Laser swingarm alignment

[Guest ratchethack]

No doubt a few of the old-timers (of which I guess I’m one!) will scoff at this ‘cause it sure ain’t “old school”, but I’ve found what I believe to be a quick and accurate method of aligning the swingarm. I like it because it’s a couple or three big notches above the old “string method” in terms of accuracy, it’s fairly quick and easy, and you can impress yer pals when you say you laser-aligned your Guzzi! This method can be used on any moto with dual front disk brakes.

 

1. With the bike on shop or center-stand and the front wheel resting on the floor, center the front wheel. I do this by sighting front to back along the sides of the tires about 8” inches above the floor, so that equal widths of the rear tire on each side are visible when sighting along the edges of the front tire. This part approximates the string method and need not be overly precise, but it’s important not to bump the bars or front wheel once you get it good and straight, so leave yourself plenty of room.

 

2. Rotate the rear wheel so that the valve stem is at the bottom of rotation. Using one of the commonly available laser levels from any hardware outlet (mine’s 16”), slip a loop of cord over the laser level and hang the laser on the valve stem so that it’s suspended in the middle, parallel to the floor, resting snugly against the side of the tire at front and rear, with the aperture of the laser pointing forward. The loop of cord should be just long enough to allow you hang it on the valve stem. The laser should now be pulled up firm & flat against the tire.

 

3. Take a 12” ruler, paint stirrer, or similar sized stick and 2 ea. 2” lengths of masking tape, and tape the ruler horizontally across the rear-facing edges of the front brake disks, so the ruler runs through the wheel between the spokes, just below the calipers. If you use 2 inches of masking tape horizontally on each side, you won’t have to add more tape later.

 

4. Turn the laser on and rotate the rear wheel slightly until the laser dot appears on the tape on the ruler. Mark the spot carefully. Now hang the laser on the other side of the rear wheel and repeat.

 

5. By measuring the lateral distance between the outside surface of each brake disk and the laser marks on the tape on each side, you have an accurate reference for aligning the swingarm. Now it’s simply a matter of adjustment of the swingarm stub axles until the measurements are equal. The factory tolerance is within 1.5 mm difference between each side (3 mm total lateral tolerance). I find I can easily get it more accurate than my Guzzi arrived from Mandello (2 mm total). I set mine to <.5 mm difference each side (1 mm total lateral tolerance). I use a depth gauge here.

 

6. With the swingarm stub axle jam nuts loosened, make your adjustments to the swingarm and take readings until you’re good and sick of measuring and tweaking. Snug up each of the stub axles, back each one out again ¼ turn, check again with clean tape, and secure ‘em with the jam nuts.

 

You're laser aligned! When finished, you can check your accuracy by repeating the process from the point of re-centering the front wheel.

 

Have fun, hope this helps.

[txrider]

No doubt a few of the old-timers (of which I guess I’m one!) will scoff at this ‘cause it sure ain’t “old school”,   but I’ve found what I believe to be a quick and accurate method of aligning the swingarm.  I like it because it’s a couple or three big notches above the old “string method” in terms of accuracy, it’s fairly quick and easy, and you can impress yer pals when you say you laser-aligned your Guzzi!  This method can only be used with dual front disk brakes.

 

1. With the bike on shop or center-stand and the front wheel resting on the floor, center the front wheel. I do this by sighting front to back along the sides of the tires about 8” inches above the floor, so that equal widths of the rear tire on each side are visible when sighting along the edges of the front tire.  This part approximates the string method and need not be overly precise, but it’s important not to bump the bars or front wheel once you get it good and straight, so leave yourself plenty of room. 

 

2. Rotate the rear wheel so that the valve stem is at the bottom of rotation.  Using one of the commonly available laser levels from any hardware outlet (mine’s 16”), slip a loop of cord over the laser level and hang the laser on the valve stem so that it’s suspended in the middle, parallel to the floor, resting snugly against the side of the tire at front and rear, with the aperture of the laser pointing forward.  The loop of cord should be just long enough to allow you hang it on the valve stem.  The laser now rests securely, flat against the tire.

 

3. Take a 12” ruler, paint stirrer, or similar sized stick and 2 ea. 2” lengths of masking tape, and tape the ruler horizontally across the rear-facing edges of the front brake disks, so the ruler runs through the wheel between the spokes, just below the calipers.  If you use 2 inches of masking tape horizontally on each side, you won’t have to add more tape later.

 

4. Turn the laser on and rotate the rear wheel slightly until the laser dot appears on the tape on the ruler.  Mark the spot carefully.  Now hang the laser on the other side of the rear wheel and repeat the process.

 

5. By measuring the lateral distance between the outside surface of each brake disk and the laser marks on the tape on each side, you have an accurate reference for aligning the swingarm.  Now it’s simply a matter of adjustment until the measurements are equal.  The factory tolerance is within 1.5 mm each side (3 mm total), which will be the difference between the measurements.  I find I can easily get it more accurate than my Guzzi arrived from Mandello, (2 mm total).  I set mine to <.5 mm total. i use a depth gauge here.>

 

You're laser aligned!  When finished, you can check your accuracy by repeating the process from the point of re-centering the front wheel. 

 

Have fun, hope this helps.

 

Ratchethack

46556[/snapback]

 

Great idea. I've been toying with the idea of using a laser to check rear wheel alignment but hadn't thought of this straightforward easy approach. Thanks for the tip.

[Steve G.]

