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Originally Posted by shreddr
so you are a weight weenie, i get it,
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Not really, it's just where the market has gone and given that I'm a smallish person as is my wife, even 10-year old road bikes made out of carbon, titanium, aluminum or lightweight steel will come in under 18 lbs using contemporary components and lightweight wheels and tires. The real weight weenies are getting their bikes down to 11 lbs, which is pretty insane: they ain't crash worthy at that weight. Even the UCI won't allow a bike to weigh less than 15 lbs, a standard that was set back in 2000.
Quote:
Originally Posted by shreddr
if the UCI hasn't approved disc brakes then the manufacturers aren't going to be quick to test the waters. if they were allowed there would be some experimentation i am sure.
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Actually, it's the other way around. Manufacturers are the ones who have to approach the UCI and apply for rules changes. A few years back, Cannondale and a disc brake manufacturer (at least I think it was Cannondale) had applied for the UCI's approval of discs in cyclocross (CX) events. They already had a new CX bike designed and in production and the UCI say no. At first it was a BS thing where the UCI stated the request hadn't been made far enough in advance of the season, but they subsequently held their ground and still haven't approved discs for use in UCI-sanctioned CX events. Some of the other organizations that sanction CX events have approved the use of discs but even then they aren't all that pervasive in the CX pelotons at those events.
Quote:
Originally Posted by shreddr
i would question the weight drag of a 1/8" thick 6" diameter rotor as a reason not to use them, but i know how hairs get split, and roadies are anal about any data, so if there was even one study done, then the hair splitters will avoid it.
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It's been studied and analyzed to death and even when you factor in removing brake bosses and other frame / fork changes that reduce weight in one place on a bike, the weight you put back on to add disc mounting tabs and beef up the rear stays and forks at their distal ends + the weight of the disc calipers, rotors and beefier wheels (hubs, spokes & rim), you end up with about a 300g - 400g net increase in weight + added aero drag. Given the way roadies analyze meaningless things like .5% reductions in aero drag on a given rim or rotating mass that has a factor of .2% efficiency loss during initial acceleration, any gram count that has more than two digits is considered huge, even if it's really not. After all, a good dump before you ride will reduce your loaded bike's weight by a couple hundred grams, easy....
Quote:
Originally Posted by shreddr
regarding the braking force at the edge of a rim or at the hub, this is just straight physics, the rim is spinning faster than the hub, so given an equivalent coefficient of friction and clamping force there will be more energy captured at the rim than at the hub during braking, and hence more braking force.
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Unfortunately, the coefficient of friction and clamping forces of rim and disc brakes are not equal; just spray some water on a disc rotor after even a moderately hard stop and you'll gain a quick appreciation of just how much more brake energy is developed by the disc system. Even Magura's older hydraulic rim brake systems don't develop anything that approaches the mechanical advantage a disc caliper develops even if you null out compression losses in the softer brake blocks and deflection in the rim's sidewall / brake track. There is almost no compression loss in the disc brake system and what are usually metallic disc brake pads made from the same material you'll find on our motorcycles develop friction that is several orders of magnitude higher than even the most aggressive rim brake blocks.... noting that the latter wear out rim brake tracks in short order.
Quote:
Originally Posted by shreddr
its all about the ride for me anymore, and if i am riding, its all good.
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Amen to that brother.