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#41
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Why do some forks and frames have brake rotor size limits?
Jeff Liebermann writes:
On Tue, 24 Oct 2017 23:11:15 -0400, Frank Krygowski wrote: On 10/24/2017 8:13 PM, Jeff Liebermann wrote: On Sun, 22 Oct 2017 09:06:07 -0700, Jeff Liebermann wrote: Have you considered adding a water mist brake cooling system instead? Curses, it's not going to work. The problem is that a very fine water mist sprayed at a red hot brake disk will vaporize (evaporate) the tiny water droplets before they hit the red hot brake disk. That's nice for evaporative cooling the air around the brakes, but does nothing to cool the actual brake disk. To do that would require larger droplets, a higher velocity droplet spray, or both. Dumping liquid water on the brakes would also work, but that's like having your own private rain storm, which was the original problem. Grumble... No problem. You pump it into the right end of a hollow axle, and provide channels connecting that with the inner hollows in a double-sided disc similar to an automotive disc, like this: http://www.autopartsapi.com/eEuropar...169e817e2b.jpg The water flows out radially, carrying heat with it but leaving the braking surface dry. Yep, that will work if we can figure out a way to get the water out of the hollow axle, through a series of holes drilled into the axle, without weakening the axle. Cooling channels would make the brake disk rather thicker. Never mind spraying the bicycle and rider with scalding hot water or steam while braking. Fenders for disk brakes? I was hoping that it could be done without any major modifications to the existing disk brake system. It might be possible to modify the brake shoes to inject some cooling water. That would go directly onto the hot brake disk, which is exactly where it's needed most. The water would cause some slippage, but would evaporate instantly when red hot. For lower temperatures, the water would simply be turned off and not used. This might cause some "interesting" braking effects at the transition point, but I think that can be managed with practice. 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. |
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#42
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Why do some forks and frames have brake rotor size limits?
On Thursday, October 26, 2017 at 10:22:12 AM UTC-7, Frank Krygowski wrote:
On 10/25/2017 10:53 AM, Joerg wrote: 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. My experience: Koolstops are definitely better than cheaper pads. Yes, in heavy rain, there's a bit of delay. It's never mattered to me, probably because I don't seem to require surprise emergency stops. I'm big on paying attention and anticipating problems. I always have been. These post-retirement days, I don't do much riding in the rain. (Well, I did yesterday, but that was unusual.) But I can't see ever buying a disc brake bike. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - And ISTM that this is yet another example of "safety inflation." For decades and decades, cyclists rode in all weather using caliper brakes. They removed their hands from the brake levers to shift gears. They rode at night using halogen or even vacuum headlight bulbs powered by dynamos, and in daylight with no lights at all. They had shoes without custom attachments to the pedals. They wore cloth caps, or no caps at all. They rode wearing clothing with natural, non-blinding colors. Now every one of those practices is portrayed by some as scandalously risky. Sheesh! Considering the kind of riding that Joerg does surprise emergency stops are the order of the day don't you think? If he can get large sidewall cuts in tires the rest of us have never heard of certainly he riding a hell of a lot harder than the rest of us. |
#43
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Why do some forks and frames have brake rotor size limits?
On Thursday, October 26, 2017 at 10:37:02 AM UTC-7, 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 am with you that a super strong brake hardly seems the thing you want in rain. |
#44
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Why do some forks and frames have brake rotor size limits?
