When Are Disc Brakes Necessary?

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Marin
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Location: Vienna Austria

by Marin

IMO the main advantage of discs in road / allroad / gravel bikes are that you have much more freedom in tire choice - theoretically, since most frames don't have the clearance.

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tymon_tm
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by tymon_tm

but we're talking road bikes - how much of a fattie do you need for that? 28? 30??? cause if you do, perhaps a cross bike or a gravel bike is more suited to your needs. not so long ago, 700x23 was the standard. we've probably all ridden those, some of us for many, many years. now 25 is the new 23 - I do use that size too, but can I tell a difference? hell no. do I need wider? what for?

I get some of us do ride nasty roads, perhaps gravel/loose surface paths - but that ain't road bikes natural territory. if you tweak it enough it'll do, but that's not what it's been designed for :D
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TobinHatesYou
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by TobinHatesYou

Marin wrote:
Wed Jul 11, 2018 1:45 pm
TobinHatesYou wrote:
Wed Jul 11, 2018 11:41 am
Rest assured nothing actually melted there.
These are 100% actually melted Shimano steel-aluminum-steel sandwich discs, I assure you. Tour & bike magazine also had this happen during their stress tests (13% descent, 90kg rider, dragging the brakes and then emergency stop).

Of course, with proper technique and a lighter rider this won't happen!

https://www.google.at/search?rlz=1C1GGR ... v7LDr5oZOM:

https://www.bike-magazin.de/komponenten ... a3738.html

Well the melting point of aluminum is 660C so in order to have done this you have to be exceptionally awful or performing a synthetic test.

dvq
Posts: 181
Joined: Mon Sep 25, 2017 1:36 pm

by dvq

Marin wrote:
Wed Jul 11, 2018 1:45 pm
TobinHatesYou wrote:
Wed Jul 11, 2018 11:41 am
Rest assured nothing actually melted there.
These are 100% actually melted Shimano steel-aluminum-steel sandwich discs, I assure you. Tour & bike magazine also had this happen during their stress tests (13% descent, 90kg rider, dragging the brakes and then emergency stop).

Of course, with proper technique and a lighter rider this won't happen!

https://www.google.at/search?rlz=1C1GGR ... v7LDr5oZOM:

https://www.bike-magazin.de/komponenten ... a3738.html
FWIW, those were early shimano sandwhich disc rotor designs, they've since fixed this issue.

dvq
Posts: 181
Joined: Mon Sep 25, 2017 1:36 pm

by dvq

tymon_tm wrote:
Wed Jul 11, 2018 2:32 pm
but we're talking road bikes - how much of a fattie do you need for that? 28? 30??? cause if you do, perhaps a cross bike or a gravel bike is more suited to your needs. not so long ago, 700x23 was the standard. we've probably all ridden those, some of us for many, many years. now 25 is the new 23 - I do use that size too, but can I tell a difference? hell no. do I need wider? what for?

I get some of us do ride nasty roads, perhaps gravel/loose surface paths - but that ain't road bikes natural territory. if you tweak it enough it'll do, but that's not what it's been designed for :D
Almost all of the aero disc bikes just released were designed for 28mm, some 32mm. Are you saying those are gravel bikes? I personally run 28mm hutchinsons on my Venge Vias.

Marin
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Location: Vienna Austria

by Marin

dvq wrote:
Wed Jul 11, 2018 9:27 pm
FWIW, those were early shimano sandwhich disc rotor designs, they've since fixed this issue.
No, the bike magazine test is for the MTB rotors from when these came out, the Tour magazine test is recent and showed the issue still exists.

https://www.tour-magazin.de/service/so_ ... 30097.html

dvq
Posts: 181
Joined: Mon Sep 25, 2017 1:36 pm

by dvq

Marin wrote:
Wed Jul 11, 2018 9:49 pm
dvq wrote:
Wed Jul 11, 2018 9:27 pm
FWIW, those were early shimano sandwhich disc rotor designs, they've since fixed this issue.
No, the bike magazine test is for the MTB rotors from when these came out, the Tour magazine test is recent and showed the issue still exists.

https://www.tour-magazin.de/service/so_ ... 30097.html
Yikes then, better stick to steel rotors :)

jellytots
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Joined: Sun Feb 05, 2017 4:46 pm

by jellytots

Multebear wrote:
Tue Jul 10, 2018 10:05 am

Back to topic. The thing with rimbrake vs. Disc is, that everyone is overthinking it. We wouldn’t have had the options if the big brands didn’t push for discs. Now the latest aero bikes don’t even come in rimbrake option.

You only need to consider, how much braking power you need. If rimbrake will stop the bike to your satisfaction, then you don’t need discs; it’s a nobrainer. Don’t overthink it.
+1000

Just use common sense - there's no right or wrong - it's like asking the perennially useless question of which is the "best" bike or bike part.

There will always be a more appropriate solution depending on your style and locale of riding.

