hey weight weenies....have you regretted going disc OR aero?

Discuss light weight issues concerning road bikes & parts.
robeambro
Posts: 614
Joined: Sat Jul 07, 2018 6:21 pm

by robeambro

Hexsense wrote:
Thu Oct 25, 2018 7:47 pm
Right,
With my previous 21mm internal width wheelset (28mm outside)
23c is 27.3mm wide
25c is 28.3mm wide

front wheel shouldn't be more than 25c clincher for best aero performance. Even 23c at 27.3mm is full two mm wider than what pro use (25c tubular at 25mm, they don't run oversize like modern clincher tires on wide rims).

Under around 30km/h your 32c, providing it is made thin and fast, will be faster due to better rolling resistance. But once aerodynamic take over at higher speed, you better use 25c front (and probably 28c rear). This is assumed your wheels are not 36mm wide externally or something crazy wide.
I know it's just a way of expressing it, and you are surely fully aware of how it works. However, saying that aero "takes over" seems to imply that below a certain speed aerodynamics laws just don't hold and then all of a sudden, beep, they "wake up". Of course I know that you meant to say that aero becomes the predominant force against the cyclist. but I've found that people tend to misunderstand aerodynamics when they read posts like this - not necessarily here, but on other boards I've read plenty of time people saying stuff like "there's no aero benefit under xxx kmh".

So yeah, it's just a personal crusade to make sure that people understand :smartass:
Last edited by robeambro on Fri Oct 26, 2018 10:54 am, edited 1 time in total.

by Weenie


mrlobber
Posts: 959
Joined: Sat Oct 23, 2010 9:36 am
Location: Where the permanent autumn is

by mrlobber

dcorn wrote:
Thu Oct 25, 2018 4:01 am
I don't follow. Science shows that wider, lower pressure, tubeless tires are faster than super high pressure skinny tires, with the side effect of being much more comfortable.
Science doesn't show that. Science shows that wider tires have less rolling resistance than narrower tires at equal pressures.
By reducing pressure, you get the benefit of comfort, but rolling resistance gains are given away.
Retired bikes: Cervelo S5 2015 / Felt AR FRD 2014 / Cannondale SS HM 2014 / Scott Addict SL 2014 / Scott Plasma Premium 2014 / Orbea Orca 2008 / Look 596 /

NickJHP
Posts: 271
Joined: Wed Feb 14, 2018 2:22 am
Location: Canberra, Australia

by NickJHP

mrlobber wrote:
Fri Oct 26, 2018 9:23 am
dcorn wrote:
Thu Oct 25, 2018 4:01 am
I don't follow. Science shows that wider, lower pressure, tubeless tires are faster than super high pressure skinny tires, with the side effect of being much more comfortable.
Science doesn't show that. Science shows that wider tires have less rolling resistance than narrower tires at equal pressures.
By reducing pressure, you get the benefit of comfort, but rolling resistance gains are given away.
You're ignoring the suspension losses due to to the work needed to vibrate you (and the bike) up and down over anything other than a perfectly smooth road surface. This work has to come from the riders power output, and the higher the tyre pressure, the higher these suspension losses, which affects your speed. I don't know that anyone has quantified whether the gain on one side is more or less than the loss on the other, but until they do I'll take the wider, lower pressure, more comfortable tyre every time.

Hexsense
Posts: 935
Joined: Wed Dec 30, 2015 12:41 am

by Hexsense

robeambro wrote:
Fri Oct 26, 2018 9:14 am
Hexsense wrote:
Thu Oct 25, 2018 7:47 pm
But once aerodynamic take over at higher speed, you better use 25c front (and probably 28c rear). This is assumed your wheels are not 36mm wide externally or something crazy wide.
I know it's just a way of expressing it, and you are surely fully aware of how it works. However, saying that aero "takes over" seems to imply that below a certain speed aerodynamics laws just don't hold and then all of a sudden, beep, they "wake up". Of course I know that you meant to say that aero becomes the predominant force against the cyclist. but I've found that people tend to misunderstand aerodynamics when they read posts like this - not necessarily here, but on other boards I've read plenty of time people saying stuff like "there's no aero benefit under xxx kmh".

So yeah, it's just a personal crusade to make sure that people understand :smartass:
Right, take over speed is relative. For full package of climbing bike vs aero bike it's at one speed. Just considering tire width between two tires it's another speed (dt swiss did this kind of experiment of tire width, aero drag and rolling resistance).

Aero is always beneficial, but many time aero drag is arguibly negligible at low speed anyway. It grow as cube of speed if i'm not mistaken (not exponential that many people like to claim it is), thus at very low climbing speed with no headwind it is virtually non consideration. So it is not that critical to consider or not consider aero when air speed is <10 km/h. And still, anything under 30 km/h aero matter but still not at huge magnitude that can trump any other criteria without careful consideration. For example, different in rolling resistance of wider tire can offset aero disadvantage up to a certain speed. Of course, it's not really accurate to think only the traveling speed but we need to consider relative wind speed. With strong headwind aero will matters even when you stand still.

