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General Which tyres for Paris-Roubaix? Whose time trial bike is fastest? Suspension mountain bikes or singlespeeders? Talk equipment here.

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  #21  
Old 11-06-12, 06:16
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Whatever they were thinking I doubt they were laughing much after just getting hazed by a minute and a half.

FWIW I didn't need research to tell me my best all round tyre choice was a GP4000s, I worked that out over the last decade of natural selection.
Yes, and I'm sure it was the tires, or Martin's doping program was timed just right. Between the two of us we're pushing 25 years of Oxy Conti use. Wanna push for citizen sponsorship?
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  #22  
Old 11-06-12, 09:54
simo1733 simo1733 is offline
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Originally Posted by Giuseppe Magnetico View Post
Yes, and I'm sure it was the tires, or Martin's doping program was timed just right. Between the two of us we're pushing 25 years of Oxy Conti use. Wanna push for citizen sponsorship?
I guess that the whole of OPQS must have switched to clinchers for all events by now.
Boonen will love them at Roubaix and Flanders.Just show him that article first,he won't mind dropping the tubs.
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  #23  
Old 11-06-12, 14:01
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You were doing so great discounting those clinchers until you made a broad sweeping statement about the conditions people use clinchers. What after 200 km the guy with the rock hard tubulars pumped up to 160 is beat by the guy on the 25 clinchers pumped up to 90. Not everyone pumps their tires up to rock hard. I tend to inflate my 23 to 100 ish and the 25 on the rear to 90 ish. Lots of chip seal roads here. The last time I regularly road tubular wheels they were heavy and the tires I could afford were say continental sprinters. My current favourites wheels are lighter than those old 32 spoke Campy C record hubs. Only carbon wheels are lighter than my Shamals and frankly these aluminum wheels are plenty great all rounders which are the same weight in tubular or clincher. Go tubeless and the tubular wheel is maybe 60 grams heavier. I look forward to tubeless when the time comes to replace a rim but I cannot see any real need to go back to tubular. I would rather save another grand and get a pair of mad fibre or lightweight clinchers. Then there is the actual need for all the performance gains. Like I am beating anyone? I have a lot more money now to support tubulars but why? So I can get a flat on a mountain decent? I am 57 years old with a 8000 Km a year habit over the last 27 years. I have never lost a tire after a flat but I have rolled a tubular in a crash. I can hardly imagine how badly I need that little bit of insurance and from what I have read the new tubeless tires stay on the rims a bit better than standard clinchers?
Almost all pro teams use clinchers including in the races but I agree tubulars are by far the most common. In terms of just living with them Clinchers are the leader and I expect that tubeless will get to the top.
Tubeless road has been around for over a decade..still only one real tire maker of these. Tubeless fror MTB makes all sorts of sense, for the road-nada.

Not sure what your point is. I use tubulars everyday, have very few flats and gluing the things on isn't a black art or something. For 'some' tubeless applications, it's far more messy and troublesome than a tubular.

If ya like clinchers, groovy, but the point of the OP was about RR, which is small, tire to tire and NOT the reason tubulars are still used by a BIG margin in the peloton.
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  #24  
Old 11-06-12, 14:05
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Twenty Watts is twenty Watts. It's huge for recreational cycling speeds. The article has many tires that have a ten Watt difference with the better ones. That is also large. As I said, choose the wrong tire and you will be hurting compared to someone who chooses one of the better tires.
Baldedash, a tire doesn't make one hurt vs one who has a different tire. It's not that dramatic. Marketeers want you to think so but it just isn't. If it were nobody would ever buy a 'worse' tire. Nobody would buy a Zaffiro or a Conti UntraSport.
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  #25  
Old 11-06-12, 15:29
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Baldedash, a tire doesn't make one hurt vs one who has a different tire. It's not that dramatic. Marketeers want you to think so but it just isn't. If it were nobody would ever buy a 'worse' tire. Nobody would buy a Zaffiro or a Conti UntraSport.
I beg to differ. I think we've all had that experience where you're 60 miles out on a seriously fast, no mercy group ride and half way up some monster climb you start losing contact, and you know it has nothing to do with your inability to say no to a third slice of pumpkin pie or those rides you missed due to your late-night research into the most recent developments in small-batch bourbons--it's all because you chose the wrong tires. Damn rolling resistance!
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  #26  
Old 11-06-12, 19:07
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Originally Posted by Bustedknuckle View Post
Baldedash, a tire doesn't make one hurt vs one who has a different tire. It's not that dramatic. Marketeers want you to think so but it just isn't. If it were nobody would ever buy a 'worse' tire. Nobody would buy a Zaffiro or a Conti UntraSport.
Marketing has nothing to do with it. At recreational speeds, say 25 to 35 km/hr, rolling resistance is a significant percentage of the overall resistance that has to be overcome. While a pro may ride at a speed where rolling resistance is less than 10% of the total, recreational riders are confronted with a number that can exceed 30%. Rolling resistance differences between tires can be a huge factor at recreational speeds. The difference between tires can amount to a 10%+ difference in power required to maintain speed at 30 km/hr. So with good tires someone may be cruising at 100 Watts while his buddy on medium slow tires riding beside him has to put out 110 Watts to maintain the same speed. For a pro who has a ceiling of 400 Watts this may not mean much, but to a Cat 6 who struggles to maintain 150 Watts, that 10 Watts is a signifcant step up the suffering curve.
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  #27  
Old 11-06-12, 20:41
JayKosta JayKosta is offline
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...
recreational riders are confronted with a number that can exceed 30%. Rolling resistance differences between tires can be a huge factor at recreational speeds.
...
=========================================
Where does that '30%' number come from? Is it your estimate or from some actual testing?
Also, what part of the 30% is just 'tire rolling resistance'?

