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Frequently Asked Questions (FAQS);faqs.172 There is substantial data on this and shops like Wheelsmith, that build many wheels, can tell you that for instance, no MA-2 rims have cracked while MA-40 rims fail often. These are otherwise identical rims. Hard anodizing is also a thermal and electrical insulator. Because heat is generated in the brake pads and not the rim, braking energy must cross the interface to be dissipated in the rim. Anodizing, although relatively thin, impedes this heat transfer and reduces braking efficiency by overheating the brake pad surfaces. Fortunately, in wet weather, road grit wears off the sidewall anodizing and leaves a messy looking rim with better braking. Anodizing has nothing to do with heat treatment and does not strengthen rims. To make up for that, it costs more. --------------------------------------------------------------------------- Clinchers vs. Tubulars (F.J. Brown F.Brown@massey.ac.nz) D.H.Davis@gdt.bath.ac.uk gave some useful hints on mounting clinchers, mostly involving the use of copious quantities of baby powder, and trying to convince me that clinchers aren't difficult to mount, so ease of mounting isn't a valid reason for preferring tubulars. wernerj@lafcol.lafayette.edu wrote that although average tubulars ride 'nicer' than average clinchers, there are some clinchers around that ride just as 'nice'. He also said that ease of change isn't a good reason for preferring tubulars as if you flat in a race, you're either going to swap a wheel or drop out. He pointed out that tubulars end up costing $20 - $80 per flat. ershc@cunyvm.cuny.edu gave some of the historic reasons that tubulars were preferred: higher pressures, lower weight, stronger, lighter rims. Said that only a few of these still hold true (rim strength/weight, total weight), but he still prefers the 'feel' of tubulars. leka@uhifa.ifa.hawaii.edu started this thread with his observations on clinchers seperated from their rims in the aftermath of a race crash. stek@alcvax.pfc.mit.edu comments on improperly-glued tubulars posing a threat to other racers by rolling off, and noted that this couldn't happen with clinchers. jobst_brandt@hplabs.hp.com agreed with stek, with the additional note that it is inadequate inflation that often allows tubulars to roll. Kevin at Buffalo agreed with stek and jobst about tubulars (improperly or freshly glued) sometimes rolling. ruhtra@turing.toronto.edu says he uses clinchers for cost and convenience. Clinchers let him carry around a tiny patch kit and some tyre irons, costing 60c, whereas tubulars would require him to carry a whole tyre, and would cost more. CONCLUSIONS: THE CLINCHER VS. TUBULAR WAR Tubulars - used to be capable of taking higher pressures, had lower weight and mounted onto stronger, lighter rims than clinchers. Clinchers have now largely caught up, but many cyclists thinking hasn't. Tubular tyre + rim combination still lighter and stronger. - are easier to change than clinchers. This matters more to some people than others - triathletes, mechanical morons and those riding in unsupported races. - cost megabucks if you replace them every time you puncture. ***However*** (and none of the North Americans mentioned this) down here in Kiwiland, we ***always*** repair our punctured tubulars (unless the casing is cut to ribbons). The process doesn't take much imagination, you just unstitch the case, repair the tube in the normal manner using the thinnest patches you can buy, stitch it back up again and (the secret to success) put a drop of Superglue over the hole in the tread. - can roll off if improperly glued or inflated. In this case, you probably deserve what you get. Unfortunately, the riders behind you don't. Clinchers - can be difficult to change (for mechanical morons) and are always slower to change than tubulars. Most people still carry a spare tube and do their repairs when they get home. - are cheaper to run: if you puncture a lot clinchers will probably still save you money over tubulars, even if you repair your tubulars whenever possible. Tubulars are only repairable most of the time, you virtually never write off a clincher casing due to a puncture. - have improved immensely in recent years; top models now inflate to high pressures, and are lighter and stronger than they used to be. Likewise clincher rims. Some debate over whether tubulars are still lighter and tubular rims stronger. Probably depends on quality you select. No doubt that high quality clinchers/rims stronger, lighter and mor dependable than cheap tubular/rim combination. --------------------------------------------------------------------------- Presta Valve Nuts (Jobst Brandt jobst_brandt@hplabs.hp.com) Two points here: 1. The jamb nut holds the stem when pumping so that it does not recede into the rim when pressing the pump head against the tire. This is especially useful when the tire is flat (after installing the tube). It also keeps the stem from wiggling around while pumping. I have not had difficulty in removing the nut over these many years of bicycling. When hands are very cold this is a problem, but then so is everything else. Just opening the valve nut on a Presta valve can be difficult under such conditions. 