Johan Bornman

I prefer not to use "strong" in the context of wheels. It has strange connotations. Straight-gauge spokes are strong enough but not durable enough. Double butted spokes are not as strong as straight gauge, but strong enough. They are infinitely more durable though and therefore you always build a quality wheel with double-butted. I have explained the concept of strength and durability in the context of wheels here often enough and a search should produce the results.

Sort of. A tensioned bicycle wheel is a pre-stressed structure and pre-stress allows strange things, like concrete to not crack under tension and bicycle wheels to never increase tension anywhere on the wheel when in compression.

Correct

No. This has been debated here ad-infinitum. It always causes a huge barney so I suggest you do a search. Use keywords like "stand on bottom sokes" and "reduce tension" in my posts. You'll find it.

Counter-intuitively, drop-offs and rocky sections don't increase stress on a rim but reduces it. The examples you cite are not good ones unless the bump is a sharp one and the rim bottoms out through the tyre. Only then does rim strength come into play in "rough riding".

The short answer is no. However, so many other suggestions were made that I have to explain my negative answer. Crest rims are ultra lightweight rims. Like all rims they're made from aluminium and the only way to get them lighter is to use less aluminium Use less and the rims are thinner and hence, weaker. Weakness/strength needs some definition too. The first test would be if they could withstand a reasonable spoke tension. Yes they can and they threrefore won't "pretzel" as was suggested. The second type of strength is really strength over time and that is called durabililty. Are they durable enough to withstand millions of revolutions where spoke tension is cycled? Yes, their fatigue life is very good. The third type of strength we look at is how the rims perform on impact. Here they perform very poorly. For two reasons: 1), The shallow bead (they called it Bead Socket Technology or BST but I abbreviate it to BS) doesn't absorb impact by bending but transfers the impact into the rim cavity. This is usually fatal and it happens very, very often. For this reason alone I don't recomomend these rims. If you're heavy, don't bother. Get heavy rims and don't play the silly how-low-can-you-go tyre pressure game.

My guess is that the various rubbes have turned into jelly. Hayes is fond of doing that. Remove the brake reservoir like and poke and inspect the rubbers on the lid. If they are squishy and soft and deformed, the rubbers inside have gone to rubber heaven too. Buy a rebuild kit and start from scratch.

Yes, 150mm is a guess. I don't have a new, naked fork here to figure out how far the taper extends. But I am sure you'll be able to do the calculations required to restrict the bending moment at the bottom bearing to a)under the material's fatigue limit and b)to prevent fretting damage on the bearing races. With any reasonable material such as CroMo, 600X or 700X alu, I doubt the length of the taper matters as long as it is extends just a bit further than the bottom bearing's location. Manufacturing such a steerer from scratch poses some challenges for the average Joe and indeed even the average machine shop. The taper is internal and will require a long, thin boring bar ont he lathe. I also happen to know that the tube has a flange at the bottom that prevents it from pushing through the crown. In other words, it is inserted from the stem end and pressend until the flange sits flush in its recess in the crown. This ridge prevents accurate meaurement of the bottom tube section.My 5.5mm guess takes into account a 0.5mm flange.

I'm back.

To manufacture a fork steerer with 2mm aluminium (or even steel) would be big mistake. Steerer tubes are part tapered. The end that presses into the crown is usually 5.5mm thick and that tapers down to 2mm over the first 150mm or so. Then it evens out to 2mm up to the stem end of the steerer. The alu is usualy 6000 series and my guess is you'll have to take what material is available. Should you calculate the strength for a 2mm steerer, it would be strong enough (not durable enough though) but the flex at the crown would quickly destroy the bottom headset bearing.

I love it when a plan comes together.

Next one with space (in Jhb) is end-August. One space left. I'm planning to come to Cape Town in Septermber. Plenty space left 'cause I haven't advertised it or made up my mind about the exact date yet.

Waterproof grease is a myth. It contains some calcium soap which emulsifies slilghty...only slightly, less easily than lithium soap. Once you understand bearings and water intrusion, you'll realise that the fancy grease is a foo-fee.

