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Why choose disc brakes over rim brakes for a road bike?

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Why choose disc brakes over rim brakes for a road bike?

Old 02-26-19, 10:55 AM
  #151  
noodle soup
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Originally Posted by Seattle Forrest View Post
Right now I've got IRC Roadlights in 28. Very supple. I loved the ride of Pro Ones but they're too fragile for me.

I hope you're loving your new wheels!
I bought some Schwalbe G-One Speed 30mm tires, but I think they might be a little too wide on 23mm internal width hoops.

https://www.lightbicycle.com/Road-bi...available.html

The wheelset won't be here for 2-3 weeks, so I'll have plenty of time to overthink things in the meantime.
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Old 02-26-19, 11:06 AM
  #152  
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Originally Posted by Seattle Forrest View Post
Right now I've got IRC Roadlights in 28. Very supple. I loved the ride of Pro Ones but they're too fragile for me.
How wide were those tires on the Enve wheelset?
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Old 02-26-19, 11:44 AM
  #153  
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I don't have calipers. Somebody measured Pro Ones on these rims with a good pair of digital calipers and got 33.1 mm. I would guess the IRCs are about half a mm smaller by looking at them, based on how the sidewalks line up with the rims. But obviously that's not super precise.

I wore out a set of IRC RBCCs and have nothing bad to say about them. The Roadlite is a little more supple and probably a little less protected from flats, but they're both more like GPs than Gators. I absolutely loved Pro Ones on pavement. But the IRCs are probably 95% as great, without the cuts.

Are you going to use tubes?
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Old 02-26-19, 12:02 PM
  #154  
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Originally Posted by Seattle Forrest View Post
Are you going to use tubes?
I'm going to run them tubeless, but I like that these hoops have hooks, so using tubed tires is an option.

If the 30mm G-One Speed tires end up being wider than I'd like, maybe I'll try GP5000 tubeless.
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Old 02-26-19, 12:07 PM
  #155  
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Originally Posted by RiceAWay View Post
Disk brakes are a solution to a problem that shouldn't exist.
This makes no sense. if a problem exists, it does. The concept of "should " is irrelevant.

Also, discs were not necessarily designed to remedy problems, but to offer improvements.
Originally Posted by RiceAWay View Post
Furthermore they create more problems than they fix.
Only in the minds of people who want to invent problems associated with discs.

Originally Posted by RiceAWay View Post
Firstly, mechanical disks do not operate very well, the cable play has you re-adjusting them every other ride.
Garbage. I own a set of Spyres that I have adjusted a few times .... including accounting for bedding-in and initial cable stretch---and not since. That is just a flat lie. We all know cables---the same cables which actuate rim brakes. So it isn't the cables. Therefore you would be positing that there is something inherent in a disc brake mechanism which in unable to stay adjusted.

Care to explain fully? Why would a disc caliper not be able to stay adjusted. Explain the mechanics of this please.

Of course you cannot. It is false. As I said, I have been riding a set of Spyres for almost two years and they do Not go our of adjustment. You made up a lie to support a dishonest premise.

I will admit, compared to hydro discs, cables are not nearly as powerful, but they do not go out of adjustment. Maybe you screwed up the install?
Originally Posted by RiceAWay View Post
Secondly, hydraulic road levers really are expensive and while they work well, I don't like the idea of a cut line ending my riding day.
All brifters are expensive. Hydro brifters only marginally more so. And a cut line or a snapped cable ... or a broken chain, or any number of things can end your ride. Have you ever cut a hydro line on a road ride? Yeah, neither have 99.99% of users.

Originally Posted by RiceAWay View Post
And they are sloppy to install.
No, you did a sloppy install. Good mechanics don't spill, don't slop, and know what might drip or leak or shed grease, and act accordingly. Further, disc brake systems don't need to be installed repeatedly. Most people it's once and done. Changing a really dirty chain or derailleur jockey wheels can be exceedingly messy too, if done in a sloppy manner, and chains need to be replaced every few thousand miles---so we should stop using chains, by your "logic."


