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Old 06-01-05, 04:30 PM   #26
cchandler
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Isn't there a very slight amount of drag inherit with disc brakes?
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Old 06-01-05, 04:32 PM   #27
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Oh good!

We have an alternative to the tiresome Campy vs. Shimano and the tiresome steel vs. everything else threads.
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Old 06-01-05, 04:38 PM   #28
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Quote:
Originally Posted by cchandler
Isn't there a very slight amount of drag inherit with disc brakes?
Not when adjusted properly.
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Old 06-01-05, 04:39 PM   #29
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Weight weenies hate disc brakes
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Old 06-01-05, 04:44 PM   #30
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Originally Posted by PWRDbyTRD
Weight weenies hate disc brakes
Only because the only disc brakes available right now are MTB standard - made for stopping power uber alles & with weight a seriously secondary concern.

When road bike discs get designed, they'll be smaller diameter than MTB rotors, lighter than MTB calipers, and will compete well in weight with rim brakes. Since there is no "road bike disc brake standard" yet, we'll just have to wait.
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Old 06-01-05, 05:00 PM   #31
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Quote:
Originally Posted by Retro Grouch
Oh good! We have an alternative to the tiresome Campy vs. Shimano and the tiresome steel vs. everything else threads.
I'm nothing if not good for a diversion!
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Old 06-01-05, 05:09 PM   #32
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I have a road bike with rim brakes, a road bike with disk brakes, a mountain bike with disk brakes, and a mountain bike with rim brakes.

On the mountain bike I like the disks a little better than the rim brakes. Braking power and feel is fine with either modern rim brakes or disk brakes. The disk brakes allow me to ignore bent rims a little longer and are less affected by riding in slop. I've worn through rims before mountain biking but it takes quite awhile and extreme circumstances. I'll occasionally get a small stone caught in the tight clearance between the disk and pads. It makes quite a disturbing grinding noise. IMHO either brake system is fine for 99.9% of mountain biking.

On the road bike there is no question I like the rim brakes better. The disks required some break-in and needed frequent adjustment at first and are still more finicky to adjust than rim brakes. The rim brakes didn't require any brake in. Strength of either braking system is close but I feel more confident when braking hard with the rim brakes. I've never experienced any issues with bent rims or worn rims on road bikes. The disk calipers get in the way when mounting fenders and racks.

I've heard of blowing tires off rims by overheating the air in the tire during sustained braking, thus increasing the air pressure to the point the tire fails. I had to ride the brakes on one 3500' descent because of heaves in the road but still didn't blow off the tires. I doubt it is something to worry about. Anyone ever done it?

Rim brakes are "integrated" disk brakes because the rim acts as both a rim and the disk. I didn't really think that needed further explanation.
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Old 06-01-05, 05:21 PM   #33
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Quote:
Originally Posted by phinney
Rim brakes are "integrated" disk brakes because the rim acts as both a rim and the disk
From a strictly engineering standpoint, you are absolutely correct. There are differences in function, both theoretical and actual, though. The improvements I anticipate in disc brakes on road bikes won't occur until a "road bike disc brake standard" is developed and implemented.

Such a standard would do away with the heavy hubs, large-diameter discs, and overbuilt calipers that are common on MTB bikes. I would anticipate a 3.5 to 4 inch diameter rotor (probably dual surfaced in ceramic with a honeycomb titanium center for heat dissipation) with a light-weight caliper assembly. The rotor would have good thermal conductivity to the hub for heat dissipation. The heat couldn't be transferred to the fork, because many forks these days are non-thermally-conductive carbon fiber. An integrated cable hanger at the fork crown would do away with the long run of heavy cable housing, and the design would accept all current road levers as compatible actuators.
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Old 06-01-05, 06:56 PM   #34
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RE: Carbon forks for disc brakes...


Quote:
Originally Posted by DCCommuter
At 778 grams, that fork is significantly heavier than a typical carbon road fork (350-500 grams).
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Old 06-01-05, 07:15 PM   #35
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I've seen a 1970's road bike with disk brakes. I was told they were not so hot by someone who was in the industry at that time.
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Old 06-01-05, 08:51 PM   #36
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Both of the last two posters, please read my comment concerning MTB discs vs. road discs. The latter don't exist yet! When true road discs are developed, I suspect that both the weight penalties AND the first generation technology problems will be solved. End of the weight and "old technology" arguments. MTB discs are now becoming a mature technology. They (MTB discs) are GREAT for mountain bikes. MTB discs still suck for road bikes. I don't argue this. I'm just saying that road bikes will eventually get appropriate disc brakes. When they do, the road bike discs will be as light as current rim brakes, but will be more reliable, more environment tolerant (able to work in wet or muddy conditions), and will become standard on road bikes. I might be wrong here, but I seriously doubt it.
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Old 06-01-05, 08:56 PM   #37
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Quote:
Originally Posted by markhr

Dude, that is very cool.
I was thinking of installing a disc on my front end as well.
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Old 06-01-05, 08:58 PM   #38
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Quote:
Originally Posted by suntreader
At 778 grams, that fork is significantly heavier than a typical carbon road fork (350-500 grams).
It's a CYCLOCROSS fork - meant for off road use! Of COURSE it'll be significantly heavier!
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Old 06-01-05, 09:01 PM   #39
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Quote:
Originally Posted by suntreader
RE: Carbon forks for disc brakes...




