The Great Braking Debate Thread (Disc/Rim/Cantilever/Fixie/InsertNewTechHere)

Discuss light weight issues concerning road bikes & parts.

Moderator: robbosmans

tanhalt
Posts: 396
Joined: Wed Dec 27, 2006 6:36 pm

by tanhalt

Maddie wrote:
Thu Oct 28, 2021 8:07 pm
What's the lightest carbon wheel with alloy brake track available? I remember reading nearly as light or a few 10s of grams heavier than disc wheelset. Should be tubeless, preferably with hooks.
When making those wheelset weight comparisons, don't forget to include the weight of the disc rotors for the disc wheelsets (which, with attaching hardware can add up to 250-300g). Some manufacturers lately like to tout that the disc versions of their wheels as being their "lightest ever" (cough...<Zipp>...cough), and conveniently leave out that it's the wheelset without a braking surface attached. One needs to add that back in to compare "apples to apples" with a rim brake wheelset :wink:

Here's an example:

Hed Jet 4 Black wheelset weight: claimed 1605g

Now, compare that to:
Brand new Zipp 353 NSW wheelset weight: claimed 1294g (+ 250-300g rotors/hardware) = 1544-1594g total
or,

Zipp 303 Firecrest disc wheelset weight: claimed 1355g (+250-300g rotors/hardware = 1605-1655g total

Just sayin'... :noidea:

by Weenie


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robbosmans
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by robbosmans

300g rotors??

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

by TobinHatesYou

robbosmans wrote:
Thu Oct 28, 2021 10:01 pm
300g rotors??
Two 160mm rotors at ~115g each + the weight of two lockrings.

tanhalt
Posts: 396
Joined: Wed Dec 27, 2006 6:36 pm

by tanhalt

robbosmans wrote:
Thu Oct 28, 2021 10:01 pm
300g rotors??
Total for 2 plus hardware.

Example:
Shimano DA 160mm rotor: claimed 117g
Lockring: claimed 10g

So...254g for 2 wheels. So, within the "250-300g" range mentioned above. 300 might be a bit high for the top end...but still, we're talking total mass differences of just tens of grams

PoorCyclist
Posts: 482
Joined: Wed Dec 07, 2011 1:26 am
Location: California's country side

by PoorCyclist

tanhalt wrote:
Thu Oct 28, 2021 5:21 pm

Here's a close-up after >5k miles of pavement riding (including many large climbs and descents) and ~2300 miles of mixed pavement/dirt use (heavy on the dirt).
Image
Any chance these calipers would work with a SRAM force 1x hydro lever?

I don't understand, how do you use your brake in the drops?

TobinHatesYou
Posts: 8813
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

PoorCyclist wrote:
Fri Oct 29, 2021 2:32 am

Any chance these calipers would work with a SRAM force 1x hydro lever?

I don't understand, how do you use your brake in the drops?

SRAM uses DOT fluid. Magura uses mineral oil.

tanhalt
Posts: 396
Joined: Wed Dec 27, 2006 6:36 pm

by tanhalt

PoorCyclist wrote:
Fri Oct 29, 2021 2:32 am
tanhalt wrote:
Thu Oct 28, 2021 5:21 pm

Here's a close-up after >5k miles of pavement riding (including many large climbs and descents) and ~2300 miles of mixed pavement/dirt use (heavy on the dirt).
Any chance these calipers would work with a SRAM force 1x hydro lever?

I don't understand, how do you use your brake in the drops?
It might work, but not recommended...the difficulty is that SRAM stuff runs DOT 4 or 5.1 fluid (glycol based) while those Magura calipers run their mineral oil. Now then, the seals in the SRAM stuff would be OK with mineral oil (you'd need to flush with alcohol a few times before putting mineral oil in), but not vice versa. The seals in the calipers can't handle the glycol stuff.

Aside from the fluid issues, and possible differences in master piston diameters changing leverage...IMO, the main reason you don't want to use a lever used for disc brakes on these calipers is that you'll lose the pad clearance adjustment. The Magura levers have a small wheel under them that allows you to adjust the pad spacing to compensate for pad wear. This works because it's a closed system (i.e. no reservoir, unlike a disc system) and that adjuster wheel just takes up space in the master cylinder and thus makes the system volume smaller, thereby pushing the pads out further for a given fluid volume.

