Sagan's bike at Paris Roubaix

Discuss light weight issues concerning road bikes & parts.
MRM
Posts: 352
Joined: Sun Jun 14, 2015 8:15 pm

by MRM

Cheers both! :)

TobinHatesYou
Posts: 1887
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

RyanH wrote:
Wed Apr 11, 2018 12:35 am

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

In an argument about tubeless, I'm not sure what the point is comparing a butyl tubed clincher and a latex tubed tubular...Jarno claims a latex tube is good for about 1-1.5w, so even when comparing regular clinchers to tubulars, the difference would end up being ~2-3w. Pretty consistent with Campy's findings on regular clinchers vs tubulars.

From https://www.bikerumor.com/2018/04/09/ca ... -bora-wto/

"Tubulars were the worst with a coefficient of rolling resistance of 0.002987, equivalent to 30W of resistance at 40kph for an 87kg rider+bike system. Tires with tubes came in next at a coefficient of rolling resistance of 0.002852, slightly better at 28W of rolling resistance for the same speed and system weight. But tubeless topped both with a coefficient of rolling resistance of 0.002650, the most efficient setup equivalent to 25W watts of rolling resistance."

For the Corsa Speeds:
https://www.bicyclerollingresistance.co ... speed-2016
https://www.bicyclerollingresistance.co ... bular-2017

1.4w per tire at 28km/h is again, pretty significant. If we extrapolate to 40km/h, that's 4w total. BRR tests a single wheel on a drum at 42.5kg while Campy uses a slightly heavier 2-wheel testing mule at 87kg.

Campy also took the average of the "leading" 5 tubulars vs the "leading" 5 tubeless. Considering there's actually way more tubulars to choose from right now (a point in favor of tubulars) it's reasonable to assume that tubeless has more room to improve.
Last edited by TobinHatesYou on Wed Apr 11, 2018 1:13 am, edited 2 times in total.

by Weenie


RyanH
Moderator
Posts: 2236
Joined: Tue Jan 17, 2012 4:01 pm
Location: Los Angeles, CA
Contact:

by RyanH

Those are time trial tires. As Cal already stated, and I don't disagree with, if I'm racing a time trial, give me a clincher as clinchers seem to dominate the pointy end of the charts...but, most of those tires aren't appropriate for road racing and general riding where cuts are a more of a risk.

What tubulars did Campy test? I thought I saw Continental mentioned which is butyl tube, very stiff sidewalls and generally mediocre crap.

As I mentioned above, RR is one piece of the puzzle. Flat resistance, wear resistance (to us amateurs) and wet grip are other considerations. At the end of the day though, equipment choices for road races is not a simple exercise of choosing the fastest thing...and again, that one is coming from experience, which I don't think you hold a USAC license, do you (sorry, that's an ad hominem attack, but couldn't resist)?

TobinHatesYou
Posts: 1887
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

I'm flattered that you have taken the time to look me up.

Also why are we insinuating that tubeless might have issues with flat prevention, longevity and wet/cornering/whatever grip? Remember what I said about certain members spreading FUD? If tubulars win out in those categories, there are probably numbers / published tests somewhere.

tonytourist
Posts: 1231
Joined: Sat Oct 10, 2009 7:13 am
Location: 93306

by tonytourist

Tubeless + 40 psi = perfect in Watopia

Ghost234
Posts: 423
Joined: Sun Apr 24, 2011 2:21 am

by Ghost234

For PR tubular is by far the better system. For general riding, I've been an advocate for CX and MTB tubeless but I simply do not see the advantage for road (although Mavic's new addition looks interesting).

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. Tubeless and tubular tires can run the same low pressures, tubular maybe even more so. Many of those tests that are being cited are worth a grain of salt. They are firstly under ideal circumstances and secondly are often skewed by a manufacturer to show one particular result - look at any new aero bike release and the ranking of aero bikes will always change depending on who is releasing the new item. They are not done in a proper scientific manner.