2. Breaking off stems while using a frame pump is a misunderstanding of the concept. I find new tubes along the roadside with broken off stems. The pump head is to be held in the fist and pumping force is supposed to be between the hands, not the hand and the rim. To practice this action take the pump in hand with the thumb over the outlet and pump vigorously letting no air out. No net force should escape since there is no other body involved. This is essentially what should take place when pumping a tire. That the some of the people who do not grasp this concept have deficient thinking is proved by their discarding the evidence along the road. They also have no concept of blatant littering for which there are large fines in this area. They probably think it serves the stupid tube right for breaking off. I think otherwise. It is unfortunate that bike shops do not instruct new bike owners about the use of the frame pump and some tire patch hints like don't try to ride a freshly patches tube, carry a spare and always use the spare after patching the current tube. I think we covered that extensively here earlier. If it isn't in the FAQ it should be. --------------------------------------------------------------------------- Ideal Tire Sizes (Jobst Brandt jobst_brandt@hplabs.hp.com) > I'm getting a custom frame built and wondered what > people thought of using 26 inch road wheels. Smaller > wheels ought to be lighter and stronger. and goes on to list advantages and disadvantages, most of which are less that important in deciding what size to use. What in fact brought us the wheel size (700 or 27") that we have is better understood by the women riders who have a hard time fitting these wheels into their small bicycle frames. Wheels would be larger than they are if they would fit the average riders bike, but they don't. So the compromise size is what we are riding today. > It seems to me that the most obvious reason for using 27" > wheels is tradition, but I'm not sure the advantages make > it worth trying to swim upstream. What do you think? This line of thought is consistent with the "cost be damned" approach in bicycling today. The big bucks are spent by people who want the best or even better than their peers. The more special the better. Riders consistently spend nearly twice the money for wheels and get worse rims when they choose anodized ones, whether there is merit to this finish is of no interest. They cost more so they must be better. How "custom" can you get than to have wheels no one else on the block has (maybe 25"?). If enough riders ask for 24", 25" and 26" wheels, manufacturers will up the price as their product lines multiply and the total sales remain constant. Tires and spokes will follow as a whole range of sizes that were not previously stocked become part of the inventory. Meanwhile, bike frames will come in different configurations to take advantage of the special wheel sizes. SIzes whose advantages are imperceptibly small but are touted by riders who talk of seconds saved in their last club TT or while riding to work. A larger wheel rides better on average roads and always corners better because it brings a longer contact patch to the road. A longer contact averages traction over more pavement and avoids slip outs for lack of local traction. Visualize crossing a one inch wide glossy paint stripe with a 27" wheel and an 18" wheel when banked over in a wet turn. I see this subject arise now and then and it reminds me of the concept of splitting wreck.bike into several newsgroups. The perpetrators bring the matter up for many of the wrong reasons. Ride bike, don't re-invent what has been discarded. =========================================================================== Headsets, Forks Indexed Steering (Jobst Brandt jobst_brandt@hplabs.hp.com) > In the several years I spent working in a pro shop, I have never seen a > case of "index steering" (yes, we called it that) that was _not_ caused > by a "brinelled" headset - one with divots in the races. I am 99.999 > percent certain that that is your problem. What are you going to do if > you don't fix it? I suggest that you fix the headset even if you sell > the bike, as a damaged headset could be grounds for a lawsuit if the > buyer crashes. I disagree on two points. First, because the use of the term brinelling conveys a notion as incorrect as the phrase "my chain stretched from climbing steep hills" and second, because there is no possibility of injury or damage from an "indexed" head bearing. Damage to the head bearings seems to be twofold in this case because the steering, if properly adjusted, only gets looser from dimpled bearings and would not become arrested by the dimples. So the head was adjusted too tight or it got tighter inadvertently. However, dimpling is caused by lubrication failure and occurs while riding straight ahead. This condition is worsened by a tight bearing while a loose bearing would introduce more lubricant if it were to rattle. If you believe it comes from hammering the balls into the races, I suggest you try to cause some dimples by hammering with a hammer onto the underside of the fork crown of a clunker bike of your choice. Those who pounded in cotters on cottered cranks will recall no such dimpling on the BB axle and even though this is a far smaller bearing race than a head bearing and the blows are more severe and direct, no dimples were made. Ball bearings make metal-to-metal contact only when subjected to fretting loads (microscopic oscillations) while in the same position, as in riding straight ahead on a conventional road. If you watch your front axle while rolling down the road