Disc brakes and rotational mass
04-04-16, 06:54 AM
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Apples and oranges. "Fast" refers to velocity, which is a scalar quantity of only magnitude. "Acceleration" is a vector quantity, with both a magnitude and a direction.
04-04-16, 06:58 AM
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It's just a problem that I don't need solved. Rim brakes are perfectly suitable for riding in my area but I am glad everyone is upgrading to disc. It makes the used bikes less expensive so I can get better deals on "obsolete" bikes.
04-04-16, 06:59 AM
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I wonder what affect disc brakes have on the spokes, given that the braking force is applied at the hub, instead of the rim. It seems, to me, that the spokes have to assume a much greater role in braking with disc brakes, and that must have some impact on spoke life, right?
04-04-16, 08:21 AM
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That guy was obviously drunk last night or something. Definitely over the top with the emotion and then some of the statements came out of nowhere. He probably understood very little English and misread/mistook some of our conversations here and then went ballistic.
Thanks moderators for removing that junk.
FYI, I did not start this thread to argue if disc brakes are superior or not, just inquiring about the additional rotational mass and asking about the Giant Defy bike.
I mean, who wouldn't want a shiny new bike with all the latest and greatest components on it, but that doesn't necessarily mean it is a better bike, or that to get one thing, you have to give up another. In this case, more weight on the wheel in exchange for greater stopping power. How many really need more stopping power and is the weight noticeable.... I think we have answered those questions.
Any input on the Giant Defy Advanced Pro2?
Thanks moderators for removing that junk.
FYI, I did not start this thread to argue if disc brakes are superior or not, just inquiring about the additional rotational mass and asking about the Giant Defy bike.
I mean, who wouldn't want a shiny new bike with all the latest and greatest components on it, but that doesn't necessarily mean it is a better bike, or that to get one thing, you have to give up another. In this case, more weight on the wheel in exchange for greater stopping power. How many really need more stopping power and is the weight noticeable.... I think we have answered those questions.
Any input on the Giant Defy Advanced Pro2?
As to the additional rotational mass, I'm sure technically on paper/computer there is some difference, having converted a bike from rim to disc I couldn't detect any difference, and suspect it would require lab equipment to quantify. IMO, its a non issue in the real world.
04-04-16, 08:24 AM
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I wonder what affect disc brakes have on the spokes, given that the braking force is applied at the hub, instead of the rim. It seems, to me, that the spokes have to assume a much greater role in braking with disc brakes, and that must have some impact on spoke life, right?
04-04-16, 08:44 AM
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I wonder what affect disc brakes have on the spokes, given that the braking force is applied at the hub, instead of the rim. It seems, to me, that the spokes have to assume a much greater role in braking with disc brakes, and that must have some impact on spoke life, right?
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04-04-16, 08:54 AM
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Yes and no. On the rear wheel braking forces will be lower than driving forces, so no issue at all. On the front, braking forces can exceed typical rear wheel driving forces, but the number of hard brakings simply aren't enough to have a material impact. However, I wouldn't recommend the lowest spoke count front wheels for disc use. Though if you build front wheels to rear wheel standards you should not have any issues at all.
04-04-16, 08:56 AM
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I'm glad that the current posts can see that there are certain benefits and losses with this trend, but that can be said with any upgrade (I use that term loosely).
I am of the opinion that in this particular case, there are no benefits for me but the bike I am interested in comes with them as standard equipment. I was more interested (not concerned) about the physics on the application.
In the end, we must decide fr ourselves if this is worth it for us or not. Since I am in the market for a new bike, and it comes with it, there is little decision for me to make other than buy or pass. Right now, I am passing and making what I have work for me "as is".
The one thing that disturbs me is the level of anger some people have when we don't all agree on the topic. One member (Obviously a troubled person) went into personal attacks (deleted by our mods) and started fabricating statements to justify his anger and hostility. People, we have options in life and it isn't wrong to discuss them with your peers, even if we might not agree. This should be our biggest problem in life, LOL....
I am of the opinion that in this particular case, there are no benefits for me but the bike I am interested in comes with them as standard equipment. I was more interested (not concerned) about the physics on the application.
In the end, we must decide fr ourselves if this is worth it for us or not. Since I am in the market for a new bike, and it comes with it, there is little decision for me to make other than buy or pass. Right now, I am passing and making what I have work for me "as is".
The one thing that disturbs me is the level of anger some people have when we don't all agree on the topic. One member (Obviously a troubled person) went into personal attacks (deleted by our mods) and started fabricating statements to justify his anger and hostility. People, we have options in life and it isn't wrong to discuss them with your peers, even if we might not agree. This should be our biggest problem in life, LOL....
04-04-16, 09:08 AM
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Yep, -----------part of building front wheels to rear wheel standards.
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Just because I'm tired of arguing, doesn't mean you're right.
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WARNING, I'm from New York. Thin skinned people should maintain safe distance.
04-04-16, 09:16 AM
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04-04-16, 09:21 AM
#36
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The rim wear argument is totally spurious, and IMO is the Restless Leg Syndrome of the bike world.
