|
|
Thread Tools | Display Modes |
#141
|
|||
|
|||
The death of rim brakes?
On Friday, March 15, 2019 at 6:23:52 AM UTC-7, Ralph Barone wrote:
John B. Slocomb wrote: On Fri, 15 Mar 2019 15:24:05 +1100, James wrote: On 15/3/19 1:50 pm, John B. Slocomb wrote: On Fri, 15 Mar 2019 12:36:42 +1100, James wrote: On 15/3/19 2:17 am, Frank Krygowski wrote: On 3/13/2019 6:32 PM, Joerg wrote: On 2019-03-12 11:13, AMuzi wrote: How many new bicycles have drum brakes? Vanishingly few. This was just meant as an example. Bicycles have largely remained in the stone age, like chuck wagons where a chunk of wood pressed against the steel ring of the wheels to brake. So bicycles kind of skipped a technology. Bikes didn't skip drum brake technology because bikes are primitive.. Only a very few bikes adopted drum brakes because that technology wasn't optimum for bikes. It's simplistic at best to pretend what's best for one application is best for all applications. Every design choice comes with benefits and detriments, and those are not the same for a 4000 pound car as for a 20 pound bike. Bicycle rim brakes have worked fine for over 99.999% users for the past 100+ years. When mountain bikes came into fashion, some off-roaders found a different set of benefits vs. detriments, and discs made sense for them. But then fashion and marketing took over, pushing discs toward road bikes. Yes, we'll get a few testimonials here claiming discs are "better." We get very few details on benefits vs. detriments. For a while, the trend for road bikes was very narrow tyres pumped up to very high pressure. 18 mm of tyre is pretty skinny. Gradually the tyre width had become standard at 23 mm for road bikes.. Now there is an emerging trend to ride wider tyres, with some claiming much wider tyres are not only as fast but faster! I suspect there is a diminishing return with wind resistance. Now I use a 25 mm rear tyre (that measures 27 mm), and to remove the wheel I must release the brake lever (Campagnolo) or deflate the tyre. With a 23 mm tyre I don't need to do that. With a disc brake I don't need to fiddle with the brakes regardless of tyre width. That's a benefit. In fact sometimes when you go to shove a wheel in with rim brakes and centre or dual pivot callipers, you can catch the calliper and move it from centred. Then you have to fix that or have rubbing brakes. That doesn't happen with discs. It is possible with hydraulic disc callipers to squeeze the brake lever while the wheel is out, and then have trouble moving the pads apart again to insert the wheel. That's a detriment, but doesn't affect cable actuated disc brake callipers. Hydraulic disc callipers are self adjusting like car hydraulic disc callipers. Cable actuated disc callipers are not. Benefit and detriment. Hydraulic disc systems sometimes need bleeding. This requires either a visit to a shop or a bit more kit ($30 - $50) for the home maintenance person. Detriment. Probably not good if you are out on a tour. Cables are probably more reliable. Cable operated discs work fine, and there are also cable/hydraulic systems, where the calliper is hydraulic and self adjusting, and actuated via a cable. Disc brake modulation is generally better. That is you can hold the point of not quite skidding more easily. Benefit. Disc brakes tend to work better in wet weather, or IOW, work the same regardless of wet weather. Rim brakes rarely work as well when the rims are wet. Rim brakes on carbon fibre rims has never been a happy marriage, but with disc brakes that problem is eliminated. Thus aerodynamic, strong, stiff, light weight rims are now easier to manufacture and use - made of carbon fibre. Rim brakes do erode rims. Disc brakes do not. I guess the disc rotor will wear out, but I'd rather replace a rotor than a rim. It seems to me that many people try disc brakes and find few drawbacks. That's just my opinion, unsubstantiated by statistics. Are rim brakes good enough? Sure! They have been for a long time. Are disc brakes better? Yes I think so. Not outstandingly, but better. I'm not about to have my road bike modified to take disc brakes, and I wouldn't let the choice of brakes on a new bike dictate what I bought. |
Ads |
#142
|
|||
|
|||
The death of rim brakes?