at 20+ mph you will notice that the fork ends vibrate fore and aft. This motion arises not at the blade tips but at the fork crown and articulates the head bearing in fretting motions that are not in the normal direction of bearing rotation. Any substantial steering motion replenishes lubrication from adjoining areas. Lubrication failure from fretting causes welding between the balls and races and these tiny weld spots tear out repeatedly. The result is that at the front and rear of the races elliptical milky dimples occur. Were these brinelling (embossed through force) they would be shiny and round. Various testimonials for the durability of one bearing over another may be based on good experience, however, the differences in most of these was not in the design of the bearing but rather the type of lubricant used. A ball bearing is not suitable for this use. This is in spite of their use in almost all bicycles. To reduce point loads and to protect the rolling elements from fretting motion, roller bearing head bearings have been built. In these the rotary motion is taken up in needle bearings on conical races and the fork articulation is absorbed by an approximation of a spherical cup (the steel race) against the aluminum housing. Both of these bearings are ideally loaded. The rollers all remain in contact and carry rotary motion while the plain spherical bearing remains in full contact carrying low pressure fore and aft motion. I am disappointed that roller bearings until now have not been suitably perfected to rid us of the age old bearing failure. Maybe some day soon Sun Tour, Campagnolo, Shimano or Stronglight will emerge with an easily adjustable and fully compatible bearing. The one I am using is durable but not easily adjusted and it has too great a stack height to qualify for a recommended replacement. =========================================================================== Brakes Center Pivot vs. Dual Pivot Brakes (Jobst Brandt jobst_brandt@hplabs.hp.com) Sidepull (one central pivot) brakes operate at a small angle to the rim. That means the pad moves in a nearly perpendicular direction to the braking surface and the pads can be completely worn down without adjusting their position. The unit is light and has a self contained quick release and cable adjustment feature. Its weakness is its thin arms that, in the pursuit of light weight, flex in the bending direction. With the current practice to minimize tire clearance on road bicycles, sidepull brakes cannot be used off road for lack of dirt clearance. Their return spring is anchored in a way that relative motion occurs between it and the brake arms. This motion demands lubrication and in its absence the brake does not center itself. This is a perpetual problem that has not been solved and has given rise to many designs, the latest of which is the Shimano dual pivot brake. This brake has the disadvantage that it cannot track a wobbly wheel because it is forced to be centered. The cantilever and centerpull brakes are inversions of the same design. Both have pivot points that are at 45 degrees to the brake surface, but the centerpull offers no advantage over sidepulls because it has all the same problems and not the advantages. In contrast the cantilever is the most rigid of available brakes and offers more tire clearance for off road use. The approach angel moves the brake pads in an undesirable direction so that as the pad wears it must be adjusted to prevent falling off the rim. With wear, the centerpull goes into the tire while the cantilever allows the pad to pop under the rim, never to return. Cantilever brakes have the additional problem that their reaction force spreads the forks. For this reason, U shaped stress plates are made to contain this force. For forks with telescopic suspension, braking restricts forks motion. Nearly all bicycle brakes have about the same mechanical advantage (4:1) that arises primarily in the hand lever. The "calipers" all approximate a 1:1 ratio. This is necessary to fit the reach of the average hand and the strength of the hand in proportion to body weight. That is to say all brakes are made to about the same human specification. Force and motion are a trade-off and this is the result. The Campagnolo Delta and Modolo Chronos brakes have a variable ratio that at the extremes ranges from infinity to zero, its motion being generated by an equilateral parallelogram that changes from one extreme to the other. This is an undesirable feature, especially as the pads wear and braking takes place in the zone of increased lever travel and increased mechanical advantage. The brake bottoms out abruptly. Servo activation on cantilever brakes has been offered in a design that uses the forward thrust on the brake post to add force to the application. Self servo effects are undesirable in brakes because the proportionality between braking and hand force is lost. You don't know how much braking you will get for a given hand lever force. It can vary widely and in some circumstances cause an unwanted skid. =========================================================================== Adjustments and Repairs Seat adjustments (Roger Marquis marquis@well.sf.ca.us) The following method of setting saddle height is not the only method around for setting your saddle height but it is the most popular among coaches and riders both here and in Europe. A) Adjust saddle level or very slightly nose up, no more than 2mm at the