I think the answer is that you simply call yourself a mechanic and away you go. There are no rules other than what the poor customer will tolerate. I'd prefer to suggest what it takes to be a good mechanic. 1) You should be technically fluid. This is something that comes from years and years of making mistakes in your dad's workshop. You need to know how to hold a hammer, how to saw straight, how to judge whether a nail will split a piece of wood, learn a bit about screw threads, welding, epoxy usage, various metals and their characteristics, how to cut a thread, drill a hole, file straight, know how hydraulic systems work etc etc.You should have a good command of all basic tools which should include saws, files, ball-peen hammers, spanners, punches, knives and cutters; screwdrivers and other drivers. You must know the difference between a Torque Wrench and a Talking Wench. 2) You should understand basic science. No need to be an engineer but at least matric science. You must have a basic understanding of chemical reactions of metals, salts, water, inert materials, expansions, co-efficients of expansion, galvanic action, basic tribology and the dfifference between toughness, hardness, elasticity, maleability and yield. Basic forces such as compression, tension, torsion and shear should be no mystery. 3) You should be a cyclist. 4) You must be able to measure accurately and understand measurement errors such as parallax errors and percentage errors and,the limitations of your measuring instruments. You must own a vernier. 5) You must know the difference between Ale, Pale Ale, Weissbier and Stout. You must own a bottle opener. 6) Basic welding, brazing, screw cutting, driling and light machine will be a big bonus. 7) You must have an insatiable sense of curiosity. If it ain't broke, fix it. Be confident in your knowlege and ability and don't be shy to realise (out loud if necessary) that manufacturers perpetrate some very poor products on us from time to time. 8) Your skills must span all mechanical disciplines of cycling - wheelbuilding, hydraulic suspension repair, bike build, bike set-up and a triple degree in troubleshooting. 9) You must have experience on lots of bikes over many years. If you can tick off 101% of the above, I'd call you a good mechanic. If yiou find this person, please send him/her my way. I usually get CVs where the most redeeming action is that the applicant is a non-smoker, of sober habit, a good Christian and claims a sub-6-hour Argus time. Even then, they smoke skelm.

That's the one. I teach them that and more in the absence of chip-on-the-shoulder okes who already everything and just come along for the beer. 15% of of my customers are female and they attend the regular classes - broken nails and all. However, some just want to learn how to do the very basics, feel confident about noises and minor mishaps and identify them and learn how to communicate with their mechanics. I could probably work a bit on the title of that workshop.

I doubt you'll see a click-by-click difference in rebound speed. The only time I can see it working for definite, is if I remove the damper cartridge (like in a FIT model's) and move it up and down in the bench. Then I can feel it but not see it. Witht he cartridge fitted and air int he spring, there's too much other "noise" to see a difference. I consider the setting as a small/medium/large affair and anything other than that is too subtle for observation when stationary. Some forks emit a nice schlurrping noise and then at least you can hear it but my eye isn't trained well enought o distinguish between click number two and click number 6, for instance. Futher, Fox dampers are so incredibly robust that I doubt there's anything wrong with it.

Ignore Q-factor. It is a non-issue. The crank's Q-factor is the distance from the one crank to the other or, how far your feet are apart when pedaling. In the gym on a stationary bike you'll feel your feet are slightly wider apart than on your other bikes, but so what. It is difficult to actually measure the Q-factor since the one crank points forward when the other one points backward and getting the measurement from the outside of the one crank to the same point on the other is neigh impossible.

A bent hanger doesn't present like the symptoms you describe. A bent hanger will allow the gears to shift (from small sprocket to large sprocket) but shifting will get progressively worse the further you go from the small sprocket. In other words, gear 1-2 will shift perfectly, the next one a little less satisfactory etc etc. Coming down will display the reverse. What you describe is typical of friction in the cable system somewhwere. Replace the cable, make sure things aren't kinked etc etc. Only the derailer spring assists downshift and if there is friction, it won't do so with a smart snap. Change the cable.

Make sure the movement is not between the crank and crank axle, but between the crank axle and the bearing. That means you need a new BB since cartridge BBs cannot be adjusted. They are either good, or bad. Square taper BBs are excellent quality if you buy something like a Shimano UN-54 and it sells for a song. After stripping I have found that I have the older square spindle. I also found that when assembled there is slimight movement from side to side.

OOps, another folly. FSA (being an American company that doesn't like not invented there) didn't want to stick with the 24mm crank axle standard that Shimano produced and therefore produced a crank with a 24.1mm axle. You can use FSA bearings with that or, FSA. Most people therefore choose FSA.