Here's what I did...when I ordered the Magura brakes, I selected the 4 finger lever option (to get a longer lever). I then ordered a pair of these 3D printed adapter blocks from Shapeways (turns out the design is by another WW member 8) ):
Image
https://www.shapeways.com/product/WHZMF ... e-drop-bar

This is how it ended up on the Cannondale:
Image

As you can see, the adapter not only adapts the smaller diameter MTB clamp area to the slightly larger diameter road bar size, but also changes the angle of the lever body relative to the bar, thus putting the lever in just the right spot for use in the drops. Feels exactly like a road lever when braking from the drops.

Now...if you notice, in the picture of the full bike shown earlier in this thread, I originally set up the shifting to use a bar end. I wasn't completely satisfied with that...and even tried an old SunTour "batwing" style shifter (with a custom detent plate for 10sp) mounted next to the lever for a bit...but, eventually settled on a what you see here, a wireless electronic X-shifter from Cell Cycling. That little rubber module you see next to the lever is a wireless shift button. The actuator is mounted on the driveside chainstay:
Image

Maddie
Posts: 918
Joined: Tue Oct 17, 2017 5:44 am

by Maddie

tanhalt wrote:
Thu Oct 28, 2021 10:34 pm
robbosmans wrote:
Thu Oct 28, 2021 10:01 pm
300g rotors??
Total for 2 plus hardware.

Example:
Shimano DA 160mm rotor: claimed 117g
Lockring: claimed 10g

So...254g for 2 wheels. So, within the "250-300g" range mentioned above. 300 might be a bit high for the top end...but still, we're talking total mass differences of just tens of grams
I agree, wheelsets should be compared including braking surface. Here’s my view: Brake rotors are usually 160/140mm for high end bikes. XTR/new DA rotors are 208g including lockrings (measured, not claimed). My sub 1000 USD disc wheelset from Farsports weighs 1140g (again, measured), around 1350g including rotors for the set in total (35mm deep, 45mm would add another 60g). And that’s hardly boutique material.

That’s 300g less than an alloy-carbon wheelset. Rather 100s of grams instead of 10s.

AJS914
Posts: 4783
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

Ok, here's my current rim/disc quandry:

I found my C64 dream frame at a discount (perfect size and color). It's a direct mount frame and thus is limited to 28mm tires (probably 30mm actual).

I've been thinking about a modern bike that could take 30-32mm tires on wider rims. 30mm actual is still a boost over the 25mm tires on my C59.

I have a few sets of wheels, two 11 speed mechanical Campagnolo groupsets, plus spare parts so I'm good for a long time.

Rim vs Disc part: I have all the parts and wheels to support rim, I don't need exceptional braking. I hardly brake at all in my area other than to come to a stop sign.I don't really ride in the wet unless it is by accident. Rim is easier to maintain for me. Downside of rim: less wide tires...

So the options are:

1) scratch the C64 itch with rim brakes for the sake of new frame lust

2) do nothing - the C59 is fine, wait for some other deal, bike in the future.

2a) could also sell all my 11 speed stuff and then transition to disc and/or 12 speed. Prices on ebay appear to be pretty high on Campagnolo 11 as new spare parts are drying up

GregR
Posts: 60
Joined: Thu Nov 28, 2019 9:03 pm

by GregR

:In my opinion, including disc weight with wheel weight when comparing disc and rim wheels is misleading. Better to treat the discs like the caliper. The mass of the disc is quite close to its rotational axis, so it won't have a big impact on the polar moment of inertia of the wheel.
Best is simply to compare rim weights, as they will dominate the polar moment of inertia. Spokes will contribute some, I don't know how much but I'd bet not much. The hub and disc, if present, not much either.
This will affect how the wheel accelerates. How much does this matter? Hmmm not sure. (haven't quantified it) But we can sure argue about it. Less rim material = better accelerating wheel, even if the total wheel weight is higher when the disc is included.
:popcorn:

GregR
Posts: 60
Joined: Thu Nov 28, 2019 9:03 pm

by GregR

AJS914 wrote:
Fri Oct 29, 2021 1:54 pm
Ok, here's my current rim/disc quandry:

I found my C64 dream frame at a discount (perfect size and color). It's a direct mount frame and thus is limited to 28mm tires (probably 30mm actual).

