Why do some forks and frames have brake rotor size limits?
On Friday, October 27, 2017 at 1:24:49 AM UTC-7, John B. wrote:
On Thu, 26 Oct 2017 13:37:00 -0400, Radey Shouman wrote: Joerg writes: On 2017-10-24 17:21, John B. wrote: On Tue, 24 Oct 2017 11:47:12 -0700, Joerg wrote: [ ... ] The reason can be summed up in one word: Rain :-) But last Sunday I started out my "weekend" ride in the rain. It had been raining nearly all night and the roads had a lot of water on them - note we have been having floods here in Bangkok lately - but it appeared that the rain was ending so off I went. Unfortunately my weather forecasting facility wasn't working very well and I rode 20 Km of a 30 Km ride in light rain and flooded roads in many places. I was splashing through water in some places and cars were splashing through (and splashing me) in others. Of course, Sunday is much lighter traffic then on work days but still, Bangkok is rated as one of the cities with the most chaotic traffic in the world, and I did have to stop suddenly several time, on flooded roads with wet wheels and brakes. My brakes worked just as they do in the dry. Back brake stops me somewhat slowly and front brake stops rather suddenly, both brakes together provides best stopping. No long wait after grabbing a brake lever although I did think of you with your stopping problems and I have the feeling that the brake lever pressure might be a tiny bit more to stop in the rain but if it was it was so little that it couldn't be quantified. But of course I am using quality brake pads. Why it costs me US$12.12 a wheel just for pads alone.... but they do last a year or more. It seems Californian rain and Thai rain aren't the same. When it rains heavily and I have to do a surprise emergency stop after not having used the brakes for a while there is 1-2sec of nada, absolutely nothing. It makes no difference whatsoever whether I use $17 high-falutin Koolstop rain-rated pads or $4 Clarks pads. The experience of other riders around here and in this NG is similar. I don't understand the difference myself. When it's really raining, meaning there's a continuous film of water on the road and a rooster tail shooting forward off the front tire, I ride like a little old lady, because of the delay in braking. Especially when it's dark, and leaves and other blown down crap cover the road. I suspect that may be the secret. I've never been "doored", perhaps because if I have to ride past a line of parked cars where a door might be opened I either slow down or ride further enough away that a door wouldn't hit me. Here the bike lane can be so narrow that the car door on a two-door totally covers the lane and there's no place to dodge because passing cars will spot that and not let you out. |
Why do some forks and frames have brake rotor size limits?
On Friday, October 27, 2017 at 1:37:19 AM UTC-7, John B. wrote:
On Wed, 25 Oct 2017 09:22:49 -0700, Jeff Liebermann wrote: On Wed, 25 Oct 2017 06:58:57 +0700, John B. wrote: On Tue, 24 Oct 2017 10:15:53 -0700, Jeff Liebermann wrote: On Tue, 24 Oct 2017 16:19:42 +0700, John B. wrote: On Mon, 23 Oct 2017 10:09:20 -0700, Jeff Liebermann wrote: Impressive. I'll assume it's a carbon-carbon rotor, since all F1 cars seem to using them. Undoubtedly so. But if the advantage of "carbon" bikes can be extolled that a carbon-carbon frame must have twice the bragging rights :-) I don't think it would be a good idea to brag about having a bicycle made from the same stuff that caused the Challenger space shuttle disaster. The leading edges of the wings were made of carbon-carbon. When the wings were hit by ice during takeoff, it punched some rather large holes in the carbon-carbon. ????????????? "Disintegration of the vehicle began after an O-ring seal in its right solid rocket booster (SRB) failed at liftoff. The O-ring was not designed to fly under unusually cold conditions as in this launch. Its failure caused a breach in the SRB joint it sealed, allowing pressurized burning gas from within the solid rocket motor to reach the outside and impinge upon the adjacent SRB aft field joint attachment hardware and external fuel tank. This led to the separation of the right-hand SRB's aft field joint attachment and the structural failure of the external tank. Aerodynamic forces broke up the orbiter." Sorry. Memory fault. I meant Columbia, which had the carbon-carbon and ice impact problem: https://en.wikipedia.org/wiki/Space_Shuttle_Columbia_disaster "About 82 seconds after launch from Kennedy Space Center's LC-39-A, a suitcase-sized piece of foam broke off from the External Tank (ET), striking Columbia's left wing reinforced carbon-carbon (RCC) panels. As demonstrated by ground experiments conducted by the Columbia Accident Investigation Board, this likely created a 6-to-10-inch (15 to 25 cm) diameter hole, allowing hot gases to enter the wing when Columbia later re-entered the atmosphere." Just like bicycles. Proof positive that steel is better :-) They are saying that FOAM broke a hole in the wing? What sort of foam was it - titanium? |
Why do some forks and frames have brake rotor size limits?
