Disc brake advantages?

Discuss light weight issues concerning road bikes & parts.
sparklywheels
Posts: 36
Joined: Fri Dec 07, 2018 6:12 pm

by sparklywheels

I’m not looking to reignite the war between the disc and rim camps, but a reasonable debate of the two systems. I used to ride rim brakes on a full Dura Ace bike, and traded it for a disc braked bike with Ultegra 8020. I’d like to know why people prefer discs though, I just don’t get it personally :? I’m trying to hear different sides and opinions.

Discs are supposed to stop better in wet conditions, but the DA rim brakes on Reynolds Assault rims in pouring rain down a 60-70kph winding descent didn’t leave any additional power or modulation to be desired. Many say that discs stop better than rim brakes on carbon in the wet, but I haven’t noticed any improvement.

Secondly, the stopping power in the dry isn’t nearly as good as my old rim brakes. Stop and go conditions make my hands and fingers sore (I’m relatively weak) on my disks, which I’ve never experienced on rim brakes. To make an full power emergency stop, I feel like I need to get in the drops, whereas the rim bike stopped with ease even from the hoods. I’ve ridden three other bikes with Ultegra discs, so setup is unlikely to be the issue. The discs stop, but aren’t effortless like rim brakes are.

After the disc brakes were bled improperly once, the issue was not apparent with a quick inspection and only appeared after 40km of riding. This resulted in losing the front brake. With a rim setup, one can 100% confirm that they are good to go visually, and have fewer points of failure compared to a disc system.

Finally, discs cost more, especially separate group sets. They weigh more, which doesn’t sound like much but the extra 500g or so in a mid ranged disc bike is a few seconds slower on uphill segments. Being someone that spends weeks tweaking every aspect of diet and training, it takes many weeks to take off a single pound. Oftentimes it isn’t even possible.

What are your thoughts and experiences?
Last edited by sparklywheels on Sat Feb 09, 2019 10:26 am, edited 1 time in total.

Mirco
Posts: 57
Joined: Thu Jul 12, 2018 7:09 pm

by Mirco

Another discussion? For me, Disc works fine, if correct installed, bleeded etc. No maintanance required instead of brake pads change. Concerning weight, everyone is able to lose 500g. Sometimes 500g is the difference from getting up in the morning and going to sleep in the evening.

by Weenie


guyc
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Location: Hampshire, England
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by guyc

Most people see a daily weight variation of between 1-3lbs.

500g. Barely noticeable.

ChiZ01
Posts: 188
Joined: Wed Jan 01, 2014 6:20 pm

by ChiZ01

sounds like either your new bike has too much reach where it is hard to pull on the brake from the hood, or the disk brake was not properly setup

TobinHatesYou
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Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

I often see the argument about daily weight variation, the weight of one water bottle, etc. and it never made much sense to me. Weight always matters and permanently losing 350-500g is nice. This is coming from someone who weighs 60-61kg and favors disc brakes. The advantages of discs outweigh the weight penalty for my style of riding / preferences, but to each their own. Rim brakes will be around in some capacity for a long time even if modern race bikes will be exclusively disc sooner than later.

guyc
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by guyc

My point was in response to this:

"Being someone that spends weeks tweaking every aspect of diet and training, it takes many weeks to take off a single pound"

Dieticians advise NOT weighing yourself daily for the very reason of daily variation. Once a week is good practice - naked, same time, after a bowel movement and naked. So whilst taking 500g off a bike is nice (but harder with discs) it's always worth bearing in mind that your own mass is likely to vary by more than that from one ride to the next.

Add in the variation that can occur between one riding outfit and the next, and I'd argue that pretty much the only static weight factor of a bike and rider is the bike itself.

sparklywheels
Posts: 36
Joined: Fri Dec 07, 2018 6:12 pm

by sparklywheels

guyc wrote:
Sat Feb 09, 2019 8:27 am
My point was in response to this:

"Being someone that spends weeks tweaking every aspect of diet and training, it takes many weeks to take off a single pound"

Dieticians advise NOT weighing yourself daily for the very reason of daily variation. Once a week is good practice - naked, same time, after a bowel movement and naked. So whilst taking 500g off a bike is nice (but harder with discs) it's always worth bearing in mind that your own mass is likely to vary by more than that from one ride to the next.