I've been thinking about a modern bike that could take 30-32mm tires on wider rims. 30mm actual is still a boost over the 25mm tires on my C59.

I have a few sets of wheels, two 11 speed mechanical Campagnolo groupsets, plus spare parts so I'm good for a long time.

Rim vs Disc part: I have all the parts and wheels to support rim, I don't need exceptional braking. I hardly brake at all in my area other than to come to a stop sign.I don't really ride in the wet unless it is by accident. Rim is easier to maintain for me. Downside of rim: less wide tires...

So the options are:

1) scratch the C64 itch with rim brakes for the sake of new frame lust

2) do nothing - the C59 is fine, wait for some other deal, bike in the future.

2a) could also sell all my 11 speed stuff and then transition to disc and/or 12 speed. Prices on ebay appear to be pretty high on Campagnolo 11 as new spare parts are drying up
Unless you are budget constrained or really love your existing parts, just go for the best setup you can imagine. You don't have a great use case for disc, except for the wider tires. There will be a learning curve with the disc brakes, but when you get them tuned in they are close to maintenance free for the most part. It's just new/different skills and many adults don't deal well with that after how many years of having great knowledge about how to work on the old systems.
What's great about your situation is that you will avoid the hated squeal by avoiding wet use.
TBH all paths are pretty good for you.

tanhalt
Posts: 396
Joined: Wed Dec 27, 2006 6:36 pm

by tanhalt

Maddie wrote:
Fri Oct 29, 2021 6:49 am
tanhalt wrote:
Thu Oct 28, 2021 10:34 pm
robbosmans wrote:
Thu Oct 28, 2021 10:01 pm
300g rotors??
Total for 2 plus hardware.

Example:
Shimano DA 160mm rotor: claimed 117g
Lockring: claimed 10g

So...254g for 2 wheels. So, within the "250-300g" range mentioned above. 300 might be a bit high for the top end...but still, we're talking total mass differences of just tens of grams
I agree, wheelsets should be compared including braking surface. Here’s my view: Brake rotors are usually 160/140mm for high end bikes. XTR/new DA rotors are 208g including lockrings (measured, not claimed). My sub 1000 USD disc wheelset from Farsports weighs 1140g (again, measured), around 1350g including rotors for the set in total (35mm deep, 45mm would add another 60g). And that’s hardly boutique material.

That’s 300g less than an alloy-carbon wheelset. Rather 100s of grams instead of 10s.
Well sure, one can always find "one-off" examples that go against the trend, but can you really say with confidence that those Farsports rims have the same level of engineering, reliability, and most importantly, aerodynamic data available, to say they really compare to the Heds or the Zipps in an overall performance and safety sense? If not, then you're saying the weight matters more than those other things (to you...and, I get it, this IS the WW forums :wink: ) but in reality, things like the aerodynamics can easily be shown to be a larger performance factor than the mass, even at the differences you show.

tanhalt
Posts: 396
Joined: Wed Dec 27, 2006 6:36 pm

by tanhalt

GregR wrote:
Fri Oct 29, 2021 8:11 pm
:In my opinion, including disc weight with wheel weight when comparing disc and rim wheels is misleading. Better to treat the discs like the caliper. The mass of the disc is quite close to its rotational axis, so it won't have a big impact on the polar moment of inertia of the wheel.
Best is simply to compare rim weights, as they will dominate the polar moment of inertia. Spokes will contribute some, I don't know how much but I'd bet not much. The hub and disc, if present, not much either.
This will affect how the wheel accelerates. How much does this matter? Hmmm not sure. (haven't quantified it) But we can sure argue about it. Less rim material = better accelerating wheel, even if the total wheel weight is higher when the disc is included.
:popcorn:
Inertial effect differences of the 2 setups are minor...and besides, due to the fact that humans on bicycles accelerate REALLY slowly (even in an all out sprint). So, when it comes to wheels, mass is mass. The distribution doesn't have an appreciable effect on performance (despite "conventional wisdom"). This has been shown mathematically (using real-world rider power inputs) numerous times.

