Bike Program - Ask A Mechanic
Cascade SC 03 | 971-722-5379
Issues with your bike? Don't know how to fix it? Ask our mechanics.
Q: What is the plastic thing on the back of my bike next to the gears? It has been rattling and I'm worried its dangerous.
A: That plastic thing is a type of guard that prevents the rear derailleur (the thing that moves the chain back and forth when you change the gears in the rear) from over shifting and ending up in your spokes. It's official name is a "spoke protector". Only derailleurs that are incorrectly adjusted or bent do this kind of thing. Plastic spoke protectors sometimes get brittle, and then the plastic tabs that hold them in place on the wheel may break, causing them to move around and create noise. If this is what is happening then it is generally not dangerous, merely annoying.
Q: My brakes seem to rub in some places on the wheel, slowing me down and making noise.
A: This behavior is caused by a minor warp in the rim. Rims warp when the spoke tension is uneven - this can be caused by hitting a pavement or bump. This is called being "out of true". The surface of the rim becomes uneven, and the brake pads rub in certain places. You may be able to stop the rub temporarily by loosening the barrel adjusters on the brakes, but this may cause the brakes to be too loose overall. The only real fix for this is "truing the wheel", which is a process in which the rim is straightened.
Q: My bike doesn't shift well.
A: This is a problem that can have a variety of origins. Gear mechanisms can be complex. The drivetrain may be too dirty if it is clogged with grease, dirt and grime. The cables may not be moving cleanly through the housing if they are old and worn. The tension in the cables that activates the derailleur may be incorrect, being too low or too high. The limit screws that control how far the derailleur can move may be set improperly. And last but not least, the components such as derailleurs and shifters may be bent, worn, or damaged by a crash. A mechanic can diagnose the issue by shifting through the gears with the bike in a repair stand, and listening to any noises that the drivetrain makes, as well as noting the condition of the cables, as well as the drivetrain. Basic diagnostics and gear adjustments can be done in our bike shed.
Q: My cable ends are frayed. Is this dangerous?
A: It depends. Frayed ends of gear cables are probably more annoying than dangerous, impacting shifting (although getting poked by a frayed cable end can be more painful than you might expect). Frayed brake cables are dangerous, especially if they are also rusting or worn, as they can come loose, leaving you with no reliable brakes. Fraying is fixed by applying a cable tip if the cable is not too far gone, and replacing the cable and installing a cable tip if it is. Check with a mechanic if you are unsure. The cable pictured would need to be replaced.
Q: When do my brake pads need replacing?
A: Great question. Brake pads generally come with some kind of wear indicator. Some brake pads start squealing loudly once they are worn down, some have a wear line. If they are worn almost down to the bolt/cartridge, they definitely need replacing. Do not ride with worn down brake pads, it is unsafe and may damage your rim. Make sure you buy the right brake pad for your brake system, if you are in doubt, bring a worn brake pad to the bike shop when you buy a new set. If you need help installing your brakes, or they squeal after you have installed new pads, speak to one of our mechanics.
Q: My saddle got stolen with my seat post, and I need to get a new one.
A: Seat posts come in a plethora of sizes, where as saddles may look different, but essentially all fit onto seat posts in compatible ways. Even a millimeter or two difference in seat post diameter can be unsafe. Take your bike to a bike shop and ask them to measure the inner diameter of your seat post tube with a measuring device called a vernier caliper - this will guarantee you get a safe fit.
Q: I haven't ridden a bike in a while and my butt hurts when I ride. Do I need a different saddle, or should I just suck it up?
A: Biking is fun and comfortable if you're used to it - same as any other physical activity. While some people, especially those with a cushier behind and/or tailbone issues may need a bigger saddle, a bigger, softer saddle also provides more points of contact, potentially causing more pressure. In general, bodies adjust to biking after a couple of weeks or regular riding. If your bum still hurts after you have been regularly riding a fair amount, check in with a bike store to see if its your saddle, not you. There also may be ways to adjust the saddle so it is more comfortable.
Q: I had some lights but they got stolen. I can't afford to replace them. Is it legal to ride without lights at night?
A: No. Oregon law says the following: Cyclists must have a forward facing white light, and a rear facing red reflector to be legal. If you ride without visible lights, you may get ticketed by the police. Riding without lights is also really unsafe!
Q: Is it legal to ride without a helmet?
A: In Oregon, you must wear a helmet or have your children/youths wear a helmet if they are under 16 years of age. You do not legally have to wear a helmet if you are over 16. The PCC Bike Program strongly recommends always wearing a helmet!
Q: What pressure should my tires be at?
A: That depends on what kind you have. Large balloon tires on cruiser type bikes can only handle low pressures of up to 40 PSI, while mountain bikes need medium pressures of approximately 60PSI. Small volume racing tires can take up to 120 PSI. Check the sidewall of your tire to see what the minimum and maximum pressure levels are to keep you safe. Do not overinflate, as this can be dangerous! Overinflated tires may explode in extremely hot weather such as prolonged, direct sunshine on a very hot day.
Q: I'm scared of riding on the street. Can I ride on the sidewalk?
A: Yes, it is legal to ride on the sidewalk as long as you are not moving faster than a person walking, endangering walking people, or hindering them. It is not legal to ride on sidewalks in downtown Portland. See this article for more info.