Sagan's bike at Paris Roubaix

Discuss light weight issues concerning road bikes & parts.
darnellrm
Posts: 202
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Location: NC, USA

by darnellrm

Miller wrote:
Wed Apr 11, 2018 3:16 pm
Ghost234 wrote:
Wed Apr 11, 2018 6:41 am
For PR: You are running low pressures and hitting many uneven surfaces at a high rate of speed. Not to mention you are absolutely railing corners that the tire will occasionally "flop". Running tubeless on a course like that raises the potential to burp.
No offence but this is nonsense. I have been running tubeless for 3 years and have yet to experience the mythical burp. Yes I have had tubeless tyres damaged by being slashed by flints but I have never had the tyre randomly lift a bead and expel air. It just doesn't happen.

I started with tubeless 23mm and pretty soon experienced sealant actually doing what it was supposed to do. Rapidly moved up to 25mm, lovely at 70psi, and lately have been running G-One Speed (nominal 30mm) on my new d*sc bike and absolutely adore them. Smooth as anything at 50psi and I don't feel I have given up 0.1 kph of speed, gained speed if anything, while having puncture protection just worlds better than anything I ever had when I still put rubber airbags inside my tyres.
Do you race with the tubeless setup? What is your normal kph on a ride?

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themidge
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by themidge

wingguy wrote:
Wed Apr 11, 2018 2:21 pm
themidge wrote:
Tue Apr 10, 2018 6:23 pm
(remember that everything else is assumed to be equal here, I know things like rolling and air resistance can change with weight)
No-one cycles in a vacuum.
No, they don't, do you think I don't realise that? Yes drag matters, but so does weight. Tobin wasn't talking about drag, he was talking about weight, or more specifically power/weight. Resistance due to other factors makes this discussion more complicated than it needs to be. Also, he was still wrong even if aerodynamics etc. were taken into account, because of his 'ALL'.
wingguy wrote:
themidge wrote:Flat:
Same as above, 5w/kg is 5w/kg, it doesn't matter how you get there (less weight or more power).
Watts/Kilo is irrelevant on the flats. Watts/cda is what matters there, as aside from the relatively small effects of drivetrain losses and rolling resistance it's air resistance that is the dominant factor in slowing you down. With similar positions on similar bikes the person with more total watts will go faster. Which brings us back to the hills;
It has already been established and explained how I am wrong, I must admit that I didn't think too hard about the flat one :oops: . As amusingly pointed out by another poster, J. Rodriguez has (or had) pretty fantastic w/kg, but he was shit in time trials, despite being small and therefore quite aero.
wingguy wrote:
themidge wrote:If I am 60kg (which I'm not) and you are 65kg (I dunno, are you?), and we are riding up a hill at 5w/kg, we will go exactly the same speed because we are both making 5w/kg, we just approach it from different angles. You may produce more power, but I am lighter, they cancel out.
But gravity isn't the only factor you're working against. Until it gets really steep, wind resistance is still a large factor.(And if you've got a decent headwind it's still a big factor even when it is really steep). So the bigger guy with the same w/kg but more total watts actually still has an advantage in overcoming all those factors that aren't gravity.
See first point.

Re: tubulars vs tubeless
Do the pros run sealant in their tubulars for PR, Flanders, E3 etc.? It would seem prudent what with the race being so spread out and the chance of a quick wheel being slim :noidea: .
:hello:
Cannondale Supersix 2008 (weight: 7.3kg)
B'twin Triban 540 (in bits)
Vitus "Benotto" 979 (weight: :? )

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Miller
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Location: Reading, UK

by Miller

darnellrm wrote:
Wed Apr 11, 2018 4:32 pm
Do you race with the tubeless setup? What is your normal kph on a ride?
Since you ask, usually 30kph-ish, depending on the type of ride obv, so 39.3kph on the club 10 last evening on TT bike (pro one tubeless 23/25).

darnellrm
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Location: NC, USA

by darnellrm

What pressure do you run in your 23/25mm TT setup?