On Fri, 15 Mar 2019 17:22:58 +1100, James
wrote: On 15/3/19 5:01 pm, John B. Slocomb wrote: On Fri, 15 Mar 2019 11:57:26 +0700, John B. Slocomb wrote: On Fri, 15 Mar 2019 15:24:05 +1100, James wrote: On 15/3/19 1:50 pm, John B. Slocomb wrote: On Fri, 15 Mar 2019 12:36:42 +1100, James wrote: On 15/3/19 2:17 am, Frank Krygowski wrote: On 3/13/2019 6:32 PM, Joerg wrote: On 2019-03-12 11:13, AMuzi wrote: How many new bicycles have drum brakes? Vanishingly few. (MUCH DELETED) And rim brake callipers that go around fat tyres often flex a lot and don't work so well. So disc brakes for fat tyre bikes are a better choice, and rim brakes for racing bikes with skinny tyres are pretty good. Don't use calipers. Try cantilever or the more modern Shimano V-brakes. They don't care how wide the tire is. As an addendum: While cheaper they do look a bit low budget so, as one might say, who would one want a $10 brake on a $3,000 bicycle... even if they do stop well :-) I've had canti brakes on a MTB. Yes the rims took a hammering. It comes to mind that as the braking resistance is applied at the contact of the tire and the road and that the resistance is applied to the wheel hub that a much stronger disc brake wheel would be required than when using a rim brake as the ratio between the disc brake disc and the contact with the road is approximately 26.5"/7.5" (average 2 sizes of disc rotor) = about 3.5 ratio while a rim brake is only about an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on braking forces it would appear that a disc brake wheel would have to be roughly 3 times stronger than a rim brake wheel. 36 spoke, cross three, wheels anyone? But of course an ATB is already so heavy that the addition of strong wheels is rather a matter of bringing coals to Newcastle. -- Cheers, John B. |
#143
|
|||
|
|||
The death of rim brakes?
On Friday, March 15, 2019 at 4:32:23 PM UTC-7, John B. Slocomb wrote:
On Fri, 15 Mar 2019 17:22:58 +1100, James wrote: On 15/3/19 5:01 pm, John B. Slocomb wrote: On Fri, 15 Mar 2019 11:57:26 +0700, John B. Slocomb wrote: On Fri, 15 Mar 2019 15:24:05 +1100, James wrote: On 15/3/19 1:50 pm, John B. Slocomb wrote: On Fri, 15 Mar 2019 12:36:42 +1100, James wrote: On 15/3/19 2:17 am, Frank Krygowski wrote: On 3/13/2019 6:32 PM, Joerg wrote: On 2019-03-12 11:13, AMuzi wrote: How many new bicycles have drum brakes? Vanishingly few. (MUCH DELETED) And rim brake callipers that go around fat tyres often flex a lot and don't work so well. So disc brakes for fat tyre bikes are a better choice, and rim brakes for racing bikes with skinny tyres are pretty good. Don't use calipers. Try cantilever or the more modern Shimano V-brakes. They don't care how wide the tire is. As an addendum: While cheaper they do look a bit low budget so, as one might say, who would one want a $10 brake on a $3,000 bicycle... even if they do stop well :-) I've had canti brakes on a MTB. Yes the rims took a hammering. It comes to mind that as the braking resistance is applied at the contact of the tire and the road and that the resistance is applied to the wheel hub that a much stronger disc brake wheel would be required than when using a rim brake as the ratio between the disc brake disc and the contact with the road is approximately 26.5"/7.5" (average 2 sizes of disc rotor) = about 3.5 ratio while a rim brake is only about an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on braking forces it would appear that a disc brake wheel would have to be roughly 3 times stronger than a rim brake wheel. 36 spoke, cross three, wheels anyone? But of course an ATB is already so heavy that the addition of strong wheels is rather a matter of bringing coals to Newcastle. My disc wheels haven't exploded so far, and I've been riding home-built disc wheels on cheap hubs (M525 or SP PD8 dyno) and relatively cheap rims (CR 18 or now out of production Velocity touring disc) for about 15 years. I even have a Vuelta el-cheapo disc that has held up well. I bought the first generation Cannondale CADDX CX bike with discs before they were UCI legal for cyclocross -- which is why I dropped out of racing CX as a pro in Europe. If they wouldn't accept my brakes, I wasn't going to race there. It has been my commuter for years, along with its replacement (yes, I broke the original frame -- broken frame number 7(? could be more)). My other bikes with disc wheels are doing fine, too. -- Jay Beattie. |
#144
|
|||
|
|||
The death of rim brakes?
On 16/3/19 10:32 am, John B. Slocomb wrote:
It comes to mind that as the braking resistance is applied at the contact of the tire and the road and that the resistance is applied to the wheel hub that a much stronger disc brake wheel would be required than when using a rim brake as the ratio between the disc brake disc and the contact with the road is approximately 26.5"/7.5" (average 2 sizes of disc rotor) = about 3.5 ratio while a rim brake is only about an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on braking forces it would appear that a disc brake wheel would have to be roughly 3 times stronger than a rim brake wheel. 36 spoke, cross three, wheels anyone? But of course an ATB is already so heavy that the addition of strong wheels is rather a matter of bringing coals to Newcastle. Well, you don't build a disc brake wheel with radial spokes. -- JS |
#145
|
|||
|
|||
The death of rim brakes?
