X-NEWS: cerritos.edu rec.motorcycles: 79666 Relay-Version: VMS News - V6.1B1 12/08/92 VAX/VMS V5.5-2; site cerritos.edu Path: cerritos.edu!nic.csu.net!usc!zaphod.mps.ohio-state.edu!moe.ksu.ksu.edu!engr.uark.edu!mbox.ualr.edu!chaos!dave.williams Newsgroups: rec.motorcycles Subject: rec.motorcycles FAQ of 93.02.01 (Part 4 of 6) Message-ID: <35128.89.uupcb@chaos.lrk.ar.us> From: dave.williams@chaos.lrk.ar.us (Dave Williams) Date: 30 Jan 93 20:18:00 GMT Reply-To: dave.williams@chaos.lrk.ar.us (Dave Williams) Distribution: world Organization: The Courts of Chaos * 501-985-0059 * Public Access Usenet Lines: 208 ===================== Q: The front brakes on my bike make a buzzing noise. I've looked all over and can't see any loose parts. What is it? A: You probably have drilled or slotted rotors. The holes often make a noise as they move past the pads. Some bikes have floating rotors which can make intermittent noises. In either case it's nothing to worry about. Q: Are drilled or slotted rotors more efficient than solid rotors? A: There are many different reasons rotors are drilled or slotted. Sometimes the rotors are drilled to lighten them, though your weight savings is probably negligible. Honda claims the discontinuities help braking in the rain and provide an escape route for mud or rust. Fred Puhn's "Brake Handbook" says, "Some rotors have slots or holes machined into their contact surfaces. These reduce hot-gas and dust particle buildup between pad and rotor. Although fade caused by gas buildup is less for a disc brake than for a drum brake, some fade still occurs. This is more prevalent with large brake pads, because the hot gas has a harder time escaping than with small pads. Therefore, slots or holes have greater effect in racing, where pads are large and temperatures are very high." Newcomb & Spurr's "Braking of Road Vehicles", 1967, tells us the mass of the rotor is the primary factor for preventing brake fade. When the rotor mass has absorbed enough heat, the brake will fade. Vented rotors and ducting schemes will cool the rotor faster, but it takes time; in rapid repeated braking cycles vented rotors do little better than solid ones. Carroll Smith's "Prepare To Win", 1975, says "Lately you may have seen discs with tangential slots milled in the friction surfaces or holes drilled in a tangential pattern normal to the friction surface. This is an effort to wipe the "fireband" or boundary layer off the disc before it reaches the point of contact with the pad and to provide the very hot particles of friction material worn off with some place to go other than the operating area." ===================== Q: I have a 1973 Kawasaki Z-1. My owner's manual says it should run premium leaded fuel. Will it hurt the engine to run unleaded? The local shop says they need to install hardened valve seats for $400. A: No. Your Kawasaki already *has* hardened valve seats. Engines with aluminum cylinder heads must have seat inserts, as aluminum is not a suitable seat material. Someone is trying to rip you off. *** Lights: Q: I've seen ads for light modulators that flash the headlight and brake light. Are these really useful? Should I buy one? A: In general, no. Many states and municipalities prohibit flashing lights (other than turn signals) except on authorized emergency vehicles. Check your local laws before you buy. Even if you're legal at home you still might pick up a ticket elsewhere. Flashing lights often infuriate cagers, who will then mess with you. Generally, the cagers win. The flashing is also *very* bad for halogen bulbs. Expect your headlight life to be significantly decreased. *** Personal Equipment: Q: I'm considering the purchase of a new helmet. The one I have doesn't feel too good for some reason, even though it's the right size. How can I tell when a helmet fits right? A: First off, helmet sizes are like shoe sizes - they're only a general guideline. Don't expect a size 8 to be the same size from two different manufacturers. Every brand of helmet is shaped differently inside. Of each brand, most models are also different. The only way to find a properly fitting helmet is to cruise the local shops and start trying them on. Try ALL of them on, not just the expensive or pretty ones. Proper fit is more