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

by AJS914

Back to Sagan's bike. I love this pic:

Image
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wingguy
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by wingguy

themidge wrote:
Wed Apr 11, 2018 4:51 pm
wingguy wrote:
themidge wrote:If I am 60kg (which I'm not) and you are 65kg (I dunno, are you?), and we are riding up a hill at 5w/kg, we will go exactly the same speed because we are both making 5w/kg, we just approach it from different angles. You may produce more power, but I am lighter, they cancel out.
But gravity isn't the only factor you're working against. Until it gets really steep, wind resistance is still a large factor.(And if you've got a decent headwind it's still a big factor even when it is really steep). So the bigger guy with the same w/kg but more total watts actually still has an advantage in overcoming all those factors that aren't gravity.
See first point.
Nothing in your first point addresses this, unless it was "We're not talking about drag". In which case you're not talking about anything that's applicable to reality, so what's the point?

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themidge
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by themidge

It was 'we're not talking about drag' and I've already explained why it is applicable. Weight may not be important all the time, but it is sometimes, which is why I replied to Tobin in the first place. Remember what we're talking about in the first place?

I'm intrigued, what is the king of semantics going to say next?
:hello:
Cannondale Supersix 2008 (weight: 7.3kg)
B'twin Triban 540 (in bits)
Vitus "Benotto" 979 (weight: :? )

Ghost234
Posts: 422
Joined: Sun Apr 24, 2011 2:21 am

by Ghost234

Miller wrote:
Wed Apr 11, 2018 3:16 pm
Ghost234 wrote:
Wed Apr 11, 2018 6:41 am
For PR: You are running low pressures and hitting many uneven surfaces at a high rate of speed. Not to mention you are absolutely railing corners that the tire will occasionally "flop". Running tubeless on a course like that raises the potential to burp.
No offence but this is nonsense. I have been running tubeless for 3 years and have yet to experience the mythical burp. Yes I have had tubeless tyres damaged by being slashed by flints but I have never had the tyre randomly lift a bead and expel air. It just doesn't happen.

I started with tubeless 23mm and pretty soon experienced sealant actually doing what it was supposed to do. Rapidly moved up to 25mm, lovely at 70psi, and lately have been running G-One Speed (nominal 30mm) on my new d*sc bike and absolutely adore them. Smooth as anything at 50psi and I don't feel I have given up 0.1 kph of speed, gained speed if anything, while having puncture protection just worlds better than anything I ever had when I still put rubber airbags inside my tyres.
I've burped quite a few MTB and CX tires on racing and training rides. It all depends on pressure and how you lean the bike. Anyone that races MTB at a cat 2 or above level will likely have experienced at least one burp in their time.

wingguy
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Joined: Thu Mar 08, 2012 11:43 pm

by wingguy

themidge wrote:
Wed Apr 11, 2018 7:30 pm
It was 'we're not talking about drag' and I've already explained why it is applicable.
If you're not talking about drag, you're not talking about the real world. If you're not talking about drag, what is in in the 'flat' scenario that is stopping your hypothetical Joaquim Rodriguez from breaking every bicycle speed record there is? Clearly, in the flat scenario which you brought up, you are talking about drag. So if you are talking about drag in the flat scenario, why would you want to ignore it in the climbing scenario?
Weight may not be important all the time, but it is sometimes,
And drag is important all the time. If you want to talk about what really makes people faster then you can't wish it away. In the real world, a heavier system with the same watts per kilo is faster, even uphill.

If you want to talk about who is faster in an imaginary system where gravity is the only thing slowing you down then go ahead - but again I ask the question, what is the point of that discussion?
Remember what we're talking about in the first place? I'm intrigued, what is the king of semantics going to say next?
The king of semantics says this is what you were talking about to begin with "(remember that everything else is assumed to be equal here, I know things like rolling and air resistance can change with weight)". So while you could argue, semantically, that when you said they were assumed to be equal you could have meant they were assumed to be equally zero, it's some weak-ass semantics. Because in every other case in which they are equal and non-zero, you were wrong. The heavier guy with equal watts/kg is faster.


