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Rolling resistance article

 

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klehner

Jan 25, 06 5:58

Post #1 of 87 (14162 views)
Rolling resistance article Quote | Reply

This may have been posted before, but I hadn't seen it. This is a study done on tubulars and clinchers to measure the rolling resistance in terms of watts required. There is a brief discussion (complete with neat Chrysler graphics :-) on the trade-offs among rolling resistance, comfort, puncture resistance, aerodynamics, etc. The fastest clinchers had lower RR than the fastest tubulars; the fastest tubular measured took about 34W, while the fastest three clinchers were all under 30W. The Tufo Elite Jet was an astounding 50-52W, depending on air pressure.
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Of course, with your ears stuffed with outrage cotton balls, all you heard was, rahrahra, govt comes to get your guns, rhahrahrah, stamp out your FREEEEEDOM! - slowguy


callidus

Jan 25, 06 6:04

Post #2 of 87 (14147 views)
Re: Rolling resistance article [klehner] [In reply to] Quote | Reply

Thanks for the link. Very interesting.







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Searching for the bliss of ultimate exertion.


psycholist

Jan 25, 06 6:30

Post #3 of 87 (14103 views)
Re: Rolling resistance article [klehner] [In reply to] Quote | Reply

I only had a moment to give this a quick glance before dashing out the door, but:

What's up with the tire pressures used in the study? Only 101 for the clinchers is a bit below what most folks would run. 101 and 87 is significantly below what most folks would put in a tubular. I thought part of the advantage of the tubular was that you could generally run a higher psi. Why didn't they test and compare at a higher psi?

I think this comparison is probably relevant to compare one clincher to another. As for comparing tubulars to clinchers, or tubulars to other tubulars, they're so far below the manufacturers recommended psi levels the data could be rather worthless.

Bob C.

(This post was edited by psycholist on Jan 25, 06 6:31)


Ashburn

Jan 25, 06 7:07

Post #4 of 87 (14054 views)
Re: Rolling resistance article [psycholist] [In reply to] Quote | Reply

In Reply To:
I only had a moment to give this a quick glance before dashing out the door, but:

What's up with the tire pressures used in the study? Only 101 for the clinchers is a bit below what most folks would run. 101 and 87 is significantly below what most folks would put in a tubular. I thought part of the advantage of the tubular was that you could generally run a higher psi. Why didn't they test and compare at a higher psi?

I think this comparison is probably relevant to compare one clincher to another. As for comparing tubulars to clinchers, or tubulars to other tubulars, they're so far below the manufacturers recommended psi levels the data could be rather worthless.

Bob C.


Higher pressures than that, with that sort of weight, would make the tires slower on roads. Responsible manufacturers print "maximum" pressures on their tires, not "recommended." The people at Michelin and Vittoria recommend pressures in the 100-120 range for road riding. As you can see on the tubular chart, increasing the pressure made only a very tiny difference (in watts), and that's on a testing rig. The difference is nil, or negative, on an asphalt road.

It's an urban myth that high pressure tires are faster. They're not -- only on the track does high pressure work.


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(This post was edited by Ashburn on Jan 25, 06 7:10)


callidus

Jan 25, 06 7:11

Post #5 of 87 (14049 views)
Re: Rolling resistance article [Ashburn] [In reply to] Quote | Reply

Ashburn, do you think it would be reasonable to assume that 100psi would correspond to a total weight of 85kg and 120psi would be for heavier riders - meaning there would be no need for a rider ~85kg to run higher psi?.



------------------------------------------------------------
Searching for the bliss of ultimate exertion.


gregclimbs

Jan 25, 06 7:11

Post #6 of 87 (14049 views)
Re: Rolling resistance article [klehner] [In reply to] Quote | Reply

no dugast silks?

dissapointing...

g

greg
www.wattagetraining.com


DC Pattie

Jan 25, 06 7:24

Post #7 of 87 (14024 views)
Re: Rolling resistance article [klehner] [In reply to] Quote | Reply

I wish they would have included the Tufo clincher-tubulars as well. Also, if I remember correctly from a pervious post, narrower tires do not improve rolling resistance, is that right?

Dave in VA


klehner

Jan 25, 06 7:33

Post #8 of 87 (14009 views)
Re: Rolling resistance article [DC Pattie] [In reply to] Quote | Reply

In Reply To:
I wish they would have included the Tufo clincher-tubulars as well. Also, if I remember correctly from a pervious post, narrower tires do not improve rolling resistance, is that right?