On Sat, 16 Mar 2019 18:57:21 +1100, James
wrote: On 16/3/19 10:32 am, John B. Slocomb wrote: It comes to mind that as the braking resistance is applied at the contact of the tire and the road and that the resistance is applied to the wheel hub that a much stronger disc brake wheel would be required than when using a rim brake as the ratio between the disc brake disc and the contact with the road is approximately 26.5"/7.5" (average 2 sizes of disc rotor) = about 3.5 ratio while a rim brake is only about an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on braking forces it would appear that a disc brake wheel would have to be roughly 3 times stronger than a rim brake wheel. 36 spoke, cross three, wheels anyone? But of course an ATB is already so heavy that the addition of strong wheels is rather a matter of bringing coals to Newcastle. Well, you don't build a disc brake wheel with radial spokes. But they do built a rim brake wheel with radial spokes }-) I think that if I were riding around in the mud and mire I probably would want discs but I don't do that. Anywhere that I want to go has paved roads leading to it. I find it rather revealing that in 1880 the League of American Wheelmen, a bicycle advocate group, was formed and one of the first things that they lobbied for was smooth roads. Now that smooth roads, in the U.S. at least, probably make up the majority of the roads people have discovered riding out in the bush where there hardly aren't any roads at all. I suppose that the moral is that once a bicyclist finally gets something they immediately want something different :-} -- Cheers, John B. |
#146
|
|||
|
|||
The death of rim brakes?
with John B Slocomb wrote:
On Fri, 15 Mar 2019 15:24:05 +1100, James wrote: *SKIP* And rim brake callipers that go around fat tyres often flex a lot and don't work so well. So disc brakes for fat tyre bikes are a better choice, and rim brakes for racing bikes with skinny tyres are pretty good. Don't use calipers. Try cantilever or the more modern Shimano V-brakes. They don't care how wide the tire is. Of course they (v-brakes) do. My success story. My prefered LBS (at the moment, they've changed their ways) had really brain-dead parking -- right triangle from side-view, with very narrow parking holes, with maybe 30cm height. My 700Cx49 just couldn't possibly fit in. What effectively disabled me from reaching (with 180cm cable) front wheel. So, one day, I park with this abomination, do my LBS stuff, unpark, and ride away. And then over each change in road's smoothness (natural or not) I detect some unusual sound. That made me wonder. At some point I had to go on a curb, so I was looking around front wheel and then,.. Holy Chain! As I lift fork I see front wheel droping out dropouts (quick-release had been involved), is blocked by v-brakes, hits a sidewalk, and is placed back into dropouts. I speculate that some random dude (with evil intentions) undid quick-release as this bike was parked and had found out he had to release v-brakes, then exhaust tyre, and only then he could possibly labour the wheel out (because neither releasing nor exhausting help much, these steps just enable). And getting real dirty on the way. That's how V-Brakes Save The Day! p.s. Also, example of proper quoting. -- Torvalds' goal for Linux is very simple: World Domination Stallman's goal for GNU is even simpler: Freedom |
#147
|
|||
|
|||
The death of rim brakes?
James wrote:
On 16/3/19 10:32 am, John B. Slocomb wrote: It comes to mind that as the braking resistance is applied at the contact of the tire and the road and that the resistance is applied to the wheel hub that a much stronger disc brake wheel would be required than when using a rim brake as the ratio between the disc brake disc and the contact with the road is approximately 26.5"/7.5" (average 2 sizes of disc rotor) = about 3.5 ratio while a rim brake is only about an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on braking forces it would appear that a disc brake wheel would have to be roughly 3 times stronger than a rim brake wheel. 36 spoke, cross three, wheels anyone? But of course an ATB is already so heavy that the addition of strong wheels is rather a matter of bringing coals to Newcastle. Well, you don't build a disc brake wheel with radial spokes. I missed commenting to John earlier. Your visualization of the problem isn't quite right. With rim brakes, the spokes do not see any braking forces, since the brakes sit between the spokes and the tire. No matter what size of disc brake you have, the spoke forces are the same, since the braking force is applied to the hub, which then transfers it through the spokes to the rim/tire. In the limit, the hub is stationary and the wheel is sliding. In this case, the size of the disc determines how much tangential force is applied to the disc, but the force on the spokes is determined by the number of spokes, the lacing pattern and the hub diameter. |
#148
|
|||
|
|||
The death of rim brakes?