Originally Posted by RiceAWay View Post
Thirdly, On rim brakes most of the stopping forces are placed on the strongest parts of the frame - the top of the fork at the headset bearing and the top of the seat stays near the seat tube. On disk brakes the stopping forces are placed at the very end of the fork with a long lever arm to put pressure against the top of the fork. And BEHIND the seat stay, chain stay intersection. On Carbon Fiber bikes these sorts of concentrated forces on long lever arms are bad news for longevity.
On frames Designed for rim brakes, the places where that force is to be applied is strengthened. On bikes designed for discs, the places where that force is applied is strengthened.

Check out any bike designed Only for discs. The fork crown can be much more delicate and more aero because it doesn't have to withstand forces coming in perpendicular to it's natural strength. On a rim-brake bike the fork crown has to be extra beefy because the brake force hits from the worst possible angle--perpendicular to eh head tube, side-loading the bearing, and bending the tube.

Again, this is just garbage.

You don't like discs? Don't buy them. Cool.

Come here inventing crap? Not helpful, and it says a lot about your character.

Why not be honest and unemotional? After all we are talking about bicycle braking systems. No need to distort reality and invent tales---physics, mechanics, they don't change just because you get all worked up.

Last edited by Maelochs; 02-26-19 at 12:12 PM.
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Old 02-26-19, 12:48 PM
  #156  
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Originally Posted by RiceAWay View Post
Disk brakes are a solution to a problem that shouldn't exist. Furthermore they create more problems than they fix. Firstly, mechanical disks do not operate very well, the cable play has you re-adjusting them every other ride. Secondly, hydraulic road levers really are expensive and while they work well, I don't like the idea of a cut line ending my riding day. And they are sloppy to install. Thirdly, On rim brakes most of the stopping forces are placed on the strongest parts of the frame - the top of the fork at the headset bearing and the top of the seat stays near the seat tube. On disk brakes the stopping forces are placed at the very end of the fork with a long lever arm to put pressure against the top of the fork. And BEHIND the seat stay, chain stay intersection. On Carbon Fiber bikes these sorts of concentrated forces on long lever arms are bad news for longevity.
These are just made up concerns :-) If this wasn't a bike forum I would assume you are trolling.

I wasn't really talking about mechanical discs and hydro discs are about most thoroughly tested technology in existence. Literally billions of vehicles has them. Nothing to worry about. At all ...
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Old 02-26-19, 01:03 PM
  #157  
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Originally Posted by Racing Dan View Post
Literally billions of vehicles has them. Nothing to worry about. At all ...
Except for braking hard enough to glaze your pads just before the twisting forces break your fork/stay, folding it upon itself, cutting the line and spraying fluid everywhere.

Allegedly.
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Old 02-26-19, 01:09 PM
  #158  
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Originally Posted by WhyFi View Post
Except for braking hard enough to glaze your pads just before the twisting forces break your fork/stay, folding it upon itself, cutting the line and spraying fluid everywhere.

Allegedly.
Ok, your concern is justified. May I suggest a dropper post. That way you can brake with your feet if this scenario unfolds ;-)
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Old 02-26-19, 01:19 PM
  #159  
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I had mechanical discs about 15 years ago on a CX bike. That bike rode harsh. It may have been the fork, it may have just been the bike. My current bike is much newer, and not a harsh ride at all, with disc brakes. It's definitely possible to make a frame that rides well with discs. Maybe this was an issue back in the day, maybe not, but it isn't now. There's been a lot of improvement to ride quality in general ... a lot of it comes from the move to wider tires.
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Old 02-26-19, 01:19 PM
  #160  
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Originally Posted by Racing Dan View Post
Ok, your concern is justified. May I suggest a dropper post. That way you can brake with your feet if this scenario unfolds ;-)
Flintstone braking!
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Old 02-26-19, 01:22 PM
  #161  
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Originally Posted by WhyFi View Post
Except for braking hard enough to glaze your pads just before the twisting forces break your fork/stay, folding it upon itself, cutting the line and spraying fluid everywhere.