Anyway, I'd totally advocate this with you if drag grow linearly with speed. But there are range of speed when aero drag (as cube of speed) grows from 0.x watts or single digits or even low double digits of watts (insignificant) to three digits (significant), It's not too wrong to count that range as a kick in point and anything below as a non consideration range for aero. Physics don't stop working, it just work in a small magnitude that it doesn't matter (much). So I'm not serious when people say things like that. It's easier to understand for them.

jencvo
Posts: 80
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?

RocketRacing
Posts: 886
Joined: Thu May 10, 2018 2:43 am

by RocketRacing

Aero vs light. I am on this forum so you know my bias.

In my build (used felt F2 with mavic rsys slr wheels) i struggled with wheel and bar choice... aero vs light. In the end I went light because i felt (no pun intended) that the bike was already well on the way to being lightweight. So now all my choices are with weight/comfort/asthetics in mind. The theme is light, and it is geared to be a climbing beast.

Yes, i have done my homework, and aero is faster. But most of the aero gains are found in the rider anyway... so i have an aero helmet, aero jersey, and I am working on a lower position. Without much training I seem to be naturally flexable, so a low flat back position comes naturally.

My next road bike will be an aero bike. It will be a no holds barred, fully aero optomized bike with no consideration for weight. I want to even test a few tri bikes (Felt IA). I love the tech. And when i go aero, it will be full aero.

All my bikes have a theme. I like varied experiences on my bikes.

Zigmeister
Posts: 938
Joined: Mon Jan 24, 2011 8:09 pm

by Zigmeister

Going Aero? Never regret that since Aero bikes are pretty much capable of being as light as regular bikes, and it won't matter to a high level cyclist anyway all of the talk of weight being an issue even if it is 4-8oz more running an aero setup. I know, this is weight weenies, whatever. Weight is only really going to matter, just like Disc brakes, for climbing scenarios. If that is 80% of your riding, then fine, but we know plenty of people can climb well enough on aero frames. Like Team Sky...hummm...aero frame winning the TDF...kooky talk.

Disc brakes requires you to change everything about your bike basically. You need a new frameset, wheels blah blah blah...what a complete sham to get money out of people and get them to upgrade the most expensive parts of a bike, for most is not a useful upgrade at all. Guess people just like to spend money on stuff. I see plenty of guys who are always have the latest gear on the group rides. Unless you are doing massive climbs/descents or wet riding, there is no added benefit of disc...Disc brakes are a solution looking for a problem for most, and hype to get people to spend loads of money for no reason. Have fun with that.

robertbb
Posts: 1051
Joined: Thu Jul 23, 2009 3:35 am
Location: Melbourne, Australia

by robertbb

Zigmeister wrote:
Sun Oct 28, 2018 9:47 pm

Disc brakes requires you to change everything about your bike basically. You need a new frameset, wheels blah blah blah...what a complete sham to get money out of people and get them to upgrade the most expensive parts of a bike, for most is not a useful upgrade at all. Guess people just like to spend money on stuff. I see plenty of guys who are always have the latest gear on the group rides. Unless you are doing massive climbs/descents or wet riding, there is no added benefit of disc...Disc brakes are a solution looking for a problem for most, and hype to get people to spend loads of money for no reason. Have fun with that.
Right. It's almost like we're being told descending mountains or riding in the wet is unsafe... or impossible... with rim brakes. I wonder if there is anyone out there who has successfully negotiated a spirited descent without disc brakes? Anyone at all? :lol:

joejack951
Posts: 629
Joined: Fri Feb 18, 2005 6:50 pm
Location: Wilmington, DE

by joejack951

robertbb wrote:
Sun Oct 28, 2018 11:55 pm
Right. It's almost like we're being told descending mountains or riding in the wet is unsafe... or impossible... with rim brakes. I wonder if there is anyone out there who has successfully negotiated a spirited descent without disc brakes? Anyone at all? :lol:
It's almost like we're being told we can't enjoy riding a bike without:

1. 8/9/10/11/12 cassette cogs
2. 3 chainrings
3. a front derailleur
4. round frame tubes
5. skinny tires on narrow rims
6. mechanical shifting
7. etc.

Reality is, most of us ride bikes for pure enjoyment. If you enjoy cycling more because of some latest new tech, I'm not going to argue with you about it. All this fretting over how other people spend their money gets really old.

For the record, I like disc brakes, I like 11 speed cassettes more than 10, I like triples but have found that I can live with a compact double, I don't own an aero bike but would like one, and I don't use electronic shifting currently and would only consider it for a time trial bike.

RocketRacing
Posts: 886
Joined: Thu May 10, 2018 2:43 am

by RocketRacing

Zigmeister, agreed.

Most aero bikes have a weight penalty... especially when you try to go weight weenie as aero wheels/bars/seatposts/stems are just not as light. Same for the frames. There is no darimo/schmolke of aero components.

