

EDITED: After a little more thought I over did this. The relevant ratio is the distance between adjuster nuts (say 12" v.s. the wheel base 60") there is no additional factor of 2. Ratios edited below.

I was posting this yesterday and the mahine locked up before I could hit the send button.

The relationship between rear adjuster bolt and front wheel movement is approximately 5:1 for a GS (Ratio = wheel base /(swing arm adjuster spread) = 60"/12"=5.


So depending upon the pitch of the adjuster bolt you have it could be:

1.25mm pitch x 5 = 6.25mm/adjuster turn
1.0 mm pitch x 5 = 5mm/adjuster turn

So if you want to be within 1 mm alignment (wheel to wheel) and you have a hex head adjuster

for 1.25mm adjuster pitch, 6/6.25 of Hex flat to go 1mm at front wheel.
for 1.00mm adjuster pitch, 6/5 of Hex flat to go 1mm at front wheel

(basically 1 hex flat is approx 1mm)

So after doing the first alignment and adjusting your chain, keep track of the adjuster Hex flats will keep you in alignment (transfer the same turns you adjusted for the chain to the right side) . This will work even if you forget your caliper at home.

 

[posplayr]

Bump; I edited this post

EDITED: After a little more thought I over did this. The relevant ratio is the distance between adjuster nuts (say 12" v.s. the wheel base 60") there is no additional factor of 2. Ratios edited below.

I was posting this yesterday and the mahine locked up before I could hit the send button.

The relationship between rear adjuster bolt and front wheel movement is approximately 5:1 for a GS (Ratio = wheel base /(swing arm adjuster spread) = 60"/12"=5.


So depending upon the pitch of the adjuster bolt you have it could be:

1.25mm pitch x 5 = 6.25mm/adjuster turn
1.0 mm pitch x 5 = 5mm/adjuster turn

So if you want to be within 1 mm alignment (wheel to wheel) and you have a hex head adjuster

for 1.25mm adjuster pitch, 6/6.25 of Hex flat to go 1mm at front wheel.
for 1.00mm adjuster pitch, 6/5 of Hex flat to go 1mm at front wheel

(basically 1 hex flat is approx 1mm)

So after doing the first alignment and adjusting your chain, keep track of the adjuster Hex flats will keep you in alignment (transfer the same turns you adjusted for the chain to the right side) . This will work even if you forget your caliper at home.

 

[Footy.]

Bump; I edited this post

Yes i agree, keeping account of the "flats" achives the same accuracy after your initial alignment. This is the easiest way to adjust chain tension.

But when we remove our rear wheels for any reason, we have to back the adjusters right off to allow them to swing down so the wheel will go right up forward to peel the chain off. Keeping account of how many adjuster turns this means will be a real pain.

I know now that it doesn't matter on my bike how far in and out the bolts are, as long as the brake side adjuster bolt head ends up 35 Thou further out. Then i will always retain the original (Hard work to do) correct alignment, even after the wheels been out.

Regards.

Footy.

 

[posplayr]

But when we remove our rear wheels for any reason, we have to back the adjusters right off to allow them to swing down so the wheel will go right up forward to peel the chain off. Keeping account of how many adjuster turns this means will be a real pain.

.

Footy,

OK I'll keep that in mind next time I have to pull the wheel.

Swingarm hashmarks have had a bad wrap for being "notoriously" inaccurate; the fact that 1 turn on the adjuster is worth 5mm at the F wheel it is easy to undestand why.

Regards.
Jim

 

[Baatfam]

I Would like to see that device, but from your description " pivot center to axle center" not sure if you mean axial center or mid point. Regardless, this doesnt take into acount any other issues such as frame tweek. Without knowing much more, a dragster is not so worried about front wheel alignment but rather drive wheel alignment in the frame.

The laser and string methods are directly measuring one wheel with respect to the other for both alignment (parallel) and being on center (no lateral offset).