Jeff Liebermann writes:
On Thu, 26 Oct 2017 13:40:21 -0400, Radey Shouman wrote: Surely the first step is just internal air passages in the brake disks, as used in motor vehicles for years and years. Any other coolant is a big step up in difficulty. Unfortunately that would be a major modification. Air is a lousy way to move heat. https://www.engineeringtoolbox.com/thermal-conductivity-d_429.html Air 0.024 W/mK Aluminum 205 W/mK Cast iron 58 W/mK Water 0.58 W/mK (ignores enthalpy from vaporization) If the brake disk were red hot, it would take quite a bit of air blown at the disk to cool it down. Water would drop the temperature far quicker. I'm not certain, but my guess(tm) is that the holes in the automobile brake disk were to reduce weight, not for air cooling. Air is a great way to move heat, the supply is free, the flow rate is much higher than the practical water flow rate. I'm thinking of the vents that run parallel to the braking surface, so the disk acts as a centrifugal air pump while the wheel is turning. I thought that most cars used these for the front brakes nowadays. Ventilation does add to both thickness and weight. Rather than transplant an automotive brake disk onto a bicycle, it might be easier be a bit creative. I could build a sandwich of two disks, with copper or aluminum pipes in between. Getting water into the pipe(s) will be a problem, but I have some ideas. As the brake disk spins, hot water is ejected. One disk is larger diameter than the other. The break shoes hit only the large diameter disk. The small disk is just there to increase the surface area and support the pipe(s). The axle length and dropout spacing will need to be tweaked to accommodate the increased diameter. Or, if you want something cheaper, make the brake disk hollow and out of two solid disks. Essentially a can. Drill some tiny holes around the circumference. Fill the can with water before every downhill run. The spray of hot water will keep the disk cool. Or, if you want something crude, and inverted water bottle dripping water onto the brake disk. Aim the drip just ahead of the calipers so that the disk will need to rotate a bit less than 360 degrees before getting to the calipers. The water should have evaporated before it can "lubricate" the brakes. Unfortunately, if you drip water on a cold brake disk, it's likely to get the brake pads wet, which will probably result in a regrettable incident. Maybe this isn't such a great idea. Ok, maybe a direct contact method. Clamp a wire brush onto the seat stay and press the brush against the brake disk. Pump water through the brush and onto the brake disk as needed. Hopefully, the red hot brake disk will not melt the wire brush bristles. That should get the water to where it's needed without worrying about it evaporating before it makes contact. Hmmmm... this tea tastes funny. -- |
Why do some forks and frames have brake rotor size limits?
On 10/27/2017 10:10 AM, wrote:
On Friday, October 27, 2017 at 1:37:19 AM UTC-7, John B. wrote: On Wed, 25 Oct 2017 09:22:49 -0700, Jeff Liebermann wrote: On Wed, 25 Oct 2017 06:58:57 +0700, John B. wrote: On Tue, 24 Oct 2017 10:15:53 -0700, Jeff Liebermann wrote: On Tue, 24 Oct 2017 16:19:42 +0700, John B. wrote: On Mon, 23 Oct 2017 10:09:20 -0700, Jeff Liebermann wrote: Impressive. I'll assume it's a carbon-carbon rotor, since all F1 cars seem to using them. Undoubtedly so. But if the advantage of "carbon" bikes can be extolled that a carbon-carbon frame must have twice the bragging rights :-) I don't think it would be a good idea to brag about having a bicycle made from the same stuff that caused the Challenger space shuttle disaster. The leading edges of the wings were made of carbon-carbon. When the wings were hit by ice during takeoff, it punched some rather large holes in the carbon-carbon. ????????????? "Disintegration of the vehicle began after an O-ring seal in its right solid rocket booster (SRB) failed at liftoff. The O-ring was not designed to fly under unusually cold conditions as in this launch. Its failure caused a breach in the SRB joint it sealed, allowing pressurized burning gas from within the solid rocket motor to reach the outside and impinge upon the adjacent SRB aft field joint attachment hardware and external fuel tank. This led to the separation of the right-hand SRB's aft field joint attachment and the structural failure of the external tank. Aerodynamic forces broke up the orbiter." Sorry. Memory fault. I meant Columbia, which had the carbon-carbon and ice impact problem: https://en.wikipedia.org/wiki/Space_Shuttle_Columbia_disaster "About 82 seconds after launch from Kennedy Space Center's LC-39-A, a suitcase-sized piece of foam broke off from the External Tank (ET), striking Columbia's left wing reinforced carbon-carbon (RCC) panels. As demonstrated by ground experiments conducted by the Columbia Accident Investigation Board, this likely created a 6-to-10-inch (15 to 25 cm) diameter hole, allowing hot gases to enter the wing when Columbia later re-entered the atmosphere." Just like bicycles. Proof positive that steel is better :-) They are saying that FOAM broke a hole in the wing? What sort of foam was it - titanium? Alien invasion with their killer reflector weapons: http://www.yellowjersey.org/photosfr...t/trekaggr.jpg -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
Why do some forks and frames have brake rotor size limits?