Allegedly.
Allegedly that's how this fork was broken( on a Chinabomb build), but the fact that both blades are broken leads me to doubt the owner's story.

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Old 02-26-19, 01:48 PM
  #162  
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Originally Posted by ljsense View Post
To me it seems like disc brakes are unnecessary. But they sell so well, so I'm curious why -- why would or did you get road disc brakes? What do you think of them?
Disc brakes are more predictable, can use better suited materials and parallel automotive brake development for improved safety and reduced assembly and maintenance hassle. They are simply better brakes.
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Old 02-26-19, 02:32 PM
  #163  
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Cervelo's road frames are lighter for disc than rim brakes. The bike is still about 300 grams (2/3 pound) heavier once you put the group on the frame, but that's a much smaller penalty than most people think. Improved rim design makes up for a lot of the aerodynamic penalty, you're probably more aero on discs when the wind is coming at you from the right.
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Old 02-26-19, 02:33 PM
  #164  
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Originally Posted by Racing Dan View Post
These are just made up concerns :-) If this wasn't a bike forum I would assume you are trolling.

I wasn't really talking about mechanical discs and hydro discs are about most thoroughly tested technology in existence. Literally billions of vehicles has them. Nothing to worry about. At all ...
Made up concern? Do you have a picture of the hydraulic line runs on a bike? On mine the hydraulic lines didn't fit into the provided catches and they hung out in places able to catch on passing brush. Even on the more modern CX bike I have now the hydraulic tubing runs do not work properly.
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Old 02-26-19, 03:24 PM
  #165  
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Originally Posted by RiceAWay View Post
...and they hung out in places able to catch on passing brush.
Lol.
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Old 02-26-19, 03:59 PM
  #166  
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Originally Posted by WhyFi View Post
Lol.
Yeah. He lost credibility on that one.
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Old 02-26-19, 04:19 PM
  #167  
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Originally Posted by Maelochs View Post
I will admit, compared to hydro discs, cables are not nearly as powerful, but they do not go out of adjustment. Maybe you screwed up the install?
Small point of clarification - while they may not "go out of adjustment" in that they don't just change their setup on their own mechanical discs DO wear rapidly and do not compensate for that wear on their own. In the spectrum of road it doesn't on the surface seem like a big deal or a frequent occurrence but when disc first hit on the cross scene and we were forced to use mechanical discs we frequently blew through enough of a pad in 1 lap of a messy race that all braking power would be lost. Luckily we can pit and grab a new bike. So.... mechanical calipers are not self compensating for pad wear. Hydraulic ones are.


Originally Posted by Maelochs View Post
No, you did a sloppy install. Good mechanics don't spill, don't slop, and know what might drip or leak or shed grease, and act accordingly. Further, disc brake systems don't need to be installed repeatedly. Most people it's once and done. Changing a really dirty chain or derailleur jockey wheels can be exceedingly messy too, if done in a sloppy manner, and chains need to be replaced every few thousand miles---so we should stop using chains, by your "logic."
Another point of clarification - mechanical disc brakes should be adjusted periodically through use due to pad wear increasing the gap between the pads and the rotor to the point of affecting the stroke/pull of the brake lever, modulation capability and overall feel and performance of the brakes. Hydraulic brakes absolutely and positively need to undergo maintenance. If you are riding a lot I would perform the maintenance on them annually just like with any other system on the bike. Maintenance includes inspecting pads, measuring rotors, changing and flushing the system's fluid, and a bleed for each caliper. We find there's a lot of damage over time when hydraulic systems are not maintained.

In my personal experience this is way more important to stay on top of with the Silicone systems like SRAM/AVID as opposed to the mineral oil systems like Shimano.

By contrast you can absolutely set up someone on a cabled rim brake system and they can ignore it for a decade with fairly good use and it will still function correctly. I see it daily in the shop.