It is the center of the swing arm pivot bolt to the center of the axle...a center punched mark is very helpful...
The tool is just a long rod with pointed arm at one end and a sliding/locking pointed arm at the other...
I'd take a picture, but I've always borrowed one at the track...at home, I just use a tape measure, which works OK.

But you are correct...this only assures the wheel is aligned with the swing arm and doesn't take into account if the frame is tweaked...
We like to assume our frame is straight.... And we don't use the front wheel much anyway....

I've used this method on my street bikes, and it seems to work fine...but I never verified it with a different method...

 

[tone]

So far I've seen the string method & Matchless's variation using a laser level.

Anyone got any other methods worth looking at?

Dan

http://www.thegsresources.com/_forum/showthread.php?t=147705

Last post is my method but the rest is worth reding

String = a waste of time & effort
lazer = more accuate but much more difficult to do

tone

 

[Road_Clam]

I guess my question is is after my eyes bloodshot from reading this thread about how to check and verify or question ideal wheel alignment... is it worth it on a 25 year old street driven motorcycle that does not exibit any type of obvious ill handling, or unusuall tire wear behavior? In the past 6 motorcycles i've owned, not one of them did I ever suspect the need for a "chassis alignment" . Just my opinion, but if some of you are loosing sleep over + or - 1mm you shouldnt be screwing around with string and lasers, do it the RIGHT way and take your bike to a motorcycle specific chassis shop .

Contrary, race bikes, or a bike that tried to move a tree or guardrail, well that's a different story...

 

[posplayr]

http://www.thegsresources.com/_forum/showthread.php?t=147705

Last post is my method but the rest is worth reding

String = a waste of time & effort
lazer = more accuate but much more difficult to do

tone

Tone,
I will have to respectfully disagree that it is a waste of time & effort to use a string. Clearly if it can be made to work to measure wheel alignment in the 1-2mm regime then it is worth the effort. I think it even better than that if done properly.

The sting method (and I use that term loosely because there are variations) is generally applied to a road ready bike except for the wheel alignment. It probably works just as well for checking frame alignment against the bare wheels alone.

So for the sake of discussion I will only contrast the string v.s. a laser for measuring straight lines as that is what will be used in whatever variation of alignment employed. Any method that can be conceived of for alignment will invariably project two straight line from either side of the rear wheel wheel to the front of the wheel. This is true for strings as well as lasers.

Of course in your description you said to get a straight edge that was really straight; but that begs the question how do you know the edge is straight. Well I confirmed the accuracy of my straight edge with a thin string. It was 1/16" at 6 foot. So one way or another your straight edge is predicated on some form of "at home" straightness measure.

So the question then becomes:

a.) how straight are the lines?
b.) how well can I position (with certainty those lines)?

For a.) everybody knows that a laser is light and is essentially a perfect coherent light source, but alas nothing is perfect and there is beam divergence. For a decent laser Beam divergence is typically 1 mrad so at 2 meters the beam is approximately 2mm is diameter. The question then is how well can that spot be located at with 1ft (one wheel) and at 7 ft (the other wheel)? Having tried this myself, trying to put a measure a laser at it's edge can be a little difficult so if you have a special fixture that is carefully factory aligned (probably with a string) then I would say that the real accuracy of being able to read a full spot is probably within a 0.25mm .

If you are sighting down a straight edge for example , it is difficult to tell when you are splitting the beam for true 1/2 and at best you are probably to a +/-1/8mRad accuracy which is +/-1/4mm at 6 foot.

In contrast how bad is the string? Well it depends allot on how you use it. The string will be quite straight and only suffer moderate catenary is you keep it thin and taught. If you use the string to measure horizontal distances then there is no error in the string as all of the catenery is in the vertical plane.

The real trick with use this string is how well (read accurately and consistently) it can be placed adjacent to a wheel or a tire . If you set the string up so it touches the wheel and then expect to site down the string to ensure it is straight, then you will likely be many mm off in your alignment and I would have to agree it is not going to be worth the effort. On the other hand if you position the string next to the wheel or tire and to make sure that the string is located against both left and right sides the same use the string strum technique.