I guess I'm from a different planet. I never realized you had to align the rear wheel on a shaft drive bike.

Ciao, Steve G.

[Guest ratchethack]

I guess I'm from a different planet. I never realized you had to align the rear wheel on a shaft drive bike.

                                                                               Ciao, Steve G.

46577[/snapback]

 

The rear wheel is aligned as long as the swingarm is aligned, unless something is out of whack, as from a crash. Having the swingarm out for any reason would be a good time to align it as an alternative to taking stub-axle measurements to try to replicate the prior setting, and it's just about as easy to do. I aligned mine when I had the transmission out for service under recall.

[txrider]

The rear wheel is aligned as long as the swingarm is aligned, unless something is out of whack, as from a crash.  The swingarm should be aligned whenever it has been removed.  I aligned mine when I had the transmission out for service under recall.

46578[/snapback]

 

Would that be by adjusting the swingarm pivots side to side?

[Guest ratchethack]

Would that be by adjusting the swingarm pivots side to side?

46586[/snapback]

txrider, my apologies. Somehow I omitted copying in the last point in my procedure. I just edited it in, see #6 above.

[andy york]

I like that proceedure alot for checking things out. Or you can measure the pivot pins with a dial indicator before you remove the swingarm.

 

andy

[Guest ratchethack]

Or you can measure the pivot pins with a dial indicator before you remove the swingarm.

46592[/snapback]

That's right, but at best, this only gets you back to where Luigi (or whoever touched it last) set it.

[txrider]

txrider, my apologies.  Somehow I omitted copying in the last point in my procedure.  I just edited it in, see #6 above.

46587[/snapback]

 

Got it and the timing is perfect since my swingarm is off right now. I measured the pivot nuts before removal and they were not equal. I will use this on reassembly. Thanks again.

[Guest ratchethack]

txrider, keep in mind that with the swingarm properly aligned, the chances that your stub axle measurements will be equal (as measured from the surface of the pork chops to the end of the stub axles) are slim to zip. Setting them equal is more'n likely a guarantee that you'll be out of whack. Think of the absolute precision it would require at the factory on each chassis component to make sure they're exactly equal at the same time the alignment of the wheels is spot-on. FWIW, using a dial indicator, mine measured .184" difference between them as delivered from the factory, and .118" difference after laser alignment. What's important is getting the centerlines of the wheels in as close to the same plane as possible, so they'll track on the same line - that is, with no offest perceptible enough to induce less than ideal road manners.

[txrider]

txrider, keep in mind that with the swingarm properly aligned, the chances that your stub axle measurements will be equal (as measured from the surface of the pork chops to the end of the stub axles) are slim to zip.  Setting them equal is more'n likely a guarantee that you'll be out of whack.  Think of the absolute precision it would require at the factory on each chassis component to make sure they're exactly equal at the same time the alignment of the wheels is spot-on.   FWIW, using a dial indicator, mine measured .184" difference between them as delivered from the factory, and .118" difference after laser alignment.  What's important is getting the centerlines of the wheels in as close to the same plane as possible, so they'll track on the same line - that is, with no offest perceptible enough to induce less than ideal road manners. 

46618[/snapback]

 

I understand. Now to move off topic just a little how much do you snug up the stub axles against the swingarm bearings? I've read several different recommendations on this.

[Guest ratchethack]

how much do you snug up the stub axles against the swingarm bearings?  I've read several different recommendations on this.

46684[/snapback]

Sorry for the late response, Txrider, I've been out of town for a few days. I'd like to have a torque figure for this, but haven't found one either. Hmmmm.....no response from anyone else..... Just reasoning out what's involved, I crank it in "by feel" until I sense the bearings taking on the full load. I continue tightening until resistance starts to spike up more rapidly, then back off 1/4 turn. I don't think you could damage the bearings or tweak the chassis with up to 10-20 ft. lbs load on it, but I don't go that high. You want to set it under slight tension only, and as long as it's not dramatically overloaded (I'm speculating and generalizing at the same time a little bit here) a reasonable range of low-level load is no doubt acceptable. Anti-seize on the stub axle threads & jam nuts provides insurance against seizure & removal of those delicate aluminum threads next time due to electro-chemical reaction between the steel and aluminum. I used a stainless steel shotgun bore brush with a rotating motion followed by swabbing with laquer thinner to clean out the threads before I buttoned 'er up.

 

Hope this helps.

 

Ratchethack

[txrider]

It certainly does help and thanks. Coincidently, I used a bore brush last night to clean the threads but a .45 type was all I had so turned it with good results. I made washers out of 0.020" stainless round shims to fit under the lock nuts which should keep the nuts off the aluminum porkchop. Had a time with a Dremel ( be nice to have a lathe) reducing the od but they turned out after a final pass on the drill press and drum sander.

[jrt]

Now that's a good idea, txrider. You should send it on to Greg Field for his 'tips' column in the MGNCO newsletter.

 

Actually, Ratchethack, you should send your writeup in as well. I'm sure lot's of folks would benefit from it- Tonti riders, spine and loopframes all use the same basic setup.

 

Jason

[savagehenry]

Just got done pulling the swing arm, among other bits, to be ready for the summer. Guess what? Measurement of the pins showed they were both set to the same depth (.138, taken with a depth mic), and the bike was originally serviced by Fast by Ferracci. I never had any handling issues, so it will be interesting to see where I end up after I align the swing arm when I put it back.