important than gaudy stripes or fancy certification. A properly fitting DOT-rated helmet is safer than a badly fitting Snell-rated helmet. The helmet should fit snugly. It shouldn't clamp your ears like a vise, perch on top of your head like a ferret wearing a coffee cup, or try to cave in your forehead. It shouldn't have any loose areas either. As long as the chin bar doesn't try to move your jaw back to your ears you're OK; in some helmets you're not *supposed* to be able to touch the chin bar. Many newer-design helmets have extensive padding in the cheek area. This padding can cause interference with glasses. You can sometimes get the cloth liner loose and cut reliefs with a razor blade. You can also pull the liner loose and add extra foam to adjust the fit in any loose areas. It's not a good idea to try to cut the styrofoam section away to adjust the fit - find a different helmet. Some people get upset at the idea of altering the fit of their helmet. The decision is up to you. ===================== Q: The wind and engine noise from my bike get to me after a while. Is it safe to wear earplugs when I'm riding? A: I've never had a problem. I keep a couple sets of cheap foam plugs in my bike's storage compartment; when I expect a ride to last more than half an hour or so I put them in. They lessen the noise a lot without blocking out sirens or screeching brakes. In some places it is legal to drive if you're deaf, but not if you are wearing earplugs. Check your local laws. ===================== Q: What's a good buy for a leather jacket? A: ronen@gg.caltech.edu writes: Things to look for in a leather jacket: OVERALL SUMMARY: - Thick leather is a must. This is what makes the difference between a motorcycle jacket and a fashion jacket. Protection: - Thick leather: heavy motorcycle leather (not "fashion" weight) 3-3.5oz weight or ~1-1.3mm thickness - Elbow pads - Shoulder pads Cut & Fit: up your back or the sleeves sliding up and leaving a gap at the wrist. - Sleeves really long - Back should feel a little "hunch-backed" when standing upright (more important on sport bikes than cruisers) - Try it sitting on the bike. - Fits closely in the forearms (sleeves zippered) - Down only to hips if you dislike bunching up that longer touring gear does. - Make sure to leave room inside the jacked for sweaters & such. - Don't buy anything you haven't tried on [conflicts w/ later suggestions for buying mail order] Comfort/Convenience: - Zipper front - Flap behind zipper to keep out the cold - High collar - Snap-down collar to keep it from slapping your cheek/neck - Vents (zippered) to let in air during summer; grommets at armpits - Removable (zip out) lining - Zippers at wrists to keep sleeves from sliding up (while you're sliding down the road) - Lower back support panel for when you fall down. - Stiff leather won't flap in the wind. - (Tie a leather thong through hole in zipper tab for easy zipping w/gloves) Durability: - Full-grain hides are preferred for repeated abrasion resistance, but split or top grain will probably work the first time you fall down. - Double-stitching Where to buy cheap: - Sears surplus outlet - J.C. Whitney catalog - Mail-order places (see ads in riding magazines) - Pawn shops - Check police stations for Highway Patrol officers wanting to sell used gear. (If calling used/pawn/surplus stores: Try to get as much info as possible over the phone. Give your size, etc. Be sure to say motorcycle jacket, otherwise they will say "Sure, come on over we've a fur lined brown leather coat and a pair of disco leather patch pants.") Miscellaneous: - [The MSF course I took emphasized comfort first, protection second -- being uncomfortable increases the likelihood of an accident, and it's most important to decrease that likelihood. Next important is protection, so that if an accident does happen, the damage is minimized. Discomfort includes too hot, too cold, too wet, too dry.] - Get a jacket you really like (off the bike too); if you're like a lot of folks, you'll wear it all the time anyway. - Don't worry about stiffness; some new jackets need to break in. - Hein Gericke jackets have it all, if you're willing to pay the price. Sometimes discounters may have them cheaper than most dealerships. (end of part 4)