We obviously want the string straight so that means the string can's be pressed against the wheel. It can however be very close. To insure it is not pressed against the wheel strum the line to ensure it will vibrate up and down, but not how long it continues to vibrate. Adjust the distance so that the fibers of the string cause the vibration to diminish consistently on both sides but still vibrate vertically[This is the main trick required to get accuracy with a string]. I used a very thick string that was approx 1mm in diameter (it is easy to use something much thinner down to 0.2mm). With the vibration method described, you can very easily determine position within +/-1/8 of the string diameter. Of course the hairyness of the string matters to some extent.

So for my string, it was 1mm and I was easily achieving measure positional accuracy to within +/-1/8 mm. At the other end you are typically using a caliper to measure offset between the wheel and the string once you have your strings properly strum positioned. I'm using a veneer caliper and a 1mm thick string; it is easy to achieve +/-1mm of accuracy there as well.

So my conclusion is that using a "considered" string approach, 1mm accuracy can easily be attained and that is all that is ever really required for either wheel or frame alignment. Infact, you would be hard pressed without specially machined and calibrated fixtures to even measure the straightness of a straight edge with a laser. I had both (laser(3 in fact) and string) and finally settled on measuring divergence from a string in the horizontal plane.

Jim

 

[posplayr]

I guess my question is is after my eyes bloodshot from reading this thread about how to check and verify or question ideal wheel alignment... is it worth it on a 25 year old street driven motorcycle that does not exibit any type of obvious ill handling, or unusuall tire wear behavior? In the past 6 motorcycles i've owned, not one of them did I ever suspect the need for a "chassis alignment" . Just my opinion, but if some of you are loosing sleep over + or - 1mm you shouldnt be screwing around with string and lasers, do it the RIGHT way and take your bike to a motorcycle specific chassis shop .

Contrary, race bikes, or a bike that tried to move a tree or guardrail, well that's a different story...

Most of these discussion come up in sport bike threads, and are primarily applied for GS's only when suspension mods are introduced. The issue of rear spacers lways comes up due to the various clerances issues. And it is a good idea to isure that the wheels are still in alignment. I dont think anybody is "worried about 1mm". The accuracy of alignment has been discussed in the thread Tone posted. The issue of what is good enough so I know to stop does come up.

While you have admitted to bloodshot eyes, you might have missed the point of at least part of this thread.That would be that using a string to check the wheel alignment can achieve +/-1mm accuracy which is all that any application would ever require. There is in fact no reason to go to a frame shop as you suggest. While you obviously don't care much about wheel alignment, there are several here that do so we are all huddle in this thread talking about just that. We perfer to not waste time and money going to an alignment shop.

 

[Guest]

I line up them thar little liney thingys on the swangarm doo hickey.

 

[salty_monk]

Well... my swingarm doohickey seems pretty accurate against swingarm & tape measure, laser, straight edge. Now I just got to get the sprockets in tolerance...

 

[tone]

Tone,
I will have to respectfully disagree that it is a waste of time & effort to use a string. blah blah edited to save server space

Jim

Hi Jim, while i see your point that a string could be reasonably accurate if used carefully it is still a string hence bendy & easilly moved resulting in most cases with an inaccurate reading, as you point out there can be a variance with string as you could be measuring either side of it or moving it as stated above

With an accurate straight edge you will be measuring to the same point each time (EG the very edge) & there is much less likelyhood of accidently moving it

Fao my straight edge has a machined edge & has been checked for true on a surface plate hence i KNOW it really is a STRAIGHT edge

I have proven the reliability of my method by checking bikes i'd previously aligned on a jig I have also disproven the reliability of the string method in the same way

In summary...... string if you want it near enough, straight edge or jig if you want it right

Cheers tone