Sagan's bike at Paris Roubaix

Discuss light weight issues concerning road bikes & parts.
dvq
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by dvq

CallumRD1 wrote:
Tue Apr 10, 2018 6:28 pm
This is not quite true. While on the uphill you're essentially correct, on the flat it isn't true at all. If I'm 60 kg and you're 65 kg, our same 5 w/kg will give us powers of 300 W and 325W. We will have nominally similar frontal areas and aerodynamic profiles, so the extra 25 watts will mean that the 65 kg rider will go faster, just with a little more energy expendature getting up to speed. Once at a constant speed, body weight is almost insignificant; more power gives a faster speed even if the W/kg is the same. Similar logic applies to the downhill.
Someone here finally gets it.

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ergott
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by ergott

TobinHatesYou wrote:
Mon Apr 09, 2018 7:47 pm
1) Flat prevention.
2) I can run 50psi on 28mm.
3) Tubeless is 5W faster (2 tires) according to Campagnolo.
4) I will take an additional 5W over 300g weight savings every single time, unless I want to go slower.
Vittoria Corsa Speed (open TLR) 2016 High Amazon 23 25 225 7.7 8.3 9.2 10.9 8 / 5 5 / 5 Review
Vittoria Corsa Speed (tubular) 2017 High+ Amazon 23 23 209 9.1 9.9 11.1 12.7 8 / 3 5 / 5 Review

https://www.bicyclerollingresistance.co ... ke-reviews

I think there's a lot more reliable testing here and results are more in line with what I've seen elsewhere. The best tubular tires absolutely compare to tubeless in Crr. The tubular tire is lighter and the wheel it's glued to is too. There is some evidence that the tire/rim transition of tubeless is more aerodynamic (in general), but I haven't seen much data on that.

The arguement for really low pressure for tubeless kills the superior Crr they exhibit so take that into conideration when riding around at 55psi. You are giving up watts whether you like it or not.

Personally I use both. For performance road, I still prefer tubular tires mounted to carbon wheels. I get low weight and good aerodynamics. Just ordered some Vittoria tires for this season. I use tubeless for high volume tires. My do-it-all bike has 42mm tires and I run them at 35psi. They still roll really fast considering and I'm less likely to kill a rim with the current state of the roads around me (they look war torn!) I moved away from 23-25mm tubeless because I found sealant to be less effective at pressures around 75-80. Then it's just a messier version of clinchers. Perhaps that's because I see a lot of glass and other sharp objects out there. With high volume/low pressure tires (650X42) the tire is less likely to be cut.
Last edited by ergott on Tue Apr 10, 2018 9:16 pm, edited 1 time in total.

by Weenie


RyanH
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by RyanH

Apparently the internet hasn't taught Tobin about cda (maybe he hates cda, I dunno :noidea:), I'm not even sure why I'm bothering but:

Image

Image

Swannie
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by Swannie

Wich chainrings was he using? Regular 53/39 or bigger?

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ergott
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by ergott

Sorry duplicate

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euan
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by euan

themidge wrote:
Tue Apr 10, 2018 6:23 pm
Flat:
Same as above, 5w/kg is 5w/kg, it doesn't matter how you get there (less weight or more power).
As shown by world class time trialist Joaquim Rodriguez
"Step forward the climber and all those who worship at the altar of lightness" - R. Millar

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Lelandjt
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by Lelandjt

Swannie wrote:
Tue Apr 10, 2018 9:10 pm
Wich chainrings was he using? Regular 53/39 or bigger?
I'm curious too. At one point (maybe 20k out) the announcer said he was going 53kph and his cadence looked lower than my 53/11. I suspected he was going slower than the announcer thought cuz the cadence seemed low and he didn't look like he was working anywhere near as hard as I do to hold 30+mph on flat ground (tail wind?).

RyanH
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by RyanH

The speed displayed on Eurosport and another channel said 45-50ish kph multiple times, which just blows my mind that they were able to do that speed after, what, 250k?

TobinHatesYou
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by TobinHatesYou

RyanH wrote:
Tue Apr 10, 2018 8:53 pm
Apparently the internet hasn't taught Tobin about cda (maybe he hates cda, I dunno :noidea:), I'm not even sure why I'm bothering but:

https://farm1.staticflickr.com/800/3956 ... c612b4.jpg

https://farm1.staticflickr.com/817/3956 ... b25c_z.jpg

You linked two images where the 65kg rider was over 1km/h faster at multiple static drag coefficients, which doesn’t help your argument at all. What you at least should have done is estimate the increase in drag and change the coefficients slightly...but honestly the difference is so small it wouldn’t have made much of a difference.

