~ Auto Buzz ~: IENATSCH TUESDAY: How to “String” a Motorcycle Motorcycle alignment: You can ignore swingarm marks if the string says your bike is straight.

I learned a few things at the Barber AHRMA races: How much I missed racing, how much fun Middleweight Superbike is, and how to align a motorcycle with string. (Photo by Bobby Pignato)

Stuart Anderson tuned Chris Carr’s GPz550 for me at Barber’s AHRMA Vintage Festival and part of the tuning, and education he gave me, was how to align a motorcycle using strings. To be more precise, this procedure puts the rear wheel in line with the front wheel. We all believe we do that when we adjust the chain. We hover back and forth from side to side, checking and incrementally adjusting chain tension to the marks on each side of the swingarm. Some of us measure the length of the adjusting bolt to “double check” that things are straight. But when we stop to think about it, this process is taking for granted that the factory’s marks and bolt lengths are absolutely perfect. “Yeah,” Stuart laughs, “there’s your problem. That’s almost always the problem.”

Can you hear Stuart cussin’? Every chain adjustment effects ride height, and visa-versa, on the shortened ZRX swingarm fitted to the GPz. This system also takes quite a bit of time to get the adjustment exactly right side-to-side, which directly effects rear-wheel alignment. No big deal you say? Then think of a gearing change: you change sprockets and you are changing chain adjustment, ride height and have to re-align. Of all those tangibles, ride height is the biggest deal to a rider.

But I digress. I flew home and immediately stringed (strung?) my ’86 GSX-R1100 rebuild project featured in this blog (IENATSCH TUESDAY: Projects Old and New). Please read to the end of this story for my results. I plan to string everything in the garage, old and new. How easy is this? Darn easy! For example: Since I wasn’t too happy with my pictures while stringing the 11, I thought I’d rig the string on my GSX-R750 “just for photos,” but then quickly perfected the alignment with the string. Tools needed: Rear-wheel stand (centerstand could work if the string can run cleanly past it). Chain-adjusting tools, including a heavy hammer to help snug the wheel forward. Measuring device like a ruler. String, non-stretching if possible. Pair of jackstands or other heavy items to hold string ahead of front wheel, Stuart uses esoteric Bultaco crank halves. Knee pads are optional but recommended for you older fellers, but usually old fellers are smart and have a bench to work on…though most work benches are a bit too short.

This is the starting point, shown here on an older GSX-R750 with all necessary tools. The rear wheel is aimed to the right. (Yes, that’s an original GSX-R rear stand, just sayin’…)

Okay, let’s make this simple: we can use a tightly-pulled string to show the direction in which the rear wheel is aimed. This string will just touch the front and rear edges of your rear tire (or wheel if you don’t have a tire mounted) and then shoot forward, beneath the engine, to a point beyond your front tire. Stuart much prefers stringing with the tire in place and is wary of spoked wheels being out-of-true and of bent cast wheels. To make sure the front wheel is straight, measure the distance between the string and the front and rear edges of the front wheel on one side. This isn’t your alignment measurement; this is simply to be sure your front wheel is straight. If you accidentally bump the handlebars or wheel or fender during the process it’s no big deal because you can simply readjust the front wheel to be parallel with the string on one side. “And don’t get all sweaty about one or two millimeters,” Stuart advises. So…you’ve got your string wrapped/tied around the rear wheel and tire tightly enough to stay in place and low enough to run beneath the engine, but as high as possible. Your bike is in gear so the rear wheel won’t rotate with string tension. The string is long enough to extend ahead of the front wheel and you’ve secured each end to something heavy like jackstands.

Okay, all set from the rear of the 1100. Tying the string around the rear wheel/tire helps hold it in place and tie it just above a spoke, again to help hold it in place. Stuart saw this shot and advised to have the string as high as possible, higher than it is shown here, to lengthen the two points at which the string touches the rear tire.