So no...if one wants to use a wheelset weight as a gauge of the wheelset's contribution to the total bike mass, then one should be comparing functionally equivalent setups. A rim brake wheelset has the braking surface included, a disc brake wheelset without the disc is missing the braking surface. Comparing at functional equivalence means including the disc rotors and fixing hardware. That's "apples to apples"...otherwise, people start believing the hype that disc wheelsets are now lighter than their older, clincher rim brake counterparts. That just hasn't happened yet, despite the lack of further development on rim brake wheels and the latest concentration on disc rim development.

CampagYOLO
Posts: 119
Joined: Thu May 06, 2021 3:58 pm

by CampagYOLO

AJS914 wrote:
Fri Oct 29, 2021 1:54 pm
Ok, here's my current rim/disc quandry:

I found my C64 dream frame at a discount (perfect size and color). It's a direct mount frame and thus is limited to 28mm tires (probably 30mm actual).

I've been thinking about a modern bike that could take 30-32mm tires on wider rims. 30mm actual is still a boost over the 25mm tires on my C59.

I have a few sets of wheels, two 11 speed mechanical Campagnolo groupsets, plus spare parts so I'm good for a long time.

Rim vs Disc part: I have all the parts and wheels to support rim, I don't need exceptional braking. I hardly brake at all in my area other than to come to a stop sign.I don't really ride in the wet unless it is by accident. Rim is easier to maintain for me. Downside of rim: less wide tires...

So the options are:

1) scratch the C64 itch with rim brakes for the sake of new frame lust

2) do nothing - the C59 is fine, wait for some other deal, bike in the future.

2a) could also sell all my 11 speed stuff and then transition to disc and/or 12 speed. Prices on ebay appear to be pretty high on Campagnolo 11 as new spare parts are drying up
You seem pretty certain that you don't need disc brakes so get the C64.
A quality Italian tyre like a Veloflex Corsa Evo TLR is super comfy in 28mm, as comfy as 30-32mm tyres from other brands and would be culturally appropiate for the frame!

by Weenie


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Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

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tanhalt
Posts: 396
Joined: Wed Dec 27, 2006 6:36 pm

by tanhalt

AJS914 wrote:
Fri Oct 29, 2021 1:54 pm
Ok, here's my current rim/disc quandry:

I found my C64 dream frame at a discount (perfect size and color). It's a direct mount frame and thus is limited to 28mm tires (probably 30mm actual).

I've been thinking about a modern bike that could take 30-32mm tires on wider rims. 30mm actual is still a boost over the 25mm tires on my C59.

I have a few sets of wheels, two 11 speed mechanical Campagnolo groupsets, plus spare parts so I'm good for a long time.

Rim vs Disc part: I have all the parts and wheels to support rim, I don't need exceptional braking. I hardly brake at all in my area other than to come to a stop sign.I don't really ride in the wet unless it is by accident. Rim is easier to maintain for me. Downside of rim: less wide tires...

So the options are:

1) scratch the C64 itch with rim brakes for the sake of new frame lust

2) do nothing - the C59 is fine, wait for some other deal, bike in the future.

2a) could also sell all my 11 speed stuff and then transition to disc and/or 12 speed. Prices on ebay appear to be pretty high on Campagnolo 11 as new spare parts are drying up
Yeah...it's too bad the Shimano engineers didn't have the foresight to move the direct-mount pivots outwards a bit when they defined the direct-mount configuration. They could've easily designed it for a brake that could accept 30-34mm width tires...but, now we're stuck with that.

Personally...and a suggestion for "Option 3"...I'd try to find an old steel frame that you like and put the Campy 11 speed stuff on that. Those older frames usually can easily accommodate at least a 30mm wide tire. A friend of mine here locally found an awesome Atala frameset and did just that. It's a really sweet bike...sweet riding, included. Check it out:
Image

https://www.instagram.com/p/BivRxNLBnnv ... _copy_link

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