On 10/27/2017 9:58 AM, Joerg wrote:
Finally after many decades the bicycle industry woke up and adopted what the automotive guys had all along, disc brakes. Why should I accept an inferior brake system on a new bike when there is a much better one? sigh There are advantages and disadvantages to this equipment choice, just as with other equipment choices. The disadvantages of discs have been discussed. If they don't matter or apply to you, fine; but they matter to others. But I'll note that you're currently in a project to increase your disc's diameter from something like 160mm or 180mm up to 200mm or more. You seem to feel bigger diameter is better. Well, even "better," why not go up to roughly 622mm? That's what lots of us prefer, with cable actuation. -- - Frank Krygowski |
Why do some forks and frames have brake rotor size limits?
On 2017-10-27 07:11, jbeattie wrote:
On Friday, October 27, 2017 at 6:59:47 AM UTC-7, Joerg wrote: On 2017-10-26 17:16, John B. wrote: On Thu, 26 Oct 2017 17:08:10 -0400, Radey Shouman wrote: [...] And the slowly dying rims generate some really messy black sludge, at least in my experience. I'm not sure why the "wax your chain to stay clean" cohort hasn't noticed. It is probably heresy to mention it, but some people wash their bikes, particularly after riding in the rain. Amazing how easily all that black sludge washes off with soap and water :-) Oh yeah, now we have to wash out bikes after each rain ride. Standing out there in the rain with sponge and shampoo. Great. The process can be pretty quick. Stand or lay the bike on the lawn and hose it off carefully. You don't even have to put it on a washstand. Do I do this? Rarely, but I was riding with my neighbor who does, and it takes him about three minutes. I even did it last weekend as kind of a bonding experience. He handed me the hose, so I gave the bike a rinse. The bike was also pretty clean before we left on our rain ride. If it were my commuter, a rinse would have just re-arranged the mud. Same here, my road bike is never particularly clean because of unpaved road sections. Rinsing would just smear the dirt around. I can't understand the fuss of many riders about their bikes. Almost before every ride they have to pump up, Saturdays they spend cleaning their various machines. I just like to ... ride. Thanks to thick tubes I don't have to pump before a ride, I can just stash my water bottles and food, replenish the bike wallet for a brewsky on the way home and go. When I get home I park my bike in the garage, take the empty bottles and walk into the house. Why should a bicycle require more pre- and post-ride effort than a car? OT, I was riding my son's 29er up Emigration Canyon a while back and encountered a mud flow and sprayed crap all up the back of the seat tube. We didn't bother rinsing that off, and when I came to visit the next time, it was still there, hardened like cement. It was some sort of clay or adobe. Some mud is super-tough and should be rinsed off immediately. Dirt on an MTB is a badge of honor. So far I've never cleaned my MTB because it'll be dirty again 10 miles later. http://www.analogconsultants.com/ng/bike/Muddy3.JPG After a free bike wash due to rain: http://www.analogconsultants.com/ng/bike/Muddy3.JPG The remainder is caked in so hard that the soft side of a green-yellow kitchen sponge won't get it off. The scrub pad of it might but then the paint job is going to be scuffed and it'll collect dirt like a magnet. Urban dwellers can buy spray-on dirt so their ride looks more manly. No kidding. https://www.theguardian.com/science/2005/jun/14/uknews -- Regards, Joerg http://www.analogconsultants.com/ |
Why do some forks and frames have brake rotor size limits?
On 2017-10-27 09:25, Frank Krygowski wrote:
On 10/27/2017 9:58 AM, Joerg wrote: Finally after many decades the bicycle industry woke up and adopted what the automotive guys had all along, disc brakes. Why should I accept an inferior brake system on a new bike when there is a much better one? sigh There are advantages and disadvantages to this equipment choice, just as with other equipment choices. The disadvantages of discs have been discussed. If they don't matter or apply to you, fine; but they matter to others. Many others just don't know any better. I have witnessed several people riding a bike with hydraulic disc brakes for the first time and the reaction was usually "WHOA!". Same with me, it almost sent me over the bar. But I'll note that you're currently in a project to increase your disc's diameter from something like 160mm or 180mm up to 200mm or more. You seem to feel bigger diameter is better. Because bigger is better here. Well, even "better," why not go up to roughly 622mm? That's what lots of us prefer, with cable actuation. The disadvantages have been discussed ad nauseam. A rim brake is not a disc brake. Not even close. -- Regards, Joerg http://www.analogconsultants.com/ |
Why do some forks and frames have brake rotor size limits?
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Why do some forks and frames have brake rotor size limits?
On 10/27/2017 4:34 AM, John B. wrote:
On Wed, 25 Oct 2017 08:59:46 -0700 (PDT), wrote: I see no reason whatsoever for disk brakes and their complications even on most MTB's since a good V-Brake is longer lasting, just as effective, cheaper and doesn't require special wheels and frame and fork changes. Well, "cause I want 'em" is, I guess, a valid reason. But not necessarily proof of superiority :-) "I want 'em" is the ultimate decision point for lots and lots of consumer goods. Of course, people learn to "want them" after consuming tons of advertising bull****. I guess it keeps our economy going. -- - Frank Krygowski |
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