The Morton Method of Replacing a Broken Dual Sport Motorcycle Rim
November 15, 2015
CONTRIBUTING WRITER: FRANK MORTON
A recurring shoulder has limited my riding time, but clearly has not dampened my ability to damage my bike! Think I did this by running too fast through a rocky area with too little tire pressure.
When I spotted this damage I was overwhelmed with questions: Do I buy a new wheel? Do I take it to a shop and have it fixed? Do I buy a new rim and try to fix it myself? If I try myself, can I actually get the spokes in right and true the wheel? And where did I put my coffee cup?
Well, in keeping with Dual Sport Alchemy’s grassroots DYI mentality and staying true to my nature as a tightwad, I figured I’d give it a try.
The first thing I did was build a jig that would ensure I set the rim at the correct position relative to the hub. For that, I simply took a piece of OSB (plywood if you will) larger than the wheel and drilled a hole in the center that the axle would fit into. I set the wheel on the OSB, sprocket side down (seemed the most stable position), and ran the axle through the wheel and into the hole I drilled. Next I cut four wooden blocks such that they would fit between the OSB and the rim, and screwed them to the OSB at the 12 ,3, 6 & 9 o’clock positions.
At this stage I used a marker pen to identify where the original rim sat on the blocks. These marks helped me set the new rim on the blocks right were the old one did.
Had I to do it over again, I would likely place more blocks around the rim, perhaps up to 8. I’m thinking that it may have streamlined the process.
The second step was to spray all the spoke nuts with penetrating oil just to ensure that they would come loose without a fight, then I zip-tied all the spokes where ever they crossed one another.
By doing this my hope was that they would remain in their correct pairs and make it easier to line up into the new rim. It worked like a charm. All the spokes just hung right where they were supposed to. All I had to do was remove all the spoke nuts, lift the broken rim off and set the new one in place. All the spokes lined right up, so I started ‘bolting’ them into place, starting at the wooden blocks first, then working my way around snugging the nuts lightly as I went.
What I noticed as I was beginning to tighten the spoke nuts, was that if I tightened the ones attached to the top most spokes, the rim would lift off the block. If I tightened the ones attached to the bottom most spokes, the hub would actually lift off the table. If you try this yourself, you’ll see immediately what I’m getting at.
Once the spokes nearest the blocks were snugged down, I began the process of attaching the rest of the spokes, trying to mimic the amount of torque I had used to attach the previous group.
The last step now was to ‘true’ the wheel. Again, I built a jig to hold the axle and wheel, and used a straight edge to measure side to side as well as circumference accuracy. As I think about it now, I could have just as easily put the wheel back on the bike and not needed a jig.
FRANK’S RUSTY PIECE-O-CRAP JIG, PATENT PENDING
Truing the wheel really isn’t as hard as it would seem, but can be time consuming. And it’s much harder, I think, to explain than to actually do it. Don’t be intimidated! Here’s how the process goes: let’s say that you’re facing the wheel on your jig (or bike), and as you spin it, you see that in one small spot, the rim pulls to your left. Loosen the nuts on the spokes that pull it to the left, and tighten those that pull it to the right.
A question you might ask here is how many spokes and how loose/tight to make them. Sort’a depends on the severity of the distortion. If it’s just a slight distance, I would likely loosen one at the center of the distortion, and one on either side of it. The two spokes on each side of the center one would be loosened about half as much as the center one. See where we’re going with this? To pull it to the right, I’d tighten the one in the center first, then two on either side about half as much as the center. The larger the distortion, the more spokes I would work with. The good news is that it’s easy to catch on to how it all works very quickly.
To true the wheel’s circumference, work exactly the same way, but this time you’ll tighten both left and right pulling spokes equally.
After you have the wheel trued, start gently tightening all the spokes, always watching that you don’t pull it out of true. Eventually you’ll have all the spokes tightened equally, or as equally as your calibrated wrists can measure, and the wheel will still be true. Oh, if you’re wrists aren’t calibrated, you can spend a lot of money for a spoke torque wrench. Yeah, they really do make one, but I wasn’t about to spend money on one when it could go towards something I really need, like more coffee!
About the Author: Frank Morton might have had a short-lived career as a Sensitivity Trainer had he not decided to enlist in the Marine Corps the day after graduating High School and go to Vietnam. After his Tour of Duty he joined the Oregon State Police and spent several decades fighting crime and scraping dead people off highways. Now retired, he enjoys quilting, floral arrangements, bridge club, and body-slamming himself and his Yamaha WR250R into the dirt.