Theologian
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Joined: Sat Jun 23, 2018 3:34 am

by Theologian

Disc looks cooler! Personal preference.

Stitchking
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by Stitchking

If you've ever tried to build an aero bike like the madone you'll understand the benefit of hydraulic lines vs mechanical cables. Any of those integrated bar stems with sharp 90 degree bends are horrible for cable friction.

Ive also had a bad crash recently and had my disc bike written off, currently riding my old rim brake bike.

Recovering from a broken schaphoid, the difference in lever force needed to stop on rim brakes vs disc brakes is massively noticeable. Ive run out of brakes several times thinking the bike will stop like it did with discs.

Theyre not light, and this is weight weenies, so i dont think they'll ever be super popular here. But they are definitely massively better brakes.

Personally, i dont think ill ever buy another rim brake bike.

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alcatraz
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Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

If you are heavy, weight penalty of disc brakes is negligable.

If you are light you stop fine on rim brakes. If not then first upgrade your brakes.

For rainy countries and commuting, discs have another advantage. (however not very big if you are a light rider, almost nonexistant if you also use alloy rims)

Bordcla
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by Bordcla

Calnago wrote:
Wed Jul 11, 2018 2:56 am
@Bordcia... how many rims have you ever worn out a rim from normal braking? I mean give us a number. And carbon is much harder to wear through than aluminum. Aluminum is relatively very soft. Personally I have never worn out a carbon rim, and only one set of alloy rims that I used for loaded multiweek touring. I specifically asked this exact question in a thread quite some time ago just to see who is really wearing out carbon rims. The response was like next to no one.
As for the last part of your question, if disc brakes were all we had for the last 50 years, then all of a sudden rim braking showed up, I’d bet the marketers would be all over it....
- save 500g
- no more bleeding hydraulic lines
- no more finicky pad/rotor adjustments
- swap wheels in an instant
- quick release, no more thru axles required to stabilize uneven forces on the stays and forks from discs.
- frames can be lighter, or the same weight but stronger since that 500g can now be added back to the frame, thus stiffening up things where it counts... in the frame.
- the racers choice
- “neutral support” now really means neutral support.
Yes... it would be a much easier sell than disc brakes appear to be.
I destroyed a set of Dura-Ace C24s in a rainy hilly fondo (10-15%+ descents) because the roads were sandy. Admittedly, those were a mere $1K, but that doesn't have to be.

As also mentioned, the argument that you can lock up wheels with rim brakes is silly. Locking up the wheels is a sure way to crash. Modulation is infinitely superior with discs, come rain or shine.

The only instance on which I'd pick rim brakes instead of discs is if building a pure hill-climb machine where I'd remove one brake anyway, chop off my bars, etc.

For something functional, discs are the way to go, 400 or so extra grams notwithstanding.

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Calnago
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by Calnago

Bordcla wrote: As also mentioned, the argument that you can lock up wheels with rim brakes is silly. Locking up the wheels is a sure way to crash. Modulation is infinitely superior with discs, come rain or shine.
I agree with this. Locking up the wheels is easy with either system. I disagree with a general statement that modulation is infinitely superior with discs. That has to be compared on a case by case basis.


Bordcla wrote: The only instance on which I'd pick rim brakes instead of discs is if building a pure hill-climb machine where I'd remove one brake anyway, chop off my bars, etc.

For something functional, discs are the way to go, 400 or so extra grams notwithstanding.
500 grams on a high end road race bike is never “notwithstanding”.
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gwilliams
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by gwilliams

It’s great that disc is an option, and something I won’t dismiss, but I currently find the power of S/R rim brakes more than ample.

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jencvo
Posts: 325
Joined: Thu Oct 18, 2018 12:01 pm

by jencvo

Hi guys. In a few weeks I will start a build for a new road bike. I'm 83kg so I can see the benefit of consistent braking with discs. However, I don't ride in the wet unless caught out (thanks Wahoo Kickr), nor in the mountains. There's tons of rolling hills out here, but I ride them, not hold my brakes down each one. One thing that also bothers me with going disc is the compatibility with my indoor trainer, I'd have to buy a whole new wheel for it, then change adapters every time my wife uses it (rim brake bike), all on top of maintenance, setup, complexity, etc. associated with discs. Those are all the cons I see, with the pro being better braking in wet and long descents.

Here's the alternative to all of this I'm thinking about. Merlin Cycles is selling Mavic Cosmic Pro Exalith clinchers (https://www.merlincycles.com/en-us/mavi ... 97616.html), 10% off this weekend, so about $960. They are nicely aero but use exalith over alloy braking surface. What do you think of those? Would this be a sufficient options instead of discs, I've been running alloy braking my entire life and never had problems even descending or in the wet. Another option is Campagnolo Bullet Ultra 50, same thing, alloy braking. I feel like with proper pads they can be almost as efficient, but saving myself all the rest of the pains of going with discs in my situation. Any advice?

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