John B. Slocomb wrote:
On Sat, 16 Mar 2019 18:57:21 +1100, James wrote: On 16/3/19 10:32 am, John B. Slocomb wrote: It comes to mind that as the braking resistance is applied at the contact of the tire and the road and that the resistance is applied to the wheel hub that a much stronger disc brake wheel would be required than when using a rim brake as the ratio between the disc brake disc and the contact with the road is approximately 26.5"/7.5" (average 2 sizes of disc rotor) = about 3.5 ratio while a rim brake is only about an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on braking forces it would appear that a disc brake wheel would have to be roughly 3 times stronger than a rim brake wheel. 36 spoke, cross three, wheels anyone? But of course an ATB is already so heavy that the addition of strong wheels is rather a matter of bringing coals to Newcastle. Well, you don't build a disc brake wheel with radial spokes. But they do built a rim brake wheel with radial spokes }-) Certainly. But only for front wheels, since rear wheels have accelerating torque applied through the spokes, regardless of the braking method. I think that if I were riding around in the mud and mire I probably would want discs but I don't do that. Anywhere that I want to go has paved roads leading to it. I find it rather revealing that in 1880 the League of American Wheelmen, a bicycle advocate group, was formed and one of the first things that they lobbied for was smooth roads. Now that smooth roads, in the U.S. at least, probably make up the majority of the roads people have discovered riding out in the bush where there hardly aren't any roads at all. I suppose that the moral is that once a bicyclist finally gets something they immediately want something different :-} -- Cheers, John B. |
#149
|
|||
|
|||
The death of rim brakes?
On 16/3/19 7:38 pm, John B. Slocomb wrote:
On Sat, 16 Mar 2019 18:57:21 +1100, James wrote: On 16/3/19 10:32 am, John B. Slocomb wrote: It comes to mind that as the braking resistance is applied at the contact of the tire and the road and that the resistance is applied to the wheel hub that a much stronger disc brake wheel would be required than when using a rim brake as the ratio between the disc brake disc and the contact with the road is approximately 26.5"/7.5" (average 2 sizes of disc rotor) = about 3.5 ratio while a rim brake is only about an inch and a half difference so say 26.5/23.5=1.1 ratio. Based on braking forces it would appear that a disc brake wheel would have to be roughly 3 times stronger than a rim brake wheel. 36 spoke, cross three, wheels anyone? But of course an ATB is already so heavy that the addition of strong wheels is rather a matter of bringing coals to Newcastle. Well, you don't build a disc brake wheel with radial spokes. But they do built a rim brake wheel with radial spokes }-) Yes, I use some I built. It's mostly a fashion thing. The weight reduction by shorter spokes isn't worth worrying about. In most cases a regular 3x spoke wheel is sufficient to transfer brake forces from the hub to the rim. Imagine the possible force on spokes possible from a 28 tooth chain ring to a 34 tooth rear sprocket? I think that if I were riding around in the mud and mire I probably would want discs but I don't do that. Anywhere that I want to go has paved roads leading to it. I find it rather revealing that in 1880 the League of American Wheelmen, a bicycle advocate group, was formed and one of the first things that they lobbied for was smooth roads. Now that smooth roads, in the U.S. at least, probably make up the majority of the roads people have discovered riding out in the bush where there hardly aren't any roads at all. Where I live there are hundreds of kms of gravel roads that are too rough for my road bike (I've tried). Where as my options are limited by bitumen only roads. Only the main connecting roads are bitumen, and they are high speed roads where drivers dislike passing cyclists safely. I think that people have realised that there are many unmade roads to explore, and there are few cars on them to worry about. -- JS |
#150
|
|||
|
|||
The death of rim brakes?
On 17/3/19 2:56 am, Ralph Barone wrote:
I missed commenting to John earlier. Your visualization of the problem isn't quite right. With rim brakes, the spokes do not see any braking forces, since the brakes sit between the spokes and the tire. The spokes may not see any torque between the hub and rim, but are certainly forces due to braking that the spokes see. -- JS |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
DuraAce 7800 brakes v. 6600 brakes | RS | Techniques | 4 | February 1st 09 05:13 AM |
Delta Brakes for sale, capy c group brakes vintage! | [email protected] | Marketplace | 0 | December 1st 08 12:47 PM |
Generic Brakes vs Dura-Ace 7700 brakes ? | RS | Techniques | 19 | June 10th 06 01:30 AM |
ANyone fail cast tender eye, death be to you, death come quickly | whoreBanger | Australia | 0 | June 3rd 06 11:47 AM |
disc brakes on front, v-brakes on rear | Per Elmsäter | Mountain Biking | 24 | October 21st 03 10:42 PM |