woodcraft

I would have added to the more recent thread, but it got locked...


We've covered stopping power, modulation, wet braking, weight, and slashing risk,

but not aero differential.

Hambini claims a 8-9 watt penalty for disks over rim brakes at 40k/hr.

because of the larger profile, and spinning rotor itself- especially on the front wheel.

Campag4life

8-9 watts at 40 kph seems high but certainly would help explain why so many pros at the elite level don't ride disks considering some of their positive attributes.


Sure didn't slow Kittel's dominance in the sprint in the Tour de France before he dropped out. On his disk brake Venge VIAS he literally sprinted away from the competition and that was at 70 kph not 40 kph where watt penalty would be much higher. I question the veracity of that value but of course its possible I suppose.

Kapusta

I think that among the pure race bikes designed for (and marketed to) people who have illusions that their local bike club is a pro peleton and think of 25s as wide tires, rim brakes will persist.

What is changing (and will continue to change) is that these bikes will be relegated to the niche they deserve, and no longer be considered the "default" style of road bikes.

Meanwhile, among the more versitile style of bikes gaining in popularity, disc brakes are going to be the norm.

Dave Mayer

I don't get how discs are necessary to enable fatter tires. My Lemond 'cross bike has a huge clearance for tires, as do my TRP mini-Vs. BTW, the TRPs are fantastic stoppers, better than any mechanical discs I've ever used.

I can skid the rear wheel on dry pavement, or raise the back of the bike off of the ground if I clamp on the front brake. I think that is enough braking power.

I also don't get the fat tire thing. Sure, weekend warriors in the First World are getting fatter, and more club-level riders are on clinchers (vs. tubulars), which was not the case 30 years ago. Both of this means riders need bigger tires for impact and pinch-flat resistance.

But if you are riding tubulars, which are pretty much immune to these problems, you can realise the benefits of smaller, lighter tires and rims, and still ride at relatively low inflation pressures.

HTupolev

I think a lot of people consider small calipers and discs to be the only options for road. Which, if you're only looking at bikes marketed explicitly under "road" categories, is somewhat true at the moment.

In my experience, pinch flats are much less common than punctures on pavement, except with people who neglect their bikes and spend a lot of time running their tires near-flat. I don't think it's seen as a big enough issue to overpower the desire to not have to either throw out a tire or perform a cumbersome sewing repair in the event of a much more common puncture flat.

Width is also not just a compromise for pinch resistance. Narrow tires have higher hysteresis losses when they're run squishy, and high tire drop can have other issues like casing wear and increased sidewall exposure. On the other hand, narrower tires do weigh less and have potential for improved aerodynamics... but the real world is complicated, and what's "optimal" in any given scenario has never really been well-characterized.
Perhaps most importantly, that characterization partly doesn't happen because net effects of tire width on paved performance are pretty tiny, hence a "why not" attitude toward wider tires.

UmneyDurak

I have worn out a few, although they were probably ****ty rims.

cthenn

Use better pads. Shimano pads suck and hold metal shards. Usually would get that grinding noise from time to time until I picked the crud out of my pads. I use Kool stop Dura 2 pads and I've never gone back. Superior in every way to Shimano pads.

Maelochs

Oi. Always more of the same.

All of this has been discussed repeatedly in every other disc thread. No one has come up with anything new.

How can people be so insecure that they cannot make a choice without demanding that everyone else make the same choice?

tagaproject6

Being the "future" seem to imply that it will be the end-all-be-all of bicycle braking. I believe it will be an additional option on road bikes. And the consumer will and should be free to make the choice. If the bike industry, as a whole, decide to get rid of rim brakes all together is another matter.

Doge

I mentioned I drove 1300 miles this last weekend. My wife mentioned this one car flashed brake lights about 15 times to my one braking. Some people like using brakes. I think the disc is a good choice for those types on bikes, if they ride bikes. I don't like using brakes.

Last week I was at the National Hill Climb Championship. Descending from 14,100 ft ~7% about 5% of the bikes had discs, mostly the tandems. I saw 1-2 (out of 300+riders) that had discs on the road bikes. None of the fast riders did. But then again, it is a preference.

I guess I'd ask if the performance road cyclists on the highest mountains mostly don't use discs, why is it even a thing for road cycling? I don't know what they offer (on dry pavement) for those that know how to ride. https://thesportscorp.zenfolio.com/p129330276

Dave Mayer

Like almost everything in life, it's not merely a arbitrary preference, but it is an intelligence test.

Seriously? Riders in a hill climbing contest on discs?

Doge

They road down.

twodownzero

Except it's not so much obviously better. It's better under certain circumstances, but on the whole, it's a minor improvement at best.

The legal standard is "unreasonably dangerous." Rim brakes are not "unreasonably dangerous." They have been part of bicycles for over 100 years. For 95+% of riders and conditions, they are equal in performance to rim brakes.

Drum brakes are not inferior to disc brakes in stopping power. Many semi trucks still use large drum brakes. They don't shed heat as well as discs and are more complicated to replace, but drum brakes work just fine when they are installed and adjusted correctly. And they are superior when used as a parking brake because of their friction area. Who told you drum brakes were "inferior"? I'm sorry to say, that person is wrong. My 30 year old truck can lock its rear wheels if I'm not careful.

redfooj

semi trucks still use large drum brakes because they are costly to upgrade.

they are ubiquitous in europe. who says drum brakes are inferior? the national highway traffic safety board.

https://www.nhtsa.gov/sites/nhtsa.do...oths809700.pdf

Class 8 Truck Tractor
Braking Performance Improvement Study

Four configurations of pneumatic foundation brakes were evaluated and compared for high-speed stopping
performance on two Class-8 6x4 truck tractors.