Loosen your axle as usual for a chain adjustment. Be sure to leave the axle very-gently snugged so your rear wheel isn’t slopping around. At this point you’re ready to start checking your bike’s alignment. It’s also the point you can draft a willing helper because two people make this job go much more quickly, even if your helper isn’t too willing and likes to complain about cold cement floors and junky old bikes. The flapping lips of uninspired help is still preferable to a solo alignment! Also interesting: how the uninspired help loves the job when it’s her bike! But I digress. With the setup done, follow these steps:

Crouch on each side of the rear wheel and have your willing or unwilling helper slide the jackstands precisely enough so that the string just touches the front edge of the rear tire. It’s already touching the rear edge because it’s tied around the rear part of the wheel and tire. Having it touch the front edge gives you the direction in which the rear tire is aimed. Do that on both sides. Stuart recommends “strumming” the string gently to get a good feel for how much it is touching the front edge.
With measuring device in hand, crouch on each side of the front tire and measure the distance between the string and the front edge of the rim or tire. Now we’re getting to the heart of the matter. You want the string to be equidistant from the rim on each side.
If it’s not equidistant, you’re back to the rear wheel. Use the chain-adjusting mechanism to not just adjust the chain tension correctly, but to better-align the rear wheel. This will take a little give-and-take from side-to-side because you probably can’t just crank on one adjuster to get the alignment right because your chain tension will change too drastically. Remember to have your helper slide the jackstands so the string just touches the front edge of the rear tire before remeasuring at the front wheel.
At this point you have quit referring to your bike’s chain-adjustment marks. You are using the string in place of the marks and the adjusters to fix alignment and chain tension. You don’t care if the marks match side-to-side.
A few back-and-forths should get the job done. But wait. Check it one more time after you tighten the rear axle to make sure nothing shifted at the last moment. Stuart tightens and loosens the axle occasionally during the process to get a feel for any changes, especially with eccentric adjusters.
Take note of where the stock chain-adjustment marks are now that the wheels are truly aligned and the chain tension is within spec. From now on you will simply count “number or turns” on each adjustment bolt when adjusting chain tension, or “number of flats” as Stuart refers to the six sides of a bolt head. For eccentric chain adjusters Stuart likes to restring the bike every time he adjusts chain tension, but he’s one of those perfectionists. On his race bikes he’ll mark each side of the tensioner with a “+ .25” or other reminder.

The string alignment will dictate your axle position. Here, you can see the 1100 adjusters are half a mark off when the wheels are truly aligned. These close-up pictures reflect the 30 years of abuse that has been a joy to reverse (GSX-R fans, please check how this blog started: IENATSCH TUESDAY: A 30-Year-Old DIY Experiment)

*A note here: Stuart and every other professional roadracing mechanic I know recommends running chain tension at the loosest end of the factory recommended specification. “A tight chain takes out countershaft-sprocket bearings and binds suspension,” says Stuart. Okay fine, but there is a problem. An inherent problem is the fact that rubber and string are not all that precise. Tires probably don’t pop out of the mold exactly perfect. It’s easy to get the string slightly more-or-less tight against the tire edge each time when you’re just learning. Spoked wheels could be out-of-true, cast wheels might have a dinged edge. “Again, don’t get too worried about those issues,” Stuart advises. “If I can get my alignment within a few millimeters I’m pretty happy.” And that’s advice from a guy who has won a lot of stuff. Stringing is also an excellent way to uncover bent frames, swingarms, forks and wheels. If your bike won’t align, you could have one of these issues. Might not be a bad idea to string a bike you’re looking to buy.

On the left is where the 1100 started, the right is where it ended.

Finally, back to my ’86 GSX-R. By habit I had carefully aligned the chain-adjustment marks the last time I adjusted the chain. They were perfect, exact, and my dad would be proud. I live on a dirt road and the rear tire has a habit of spinning wildly under excessive throttle. The rear tire always stepped out to the right, regardless of road camber, and I initially checked the torque on the swingarm bolt and suspected worn swingarm bearings on my 29-year old sweetiepie. The tendency to go sideways was so pronounced that I was sure the swingarm was poorly supported. After stringing my bike per Stuart’s example (and discovering the alignment off by more than half a mark), the bike stays straight when the rear tire spins. The rear tire was cocked sideways in the swingarm and putting it straight immediately cured the step-out issues. Sure, that’s on a dirt road goofing around…but dirt-road grip is just pavement grip at a lower level. Thanks Stuart Anderson. More Next Tuesday!