But... agreed that all the data says that aero gains far ourweigh weight losses... something like a 10:1 ratio (though it depends on gradients and speeds of course... but the point is that aero gains are worth it, and weight losses are truly marginal at best). There was an interesting gcn episode (take it for what it is worth) where buddy did a hillclimb build. The zipp engineers (take it for what it is worth) advised 808’s for his climb because math said that at the speeds he expected to go, the aero benefits of the deep section wheels still outweighed any weight penalty!

Disc brakes... such a hot topic, and i don’t want to go there, but no question my disc brake bikes are not that much better than my ultegra rim brakes in the dry. Where disc brakes are unarguably superior is carbon wheels in the wet. No question there.

And yeah it is a big investment to swap over... but once you get a disc frame and wheelset, there would be no worry of wearing down or damaging the brake tracts on a 3000$ set of wheels. Just swap on new disc rotors. I like my wear and tear items to be 30$, not 3000$.

Pros and cons. But if better braking increases safety, i think it needs to happen eventually.

RocketRacing
Posts: 886
Joined: Thu May 10, 2018 2:43 am

by RocketRacing

joejack951 wrote:
Mon Oct 29, 2018 2:08 am
Reality is, most of us ride bikes for pure enjoyment. If you enjoy cycling more because of some latest new tech, I'm not going to argue with you about it. All this fretting over how other people spend their money gets really old.

For the record, I like disc brakes, I like 11 speed cassettes more than 10, I like triples but have found that I can live with a compact double, I don't own an aero bike but would like one, and I don't use electronic shifting currently and would only consider it for a time trial bike.
Yup.

I love to ride bikes, but i love the tech too. I am a combo of a weight weenie and a tech weenie, and my roadbike now reflects that. Researching and upgrading is part of the fun for me. That is why i like to start with frames. My next bike will be an aero weenie bike... and i might get a nice one so I can just leave it alone. Lets see how long that lasts...

And di2 was ok... but man do i love etap. The simplicity/purity of it is great. E shifting is not such a big deal on the back... but so nice on the front. And there is something about knowing in your head that the only wires are for your brakes. It is kind of like a light bike... in the real world it is a marginal gain at best, but in your head it means everything... and that is important.

MoPho
Posts: 534
Joined: Sun Jul 10, 2011 7:48 pm
Location: NorCal/SoCal

by MoPho

Zigmeister wrote:
Sun Oct 28, 2018 9:47 pm


Disc brakes requires you to change everything about your bike basically. You need a new frameset, wheels blah blah blah...what a complete sham to get money out of people and get them to upgrade the most expensive parts of a bike, for most is not a useful upgrade at all. Guess people just like to spend money on stuff. I see plenty of guys who are always have the latest gear on the group rides. Unless you are doing massive climbs/descents or wet riding, there is no added benefit of disc...Disc brakes are a solution looking for a problem for most, and hype to get people to spend loads of money for no reason. Have fun with that.

Well OK then
Fun Fact #1: Most people buy complete bikes, "changing everything" is irrelevant to that process, rim or disc
Fun Fact #2: Aero bikes require you to change everything too. You need a new frame, new integrated brakes, new wheels if you don't already have aero wheels (no point in having an aero frame without aero wheels, right?! ), new aero bars and stem, blah blah, blah... what a complete sham to get money out of people and get them to upgrade the most expensive parts of a bike, for most is not a useful upgrade at all.
Fun Fact #3: No one won a group ride because of the bike they are riding, and it's debatable that anyone won (or lost) a bike race because of the bike specs
Fun Fact #4: Using your wallet to buy "speed" doesn't make you more fit, the bike is only as fast as you are.
See, that was fun ;)


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Lewn777
Posts: 833
Joined: Thu Mar 09, 2017 5:35 am

by Lewn777

Disk bikes are a total logic fail for road bikes.

The reason is simple: If you remove a wheel and change it for another of a different brand the disk won't line up with the caliper.

You then need a plastic tire lever. Remove the wheel, push the pistons back into their bores with the plastic tire lever. Then pump the brakes back to their normal position. That is if you have clean pistons and no dirt or air in the system. If you're more unlucky you'll need to loosen the calipers and use an alignment tool too.

You can't do that in a race in case of a flat so you need the exact same brand of wheel or you'll end up with rubbing or not even fitting on the bike. You can do it at home but it takes 5-20 minutes per wheel.

Personally I want aero wheels and climbing wheels and then maybe something in-between between two bikes. Disk brakes just don't make sense.

TobinHatesYou
Posts: 4188
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Do you race?

Rotor spacers exist for both 6-bolt and centerlock, though some people warn that centerlock spacers might be dangerous.

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Lewn777
Posts: 833
Joined: Thu Mar 09, 2017 5:35 am

by Lewn777

Like was said before, a solution looking for a problem. Added weight, expense, complexity, reduced compatability opening up a pandoras box of the new standards special olympics.

Both road disk brakes and tubeless are half-baked poorly standarised technologies ported across from mountain bikes. Score C- must try harder.

I'll happily buy disk brakes when the bikes are only a few hundred grams heavier and they've left standards alone for at least three years. But honestly I doubt that will ever happen.

by Weenie


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