nose. B) Put on the shoes you normally ride in. Have wrench ready (usually a 5mm Allen). C) Mount the bike and sit comfortably, leaning against a wall. Hold the brake on with one hand (or mount the bike on a turbo trainer if you have one). D) Place your HEELS on the pedals, opposite the clip, pedal backwards at 30+ rpm without rocking your pelvis (very important). E) Adjust seat height so that there is about: 1) ZERO TO ONE HALF CM. for recreational riders (-50 mi/wk.), 2) ONE HALF TO ONE CM. for experienced riders (50+ mi./wk.), 3) ONE TO TWO CM. for endurance cyclists (250+ mi./wk.), between your heel and the pedal. If your soles are thicker at the cleat than at the heel adjust accordingly. Don't forget to grease the seat post. F) Ride. It may take a couple of rides to get used to the feel and possibly stretch the hamstrings and Achilles slightly. --------------------------------------------------------------------------- Cleat adjustments (Roger Marquis marquis@well.sf.ca.us) [Ed note: You may also want to consider going to a bike shop that does Fit Kit and have them do the Fit Kit RAD to adjust your cleats. Many people recommend it.] A) Grease the cleat bolts and lightly tighten. B) Sitting on the bike, put your feet in the pedals and adjust until: B1) The ball of your foot is directly above or, more commonly, slightly behind the pedal axle and: B2) There is approximately 1 cm. (1/2in.) between your ankle and the crank arm. C) Tighten the cleat bolts 80% and go out for a ride. If another position feels more comfortable rotate your foot into that position. D) Carefully remove your shoes from the pedals and tighten the bolts fully. If you cannot get out of the pedals without shifting the cleats leave your shoes on the bike and draw an outline around the cleat. --------------------------------------------------------------------------- SIS Adjustment Procedure (Bob Fishell spike@cbnewsd.att.com) Shimano's instructions for adjusting SIS drivetrains varies from series to series. The following method, however, works for each of mine (600EX, 105, and Deore'). [Ed note: Works on Exage road and mtb also.] Your chain and cogs must be in good shape, and the cable must be free of kinks, slips, and binds. The outer cable should have a liner. clean and lubricate all points where the cable contacts anything. SIS adjustment: 1) Shift the chain onto the largest chainwheel and the smallest cog, e.g., 52 and 13. 2) WITHOUT TURNING THE CRANKS, move the shift lever back until it clicks, and LET GO. This is the trick to adjusting SIS. 3) Turn the crank. If the chain does not move crisply onto the next inside cog, shift it back where you started, turn the SIS barrel adjuster (on the back of the rear derailleur) one-half turn CCW, and go back to step 2. Repeat for each pair of cogs in turn until you can downshift through the entire range of the large chainwheel gears without the chain hesitating. If you have just installed or reinstalled a shift cable, you may need to do this several times. 4) Move the chain to the small chainring (middle on a triple) and the largest cog. 5) turn the cranks and upshift. If the chain does not move crisply from the first to the second cog, turn the SIS barrel adjuster one-quarter turn CW. If the drivetrain cannot be tuned to noiseless and trouble-free SIS operation by this method, you may have worn cogs, worn chain, or a worn, damaged, or obstructed shift cable. Replace as needed and repeat the adjustment. =========================================================================== Tools and Workstands Where to buy tools You can buy tools from many sources. Some tools can be purchased at your local hardware store (wrenches, socket sets, etc), while the special bike tools can be purchased from your local bike store or one of the mail order stores listed elsewhere. You can buy every tool you think looks useful, or just buy the tools you need for a particular repair job. Buying the tools as you need them will let you build up a nice tool set over time without having to drop a lot of money at once. Some common tools you will need are: Metric/SAE wrenches for nuts and bolts (or an assortment of adjustable wrenches). Screwdrivers, both flat and phillips. Metric allen wrenches. Pliers. Wood or rubber mallet for loosening bolts. Special tools and their uses: Cone wrenches to adjust the hub cones. Chain tool to take the chain apart for cleaning and lubrication, and to put it back together. Tire irons for removing tires. Spoke wrenches for adjusting spokes. Cable cutters for cutting cables (don't use diagonal pliers!). Crankarm tools for removing crankarms. Bottom bracket tools for adjusting bottom brackets. Headset wrenches to adjust the large headset nut. --------------------------------------------------------------------------- Workstands There are a variety of workstands available, from about $30 to over $130. Look at the mail order catalogs for photos showing the different types. The type with a clamp that holds one of the tubes on the bike are the nicest and easy to use. Park has a couple of models, and their clamp is the lever type (pull the lever to lock the clamp). Blackburn and Performance have the screw type clamp (screw the clamp shut on the tube. If you have a low budget, you can use two pieces of rope hanging from the ceiling with rubber coated hooks on the end - just hang the bike by the top tube. This is not as steady as a workstand, but will do an adequate