Little Known Safety Problems
by Guy Minnick
from the December 2006 WheelPeople
Working in bike shops for over 20 years, I’ve heard many stories behind crashes. There have been some manufacturing and design issues that have come up, but a lot of crashes have been caused by small events that were ignored by the rider, leading to worse problems. This article will alert you to potentially dangerous conditions that are often overlooked on both new and old bikes.
Under the category of design flaws, the worst that comes to my mind were the late 1970’s Viscount cast-aluminum forks that would break without warning. Replace any that are still on the road. There are many mountain bikes, hybrids, and touring bikes using old-style cantilever brakes, which stop quite well. The problem is that if your main brake cable snaps, the straddle wire will drop onto the tire. With knobbies this will lock up the wheel and send you flyingmake sure there is a safety hook, usually in the form of a reflector bracket, to prevent this from happening. Long toe clips or big shoes on short-wheelbase bikes can cause your own foot to interfere with the steering, especially at slow speeds. While some cyclists accept this risk, check for clearance on all performance bikes and at least be aware of the problem. There are some bikes on which the cables can catch on the front reflector or other protrusion under the bars, or the cables are just too short. Swing your handlebars fully in both directions to look for this problem.
When I think of little maintenance issues that can lead to major crashes, the most common is the bent rear derailleur. Often a minor bump knocks the derailleur inward, but the bike is still rideable. The symptoms are noisy gears, combined with difficulty shifting into high gear (the smallest cog in back). The danger here is that when you shift to the low gear (the largest cog in back) the derailleur will swing too far inward and catch in the spokes. This usually destroys the derailleur and bends the wheel and derailleur hanger. Stand behind your bike and check that your derailleur is verticalif not, have it aligned before riding again. You can see this condition on other rider’s bike when you are riding behind them.
Another “two-part” crash is the dented wheel. Many people continue riding after hitting something, not realizing that the dent can cause the brake to grab or bring the tire sidewall into the brake-shoe zone so the pad quickly eats through the tire, causing a blowout. Speaking of brake shoes, check yours for “shelving.” If mounted even just a little bit too low, the pads can develop a lip that can hook under the rim, preventing the brakes from releasingnot a good thing if you are in the middle of an intersection! Replace any shoes with this condition. With cantilever or linear-pull brakes, whose pivots are on the frame, the shoes ride downward as they wear. Really low shoes can swing completely under the rim and lock into the spokes. On the other hand, with side-pull brakes, they migrate upward toward the tire. Squeeze your brakes hard while watching the action of the shoes, and check the tire sidewalls for wear. The rim itself can be worn thin enough by the brake pads to cause structural damage. Many modern rims have wear indicators stamped into the metal, but on older bikes you can only judge by feeling how concave the braking surface has become. Replace a wheel that is deeply grooved.
Anyone riding a bike with horizontal dropouts (i.e., the wheel mounting slots) in the rear should check the quick-release or axle nuts for tightness. If at all loose, when you pedal forcefully, the wheel can slip forward, jamming the tire against the frame. This will slow you down just as you are really trying to go! Also see Sheldon Brown’s more detailed advice on quick releases at http://www.sheldonbrown.com/skewers.html.
Do the shoes you pedal in have laces? Tie them in a double knot on the outside of your foot to prevent them from catching in the sprockets or winding around the pedal shaft. A shoelace can bind your foot to the pedal, causing you to fall when you stop. How about your pump? If not secured, it can bounce off and fall into your wheel (or a fellow rider’s), causing a crash. Hand grips can slip off just when you need them the most, especially in wet weather. Make sure yours are glued on if at all loose. Plug the ends of any exposed handlebars to avoid the unfortunate “apple core” injury in a crash.
Of course, sometimes crashes are actually caused by the rider’s own adjustments. Most importantly, never raise the seat post or handle stem above the “safe limit” mark. These marks are sometimes hard to see. If unsure, have them checked. Exceeding the limit can cause the post or stem to break off. If you have done work on your bike, double check everything. On a recent ride, someone who had just changed his pedals had one fall off!
The more you know about bikes, the more confidently you will ride. Be alertdon’t ignore noises or anything that doesn’t feel right. A part that rattles may be about to fall off. Look at your fellow riders’ bikes, too, and speak up if you see a problem. Let’s make safety something we’re all conscious of.
Guy Minnick is the Service Manager at The Bikeway Source, Bedford, MA.