Checking Wheel Alignment
From: Rob Lentini <lentini@AZStarNet.com>
Date: Tue, 7 Mar 95 12:48:16 MST
OK, here’s how to check wheel alignment on a motorcycle. We’re going to measure the lateral alignment of the front to rear tire when both are parallel–going in the same direction.
Place the motorcycle on its centerstand and put the transmission in 1st gear. Tape the center of a 14 ft length of string to the rear tire tread, about 45 degress or so up from the bottom of the tire and to the rear of the motorcycle. Draw each resultant 7 ft section of the string forward to the front tire so that the string is extending to the left and right of the front tire.
Stoop in front of the front tire and, while pulling each string forward to straighten it, adjust the string to where it just contacts the rear tire’s shoulder on the forward section of the rear tire. Turn the front tire until its shoulders are parallel with the string you are pulling to either side of it. You now have a plane projected foward to the front tire on both sides allowing you to measure lateral alignment. Any misalignment is simply the dimensional difference from each string to the front tire shoulder. It’s very important that your measurement not be influenced by the string touching anything else, such as mufflers, stands, etc.
If the right string is closer to the front wheel than the left, your rear wheel is aligned to the left of the front wheel. This will result in “pulling to the right”. Why? Because the center of gravity is moved to the right with rear wheel misalignment to the left. The machine wants to fall to the right, and will have to be corrected with constant left handgrip pressure.
Now then, just because you measure some misalignment doesn’t mean there’s a problem! Joe Senner has 5mm left misalignment at the rear, and the bike tracks fine until the tires are gone. This is probably more of a function of road crown wear. Conversely, Howard Guenther, even with new tires, has a SERIOUS pull to the right. Something’s wrong here, maybe the alignment, maybe not.
As I stated in another post, K-bike alignment may be adjusted by adding/deleting wheel hub shims. On older Rs it can also be done, but I’m not an authority on this. I do know you can fit a slightly larger tire to a /5 and space the hub out for swingarm clearance. Anyone know how to go the other way–move the wheel to the right? Howard may need to know how!
Another method to check wheel and frame alignment
From: John Bellis <email@example.com>
Date: Sat, 9 Oct 1999 01:57:56 +0800
Ever since I was sold an RG 500 with a handling problem, I have never solely relied on the stringline method of wheel alignment. It’s possible to “wheel align” a badly bent bike and still have it self-steering dangerously either left or right.
My method will reveal to you a bent frame, (should it be bent) and will give heaps better alignment on a good frame than by the stringline method alone. Nearly all modern bikes have front and rear disks. First obtain a small 12 inch magnetic spirit level and put it on the rear brake disc. With the bike on a solid level floor, straighten the bike up so that the back wheel is exactly perpendicular according to the spirit level. Chock the bike up in this position so it doesn’t move. Proceed to the front wheel, attach the spirit level to the disc there now and by gently turning the handlebars, position the front wheel so that it too is perfectly perpendicular according to the spirit level. Go back and forth rechecking to make sure both wheels are 100% perpendicular. You will notice the front wheel flops downwards to either side when you steer sideways and will (should) only be perpendicular when the handlebars point the bike straight ahead.
If you can immediately see the handlebars are off line, then the frame is bent. (I was horrified to see the ‘bars on my RG 500 out of alignment by at least 25-30 degrees, when both wheels were perfectly perpendicular to the ground.)
Now use the stringline method to stringline/adjust the wheels into alignment when both wheels are perpendicular to the ground. If you can’t do it (it will not align), then take your bike to a professional frame straightener and get it checked out and repaired. In my case the 3 month warranty had just expired on the bike and I foolishly kept riding it in its unsafe condition. A power slide through dust on the road triggered off a tankslapper which threw me into a signpost (4 broken ribs) and wrote off the bike. I was insured, so at least I got my money back. By the way, I take my spirit level with me when I go to view a used bike for sale, once bitten……..
Hope this helps someone.