Dreaded1

I picked up my first new road bike in 20 years this year, it came with disc. No difference in price between it and the non disc version. For my riding level and weight, the weight penalty of disc really doesn't matter to me. I haven't noticed any difference between rim and disc brakes while riding. When I squeeze the lever, the bike stops, and that's what I need it to do. On one of my last group rides I made a bad decision to take a drink when I didn't know where the next turn was. Turns out it was A LOT sooner than I expected. I was able to grab a handful of rear brake while holding my water bottle, avoid the crash and not lock up the brakes. I am not saying I could not have done this on rim brakes, but I was impressed with how the discs were able to help me avoid taking out the other 3 riders.

Plus to the uninformed it looks like a more expensive bike, then it actually is, when I have it mounted on the back of my car.

joejack951

I don't like braking either but unfortunately for me, the towns I ride through don't close the streets to other traffic so I'm frequently forced to stop or slow for other traffic and/or traffic control devices. Yes, this has nothing to do with racing. But it is the type of cycling most cyclists do. In the conditions I tend to ride in and the terrain I ride I have found disc braking to be easily better than rim braking.

Doge

My example that more than one didn't catch was riding down was not a race. Unless the view is racers don't need discs even when not racing. The profile is normal for bikes I see racers use. Not because they are racing, but they prefer higher performance and that is what they get with rim brakes. Just like cars, there will always be a market for higher performance bikes while others don't see that as important.
I'm a big overweight non-racer who's used both types of brakes. Most the riding my son does he uses rim brakes. He will use a disc on MTB and a cross bike.

I'm thinking many folks must just have bad rim brakes, or something.

Here is where I'd prefer a disc on a road bike:
-I generally use the same wheels
-There is grit on the road
-There is a lot of water on the road
-City riding with many lights. Just because I'd rather wear down the disc/pads than the rims

But for just "normal" fast riding on an open-ish road, good rim brakes work very well. They work as well as I need them to and I'd prefer not to have the extra frame weight, cable/fluid weight and being more tied to what wheels I ride.

Nick Bain

Look at what is currently for sale. I doubt it, considering trek has put its integrated brake on the Emonda SL when it used to be only the SLR frame.

Is that sense I would compare it to Hybrid car technology, since Gas efficiency also continues to improve & hybrids are still niche.

Mt. Tam

Although modulation and effective stopping in wet/grimy weather seem to be the highlights I see most in defense of discs, to me the main highlight should be preventing wear on a carbon wheel. If I'm going to buy a nice set of wheels, I'd like them to last longer, simple as that.


I have a set of Reynolds 58 Aero's which brake well, until I glaze the brake pads on any bigger decent (like coming down from Tam) even with no dragging and pulse squeezing. I have to address the brake pad surface after a hilly ride, for fear that my brake track will be damaged or get premature wear. For someone like me who lives in a hilly area, like Marin, I want to know that the carbon surface integrity is a non-issue.

HTupolev

What's the full context? If they were riding down on bikes they raced up, then wouldn't the bikes be uphill-racing bikes, regardless of what a rider would normally prefer on a descent? I'm not sure that the distribution of brake styles would change much, but it's an important distinction in terms of what a given distribution means.

topslop1

At this point, I am so confused.

Kapusta

As long as people think that shear power is the only measure of braking performance, they will never really "get" disc brakes.

I remember when I got my first set of disc brakes on my mountain bike 15 years ago. My first thought was "meh". They did not seem a whole lot more powerful than my v's with good pads (I already had one-finger braking). It took me a few rides to understand that the real benefit (in addition to consistency in the wet and mud) was the control, particularly on loose or otherwise slippery surfaces.

Obviously, this is a much bigger factor in mountain biking then road biking. But it is still a factor, especially any time you find yourself braking on wet roads, dirt roads, or in a patch of gravel.

Doge

About 200 were fondo riders. I expect they were riding their regular bike.
In addition to that 200, the open class had 30 racers, and then there were about 70 in all the other classes - racing.

Most (>80%) those were riding their normal racing/training bikes. This was not a TT and there is a minor, but real distinction. Brakes and the big gears were used by some on the assent.

Also there were juniors, women, older age classes.

And to the "racer" part. USA racers can ride what they want. Braking is an important part of racing. 90% of racer riding time is spent not racing. They are normal every day riders - going faster. They would logically have more need for better brakes. And they do.

If performance racers don't need them, or choose them for training, going down hill, why do "normal riders"? If anything it should be the opposite.

profjmb

Second. Haven't finished reading the thread yet, but it's partly about selling bikes. Gonna start a thread about innovations that have, or have not been, worth upgrading. I'd say disc brakes for road bikes is in the "not worth it" category.

Kapusta

"It's what the pros use" does not cut it for me.

I don't assume pros always know what is best in regards to adopting new trends. This is especially true of road racing that is heavily steeped in tradition and highly followed norms.

For example, only recently are we seeing tires larger than 23mm in the TdF. For years people have been pointing to the benefits of larger tires, but the pros were very slow to change. I am sure that on these internet boards, people were pointing to the fact that the pros used 23s as proof that they were faster than 25s. They must be, the pros use them. As it turns out, the pros were wrong.

I am much more familiar with the mtb world, and watching xc racing was similar. Many non-pro riders had ditched the narrow bars, long stems, and bar ends in favor of wider bars and shorter stems YEARS before many of the xc pros did. Same is true for the adoption of full suspension.

So, the fact that pros are not flocking to disc just a few years after their introduction to road bikes does not mean a whole lot to me. Give it ten years, then we'll know.