Dave in VA
As the article describes, narrower tires have increased rolling resistance.
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Of course, with your ears stuffed with outrage cotton balls, all you heard was, rahrahra, govt comes to get your guns, rhahrahrah, stamp out your FREEEEEDOM! - slowguy


ajfranke

Jan 25, 06 7:49

Post #9 of 87 (13974 views)
Re: Rolling resistance article [klehner] [In reply to] Quote | Reply

Interesting article Ken. Not exactly sure why I spent all that money on those race tubulars.


Martin C

Jan 25, 06 7:54

Post #10 of 87 (13966 views)
Re: Rolling resistance article [ajfranke] (Deleted by Administrator) [In reply to]

 


fade

Jan 25, 06 8:06

Post #11 of 87 (13942 views)
Re: Rolling resistance article [Ashburn] [In reply to] Quote | Reply

How then does one account for the following (from the article)?

"In general terms, the total drag of a cyclist will consist of 80% tire rolling resistance and 20% wind resistance at 10 km/h or 6 mph. At 40 km/h or 25 mph the numbers will reverse, with total drag consisting of 80% wind resistance and 20% tire rolling resistance."

&

"When pumped up very hard in excess of 9.5 bar (~140 psi), rolling perfomance will improve quite dramatically."

It seems to me that these two points taken together mean that going fast would require a tire which, together with the rim formed as smooth an aero section as possible, was quite wide, and was pumped up very hard indeed.

The higher the internal pressure the less the tire will deform when loaded, which I would have thought would give a contact patch more in line with the fatter tire diagram.

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cbritri

Jan 25, 06 8:35

Post #12 of 87 (13893 views)
Re: Rolling resistance article [Martin C] [In reply to] Quote | Reply

The pic in the article shows they used a steel drum test which I think was talked about in other threads. Basically that test will return a higher value for tubulars vs. clinchers, but we don't race on steel roads. I think the test is probably good for comparing tubie vs tubie and so on, but not clincher vs tubular.

I am no expert on this, just repeating what others have said. I am debating a race wheel purchase. With all the info I have heard from people in the industry and watching pro's I believe that tubulars have to be faster. As much as I hate to say that. I think tubulars are a pain in the ass to deal with, but if they are faster, I will just bite the bullet and go for it.
Brian



last tri in 83

Jan 25, 06 8:37

Post #13 of 87 (13887 views)
Re: Rolling resistance article [klehner] [In reply to] Quote | Reply

If I am reading the clincher info right, buy Michelins. Best RR annd puncture resistence?

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jens

Jan 25, 06 8:38

Post #14 of 87 (13884 views)
Re: Rolling resistance article [cbritri] [In reply to] Quote | Reply

In Reply To:
The pic in the article shows they used a steel drum test which I think was talked about in other threads. Basically that test will return a higher value for tubulars vs. clinchers, but we don't race on steel roads. I think the test is probably good for comparing tubie vs tubie and so on, but not clincher vs tubular.

I am no expert on this, just repeating what others have said. I am debating a race wheel purchase. With all the info I have heard from people in the industry and watching pro's I believe that tubulars have to be faster. As much as I hate to say that. I think tubulars are a pain in the ass to deal with, but if they are faster, I will just bite the bullet and go for it.


Would you care to elaborate why a tubular will return a higher value than a clincher on a steel drum, but not on the road?



-jens


docfuel

Jan 25, 06 8:44

Post #15 of 87 (13864 views)
Re: Rolling resistance article [jens] [In reply to] Quote | Reply

AS I understand it, if the tire has to bounce over every little bump, this slow one down. The bike is going up and down, thus increasing resistance. The stell drum or smooth velodrome has none of this.
_________________
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Take everything I say with a grain of salt. I know nothing.


klehner

Jan 25, 06 8:46

Post #16 of 87 (13860 views)
Re: Rolling resistance article [last tri in 83] [In reply to] Quote | Reply

In Reply To:
If I am reading the clincher info right, buy Michelins. Best RR annd puncture resistence?
Seems like a good compromise. I happen to use Michelin Pro Races (and the last Conti tires I have on my wheels will be replaced post haste; I'm sick of the sidewalls/base coming apart).
----------------------------------
Of course, with your ears stuffed with outrage cotton balls, all you heard was, rahrahra, govt comes to get your guns, rhahrahrah, stamp out your FREEEEEDOM! - slowguy


jens

Jan 25, 06 8:52

Post #17 of 87 (13846 views)
Re: Rolling resistance article [docfuel] [In reply to] Quote | Reply

In Reply To:
AS I understand it, if the tire has to bounce over every little bump, this slow one down. The bike is going up and down, thus increasing resistance. The stell drum or smooth velodrome has none of this.