At 778 grams, that fork is significantly heavier than a typical carbon road fork (350-500 grams).

The weight issue is moot, if you cant stop because the rim brakes are wet then they are useless.Like I said in my previous post, most folks dont ride when its wet, especially on race bikes.Ive had 4+ years of experience riding in the crappy weather, I chose the fixed gear solution, but I know some guys that use discs, and they work quite well.The other thing is,with rim brakes when the weather gets bad two other things happen, rim brake pads wear very very quickly, and so does the rim.One guy here locally goes thru a set of race type brake pads about every 7-10 days of riding in the winter, and every 3 weeks or so in summer.Rims last about 3 months give or take.Granted this is in the city while riding for a living, but it illustrates the issues one faces with this choice.Unless your actively racing, weight, unless taken to extemes, is a non issue.Putting a disc tab cross fork on a road bike and running a disc up front is a pretty viable option really, its works pretty darn well, doesnt interfere with fenders,although fenders on a race bike isnt always easy period.However, given the demographics and riding habits of the typical road bike rider Im not suprised at all that disc brakes arent very common, they wouldnt see any use where they make any sense typically.
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Old 06-01-05, 09:41 PM   #40
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Quote:
Originally Posted by FarHorizon
Not when adjusted properly.
I believe he was talking about aerodynamic drag. USPS/Disco, Trek, and Shimano pulled some old AX brakes out of the back of the warehouse to make Lance's new TT bike more aero and lighter last year.
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Old 06-01-05, 10:57 PM   #41
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Quote:
Originally Posted by Senna94
Dude, that is very cool.
I was thinking of installing a disc on my front end as well.
thanks dude - do it, you won't regret it. There's a weight penalty as pointed out in this thread but the braking is much better and I don't have to keep replacing worn rims.

London was wet yesterday and I had no fade on the way to work even when it was chucking it down. In fact, the problem was mainly locking up the wheels and sliding really easily on greasy roads(hasn't rained in a while so the oil on the roads lifted).

edit for clarity
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Old 06-01-05, 11:38 PM   #42
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After owning disc brakes I don't think I'd be willing to go back to rim brakes.
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Old 06-01-05, 11:39 PM   #43
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Quote:
Originally Posted by FarHorizon
Both of the last two posters, please read my comment concerning MTB discs vs. road discs. The latter don't exist yet! When true road discs are developed, I suspect that both the weight penalties AND the first generation technology problems will be solved. End of the weight and "old technology" arguments. MTB discs are now becoming a mature technology. They (MTB discs) are GREAT for mountain bikes. MTB discs still suck for road bikes. I don't argue this. I'm just saying that road bikes will eventually get appropriate disc brakes. When they do, the road bike discs will be as light as current rim brakes, but will be more reliable, more environment tolerant (able to work in wet or muddy conditions), and will become standard on road bikes. I might be wrong here, but I seriously doubt it.
I read your post. True "road bike disk brakes" were done before the mountain bike. They had to be road bike specific. They were not designed the way you suggest but that's what they were. My point is that even MTB disk brakes are not first generation.

Just like suspension seat posts were done in the 1800's and the seats with a cutout in the middle were done before too. They are being improved not newly invented.
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Old 06-01-05, 11:56 PM   #44
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Quote:
Originally Posted by phantomcow2
No they dont work is the rim is bent, but it depends on what you mean by bent. If its out of a true maybe 3mm it will work. I like to keep decent spacing between pad and rim, i use my speed dial to adjust the leverage....

Maybe my bike is different, but i have never seen a tire explode from heat generated by rim brakes. Disc brakes generate far more heat....