By contrast
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Old 02-26-19, 04:21 PM
  #168  
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Originally Posted by RiceAWay View Post
Made up concern? Do you have a picture of the hydraulic line runs on a bike? On mine the hydraulic lines didn't fit into the provided catches and they hung out in places able to catch on passing brush. Even on the more modern CX bike I have now the hydraulic tubing runs do not work properly.
This is not a thing.

After all the years of doing in race support for anything from grassroots to world cup pitting for cyclocross I have never witnessed a single hydraulic line catch on anything, rupture, or otherwise fail. I am sure it has happened but I have never witnessed it or seen it in the pits. By the same token I have seen many situations where a rider has snagged or broken their cable for the derailleur. Never a brake cable but derailleur for sure.
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Old 02-26-19, 05:13 PM
  #169  
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Originally Posted by Psimet2001 View Post
This is not a thing.

After all the years of doing in race support for anything from grassroots to world cup pitting for cyclocross I have never witnessed a single hydraulic line catch on anything, rupture, or otherwise fail. I am sure it has happened but I have never witnessed it or seen it in the pits. By the same token I have seen many situations where a rider has snagged or broken their cable for the derailleur. Never a brake cable but derailleur for sure.
+1.

I've see brake lines that were damaged on mountain bikes, but usually the brake line was the least of the problem.

No problems with brake lines out in the open on my bike.





(Edit) sorry for the trekmogul style photos

Last edited by noodle soup; 02-26-19 at 05:20 PM.
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Old 02-26-19, 07:41 PM
  #170  
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Originally Posted by rms13 View Post
I had one gravel bike with hydraulics but have since been sticking with rim brakes. The braking was improved but I hated the bulbous hoods on the bike and hated the aesthetics of the discs. That was one generation ago and things have already improved. As the hoods get closer to mechanical brake size/shape and discs get smaller I won't have much of an argument against them.
They certainly have already improved: my 2018 bike has the Shimano Ultegra groupset, and the shifters/hoods really don't look significantly different from rim brake models. However, the 105 ones do, they're bigger and more bulbous. As for discs getting smaller, I wouldn't count on that: smaller discs have less mechanical advantage, so reducing their diameter would result in a significant performance hit. I think people are just going to get used to the way they look.
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Old 02-26-19, 07:49 PM
  #171  
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Originally Posted by dwolsten View Post
I think people are just going to get used to the way they look.
Frankly, I think that discs look cleaner than a rim brake caliper hanging off of the fork/stays.
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Old 02-26-19, 08:05 PM
  #172  
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Originally Posted by daoswald View Post
To eliminate wheel rim side wear-through on expensive rims. Conceivably no need for rim brake surface could allow for reduced rotational inertia/mass.

Better performance for someone doing frequent, extended, intense descents with no potential for overheating a tire.

Greater clearance for wide tires assuming frame can accommodate.

But to some extent they are a solution in search of a problem. I have them on one bike, not on the other, and don't much mind either way.
I will add: Long descents: And overheating the rim, aluminum loses strength at much lower temperatures than steel, and aluminum also has a big coefficient of thermal expansion so this also stresses the spokes and spoke holes when the aluminum is hot and weaker.

I want discs on my next bike. What bugs me is the pads are way more expensive to replace, and proprietary designs, you can't just walk into any bike shop and expect them to carry pads that will fit your calipers.

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Old 02-26-19, 08:33 PM
  #173  
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Originally Posted by RiceAWay View Post
Firstly, mechanical disks do not operate very well, the cable play has you re-adjusting them every other ride.
This can actually be true for mtb, but not really for road. I have used BB7s for years on my mtbs. And when riding in the mountains with long descents I did need to twiddle the adjustment knobs every few rides, sometimes even each ride in particularly demanding terrain. It takes about 30 seconds to do front and rear.

I also have bb7s on a road/gravel bike. I adjust those about every 10-15 rides. Again, 30 seconds and done.

