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Might Dump Road Disc Brakes for Rim Brakes
The ride: Redline Conquest Disc-R road bike which came equipped with
Avid mechanical road disc brakes, purchased in January 2004. The experience: The advantages of disc-brakes for this rider on this bike Advantages of disc brakes for this rider on this bike: Quicker brake response when riding in very wet or slushy weather Disadvantages of disc brakes for this rider on this bike: Break pad wear consumes about the same amount of dollars per mile as tire wear. Chronically warped rotors translate to reduced braking performance. Calipers interfere with mounting of fenders. (Panniers not an issue with this rider.) Disc brake system adds weight. Wheel procurement is greatly complicated by parts compatibility issues. I've been using this road bike that came with disc brakes since it was new and now must replace the wheels. The rear wheel failed early on; it was assessed by two bike shops and myself as being of a shoddy build after a spoke broke and the rim warped. In the past, I've had new machine-built wheels re-tensioned before I put them to use and got many more miles out of them than I did out of this wheel. The front wheel was re-tensioned before it started to self-destruct but I wound up destroying in an accident where I sank it into a deep pavement crack that brought the bike down from 20+ mph to zero in about 1/3 of a wheel rotation. (You can tell by where the rim is crushed.) Fortunately, the frame is undamaged and rides well. Moreover, the broken bones suffered are now healed and I've got enough spare coin to get the bike back up to speed also. With a spare wheel in front, it's running without the disc for the brake there. With the disc pads worn to their limits, they've been tossed and to the rear I've swapped in an R-600 long-reach caliper with Kool Stop salmon pads for performance testing purposes. I'm impressed at the braking performance of the rim brake compared to that experienced with discs. Now that I'm still thinking about a replacement wheel set, I keep bumping into the quandaries presented by the disc brake setup. It kind of makes me stuck with a limited selection that actually makes parts procurement a lot more complicated. I'm remembering how much simpler life used to be when I had a bike that would simply take any 700C wheelset. Installing and adjusting the new rim caliper was easy. Even with the rear wheel slightly out of true the brake is more than adequate. On Usenet and other threads people talk about how easy it is to adjust the disc brake pads, but rarely have I read any mention about the effort required for adjusting the rotors (See http://utahmountainbiking.com/fix/diskrtr.htm for specifics.) In my view, to overlook rotor adjustment when it comes to brake maintenance is on par with talking about tire inflation when it comes to wheel building but never mentioning the spokes. Anyway, I'm thinking about dumping the disc brakes altogether in favor of long-reach rim brakes and the simplicity of being able to use standard wheelsets on the bike. My only reservation is over losing that quick response time provided by disc brakes when riding through a downpour: I still think, despite all I've learned, that it might be good to keep a disc in front for that ten or twenty minutes out of the year when the rim is soaking wet but I might want to stop in a hurry. Comments? /* Seattle Mykal */ |
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#2
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Might Dump Road Disc Brakes for Rim Brakes
mykal wrote: ... Anyway, I'm thinking about dumping the disc brakes altogether in favor of long-reach rim brakes and the simplicity of being able to use standard wheelsets on the bike. My only reservation is over losing that quick response time provided by disc brakes when riding through a downpour: I still think, despite all I've learned, that it might be good to keep a disc in front for that ten or twenty minutes out of the year when the rim is soaking wet but I might want to stop in a hurry. Comments? It all sounds reasonable to me, except perhaps the last sentence. I can accept the advantages of disk brakes for muddy conditions that grind way rims, or for snowy conditions that freeze up the rims and brakes. But for all the riding I've done in downpours, I can't recall enough problems to justify switching to disks. My only real problem occurred back in the early 1970s, with chrome steel rims with dimples. On a downhill in a downpour I found I had _zero_ brakes. But once I could afford a better bike with aluminum rims, wet weather braking was simply slower, not nonexistent. So I plan ahead. Panic stops are extremely rare for me anyway. I'd dump the disks. - Frank Krygowski |
#3
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Might Dump Road Disc Brakes for Rim Brakes
For the wheels, your *rims* are trashed, not your wheels. Buy
replacement rims and lace 'em up (correctly tensioned this time). MUCH cheaper than buying new wheels. For the brake rotors - why are you bending rotors? Unless something hits them - very, very unlikely on the road - they'll stay true forever. Even on mountain bikes that are regularly crashed and abused, bending a rotor is extremely rare. Other than replacing them when bent, there is no "adjustment" required for disk rotors. And are you really wearing out disk brake pads? Usually they last 2-3 times what a set of rim brake pads do. On the road I'd expect a set to last many years. I find setting up the Avid brakes extremely finicky and time consuming - just as bad as normal roadie brakes - but at least they stay in adjustment for the rest of the year once they're set. |