OK. So why does a tubular bounce less than a clincher?



-jens


cbritri

Jan 25, 06 9:03

Post #18 of 87 (13816 views)
Re: Rolling resistance article [jens] [In reply to] Quote | Reply

This is what joshatzipp had to say. I respect his opinion. It is kind of a long write up but worth the read.

"I have seen the same theoretical data that you talk about showing higher RR for tubulars than clinchers, but this isn't actually nearly as clear cut a case as that data would suggest. Mainly, all RR tests use a simple machined drum for testing the tires and that is not very true to real life. Some data was taken a few years ago using a different system, similar to that developed at CALSPAN in California. This system is more like a treadmill but the belt is steel with various types of tarmac surfaces bonded to the surface. In these tests the tubular tires actually fare slightly better than clinchers on more realistic, rough road surfaces; more or less because the structure of the tire allows the tire to conform to the rough surface with fewer losses. The clincher tire on a smooth drum only needs to defore really at the contact patch and partially in the casing, but on rough pavement the additional deformability of the tubular tire carcass seems to be helping out. The other thing to remember for all the tubular bashers is that clinchers only show better or equal in these tests when used with thin latex tubes, these tubes have significantly less RR than butyl so if you want to run clinchers for racing you really have to run latex tubes, which is something that very few people do. Overall that's why the 13 minute over IM distance is not so realistic, if it were you would see it affecting results, and you would have certain pros with wildly different bike splits in similar events when they switch sponsorship between clincher and tubular wheel manufacturers and so on, but it just doesn't happen that way. I think that the other thing generally not mentioned is that most tubular tires have a puncture resistance belt under the rubber that adds a bit of weight and RR, but improves durability of the tire. Clincher tires that test very well for RR usually don't have similar puncture resistance belts, but these are not the clincher tires most of us want to use and we certainly don't recommend racing on them as a flat will cost you way more time than any RR savings will get you.

Also, the tire bed shape is critical. Older aluminum rims (which are used in many of these older RR tests) would have a large single radius curve shaped tire bed, generally 23-25mm diameter, and eyelets that protrude into the tire bed. These rims can significantly increase RR when a tire is used that has an effective inflated diameter smaller than the rim bed as the entire casing of the tire is deflected at the contact patch. This is made worse by the stitches under the base tape which protrude slightly, requiring additional glue to fill the airspace, and further deforming the casing locally. With some proper design the tire bed can very closely mimic the tire profile eliminating these problems, and also resulting in the need for significantly less glue as the glue can be very thin on the rim. Also the elimination of eyelets eliminates excess glue as well as what were effectively high-spots in the wheel that show up in testing as an increase in RR. The same 21mm tire will show 15-20% less RR on a Zipp rim due to these design elements than on an older GL330 or similar tubular rim, and that is not at all trivial. This is another reason we strongly recommend 21mm tires on all of our wheels.

triguy is correct that we have probably done more work than anybody in studying the tire/rim interface, but is not right in saying that clinchers are superior here. With considerble work on both models we have ultimately ended up with nearly equal drag on clincher/tubular products. To get there, the clincher rims are generally slightly wider and have a little bit of a different shape, but at least with our product there is no appreciable difference between tubular and clincher in terms of aerodynamics.

As for the question why the pros run them, there are a few very simple answers. 1. they flat less, since most flats in pro racing are pinch flats (the roads are generally pre-swept or somewhat cleaned) tubulars eliminate the majority of flats. Plus road pros race on all sorts of crap pavement and cobbles where clincher tires just don't hold up 2. in a downhill or fast situation a flat with a tubular is far safter than with a clincher as the tubular flat can be ridden with much less drama. The tubular flat can also be ridden faster and longer giving the team car more time to get to the rider, so he isn't stuck on the side of the road. 3. they can be run at lower pressures. Everybody always talks about how tubulars can be run so high, but really the pros want lower pressures for better grip (particularly in the wet) and more comfort. It is common to see road pros in Europe running 90-95 psi in the rain and 100-110 in the dry, so on the roads they generally ride, these pressures would be very problematic with clinchers.