Brake rim wear was never an issue for the vast majority of road bike riders. Very few (outside of the Pacific Northwest) ever wear rims out, either because they don't ride enough, or because the wheels were destroyed by other means before the brakes wore them enough to worry. Note: the story is different for mtb, but we're only talking about road here.
Typical brake wear life of road rims exceeds 25,000 miles, and many here on BF report wheel life that exceeds 50,000 miles. By comparison, disc owners can expect to go through a number of rotors before then, so the total cost of ownership, even factoring rim wear is still higher for discs.
Again, I don't say there's no place for disc brakes, because they do have a place. There are road riders for which wet performance is a major consideration, and those same people will be more concerned about rim wear. Disc brakes also make tricycle design simpler, so will always be popular on 3 wheeled recumbents.
But other than those and possibly other niches, it's all one big snow job, and one more example of a "solution" to a problem that didn't exist beforehand.
BTW- With 10s of thousands of wet miles under my belt I've yet to wear out a rim. That's including my road rims with wall thickness of only 1mm when new. I got close on one of my commuter's wheels after 25,000 miles or so, but a nice lady in an SUV saved me form "disaster" by killing off both wheels first.
Brake rim wear was never an issue for the vast majority of road bike riders. Very few (outside of the Pacific Northwest) ever wear rims out, either because they don't ride enough, or because the wheels were destroyed by other means before the brakes wore them enough to worry. Note: the story is different for mtb, but we're only talking about road here.
Typical brake wear life of road rims exceeds 25,000 miles, and many here on BF report wheel life that exceeds 50,000 miles. By comparison, disc owners can expect to go through a number of rotors before then, so the total cost of ownership, even factoring rim wear is still higher for discs.
Again, I don't say there's no place for disc brakes, because they do have a place. There are road riders for which wet performance is a major consideration, and those same people will be more concerned about rim wear. Disc brakes also make tricycle design simpler, so will always be popular on 3 wheeled recumbents.
But other than those and possibly other niches, it's all one big snow job, and one more example of a "solution" to a problem that didn't exist beforehand.
BTW- With 10s of thousands of wet miles under my belt I've yet to wear out a rim. That's including my road rims with wall thickness of only 1mm when new. I got close on one of my commuter's wheels after 25,000 miles or so, but a nice lady in an SUV saved me form "disaster" by killing off both wheels first.
04-04-16, 10:01 AM
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04-04-16, 11:18 AM
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With the trend going to disc brakes, what happened to the concern of rotational mass? The disc will certainly add weight to the wheels, albeit in the center, where it will be least noticeable, but there none the less.
Am I missing something here or are the people hopping on the trend wagon?
Am I missing something here or are the people hopping on the trend wagon?
04-04-16, 11:51 AM
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The wheel will eject even with lawyer lips as the primary culprit is loose quick release axle with a vertical drop out.
This has been remedied by a subtle redesign of the front drop outs, a slight re-positioning of the brake caliper and a longer quick-release lever to allow stronger clamping force to be applied with less perceived effort.
https://ambmag.com.au/wp-content/uplo...a5-749x500.jpg
04-04-16, 12:50 PM
#40
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That's not true for road bike discs and was barely true for mountain bike discs in the early 2000s.
The wheel will eject even with lawyer lips as the primary culprit is loose quick release axle with a vertical drop out.
This has been remedied by a subtle redesign of the front drop outs, a slight re-positioning of the brake caliper and a longer quick-release lever to allow stronger clamping force to be applied with less perceived effort.
https://ambmag.com.au/wp-content/uplo...a5-749x500.jpg
The wheel will eject even with lawyer lips as the primary culprit is loose quick release axle with a vertical drop out.
This has been remedied by a subtle redesign of the front drop outs, a slight re-positioning of the brake caliper and a longer quick-release lever to allow stronger clamping force to be applied with less perceived effort.
https://ambmag.com.au/wp-content/uplo...a5-749x500.jpg
02-15-18, 03:01 PM
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disk vs. rim brakes - the science
(Great hearing the variety of opinions here!)
You can't deny the laws of physics. Disk rotors add rotating weight to the wheel, which reduces acceleration,
requiring more effort to go fast. Although it is near the axle, where the effect is smaller.
On the other hand, if you compensated by using lighter rims, you might end up with a faster wheel!
But I would want a guarantee that the rim really is lighter, and "not suitable for caliper breaks" printed right on the rim itself!
I bet there's a lot of money and commercial interests involved here! Brakes don't do anything to make a bike faster, there function is to stop a bike. But I will buy them if I'm guaranteed my rims are lighter!
You can't deny the laws of physics. Disk rotors add rotating weight to the wheel, which reduces acceleration,
requiring more effort to go fast. Although it is near the axle, where the effect is smaller.
On the other hand, if you compensated by using lighter rims, you might end up with a faster wheel!
But I would want a guarantee that the rim really is lighter, and "not suitable for caliper breaks" printed right on the rim itself!
I bet there's a lot of money and commercial interests involved here! Brakes don't do anything to make a bike faster, there function is to stop a bike. But I will buy them if I'm guaranteed my rims are lighter!
