General Cycling Discussion - Why don't road bike have disk brakes?

Seeem to me that disk brakes on a road bike would be a better solution and create less wear on the wheels. Who don't they use them? Is it a weight issue?

Weight for one, and for another you don't need the stopping power in the mud and such because (hopefully) you aren't riding through the mud and through streams on a road bike.

some road bikes do. giants touring bike for one http://www.giant-bicycle.com/us/030.000.000/030.000.000.asp?model=10807&year=2004&search_text=touring

as to why most don't, cydewaze got it.

mine does

http://gallery.roadbikereview.com/showgallery.php?cat=500&ppuser=246067

Sorry You May Not Link To Images Consumerreview.com

Seeem to me that disk brakes on a road bike would be a better solution and create less wear on the wheels. Who don't they use them? Is it a weight issue?

My bike has them. The manufacturers haven't given us discs on road bikes yet because the technology is still MTB technology, where strong downhill brake performance is more important than everything else, including weight.

Eventually, manufacturers will come up with a "road bike disc brake standard," probably with 3.5" rotor diameters and ultra-light hubs & calipers. When this happens, almost all road bikes will have disc brakes.

Needless to say, this is just my opinion - time will tell where the market goes. I think that the eventual technical superiority of discs will win out.

http://members.cox.net/younggg/Bike1.jpg

http://members.cox.net/younggg/Bike.jpg

You need a much heavier fork to handle disk brakes. They have to be stiff but with no suspension they are not as comfortable.
You can also have problems integrating rack and fenders with disks.
On a race bike you really dont need them.
On a touring bike or winter commuter they might be useful.

You need a much heavier fork to handle disk brakes. They have to be stiff but with no suspension they are not as comfortable.
You can also have problems integrating rack and fenders with disks.
On a race bike you really dont need them.
On a touring bike or winter commuter they might be useful.

I must politely disagree with some of your statements:

1. "You need a much heavier fork to handle disk brakes." I've seen retro 70's touring bikes with lots of flexible fork rake fitted with disc caliper mounts. They work fine.

2. "They have to be stiff but with no suspension they are not as comfortable." Almost all of the MTB style bikes have both suspension AND disc brakes, so the comfort argument fails.

3. "You can have problems integrating rack and fenders with disks." I disagree - mounting tabs are mounting tabs - either the frame has them or it doesn't. If the tabs are there, the mounts are there.

4. "On a race bike you really dont need them." I partially agree with this statement. In the current generation of disc brakes, the hubs, rotors, and calipers are too heavy for race bikes. Once discs are designed specifically for race bikes, they'll take over because they're better.

5. "On a touring or winter commuter they might be useful." Agreed.

Thanks for your comments.

I just bought a Redline Conquest Disc-R which is one of a handful of road bikes with disc brakes. I use it for commuting, and I'll never again buy a bike without disc brakes, the braking is that much better.

Perfectly adjusted rim brakes are probably just as good as perfectly adjusted disc brakes. The difference is that rim brakes go out of adjustment much faster, and are trickier to adjust when they do. It's not a big deal if you're Lance Armstrong and have a team of technicians to rebuild your bike after every ride, or if you hardly ever have to brake, but I ride every day in stop-and-go city traffic, and my brakes take a beating.

Anyone know why Giant discontinued the OCR with disc brakes?

Anyone know why Giant discontinued the OCR with disc brakes?

Not a clue.

I'm running a Salsa Las Cruces Cyclocross bike with disk brakes for my commuter. Last winter I trashed a set of rims from riding in the rain. The brakes dug deep grooves in the rims. I should have wiped down the rims more often and picked the junk out of the pads. If the rotors wear down they are a lot cheaper than lacing up a new set of rims. Avid makes roadbike specific disc brakes that have the proper pull for roadbike levers. They work really well once dialed in and they are not too graby. The weight penalty is at least 1lb.

I don't think you can put disc brakes on carbon forks and carbon forks are all the rage.

http://specialized.com/bc/SBCBkModel.jsp?sid=05Crossroads

The specialized crossroads is sort of a road bike... not entirely though. More of a commuting bike I guess.

I don't think you can put disc brakes on carbon forks and carbon forks are all the rage.


here's one:

http://store.yahoo.com/phattire1/recafiroandc.html

The top of the line specialized sirrus has a carbon fork with disc brakes.

I'm glad I snagged my giant OCR touring though. I want a thin and light steel frame (the sucker is currently 27lbs stock), a 22-23lb roadie with discs wouldn't be too bad. With a couple of tweaks, the OCR touring would be just about the perfect bike for long distance commuting or touring.

I can see the use with loaded touring, especailly in the mountians, but not for road racing. Too much brake, too much weight, too expensive. I think UCI banned disc brakes in cyclocross.

Marketing and demand mostly.Most road race bikes arent ridden in the rain or bad weather.Most people with road bikes that are rec riders hide from bad weather like its the plague.