#4
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Might Dump Road Disc Brakes for Rim Brakes
sunderland wrote:
For the wheels, your *rims* are trashed, not your wheels. Buy replacement rims and lace 'em up (correctly tensioned this time). MUCH cheaper than buying new wheels. Yes, re-using the old hubs would mean I don't have to buy new hubs, and I thank you for the prompt to look into the cost savings. You might be surprised, but I found the price savings were not that much: 1) The old hubs are still good and can, in fact, be used with a set of new rims (Velocity Deep-V) and new spokes (Sapim Race) that can be purchased for $185. Add in the labor costs (for me or for the LBS) and new wheels that use the old hubs will cost around $245. 2) The old hubs are 28H and I've been leaning toward wheels that have a higher spoke count. Moreover, new wheels that are competently hand-built with equivalent rims, hubs, and spokes can be had for only $275 (provided I dump the discs) with spoke counts up to 36. 3) $275 for a quality ready-built wheelset - $245 for a wheelset built up on the old hubs = I save only $30 by using the old hubs. (!) Considering this, you might agree that its a reasonable choice to put the old hubs in the parts bin and opt for the entirely new wheelset. For the brake rotors - why are you bending rotors? Unless something hits them - very, very unlikely on the road - they'll stay true forever. Even on mountain bikes that are regularly crashed and abused, bending a rotor is extremely rare. Other than replacing them when bent, there is no "adjustment" required for disk rotors. I've found the rotors for the Avid mechanical disc brakes are easily bent or warped: An impact that will damage no other part on the bike (including electronic components and lighting) may be an impact powerful enough to bend a rotor. (!!) Thus, when the bike is locked to a public bike rack (as an example), the rotors are highly vulnerable to damage ouside my control. There are other causes of repairable rotor warping that I've heard of. Sessions of hard braking may exacerbate the warping problem when the discs get hot. Also, the rotors might have been bent when I purchased the bike or may be predisposed by unknown defects to warp or bend easily. I certainly don't know. Whatever the cause, repeated rotor warp has been an ongoing problem in my experience that strongly suggests that rims are actually the best brake rotors available for the riding I do. Regarding adjustment as required for disc rotors, I'm refering to my own experience with restoring a rotor to a laterally true state after it's been repairably bent or warped. I am pleased to report there are published procedures you can review to see what I'm talking about. At UtahMoutainBiking.com you can find good information on brake rotor adjustment. Straightening a warped rotor: http://utahmountainbiking.com/fix/diskrotr.htm. Precision rotor truing: http://utahmountainbiking.com/fix/diskrotortrue.htm Special rotor truing tools: http://www.utahmountainbiking.com/sh...iscbrakes.html In practice, I've always lacked the special tools that are available for adjusting the trueness of brake rotors, so I've resorted to less precise methods that rely upon an adjustable (Cresent-style) wrench, eyeball measurments, and my bare hands. (Needless to say, I'd love to have the special tools for rotor adjustment so I could do a precise job and see how far that would go toward providing a long-lasting repair.) To be sure, rotor truing has been one of the mainteance tasks frequently required for my bike; it's up there with fixing flat tires and lubricating the chain. And are you really wearing out disk brake pads? Usually they last 2-3 times what a set of rim brake pads do. On the road I'd expect a set to last many years. I find setting up the Avid brakes extremely finicky and time consuming - just as bad as normal roadie brakes - but at least they stay in adjustment for the rest of the year once they're set. Yes, I really wear out the disc brake pads. (A few days ago I caught the pads on the remaining disc brake (on the rear) as they were going metal-to-metal -- the retaining spring had just started to scrape the rotor -- and then I swapped in the long reach rim caliper.) After a review of online posts, I think the Avid C4 pads are softer than most pads, in order to compensate for lower clamping forces provided by this Avid mechanical (i.e.., not hydraulic) actuation system that uses conventional road hand levers. These Avid pads have about the same lifespan as the stock Shimano rim-brake pads I used on my last road bike. (Surely, I may be using brakes harder than I used to.) Yes, the initial setup of the Avid disc-brakes is very finicky, as far as bicycle maintenance goes, as is the setup of normal road brakes -- I've removed and reinstalled the Avid brakes a few times -- but the disc caliper positioning has required no further adjustment after proper setup. The disc pads do require adjustment to compensate for wear, of course, and adjustment has been be required on a daily basis when I've done a lot of hard braking -- a trace of wear on the pads can translate to a huge increase in travel at the brake lever with the Avid mechanical disk brakes that were on my bike. Fortunately, adjusting the disc-brake pads is extremely easy with the big finger-adjustment knobs on the Avid calipers. Easy, that is, unless the rotors are warped, in which case the finicky factor associated with disc-brake adjustment escalates to a level far above that involved with a complete installation and adjustment of a new rim brake. By the way, from more than one retailer one can buy a complete set of new, long-reach, dual-pivot caliper rim brakes for less than the price of replacement set of Avid C4 brake pads (!!!) /* Seattle Mykal */ |