Add in the variation that can occur between one riding outfit and the next, and I'd argue that pretty much the only static weight factor of a bike and rider is the bike itself.
Weight is taken every day and the trend is taken over multiple days. The Fitbit app does this automatically. Weight does fluctuate, but it falls somewhere on a normal ish distribution with a mean and variance. If that mean weight goes down, on average, one will be faster. All my riding kit is mostly identical sets and yes weight is accounted for there.

guyc
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by guyc

So you’re honestly telling me that a body variation of 500g means you go faster?

I’m sorry, but there are simply far too many external variables at play outdoors to be able to say that with any certainty. Even taking an average you’re talking such tiny amounts that outside of a full race it’s meaningless anyway. If you are racing at that level then fair enough, it might matter.

More to the point - is your own disc bike heavier than the DA rim bike you gave up?

sparklywheels
Posts: 36
Joined: Fri Dec 07, 2018 6:12 pm

by sparklywheels

guyc wrote:
Sat Feb 09, 2019 8:51 am
So you’re honestly telling me that a body variation of 500g means you go faster?

I’m sorry, but there are simply far too many external variables at play outdoors to be able to say that with any certainty. Even taking an average you’re talking such tiny amounts that outside of a full race it’s meaningless anyway. If you are racing at that level then fair enough, it might matter.

More to the point - is your own disc bike heavier than the DA rim bike you gave up?
Yes it matters when every place is separated by just 3-4 seconds on a climb. That’s the difference between holding a wheel and getting dropped for good.

Well my rim bike was 6.8kg ready to ride, I don’t see any disc bike hitting that weight with mid section wheels, pedals, sensors, cages and Garmin.

Mirco
Posts: 57
Joined: Thu Jul 12, 2018 7:09 pm

by Mirco

The main reason for me switching from rim brake to disc 5 years ago was related to cyclocross and cyclocross races. Using cantilever was, lets say, expensive regarding rim brake surface wear. Ok, and of course braking in wet and muddy conditions.

The switch from rim to disc on road bike was more related to „a new bike would be nice and if so, now with disc“, and the fact, the S-Works Venge Vias Sagan Edition was only available as Disc Version. Another point was, again brake surface wear. The brake performance of my 40000 km used Zipp FC tubular wheelset was more or less using cantilever in wet cyclocross condition and switching to disc now, will only wear the disc itself an the brake pads and does not require to exchange a whole wheelset after thousends of km.

ToffieBoi
Posts: 415
Joined: Fri Jan 31, 2014 4:54 pm
Location: Krakow, Poland

by ToffieBoi

I have an offer!

From now on, let's post our bike weights with our own weights included. Since, this is the Weight Weenies, the lightest combination will win.

Cemicar
Posts: 107
Joined: Mon Aug 21, 2017 7:40 am

by Cemicar

sparklywheels wrote:
Sat Feb 09, 2019 8:54 am
Well my rim bike was 6.8kg ready to ride, I don’t see any disc bike hitting that weight with mid section wheels, pedals, sensors, cages and Garmin.
Emonda with XXX4.

guyc
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by guyc

If 500g costs you that much (and I’m sceptical, because variables) and you absolutely can’t lose 500g from either you or the bike (and you can on the latter for sure because you’re running Ultegra) can I ask why you moved to a heavier bike?

sparklywheels
Posts: 36
Joined: Fri Dec 07, 2018 6:12 pm

by sparklywheels

guyc wrote:
Sat Feb 09, 2019 9:59 am
If 500g costs you that much (and I’m sceptical, because variables) and you absolutely can’t lose 500g from either you or the bike (and you can on the latter for sure because you’re running Ultegra) can I ask why you moved to a heavier bike?
Because I don’t swim in money and have a limited budget? (Actually I would only save 200g going to DA)

Because disc brakes are supposedly better and worth the weight penalty?

guyc
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Location: Hampshire, England
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by guyc

But there’s a cognitive dissonance here.

On the one hand you’re saying that 500g is critical because it costs you 3-4 seconds on a climb.

On the other hand the weight penalty is worth it.

Both can’t be right if both conditions are true.

Btw - I’m absolutely not having a go at you here. I know this is WW and weight is the MO, but when people are now regularly riding 7+kg bikes because of aero and/or discs then bikes that would have been laughed off the page 3 years ago are now the norm.
Last edited by guyc on Sat Feb 09, 2019 10:11 am, edited 1 time in total.

by Weenie


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