On Wednesday, October 25, 2017 at 8:59:47 AM UTC-7, wrote:
On Tuesday, October 24, 2017 at 5:22:03 PM UTC-7, John B. wrote: On Tue, 24 Oct 2017 11:47:12 -0700, Joerg wrote: On 2017-10-24 07:27, wrote: On Tuesday, October 24, 2017 at 2:19:48 AM UTC-7, John B. wrote: On Mon, 23 Oct 2017 10:09:20 -0700, Jeff Liebermann wrote: On Mon, 23 Oct 2017 12:48:29 +0700, John B. wrote: On Sun, 22 Oct 2017 20:51:15 -0700, Jeff Liebermann wrote: On Mon, 23 Oct 2017 07:02:08 +0700, John B. wrote: But re disc brake cooling F1 car brakes appear to work with the discs red hot. In the 1,000 degree (F) range. And they use Carbon Fiber discs too :-) And everyone knows that CF is better. "Thermal Conductivity of Carbon Fiber, and other Carbon Based Materials" http://www.christinedemerchant.com/carbon_characteristics_heat_conductivity.html "So...Is Carbon Fiber a good heat conductor? As usual the answer is "it depends." The short answer is NO not when regular carbon fiber is made up in regular epoxy and expected to conduct heat across the thickness. IF a highly carbonized pan fiber with graphite or diamond added, is measured for heat transmission in the length of the fiber it is very good and can rival and exceed copper." On the other hand, they seem to work pretty well :-) See https://www.youtube.com/watch?v=h5JcHAEmIYM for a visual indication of heat dissipation. :-) 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 :-) http://www.racecar-engineering.com/technology-explained/f1-2014-explained-brake-systems/ (4 pages) "A typical road car uses a cast iron brake disc with an organic brake pad. In an F1 car, though, the same material is used for both disc and pad, and this material is known as carbon-carbon - a significantly different material to the carbon-fibre composites used in the rest of the car" In other words, the F1 brakes are NOT made from CF. Some detail on Formula 1 brakes: https://www.youtube.com/watch?v=ev6XTdlKElw Fun destroying brakes: https://www.youtube.com/watch?v=KslGsXMgmqg The brake starting at 4:45 sure looks like CF but I'm not sure. Maybe twin disk brakes would be easier? http://nuovafaor.it//public/prodotto/75/nccrop/DOPPIO_FRENO_CROSS_ENDURO.jpg https://i.ytimg.com/vi/Pvwj-WWlKkg/maxresdefault.jpg https://gzmyu4ma9b-flywheel.netdna-ssl.com/wp-content/uploads/2011/09/Gatorbrake-dual-hydraulic-front-disc-brakes-carbon-rotors01.jpg https://lh4.googleusercontent.com/-cDfAFWrGR6Q/VHKPsm-f6YI/AAAAAAAAX10/2FCyj87xs0g/s640/14%2520-%25201.jpg https://www.minibikecraze.co.uk/wp-content/uploads/bs0978.jpg https://endless-sphere.com/forums/viewtopic.php?f=28&t=56268 Given the coefficient of friction between a 1.25" wide rubber tire (32mm) and a wet road probably dragging the feet will work. :-) Joerg's experience is with full suspension MTB's. These things are incredibly heavy and long wheelbased. He has his judgement of disks and it is no doubt quite accurate for his experience and riding. I have disks on a much lighter and shorter wheelbased bike. I know the failings up close and personal. I simply cannot imagine WHY a person would want a more complicated system than that offered by the Campy Skeleton brakes. 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. This is something I just can't understand. Indeed there is a millisecond or two delay for the brake shoe to excise the water directly in front of the initial application of the brake but after the brake shoe touches the rim it pushes any water in the way off without floating the shoe above it. 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. If you ride a lot in the rain and use a rim brake, you might go through a front rim every 1-2 years -- at least based on the experience of one of my commuter cohorts who just switched to discs. My cable discs are pretty simple and stop well -- better than rim brakes in rain. My hydraulic discs are even stronger, but it is true that it is easy to lock the rear wheel. Front braking is not a lot different than a rim brake, IMO. It's the power of the rear brake that takes some adjustment. They can also scream when wet. I was riding with a friend last week. Both of us were on discs, and his squealed in augmented fourths and then alternated like a European siren. It was annoying and funny at the same time. -- Jay Beattie. |
#45
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Why do some forks and frames have brake rotor size limits?