#5
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Might Dump Road Disc Brakes for Rim Brakes
Frank wrote:. It all sounds reasonable to me, except perhaps the last sentence. I can accept the advantages of disk brakes for muddy conditions that grind way rims, or for snowy conditions that freeze up the rims and brakes. But for all the riding I've done in downpours, I can't recall enough problems to justify switching to disks. My only real problem occurred back in the early 1970s, with chrome steel rims with dimples. On a downhill in a downpour I found I had _zero_ brakes. But once I could afford a better bike with aluminum rims, wet weather braking was simply slower, not nonexistent. So I plan ahead. Panic stops are extremely rare for me anyway. I'd dump the disks. - Frank Krygowski I may have exaggerated the amount of time that rims are really slippery when I put it at around 10 minutes out of an entire year's worth of riding. But if I'm pushing limits in wet conditions I sometimes experience prolonged instances when rim-brake pads can't seem to get good grip on the rim. Usually, when things are wet, there's a delay between brake actuation and braking action; clearly, the pads sometimes need a little time to squeegee water off the rim before the rubber of the pad effectively produces friction against the aluminum of the rim. But if I'm riding through deep puddles or in extremely heavy rain, it seems to take forever for the pads to starting getting enough friction on the rim to significantly slow the bike. When the wheels are really being doused with water (as when coated with mud) the rim brakes really are practically worthless. At the same time, I can say I've always found that slowing to a speed safe for conditions is an inexpensive and effective adaptation to extremely wet road conditions. Unless, of course, I admit to the depraved experience of riding a water-pipe "ten speed" that had those chrome steel rims with dimples that were supposed to provide more friction for the brake pads but only held more water so the rims would stay slippery long enough for the rider to exploit the more reliable friction coefficients associated with cotton denim on asphalt and the superior stopping power of parked cars. I can still see the rusty chrome steel rims, the bloody scrapes on my hands, and the holes in my wet blue jeans. /* Seattle Mykal */ |
#6
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Might Dump Road Disc Brakes for Rim Brakes
I don't work in a bike shop but many of my riding buddys do. They see
this stuff every day. Disk brakes are just a bad idea in almost every respect except the "bling" factor. It's like a big joke for those who are inside the loop. It's just something to think about. Don't shoot the messenger : ) |
#7
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Might Dump Road Disc Brakes for Rim Brakes
Quoting :
this stuff every day. Disk brakes are just a bad idea in almost every respect except the "bling" factor. It's like a big joke for those who are inside the loop. It's just something to think about. Don't shoot the messenger : ) Wait, I though messengers didn't use brakes at all because they can stop their fixies in 3 inches at 40mph just with back pressure on the pedals? -- David Damerell flcl? Today is Second Monday, Presuary. |
#8
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Might Dump Road Disc Brakes for Rim Brakes
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#9
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Might Dump Road Disc Brakes for Rim Brakes
wrote in message
ups.com... I don't work in a bike shop but many of my riding buddys do. They see this stuff every day. Disk brakes are just a bad idea in almost every respect except the "bling" factor. It's like a big joke for those who are inside the loop. It's just something to think about. Don't shoot the messenger : ) Message is well taken. Although I don't exactly know what the "bling" factor is, I've been studying up on the topic and find the term is commonly used in discussions about new-fangled consumer goods. While "bling-bling" apparently alludes to a quality of flashiness that draws consumer appeal of a generally irrational nature, I will confess that "bling-bling" is also the sound my fingers make as I pry them away from putting the disc brakes back on my bike. Sometimes I'm guilty of learning as slow as a Biopace chainring. /* Seattle Mykal */ |
#10
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Might Dump Road Disc Brakes for Rim Brakes
mykal Wrote: .... Anyway, I'm thinking about dumping the disc brakes altogether in favor of long-reach rim brakes and the simplicity of being able to use standard wheelsets on the bike. My only reservation is over losing that quick response time provided by disc brakes when riding through a downpour: I still think, despite all I've learned, that it might be good to keep a disc in front for that ten or twenty minutes out of the year when the rim is soaking wet but I might want to stop in a hurry. Mavic ceramics does provide decent braking even in the rain, considerable improvement as compared to rims with aluminum brak surfaces. But you might have to try a couple of different brake pad before you find a combo that won't squeak -- dabac |
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