Thirdly, On rim brakes most of the stopping forces are placed on the strongest parts of the frame - the top of the fork at the headset bearing and the top of the seat stays near the seat tube. On disk brakes the stopping forces are placed at the very end of the fork with a long lever arm to put pressure against the top of the fork. And BEHIND the seat stay, chain stay intersection.
Actually, the stopping force is applied at the end of the fork (the dropouts) in either braking system. The stress on the head tube and crown of the fork is basically the same. What is different is where the caliper is being pushed forward and leverage for twisting the fork blade between the brake caliper and wheel dropouts. But whatever the case, forks apparently handle it fine.
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Old 02-26-19, 09:30 PM
  #174  
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Originally Posted by Maelochs View Post
I will admit, compared to hydro discs, cables are not nearly as powerful, but they do not go out of adjustment.
Originally Posted by Psimet2001 View Post
Small point of clarification - while they may not "go out of adjustment" in that they don't just change their setup on their own mechanical discs DO wear rapidly and do not compensate for that wear on their own. In the spectrum of road it doesn't on the surface seem like a big deal or a frequent occurrence but when disc first hit on the cross scene and we were forced to use mechanical discs we frequently blew through enough of a pad in 1 lap of a messy race that all braking power would be lost. Luckily we can pit and grab a new bike.
Point taken. However ….

Originally Posted by Kapusta View Post
This can actually be true for mtb, but not really for road. I have used BB7s for years on my mtbs. And when riding in the mountains with long descents I did need to twiddle the adjustment knobs every few rides, sometimes even each ride in particularly demanding terrain. It takes about 30 seconds to do front and rear.

I also have bb7s on a road/gravel bike. I adjust those about every 10-15 rides. Again, 30 seconds and done.
I trust both of you and your information. Since this thread specified road use, I focused on that. I have never used cable discs off-road. I certainly go more than 15 rides between brake adjustments … but perhaps because I am a slower rider on flatter terrain, pad wear is less of an issue.

On the other hand, as @Kapusta notes … there is a barrel adjuster.

But, I stipulate that as @Psimet2001 points out, cable disc levers do not self-adjust. No sense arguing @bike_Wikipedia. The guy knows where of he speaks—or at least, he has completely fooled me with every post of his I have ever read.
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Old 02-26-19, 09:32 PM
  #175  
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I have bikes with MTB BB7s, road BB7s, SRAM hydros, Hylex hydros, Shimano LX hydros, ridden around 1000mi on Shimano road hydros, and a bunch of rim brake bikes. I'd say rim brakes are fine for road in the vast majority of conditions. My next road bike will probably be rim brake.

But if you only own one bike disc is more versatile for sure. Most of my bikes are disc brake as I was really into some of the pros including
- all-weather responsiveness (brakes barely working when you're descending a wet road in heavy rain is scary)
- light brake touch of hydros for bumpy gravelly descents saves your wrists/hands (huge plus on something like Hilly Billy Roubaix - I did it with road BB7s, yuck)
- no rim wear (I have worn through aluminum road rims)
- no worries for carbon brake tracks
- no need to keep rim as true
- better rim designs
- better clearance for larger tires
- options for different wheel sizes

The thing is though nowadays most of my riding is on the pavement in dry weather, with quite a lot of hills. I don't need wider than 25-28mm tires, especially with modern wider rims. I've locked up brakes on my old rim brake road bike to avoid a car, and I wasn't lacking in braking power. I'm also <140lbs so I'd appreciate the lighter weight bike and honestly I'd rather true a wheel than true a rotor. I'd also rather replace a brake cable / rim brake shoe pads than bleed a hydro system / replace disc brake pads. Also, the wear rate of an aluminum rim is maybe... 10000 miles for a front wheel? By then I'd probably want to buy new wheels anyway (or just rebuild onto the same hub). I'm also spoiled for choice and already have separate bikes for different wheel sizes. And switching out wheels, even with hydros, can still require readjusting calipers due to differences in hub tolerances, although I have really enjoyed the benefit of wheel interchangeability for a gravel/CX bike.

I did also have one case where my hydros failed on a gravel descent and I had to Flintstone reverse-paperboy to stop, partly ruining my new shoes at the time (turned out to be a bike mechanic error).
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