For the general road riding public, tubeless is a technology that may be best put to rest. I have had to help far too many people change a tire because the bead was too tight to the rim to accomodate the pressures. Even the big manufacturers like Continental and Vittoria are not moving into tubeless. The bike industry is an industry that like to copy itself (look to wide rims, tapered headtubes, carbon frames, etc.) and you simply do not see the big players moving to this technology. Clincher tires work wonderfully well and are much more servicable. For CX and MTB because you are dealing with a low pressure/high volume scenario, things change. The bead does not need to be so tight. That said, Mavic's new tubeless wheel + tire has been demonstrably easier to change a tire, so I'm willing to change my mind on this if they prove to be as good as claimed.


As far as discs, it is a better technology but I think for PR they opted for the rim brakes simply for easier wheel changes. Pro bike weights are the same, so there is no weight penalty. But PR can have you change wheels several times and that can mean making a break or falling behind. Rims brakes are always going to be available via neutral service and can be faster to make a wheel change that a disc w/ thru axle. I do think we will see a disc winner at PR soon, but faster wheel changes may present a very clear advantage for riders on this particular course.

TobinHatesYou
Posts: 1887
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Personal attacks and what seems like Strava creeping is a bit much for me, so good luck.

JakeSiney
Posts: 2
Joined: Mon Apr 09, 2018 2:02 pm

by JakeSiney

TobinHatesYou wrote:
Mon Apr 09, 2018 7:49 pm
ms6073 wrote:
Mon Apr 09, 2018 7:43 pm
RyanH wrote:
Mon Apr 09, 2018 5:21 pm
He seemed to be reaching for what I thought was his head unit coming in and out of the cobbled sectors, but that could have been him using the lockout feature.
He is definitely tightening the steer tube stem clamp bolts in this image:

Image

Yes he is there, but there are other shots of Specialized riders reaching for the dial throughout the race.
I'm pretty sure there was nothing wrong with the stem and the whole thing was just a way to publicise the new lockout mechanism. Funny how a motorbike was there to capture the moment perfectly.

User avatar
ergott
Posts: 2867
Joined: Tue Apr 18, 2006 3:03 am
Location: Islip, NY
Contact:

by ergott

JakeSiney wrote:
Wed Apr 11, 2018 11:40 am

I'm pretty sure there was nothing wrong with the stem and the whole thing was just a way to publicise the new lockout mechanism. Funny how a motorbike was there to capture the moment perfectly.
Having a rider reach to team car for tools to work on their bike isn't positive publicity.

alfus1
Posts: 77
Joined: Sun Sep 17, 2006 6:28 pm

by alfus1

Ok, the tire rolling it's very interesting, but this thread is of the Sagan's bike....

wingguy
Posts: 4198
Joined: Thu Mar 08, 2012 11:43 pm

by wingguy

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.
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;
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.

User avatar
Miller
Posts: 1390
Joined: Thu Sep 21, 2006 8:54 pm
Location: Reading, UK

by Miller

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.

User avatar
Lewn777
Posts: 369
Joined: Thu Mar 09, 2017 5:35 am

by Lewn777

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 run tubeless on mountain bikes, CX and road. I'm far from being a 100% tubeless convert for road bikes like I am for mountain bikes. However I absolutely agree with you, burping is something I've never had either in 7 years tubeless MTB, 2 years tubeless CX/gravel and 9 months of tubeless road. Burping is associated with running low pressure tubeless ready systems with MTB, up to 25psi on very hard rocky tracks. Maybe it's possible to burp up to 50psi, but that would be because you have a very loose tire, and smaller rim, due to still poor tubeless ready standardisation where you need more tape wrapped on your rim.

Mavic UST or an unofficial standardisation of those tire/rim sizes for tubeless ready make burping on road wheels from incredibly unlikely to impossible.

wingguy
Posts: 4198
Joined: Thu Mar 08, 2012 11:43 pm

by wingguy

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.
Tbh I have real difficulty imagining how a tubeless road setup could break its seal to burp some air without rolling straight off the rim as a result. And I haven't seen anyone complaining of that happening.

AJS914
Posts: 2385
Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

Doesn't burping usually happen when trying to run really low pressures like in cyclocross? I'm talking 20psi here.

by Weenie


Post Reply
  • Similar Topics
    Replies
    Views
    Last post