Look, you're obviously a smart kid, but you currently have two problems that come with being a kid. You think you've got it all figured out already, and you think that anyone disagreeing with you is attacking you. Work on those you'll go a long way :beerchug:

dcorn
Posts: 102
Joined: Thu Oct 05, 2017 4:21 pm

by dcorn

AJS914 wrote:
Wed Apr 11, 2018 5:30 pm
Back to Sagan's bike. I love this pic:

Image
Agree, pretty hilarious. And Sagan's tires look huge in that picture. I know they are a claimed 28mm, but I wonder if they run larger? I have 32c tires on my disc road bike now and they measure 30mm but look every bit as big as the tires in that picture.

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themidge
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Location: Auld Reekie

by themidge

@wingguy:
I suppose this discussion is ultimately meaningless, of course aerodynamics are the most important factor to consider when trying to go faster on a bike, I know that.
This discussion has sort of strayed from my original point that I made to Tobin, partly due to my own c*cking up :D, so I will rephrase it, if I may:
A heavier rider putting out 5w/kg will not always go faster than a lighter one also putting out 5w/kg, because sometimes the effects of air resitsance are small enough that the riders' power and weight are the only significant things which affect their speed. In that situation, 5w/kg is 5w/kg and that is that, they go at the same speed.

I don't see your disagreement with me as an attack. I enjoy debate, and I will always admit when I am wrong.
:hello:
Cannondale Supersix 2008 (weight: 7.3kg)
B'twin Triban 540 (in bits)
Vitus "Benotto" 979 (weight: :? )

wingguy
Posts: 3766
Joined: Thu Mar 08, 2012 11:43 pm

by wingguy

themidge wrote:
Wed Apr 11, 2018 10:18 pm
so I will rephrase it, if I may:
Yes, you may indeed rephrase to something completely different in meaning and intent to what you originally said :wink:

That's good enough.

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themidge
Posts: 488
Joined: Fri Jan 13, 2017 4:19 pm
Location: Auld Reekie

by themidge

Well, at least you now know what I meant, and perhaps should have said in the first place. Goodnight.
:hello:
Cannondale Supersix 2008 (weight: 7.3kg)
B'twin Triban 540 (in bits)
Vitus "Benotto" 979 (weight: :? )

Toby
Posts: 34
Joined: Thu Sep 06, 2012 4:30 am

by Toby

SUCH a long discussion to get to what I would have said if I had gotten in on this earlier.

Me and wifey have very similar w/kg. On our road bikes, we have similar climbing, but I win the flats.

In tri you see it all the time: the big folks can win the bike splits on the normal flat straight tri courses, but then they lose out on the run where weight matters again. Smaller folks with similar w/kg don't go as fast unless their bikes are set up much better.

glepore
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Location: Pa USA

by glepore

Toby wrote:
Wed Apr 11, 2018 11:32 pm
SUCH a long discussion to get to what I would have said if I had gotten in on this earlier.

Me and wifey have very similar w/kg. On our road bikes, we have similar climbing, but I win the flats.

In tri you see it all the time: the big folks can win the bike splits on the normal flat straight tri courses, but then they lose out on the run where weight matters again. Smaller folks with similar w/kg don't go as fast unless their bikes are set up much better.
+1 The smaller rider has a greater surface area ration in aero terms so suffers on the flats. On climbs, they have a greater p/w ratio and due to lower speed, aero less of a factor.
Cysco Ti custom Campy SR mechanical (6.9);Cannondale SS Evo Di2 7970 (5.79); Willier Cento Uno Air Di2 9070 (7.0); C40 Mk2 DA 7800 ; Anvil Custom steel Etap;1996 Colnago Technos Record

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