My 'belief' has always been that air resistance is 90% (or more), even at recreational speeds.

Jay Kosta
Endwell NY USA
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  #28  
Old 11-06-12, 21:58
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=========================================
Where does that '30%' number come from? Is it your estimate or from some actual testing?
Also, what part of the 30% is just 'tire rolling resistance'?

My 'belief' has always been that air resistance is 90% (or more), even at recreational speeds.
The formulae for this are well known. They present a simplified model using constants that are calculated from test data. The article in the OP shows a range of 30 - 50 W at 35 kph. Given the power required to hold 35 kph, those numbers are large, especially the 53 W (or whatever it is in the PDF; I don't care to open it again).

At 20 mph air resistance accounts for roughly 80% of the total on flat ground with no wind. At 25mph the percent goes to nearly 90. This assumes the rider is a typical weight for a competitive cyclist, like 65 kg. A heavier rider will result in a lower percentage due to air resistance. Drive train losses are small. I don't care to calculate it at the moment but I am pretty sure that a heavy rider riding at 15 mph with crappy tires can have a rolling resistance that accounts for 30% of the total.

This notion that 10 or 20 Watts is insignificant is ridiculous. All it takes is for someone to ride with a power meter and see for themselves how much effort it takes to increase a tempo effort by 20 W. A lot of recreational riders probably cruise at 100 - 150 Watts.

This Slowtwitch article I just found covers some of this. http://www.slowtwitch.com/Tech/The_P..._Bike_163.html
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  #29  
Old 11-06-12, 22:14
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But minimizing wheel/tire weight is important for races with lots of climbing (where aero drag is less of a factor) or for races where there is lots of deceleration and acceleration.
Yes, aero influence reduces as gradient steepens, however aero still trumps weight on all but the steepest of climbs. Where possible, attain both. It's not an either/or scenario, but the better options are not cheap.

Accelerations are still a very minor issue (again it's 2 orders of magnitude smaller in terms of energy cost). And even though it's a very small influence, don't forget that something with more inertia also does not slow down as fast, meaning one can ease off the pedal pressure slightly earlier before corners etc.

But if you want some numbers to demonstrate, if you accelerate from zero to 50km/h in 10 seconds, and you added 200g to the rim of a bike wheel, the extra wattage required to accelerate is <0.4% of the total power demand.

Now if you are racing a very tight hot dog circuit, then this is what you'll experience. But most changes in speed while racing are not nearly so dramatic as 50km/h, nor last as long as 10 seconds.

Finally, BTR has a nice item on this issue, see here:
http://biketechreview.com/reviews/wh...el-performance

While it's about wheels, it is pertinent because your questions/assertions were about the impact of the additional mass of a tyre (overall mass + rotational mass).
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  #30  
Old 11-06-12, 22:40
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Alex Simmons/RST Alex Simmons/RST is offline
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Originally Posted by JayKosta View Post
=========================================
Where does that '30%' number come from? Is it your estimate or from some actual testing?
Also, what part of the 30% is just 'tire rolling resistance'?

My 'belief' has always been that air resistance is 90% (or more), even at recreational speeds.

Jay Kosta
Endwell NY USA
The relative proportion of the power demand from the various resistance forces varies somewhat depending on several factors (e.g a rider's CdA) but yes, as speed drops, the relative proportion of rolling resistance increases.

For a typical club rider say at bike + body mass of 85kg, a CdA of 0.33m^2, and a Crr of ~ 0.005, then on flat windless road, the relative proportion of energy demand from air, rolling and other resistance forces at various speeds is as follows:

Speed (km/h) - Power (W) - Air% : Crr% : Other%
20 - ~ 60W - 57% : 39% : 4%
30 - ~150W - 75% : 22% : 3%
40 - ~320W - 83% : 14% : 3%
50 - ~590W - 89% : 9% : 2%


As things like Crr and CdA vary, then the relative proportions do change, but notby an awful lot.

As for the earlier comments about relative importance of a 20W difference - that's worth ~ 2 seconds per km in speed terms.

So in a 40km TT, we are talking ~80 seconds difference.

Crr matters at all speeds.
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