Allow me to edit this press release for you: Octalink was perpetrated and thankfully not widely licensed by Shimano. It wa and still is a crime against bicycle progress. Its claim to fame over square taper BBs is the old hackneyed lighter, stiffer faster. Unfortunately the oversize hollow axle meant that the bearings have to be smaller and they thus fail far, fair quicekr than the equivalent square taper BB with larger bearings. Octalink 1 was a resounding failure. It was introduced just when mountain biking became popular and the perpetrators of Octalink never thought that someone would stand on both pedals with the cranks horizontal, jump over stuff and land forcefully on the crank. The alternative landing method know as the nutcrusher, wasn't acceptable to the MTB community at large and they chose to land on their feet, so to speak. Octalink orignal, classic or as it became known after its flaw as discovered, Octalink V1, had splines that were too short and tore out of the cranks upon landing. If the bike rider was hotfoot, the lash would even loosen the bolt on the left side and ruin the crank even quicker. Instead of recalling the product, Shimano arrogantly simply produced a V2.0 and pretended it was an improvement when it in fact, was just an attempt (with wider splines) to stem the flood of ruined cranks. However, they then went one step further in stupidity and fitted roller bearings to the Dura Ace version of the BB which was a resounding and spectacular failure. Roller bearings prefer an oil bath instead of grease and the bearings thus simply don't last. Since Shimano's licensing terms were onerous, the YANKS decided to bypass the patent with a few tricks. They invented the ISIS BB which had ten, instead of eight (octa) splines. Whoopee - same small bearings and same premature failure. Luckily the ISIS consortium used wider splines. By no stretch of the imagination can Octalink be considered a success. Even Shimano abandoned it and substituted a different system.

It is the opposite of an unlimited lifespan, which I suppose is like saying how long a piece of string is. The mushroom head of the alu nipple flexes with each wheel cycle like a swimming squid. Eventually, a circular fatigue circle formes around the spoke hole and the head breaks off in a nice circle, like in the photo. In the photo you can't see the head, it is inside the rim. Brass nipples on the other hand, are stiffer and dont flex enough to go into brass' fatigue range in a very, very long time. Aluminium nipples also fail invisibly, like yours have undoubtedly done. They corrode and since alu oxide is many times larger than an alu molecule, they freeze onto the spoke through expansion. Try and turn them and You'll see, they're impossible to move. A few factors determine how quickliy they will fail 1) Distrance travelled (iin other words, number of stess/unstress cycles of each nipple. 2) Load ( in other words, how much it strains during each cycle) and 3) How far the spoke protrodes through the hole on the inside. If the spoke sticks all the way through, the nipple lasts longer since this causes less flex. Amercian Classic holds a patent to that effect. 4) Moisture and salt in the air and road water.

Relax Max. I don't see any naming or shaming. Look again. You accused the bike shop, I told you how your theory cannot be true.Unless you marked the spokes, I doubt you can tell which two they were by merely feeling the tension. Here's a suggestion. 1) Accept that aluminium nipples have a very limited life. 2) Accept that fatigue is uniform across all spokes and nipples in the same wheel. 3) Accept that replacing two nipples out of 32 is a silly idea, whether it was yours or the bike shop's. 4) Have the wheel redone with brass nipples tensioned very high. Go for a ride with your new wheel and wave nipple problems good bye.

I doiubt it was the same two that broke off. Those nipples are aluminium (alloy, as the Yanks and fellow ignoramuses say) and they have a limited life span. Their mode of faiure is 1) fatigue 2) corrosion. All of those nipples receive the equal cyclical fatiguing treatment from riding and all are, I'd like to think, exposed to the same element. Therefore, two old nipples broke and the new ones are still in that wheel. There is nothing that a bike shop can do to install them so badly thay they'll suddendly have thousands of kilometers of fatigue in them and break at the first sign of a ride again. Nothing. Your bike shop did do a good job but could have done better by suggesting the wheel is redone with brass nipples. However,brass weighs about three times what aluminium weighs and is thus too heavy for the average weight weenie. Stop blaming the mechanic if you dont understand the mode of failure. Blush, crawl into a corner and think about your sins.

2012 Course Calendar Repair and Maintenance Johannesburg 25 & 26 February 28 & 29 April 26 & 27 May 30 June/1July 25 & 26 August 29 & 30 September 24 & 25 November 8 & 9 December Repair and Maintenance Cape Town 24 & 25 March 27 & 28 October Wheelbuilding Johannesburg 11 & 12 February 15/16 September Fork Maintenance Workshop Johannesburg 07 April 2012 09 June 2012 Fork Maintenance Workshop Cape Town 23 March 2012 26 October 2012 Bike Maintenance for Ladies 28 January 2012 10 March 2012 11 August 2012