job. =========================================================================== Riding Techniques Descending I (Roger Marquis marquis@well.sf.ca.us) Descending ability, like any other skill, is best improved with practice. The more time you can spend on technical descents the more confidence and speed you will be able to develop. A few local hot shots I know practice on their motorcycles before races with strategic descents. While frequent group rides are the only way to develop real bike handling skills descending with others will not necessarily help you descend faster alone. The most important aspect of fast descending is relaxation. Too much anxiety can narrow your concentration and you will miss important aspects of the road surface ahead. Pushing the speed to the point of fear will not help develop descending skills. Work on relaxation and smoothness (no sudden movements, braking or turning) and the speed will follow. A fast descender will set up well in advance of the corner on the outside, do whatever braking needs to be done before beginning to turn, hit the apex at the inside edge of the road, finally exiting again on the outside (always leaving some room for error or unforeseen road hazard). The key is to _gradually_ get into position and _smoothly_ follow your line through the corner. If you find yourself making _any_ quick, jerky movements take them as a sign that you need to slow down and devote a little more attention further up the road. Use your brakes only up to the beginning of a corner, NEVER USE THE BRAKES IN A CORNER. At that point any traction used for braking significantly reduces the traction available for cornering. If you do have to brake after entering the curve straighten out your line before applying the brakes. If the road surface is good use primarily the front brake. If traction is poor switch to the rear brake and begin breaking earlier. In auto racing circles there are two schools of thought on braking technique. One advocates gradually releasing the brakes upon entering the corner, the other advises hard braking right up to the beginning of the curve and abruptly releasing the brakes just before entering the curve. A cyclists would probably combine the techniques depending on the road surface, rim trueness, brake pad hardness and the proximity of other riders. Motorcyclists and bicyclists lean their bikes very differently in a corner. When riding fast motorcyclists keep their bikes as upright as possible to avoid scraping the bike. Bicyclists on the other hand lean their bikes into the corner and keep the body upright. Both motorcyclists and bicyclists extend the inside knee down to lower the center of gravity. To _pedal_ through the corners make like a motorcyclists and lean the bike up when the inside pedal is down. One of the most difficult things about descending in a group is passing. It is not always possible to begin the descent ahead of anyone who may be descending slower. If you find yourself behind someone taking it easy either hang out a safe distance behind or pass very carefully. Passing on a descent is always difficult and dangerous. By the same token, if you find yourself ahead of someone who obviously wants to pass, let them by at the earliest safe moment. It's never appropriate to impede someone's progress on a training ride whether they are on a bicycle or in a car. Always make plenty of room for anyone trying to pass no matter what the speed limit may be. Be courteous and considerate and you'll be forever happy. Remember that downhill racing is not what bicycle racing is all about. There is no need to keep up with the Jones'. This is what causes many a crash. Compete against yourself on the descents. Belgians are notoriously slow descenders due to the consistently rainy conditions there. Yet some of the best cyclists in the world train on those rainy roads. Don't get caught pushing it on some wet or unfamiliar descent. Be prepared for a car or a patch of dirt or oil in the middle of your path around _every_ blind corner no matter how many times you've been on a particular road. Take it easy, relax, exercise your powers of concentration and hammer again when you can turn the pedals. If you're interested in exploring this further the best book on bike handling I've read is "Twist of The Wrist" by motorcycle racer Keith Code. There is also data out there (Cycle Magazine) on eye exercises designed to train depth perception adjustment, peripheral vision and concentration. If you know where I can find this information please send it to: NCNCA District Coaching Office Roger Marquis 782 San Luis Rd. Berkeley, Ca 94707 Xref: bloom-picayune.mit.edu rec.bicycles.misc:1371 news.answers:4256 Path: bloom-picayune.mit.edu!enterpoop.mit.edu!usc!news.service.uci.edu!nntpsrv From: iglesias@draco.acs.uci.edu (Mike Iglesias) Subject: Rec.Bicycles Frequently Asked Questions Posting Part 4/4 Nntp-Posting-Host: draco.acs.uci.edu Expires: 15 Jan 93 00:00:00 GMT Message-ID: <rec-bicycles-faq-4_921129@draco.acs.uci.edu> Newsgroups: rec.bicycles.misc,news.answers Approved: news-answers-request@MIT.Edu Organization: University of California, Irvine Lines: 1181 Supersedes: <rec-bicycles-faq-4_921018@draco.acs.uci.edu> References: <rec-bicycles-faq-1_9211290@draco.acs.uci.edu> Date: 30 Nov 92 06:22:38 GMT Followup-To: rec.bicycles.misc Archive-name: bicycles-faq/part4 [Note: The complete FAQ is available via anonymous ftp from draco.acs.uci.edu (128.200.34.12), in pub/rec.bicycles.]