02-15-18, 03:27 PM
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I thought that the "rotational mass" concern was a bit of a discredited myth, that mass was mass was mass, rotational or otherwise.
02-15-18, 03:41 PM
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After decades of riding with rim brakes I made the switch over to discs about three months ago and I have to say there is zero chance I'll ever go back to a rim brake. It's not that disc brakes stop better - it's that they stop a LOT better. Way better. And that's in dry conditions - throw some rain into the mix and they're light years apart.
02-15-18, 04:37 PM
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02-15-18, 04:48 PM
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Darn! I didn't think to look at the date of the first post, silly me. By this time it is possible that some people who responded may have even changed their earlier thoughts. In my case, my thoughts about road bike disc brakes have changed somewhat from what they were 2 years ago. Sometimes, it isn't a good thing to revive a past thread. This one is marginal, but I have seen 10 year old discussions revived for no good reason
02-15-18, 06:22 PM
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Velocity is a scalar? You sure about that? Protip - if you're going to try to come off all smart and technical, get your **** right...
02-15-18, 08:50 PM
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The rim wear argument is totally spurious, and IMO is the Restless Leg Syndrome of the bike world.
Brake rim wear was never an issue for the vast majority of road bike riders. Very few (outside of the Pacific Northwest) ever wear rims out, either because they don't ride enough, or because the wheels were destroyed by other means before the brakes wore them enough to worry. Note: the story is different for mtb, but we're only talking about road here.
Typical brake wear life of road rims exceeds 25,000 miles, and many here on BF report wheel life that exceeds 50,000 miles. By comparison, disc owners can expect to go through a number of rotors before then, so the total cost of ownership, even factoring rim wear is still higher for discs.
Again, I don't say there's no place for disc brakes, because they do have a place. There are road riders for which wet performance is a major consideration, and those same people will be more concerned about rim wear. Disc brakes also make tricycle design simpler, so will always be popular on 3 wheeled recumbents.
But other than those and possibly other niches, it's all one big snow job, and one more examplebraje of a "solution" to a problem that didn't exist beforehand.
BTW- With 10s of thousands of wet miles under my belt I've yet to wear out a rim. That's including my road rims with wall thickness of only 1mm when new. I got close on one of my commuter's wheels after 25,000 miles or so, but a nice lady in an SUV saved me form "disaster" by killing off both wheels first.
Brake rim wear was never an issue for the vast majority of road bike riders. Very few (outside of the Pacific Northwest) ever wear rims out, either because they don't ride enough, or because the wheels were destroyed by other means before the brakes wore them enough to worry. Note: the story is different for mtb, but we're only talking about road here.
Typical brake wear life of road rims exceeds 25,000 miles, and many here on BF report wheel life that exceeds 50,000 miles. By comparison, disc owners can expect to go through a number of rotors before then, so the total cost of ownership, even factoring rim wear is still higher for discs.
Again, I don't say there's no place for disc brakes, because they do have a place. There are road riders for which wet performance is a major consideration, and those same people will be more concerned about rim wear. Disc brakes also make tricycle design simpler, so will always be popular on 3 wheeled recumbents.
But other than those and possibly other niches, it's all one big snow job, and one more examplebraje of a "solution" to a problem that didn't exist beforehand.
BTW- With 10s of thousands of wet miles under my belt I've yet to wear out a rim. That's including my road rims with wall thickness of only 1mm when new. I got close on one of my commuter's wheels after 25,000 miles or so, but a nice lady in an SUV saved me form "disaster" by killing off both wheels first.
As to RLS, don’t criticize someone until you have walked a mile in his shoes. Multiple sclerosis used to de called multiple sclerosis syndrome until the medical profession figured out what it is. Just because RLS is called a syndrome doesn’t diminish the misery it causes people afflicted with it.
02-15-18, 09:17 PM
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Excuse me for a comment, but, how does someone spell them both "brakes" and " breaks" in the same paragraph?
02-16-18, 03:57 AM
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All you PNW folks .... FBinNY, has said about three times now that Except in Conditions Such As Which Prevail in the PNW, rim wear isn't an issue.
Do you guys all smoke too much pot, so you cannot comprehend words on a page, or not enough, so you are all belligerent.
Real Slow for those who are voluntarily impaired: UNLESS you ride a lot of fast downhills, heavily loaded downhills, or ride in the rain a lot, road discs aren't going to do a whole lot ofr you.
THAT is what has been said in this and about a dozen other threads.
So, so very glad to seem the same silly, sissy, slapfights breaking out again and again.
Here you go: Want discs? Get discs. Don't want discs .... I am so cruel, I am going to leave you hanging. Mwahahaha!
Do you guys all smoke too much pot, so you cannot comprehend words on a page, or not enough, so you are all belligerent.
Real Slow for those who are voluntarily impaired: UNLESS you ride a lot of fast downhills, heavily loaded downhills, or ride in the rain a lot, road discs aren't going to do a whole lot ofr you.
THAT is what has been said in this and about a dozen other threads.
So, so very glad to seem the same silly, sissy, slapfights breaking out again and again.
Here you go: Want discs? Get discs. Don't want discs .... I am so cruel, I am going to leave you hanging. Mwahahaha!