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Riding Tip #3
This isn’t so much a riding tip per se but a tuning tip that can help your riding.
One thing that folks often remark on is the fact that at speed their bike seems unsettled or unstable. It’s fine at 20 mph but at 40 mph it doesn’t inspire confidence and at 50 mph it gets downright scary. In most cases this can be rightfully diagnosed and fixed making sure that the rider has the proper position and weight distribution. But sometimes nothing seems to make the bike settle down and feel good at speed. I should say that a bike that fits and handles properly will gain stability as speed increases not the other way around.
I’ve found that in a large percentage of cases the bike can be made to behave better and feel more calm and stable at speed if the wheels are properly balanced. Most of the time wheels are balanced well enough without actually balancing them but in some cases this isn’t true. It’s very easy to get a rough feel for how well the wheels are balanced by taking the front wheel and holding it in your hands and giving it a quick spin. If it’s balanced reasonably well it will feel stable in your hands and not want to bob up and down. If it is badly out of balance it will be hard to hold stable and will bob up and down with some gusto. This is not a precise test by any means but it will give you an intuitive feel for how well the wheel is or isn’t balanced. It’s easy to picture when doing this what is happening on a fast descent if both the front and rear wheel are wanting to go up and down like this.
As rim designs and spoke counts have changed over the years this has become a bigger issue. Many high profile alloy rims are very out of balance due to their large seam. In the past the seam was set opposite of the valve stem and these two things did a reasonable job of balancing each other out but with some modern high profile rims the weight of the valve stem isn’t enough to balance out the weight of the rim seam. So as a matter of course I now balance all my wheels. It’s easy and simple to do and once you get the procedure down it will only take a few minutes to get right.
Here’s how I do it. There may be better and more precise ways to do this but the way I’ll describe is simple and reasonable accurate. I do both the front and rear wheels the same way. I’ll describe the procedure I use for the front –
1) Take your wheel with both the tire and computer magnet mounted and place it in a truing stand. If you don’t have a stand you can use an old fork or even leave the wheel in the bike (if you leave the wheel in the bike the bearings must be perfectly adjusted or you will have a very hard time with this).
2) With the wheel in the stand give it a spin and let it come to a stop. If it doesn’t stop and reverse directions a few times at least before coming to rest you need to address the bearing adjustment before going any further. The wheel should stop spinning one way and spin back the other and so on until it gradually comes to a complete stop.
3) With the wheel now stopped make a mark the rim at the lowest point (bottom dead center if you will) with a marker. I use a dry erase marker as it’s so easy to clean off later. Now do the same thing at least 3 more times. If all goes well you’ll be making marks in the same place each time. If not I would suspect bearing adjustment.
4) Assuming you keep getting the same results you now have a mark at the heaviest part of the assembled wheel. The first thing I do to balance things is to use your computer magnet. You should relocate it a spot directly opposite the mark on the rim so the magnet is at the lightest part of the wheel. After relocating the magnet do the spin and mark test again and adjust the location of the magnet as necessary to get the best results. Keep moving the magnet to the spot opposite the mark on the rim until you get a consistent result.
5) After you’ve used the magnet as best possible you’ll most likely need to go a step further and actually add a small amount of weight. I use small stainless washers (about a 10mm O.D.) as weights. For testing and setting up I just use a small piece of masking tape to hold the washer to the rim. Tape the washer to the rim at the high point and give it another spin test. You’ll know when you’ve got it right when the wheel refuses to stop at the same point each time. When right the wheel will not reverse direction and oscillate back and forth but will slowly come to a stop at a random spot. You may need more than one washer if the wheel or tire is much out of balance.
6) Lather, rinse and repeat as many times as necessary to get a random stopping point without a reversal of direction. When you get to the point where you are satisfied that you have got it right mark the location(s) of the washer(s) and remove them. You’ll then want to reattach them in a more permanent fashion. I use double-sticky foam tape. I stick the washer to one side of the tape and trim around it to give it a clean look and then remove the paper backing and stick it back on the rim where you made your mark(s).
7) Now with the balance weights firmly attached take the wheel out of the stand and give it a quick spin while holding it by the axle. It should feel smooth and balanced and not want to bob.
Note this is not a super precise deal like when balancing a car tire. On a car the weights involved are large the speeds are in most cases much greater than you’ll find on a bike so the precision needed is much greater. On a bike getting it pretty good is good enough.
Do both front and back wheels this way (if doing the rear wheel while in the bike slip the chain off the cassette so the drag doesn’t mess with your results and so it can reverse direction). Now put the wheels on the bike and go bomb down the biggest, fastest hill you can find. If you had to put many washers on to get the wheel balanced I’ll bet you notice that the bike feels more stable and calm and surefooted. Note that if you remove the tire/tube for any reason you should redo this procedure as you are balancing the unit as a whole and messing with the tire will mess with the balance.
Thanks for reading. Go fast.
Dave
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