If you break a spoke, you are going to get serious rubbing, you don't with discs. But, more interestingly is the blatant error in your second claim. Discs DO get hot, but guess what? They are a slotted (think heatsink) surface attached to the hub with is attached to the rim via spokes, so the actual rim never heats up therefore the tire isn't in danger of explosion. The heat is entirely disappated before it gets anywhere near the tire. And FYI, on the road on a long descent I know a few people who have lost tires/brake pads/rims to overheating.
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Old 06-01-05, 11:57 PM   #45
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Quote:
Originally Posted by 2manybikes
I read your post. True "road bike disk brakes" were done before the mountain bike. They had to be road bike specific. They were not designed the way you suggest but that's what they were. My point is that even MTB disk brakes are not first generation...They are being improved not newly invented.
Point taken, 2manybikes. You are, indeed, correct. The improvements that are needed for disc brakes to become standard on today's road bikes have not yet been made. I believe that the needed improvements shall be made, though, and that once available, such discs are likely to become (at least) widespread and (perhaps) dominant in the road bike world. Since this is merely prognostication, only time will tell if I'm correct or not. My suspicion is that the technical superiority of disc brake technology will eventually predominate in the road bike world as it already does in aircraft, automobiles, and mountain bikes.
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Old 06-02-05, 12:09 AM   #46
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You all do know that the limiting point for either disc brake system (rim or rotor) is the adhesion of the tyre on the road surface? It doesn't matter a hoot how much stopping power one or the other can theoretically provide, once that point of adhesion is exceeded, you're in lock-up mode.

I like the rim disc system -- it's simple, efficient when properly adjusted for mechanical advantage and with pads that are of appropriate compound.

The only distinct advantage I can see for disc brakes is the heat factor on very steep downhills with sharp, low speed corners. But I have not encountered melted tubes from that yet, so I am happy with my current set-ups.
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Old 06-02-05, 12:39 AM   #47
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Quote:
Originally Posted by FarHorizon
Point taken, 2manybikes. You are, indeed, correct. The improvements that are needed for disc brakes to become standard on today's road bikes have not yet been made. I believe that the needed improvements shall be made, though, and that once available, such discs are likely to become (at least) widespread and (perhaps) dominant in the road bike world. Since this is merely prognostication, only time will tell if I'm correct or not. My suspicion is that the technical superiority of disc brake technology will eventually predominate in the road bike world as it already does in aircraft, automobiles, and mountain bikes.


I think it probably will take place. As usual it will be a tough sell at first. It may be tough to get the weight down. Already there are disk specific rims with no braking surface, so maybe a special rim will help get the weight down. The very light ceramic bearings are being used in bicycle wheels. CF hubs are now around. Part of the solution is already here I think. I can see a CF fork with a molded in CF caliper half that is pretty light. Maybe with heat sinks molded right in?

One problem is that as technology helps get the disc brake lighter, it also may help get the wheel and rim brake combo lighter too. It's hard to say what will happen but I'm sure there will be some road disks on the market at some point even if they don't turn out to sell well. I think the old disk brake I saw had a steel disc and it looked pretty heavy, I don't know why they stopped making them for sure, but I'm having breakfast with a guy who was in the business at the time tomorrow. He showed me some before, now I'm curious. I'm going to pick his brain tomorrow. I vaguely remember him saying they made scraping sounds all the time. I think they may have been hard to adjust.
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Old 06-02-05, 12:55 AM   #48
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Please post feedback once you've talked with your friend. I'd be very interested in his comments. Thanks!
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Old 06-02-05, 01:11 AM   #49
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Quote:
Originally Posted by phantomcow2
Maybe my bike is different, but i have never seen a tire explode from heat generated by rim brakes.
I have
Quote:
Originally Posted by phantomcow2
Disc brakes generate far more heat.
On a rotor that is sufficiently far enough away from things that are affected by heat
Quote:
Originally Posted by phantomcow2
Lets not kid outselves about the soft metal of rims. It isnt so soft it gets eaten away in a few thousand miles,
It can depending on circumstances and what you determine to be "a few thousands"
Quote:
Originally Posted by phantomcow2
yes rims have to be made from a somewhat soft metal to avoid cracking from tension but...with machined sidewalls i dont see it as such an issue.
The machining process only gives you a nice surface to work with. It doesn't make the rim stronger or make the brake surface last longer
Quote:
Originally Posted by phantomcow2
You will have to replace them, but in my opinion by the time the rims seriously need replacing most people will want to change wheels anyways.
Usually because it's cheaper that way
Quote:
Originally Posted by phantomcow2
Rim brakes do degrade performance in very wet weather, but there are good pads which counter this reasonably well.
Not as well as discs
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Originally Posted by phantomcow2
Maybe its just be but i have noticed my rims getting very hot.
To think you had doubts
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Originally Posted by phantomcow2
If using V brakes, installing/removing a wheel only requires you to lift the little bridge thing from the noodle, its as easy as a SRAM powerlink
On a road brake it's a little lever. You miss the point it's an extra step
http://www.bikeforums.net/showthread...087#post833087
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Old 06-02-05, 01:53 AM   #50
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Does the weight of the disk brake mean the front wheel has to be dished to the side? I honestly think that rim brakes are a much sleeker and aesthetically pleasing braking solution, and roadies are all about aesthetics.
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