I have a feeling discs will gradually start getting mainstream though, they arent hard to retrofit, and they do work much better.I know 3 guys that ride for a living and have done exactly that.

I have seen it on some cycle cross bikes but I don't think it'll ever catch on as a main stream trend.

The reason? Professinal racers don't use them. The day Lance and Jan start using it, all other reasons against the disk brake people talking about will disappear. Start showing up from the top models in the catalogs and eventually fades out the caliper brakes. It's not which one is better but which one peple buy.

Rim brakes are "integrated" disk brakes.

Rim brakes are "integrated" disk brakes.

ROTFLMAO!

Rim brakes don't work if the rim is bent.
Rim brakes generate heat that can (and has) caused tires to explode off the rim.
Rim brakes wear away at the soft aluminum of the rim.
Rim brakes work poorly in wet weather.
Rim brakes often work not at all in ice and snow.
Rim brakes quit working once they're hot (this is why the MTB world went disc).
Rim brakes can interfere with fender mounting where desired.
Rim brakes require opening to remove tires wider than the rim.

I could go on, but why???

If you don't "get" disc brakes, that's fine. Please don't claim that rim brakes are "integrated" discs :p

ROTFLMAO!

Rim brakes don't work if the rim is bent.
Rim brakes generate heat that can (and has) caused tires to explode off the rim.
Rim brakes wear away at the soft aluminum of the rim.
Rim brakes work poorly in wet weather.
Rim brakes often work not at all in ice and snow.
Rim brakes quit working once they're hot (this is why the MTB world went disc).
Rim brakes can interfere with fender mounting where desired.
Rim brakes require opening to remove tires wider than the rim.

I could go on, but why???

If you don't "get" disc brakes, that's fine. Please don't claim that rim brakes are "integrated" discs :p
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.
Lets not kid outselves about the soft metal of rims. It isnt so soft it gets eaten away in a few thousand miles, 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. 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.
Rim brakes do degrade performance in very wet weather, but there are good pads which counter this reasonably well.
If you get water on the rims it can freeze in which case there is no stopping power, this is true.
Maybe its just be but i have noticed my rims getting very hot.
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

Disc brakes would not only add more weight, but also more polar moment. People who ride road bikes probably don't brake as much as people who ride MTB's (because of terrain differences), so discs are not necessary. I would assume if you're racing a road bike, you would brake even less because you're trying to minimize wasted energy and maximize speed.

I recall reading a couple of bits over on SheldonBrown.com about DOCUMENTED problems with disk brakes pulling the front wheel free of the fork, despite the QR being properly closed. Seem that the directional loading with disks is a LOT higher than with rim brakes. As for me, I'm more the touring type, I could see the advantages of disk brakes, there was a tandem 'bent at the local Memorial Day Ride that had hydraulic disks front and rear, and a "bail out Brake", a rear caliper break controlled by a converted bar-end shifter on the strokers handlebar. I forgot what company made the brakes, but the guy said that model was only made for a couple of years. If it's any help, it was a RANS recumbent.

Just my .02 worth

Steve W.

also you would not be able to use 2.0/1.5/2.0mm spokes for your wheels. You want a heavier guage spoke for discs and it makes a fairly substantial weight difference

Saying "rim brakes are good enough for road bikes" is like saying "drum brakes were good enough for cars." In the end, the superior technology (disc brakes) will win out.

Isn't there a very slight amount of drag inherit with disc brakes?

Oh good!

We have an alternative to the tiresome Campy vs. Shimano and the tiresome steel vs. everything else threads.

Isn't there a very slight amount of drag inherit with disc brakes?

Not when adjusted properly.

Weight weenies hate disc brakes :D

Weight weenies hate disc brakes :D

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.

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! :D

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.

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.

RE: Carbon forks for disc brakes...





here's one:

http://store.yahoo.com/phattire1/recafiroandc.html

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

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.

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.

mine does

http://gallery.roadbikereview.com/showgallery.php?cat=500&ppuser=246067




Dude, that is very cool.
I was thinking of installing a disc on my front end as well.

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!

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.

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.

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

After owning disc brakes I don't think I'd be willing to go back to rim brakes.

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.

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.

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.

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.

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.

Please post feedback once you've talked with your friend. I'd be very interested in his comments. Thanks!

Maybe my bike is different, but i have never seen a tire explode from heat generated by rim brakes.I have
Disc brakes generate far more heat.On a rotor that is sufficiently far enough away from things that are affected by heat

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"
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
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

Rim brakes do degrade performance in very wet weather, but there are good pads which counter this reasonably well.Not as well as discs

Maybe its just be but i have noticed my rims getting very hot.To think you had doubts

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 powerlinkOn a road brake it's a little lever. You miss the point it's an extra step
http://www.bikeforums.net/showthread.php?p=833087#post833087

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.