Cross sections do not increase at the scales you think they do...aka a difference of .1 is the equivalent of moving from the tops to the hoods or hoods to the drops...a massive change in body shape and position. We are talking about an 8.3% increase in weight and probably a 5% increase in frontal area.
Last edited by TobinHatesYou on Tue Apr 10, 2018 11:39 pm, edited 2 times in total.

alfus1
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by alfus1

Swannie wrote:
Tue Apr 10, 2018 9:10 pm
Wich chainrings was he using? Regular 53/39 or bigger?
53-44 but many other used 53-46 and some conti's teams, standar 53-39

Hardstyle
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by Hardstyle

Perfect winning machine.

RyanH
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by RyanH

Dude, Tobin...
TobinHatesYou wrote:
Mon Apr 09, 2018 11:39 pm
A 65kg rider putting out 5w/kg is faster than a 60kg rider putting out 5w/kg under ALL circumstances.
Note your own emphasis on ALL circumstances which would also be interpreted as "regardless of all other variables."

The 65kg rider could be 6 feet tall and the 60kg rider could be 5'3, there would be a significant difference in CdA. What you should have said was ceteris paribus or, I guess conditioned it on "how it works in Zwift." Let's deal with the real world...my 64kg track friend can ride for prolonged durations at a CdA of 0.24 to 0.25. I, at 70kg, probably would have trouble maintaining a CdA below 0.29 for more than a few dozen minutes. We both can comfortably hold 4w/kg for an hour to two hours. So, on the flats, he'd average about 40.7 kph while I'd average 40.0 kph. Oh, and btw, I didn't make these CdA numbers up, I have actual self gathered data "from the real world" to back this up. So, again, you're wrong.

MRM
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by MRM

While it's important to make sure the numbers and figures are correct, the focus of Tobin's rants (kidding :D) were about the superiority of road tubeless. If we agree that you are correct in your examples of cda, what do you think of his assertions regarding road tubeless vs. tubs with everything else being equal?

(Genuine question. I'm really not interested in a lot of the "defending my bike ideology at all costs". However there are a ton of people here who are incredibly knowledgeable like RyanH among many others, so this seems like a worthwhile discussion in that direction)

TobinHatesYou
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by TobinHatesYou

You're arguing semantics (a strawman) and yes I should have invoked ceteris paribus instead of implying it. My bad. Using real-world data is pointless when distilling the relationship between speed and weight/(power/weight)

None of this applies when the weight is added with no change in frontal area as it would be with a switch from tubulars to tubeless. So if you're going to argue real-world, then we should get back to how a 5w difference at 40km/h is well worth an added 300g.

e: MRM, it's called a strawman and it's unfortunate.

RyanH
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by RyanH

@MRM, I haven't ridden tubeless myself and of the last 40K miles I've ridden, probably 37K was on tubulars. The top reasons for me to ride tubular and continue to do so have been safety (#1), ride feel and weight.

Safety is multifaceted: it's unlikely I'll crash due to a flat tire/blowout and it's unlikely I'll damage my rims descending (Zipp a few years back, when they used to frequent this forum, stated they never had a warrantied tubular). True, it's conceivable I could roll a tub but, knock on wood, my gluing methodology has been pretty well honed and I haven't had a single tub that has been easy to peel off.

Regarding ride feel, that's where I'm a little less knowledgeable because I don't have the time on a wide variety of clinchers/wheels. My understanding is that it's unlikely clinchers can match the feel of tubulars because their sidewall has to cope with more forces than a tubular, so the best tubulars will be more supple. Tubulars are also round whereas clinchers can take on various shapes depending on rim/tire combos.

When I ponder disc builds, I waffle about if I'd do tubeless or tubular, but I always come back to the safety aspect of tubulars (and weight).

Also, data on rolling resistance is surprisingly spares when it comes to tubs but comparing like for like, the Vittoria Corsa Tubs and Clinchers perform nearly identically:

https://www.bicyclerollingresistance.co ... bular-2016

https://www.bicyclerollingresistance.co ... phene-2016

It's possible that my Veloflex tires have a higher RR, but I'd take my Veloflex tires any day over those garden hoses (eh, they're not Sprinter bad but still). I ride a bike to enjoy the experience and from my personal experience, tubs are the pinnacle of that experience.

by Weenie


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