jbeattie writes:
On Wednesday, October 25, 2017 at 8:59:47 AM UTC-7, wrote: On Tuesday, October 24, 2017 at 5:22:03 PM UTC-7, 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. This is something I just can't understand. Indeed there is a millisecond or two delay for the brake shoe to excise the water directly in front of the initial application of the brake but after the brake shoe touches the rim it pushes any water in the way off without floating the shoe above it. 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. If you ride a lot in the rain and use a rim brake, you might go through a front rim every 1-2 years -- at least based on the experience of one of my commuter cohorts who just switched to discs. 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. My cable discs are pretty simple and stop well -- better than rim brakes in rain. My hydraulic discs are even stronger, but it is true that it is easy to lock the rear wheel. Front braking is not a lot different than a rim brake, IMO. It's the power of the rear brake that takes some adjustment. They can also scream when wet. I was riding with a friend last week. Both of us were on discs, and his squealed in augmented fourths and then alternated like a European siren. It was annoying and funny at the same time. -- Jay Beattie. -- |
#46
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Why do some forks and frames have brake rotor size limits?
On 10/26/2017 4:48 PM, jbeattie wrote:
I was riding with a friend last week. Both of us were on discs, and his squealed in augmented fourths and then alternated like a European siren. It was annoying and funny at the same time. That happened to me about two years ago. It was a club ride in honor of a prominent club member who had recently passed away. I had helped his widow choose the route of the ride, and it was kind of a big deal. I was on my touring bike with cantilever brakes. The brakes were fine up to the previous day, but for some reason they began howling embarrassingly every time I stopped along this ride. And we stopped often, at all the sites in our area that had been important to our friend. I don't remember the musical interval, but I definitely remember sounding like a British police siren. We eventually stopped in the cemetery, and while others paid their respects at his grave, I was busy adding some toe-in to my brakes. But he would have understood. -- - Frank Krygowski |
#47
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Why do some forks and frames have brake rotor size limits?
On 10/26/2017 5:08 PM, Radey Shouman wrote:
jbeattie writes: On Wednesday, October 25, 2017 at 8:59:47 AM UTC-7, wrote: On Tuesday, October 24, 2017 at 5:22:03 PM UTC-7, 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. This is something I just can't understand. Indeed there is a millisecond or two delay for the brake shoe to excise the water directly in front of the initial application of the brake but after the brake shoe touches the rim it pushes any water in the way off without floating the shoe above it. 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. If you ride a lot in the rain and use a rim brake, you might go through a front rim every 1-2 years -- at least based on the experience of one of my commuter cohorts who just switched to discs. 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. Oh, I've noticed! Somehow, I've never mustered the motivation to wax my rims to prevent it. ;-) -- - Frank Krygowski |
#49
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Why do some forks and frames have brake rotor size limits?
On Thu, 26 Oct 2017 17:08:10 -0400, Radey Shouman
wrote: jbeattie writes: On Wednesday, October 25, 2017 at 8:59:47 AM UTC-7, wrote: On Tuesday, October 24, 2017 at 5:22:03 PM UTC-7, 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. This is something I just can't understand. Indeed there is a millisecond or two delay for the brake shoe to excise the water directly in front of the initial application of the brake but after the brake shoe touches the rim it pushes any water in the way off without floating the shoe above it. 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. If you ride a lot in the rain and use a rim brake, you might go through a front rim every 1-2 years -- at least based on the experience of one of my commuter cohorts who just switched to discs. 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 :-) -- Cheers, John B. |
#50
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Why do some forks and frames have brake rotor size limits?
On Thu, 26 Oct 2017 13:22:07 -0400, Frank Krygowski
wrote: And ISTM that this is yet another example of "safety inflation." For decades and decades, cyclists rode in all weather using caliper brakes. They removed their hands from the brake levers to shift gears. They rode at night using halogen or even vacuum headlight bulbs powered by dynamos, and in daylight with no lights at all. They had shoes without custom attachments to the pedals. They wore cloth caps, or no caps at all. They rode wearing clothing with natural, non-blinding colors. Now every one of those practices is portrayed by some as scandalously risky. Sheesh! Careful, Frank! Someone will confuse you with a conservative. Although these days even the "new conservatives" are no longer conservative. They're just mad that their lives suck, looking for some payback and usually blaming the wrong people. Principled actual conservatives are sadly becoming rara aves. |
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