There is really no clear cut answer here, and as with a lot of things it is largely personal opinion, but there is lots of data showing the superiority of one vs the other and so on, but in reality the differences are quite small. We prefer tubulars as they are much lighter, the tires are more puncture resistant despite being lighter, can be pressure optimized to road surface (can run much lower to much higher), generally have more consistent and higher cornering grip, and when properly glued offer an extra margin of safety. "
Brian



tttiltheend

Jan 25, 06 9:03

Post #19 of 87 (13812 views)
Re: Rolling resistance article [cbritri] [In reply to] Quote | Reply

In Reply To:

I am no expert on this, just repeating what others have said. I am debating a race wheel purchase. With all the info I have heard from people in the industry and watching pro's I believe that tubulars have to be faster. As much as I hate to say that. I think tubulars are a pain in the ass to deal with, but if they are faster, I will just bite the bullet and go for it.


Popular belief and tradition say that sew ups are faster. An increasingly large body of data says that, in fact, clinchers are faster, except for highly specialized track tires. While sew ups may have a few advantages over tubulars, being faster isn't one of them


cbritri

Jan 25, 06 9:18

Post #20 of 87 (13789 views)
Re: Rolling resistance article [tttiltheend] [In reply to] Quote | Reply

I think each probably is better for different reasons, but really it would need to be looked at as a whole system (wheel and tire). Again, I have no evidence, but as I understand it the clincher rim is a aerodynamic mess. I really would like to believe that clinchers are just as good as tubulars, if not better, but from what I have read I have made the decision as a whole the tubular system is faster.


jens

Jan 25, 06 9:18

Post #21 of 87 (13787 views)
Re: Rolling resistance article [cbritri] [In reply to] Quote | Reply

   

Right. I read this before and josh is generally credible. The truth is out there (tm). Of course, those of us who have actually tested both tubulars and clinchers on real roads know the truth.



--jens


docfuel

Jan 25, 06 11:20

Post #22 of 87 (13694 views)
Re: Rolling resistance article [jens] [In reply to] Quote | Reply

[reply][reply]
AS I understand it, if the tire has to bounce over every little bump, this slow one down. The bike is going up and down, thus increasing resistance. The stell drum or smooth velodrome has none of this. [/reply]


OK. So why does a tubular bounce less than a clincher?



-jens[/reply]

Damned if I know. I thought it bounced less, but the data on rolling resistance is consistent, in that clinchers roll better. Maybe it is that tubies usually have tread, and smooth tires roll better.??????????????
_________________
Dick

Take everything I say with a grain of salt. I know nothing.


docfuel

Jan 25, 06 13:03

Post #23 of 87 (13632 views)
Re: Rolling resistance article [jens] [In reply to] Quote | Reply

glad to know that my race wheels (tubies) are not outmoded.
_________________
Dick

Take everything I say with a grain of salt. I know nothing.


psycholist

Jan 25, 06 15:16

Post #24 of 87 (13555 views)
Re: Rolling resistance article [klehner] [In reply to] Quote | Reply

I was away all day. Just dropped in here late in the day to view this thread and see what's transpired. It's just as I suspected. The bottom line is, nobody really knows. Everyone THINKS they know, but they don't. Josh at Zipp would seem to have the most informed perspective, but even he ultimately comes to the conclusion that any real differences are small.

Whatever.

Bob C.


Tom A.

Jan 25, 06 17:48

Post #25 of 87 (13514 views)
Re: Rolling resistance article [psycholist] [In reply to] Quote | Reply

[quote]Everyone THINKS they know, but they don't. Josh at Zipp would seem to have the most informed perspective, but even he ultimately comes to the conclusion that any real differences are small. [/quote]


He may SEEM to have the most informed perspective, but that doesn't necessarily mean he does. His reply is full of more holes than a block of swiss cheese...

For example, most of the best testing clinchers DO have puncture belts (Michelin Pro Race and Vittoria Open Corsa to name a couple).

Oh yeah, here's another: the posted test results (Tour) are also with the clinchers using a butyl tube (not latex)...and they're STILL gobs better.

Let's see...one more....tubies have a structure (glue interface) which inherently causes higher energy losses for a given deformation, yet when tested on a CALSPAN type rig, somehow this structure results in fewer losses? Come again?

Anyway...I wonder what the difference is in margin on a given carbon tubular vs. the same model clincher rim? Hmmmm....

In all honesty, it actually warms my heart to see people still claiming that tubulars are as good as clinchers :-)


http://bikeblather.blogspot.com/

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