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Discussion Starter · #1 · (Edited)
out of august issue of german BIKE magazine. they tested all sorts of different tires...below are the graphs for both rolling resistance at 20 km/h and further below the resistance the tires withstood against a falling metalbar. that's the "pinchflat"test. obviously the higher the height the tire withstood the better.
of interest:
Specialized Rockster Pro at 43.6 watts - ouch!
also the Conti Explorer Supersonic at 31.3 watts is rather slow rolling. remember the Nokian NBX Lite 2.0" ? it had around 18 watts....

they also tested inner tubes all on the same tire at the same pressure. they also tested the pinchflatresistance - the higher the better:
make: weight / rollingresistance / pinchflatresistance
Schwalbe XX-Light: 99g / 22.9 watts / 60 cm
Conti MTB Supersonic: 93g / 22.3 watts / 60
Michelin C4 Latex: 122g / 21.3 watts / 60
Panaracer GreenLite: 104g / 21,2 watts / 50
Maxxis Flyweight: 94g / 22.6 watts / 55
Schwalbe Extra Light: 99g / 23.7 watts / 60
Kenda Downhilltube: 675g / 29.2 watts / 80
Maxxis Welter Weight: 182g / 23.9 watts / 60
Maxxis Downhill 1.2: 296g / 24.9 watts / 80

inner tubes filled with sealant:
Zzyzx Safe Ride: 299g / 24.3 watts / 60
Kenda Pannenschutzschlauch: 286g / 24.9 watts / 60

once more the Eclipse-Tubelesskit proved to offer less rollingresistance compared to the fastest of the inner tubes, the Michelin Latex. at 20.4 watts that's 2.2 watts per wheel less!

 

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Thanks nino. While I'm hardly a weight weenie and could care less that I'm riding 30+ pound bikes, I a believer in this rolling resistance data and the *measurable* influence it has on a ride. Time for me to pay attention and try some of these "winners" next time the tires need 'a change'n.

Might also be time to look at tubeless conversion (safe to assume Stan's gives similar results to Eclipse?).
 

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Some doubt

I too think that rolling resistance is more interesting, and in many situations also more important than weight. But I have some doubts or questions about this and similar tests, since I would believe that rolling resistance depend for each and every tire greatly on terrain and air pressure, and that the variations aren't the same for different tires.

So one of the tires in that test that rolled better than another on the surface or surfaces on which the tests were made, might very well roll worse on a number of other surfaces. And the surface variations are infinite: dry and sandy dirt road, wet and gravelly dirt road, semi-muddy grass, rought asphalt, dry sand-covered soil covered by oak leaves...

Second, the air pressure would have a great effect. Riders have different weight, riding style, and preferences, and choose different air pressures. Therefore, any manufacturer's air pressure recommendations are pretty meaningless. And one tire rolling better than another in that test and at the pressure or pressures on which the tests were made, might roll worse at other pressures and loads.

Enough critique - again I think rolling resistance is important, and I think it's great that someone at least tries to get some facts on this. I just take this type of result with a big grain of salt. Or shouldn't I?
 

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I agree that air pressure and rider weight play large factors, and I'm not even sure that a rough correlation is possible (i.e. Tire 'X' will may be 2x as efficient as Tire 'Y' at 40 psi, but the difference may decrease to 1.5x at 30 psi).

But as for variance by terrain type, aren't these results effectively measuring tire deformation under the weight of the rider? And not a particular tread's efficiency on a particular surface? That's a figure that I expect would correlate across various terrain types (i.e. Tire 'X' is always 2x as efficient as Tire 'Y' independant of asphalt, hardpack, or loose rock).

But those are just WAG's on my part; I'd like to hear the responses from the peanut gallery.
 

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Thanks for the post. I love reading these rolling resistance tests as I appreciate the standardized approach to testing them.

This time I was a bit stunned. Michelin Comp 24.1 Soft 2.2" is a 1150 gram super sticky downhill tire. Even if it was a typo and they tested the Comp 24.1 Light (single ply sticky compound 4cross tire at 850grams), I can't imagine that it it has one of the lowest rolling resistances at 28.1watts. That's crazy! I've used the Comp 24.1 Soft and I can tell you....on asphalt or trail, it does not roll fast at all. There is no way that it can roll as quickly as a xc tire.

I still like reading these tests, but really how can you interpret the results when you have such an absurd result like this. Perhaps, this bike magazine should re-evaluate it's testing methods to give us some more realistic trail surfaces.
 

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Speedüb Nate said:
...

Might also be time to look at tubeless conversion (safe to assume Stan's gives similar results to Eclipse?).
Stans and Eclipse technically do the same thing but the eclipse kit is better in my opinion.

A.) Lighter
B.) Removable stems, similar to a ust valve, you can take out the stem to clean it or if you need to use a tube. With stans you'd have to pull the entire strip off as its attached to the valve stem. This was a key reason for why i went eclipse over stans.
C.) Seems to be designed better, looks more professional.
D.) I can't vouch for the stans, but by looking at the eclipse rim tape it is designed better to hold the tire on firmly.(nice ridge)
 

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Discussion Starter · #7 ·
ot the "soft"...

it's the 850g C 24.1 Light.
there is a soft version available of that same tire, that might be the one you tested.
 

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I'd like to see the machine they test their tires on. I have a hush the roller is quite small. As long as the directional knob spacing is close, even DH tires can give low readings on it, it seems. I bet a really sliggush slick tire would still "roll good" on it, while in reality it's an anchor.
It's possible to up the pressure during a test to determin ideal tire pressure for easy rolling, but that would only make sense if the roller would similate offroad conditions with small bumps in i.e. gravel.
 

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Discussion Starter · #9 · (Edited)
it's the Conti or Schwalbe machine...

they test tires on either the Conti or the Schwalbe testmachine so the readings are pretty accurate i guess....

i found a picture of the Schwalbe testmachines of an older test where you can also see the "pinchflat"-test as well as the penetration test. tested were UST tires. DON'T compare these numbers with other tests! different pressures, different settings etcetc..

they put a 50 kilo weight on that single wheel to imitate a riders weight.as you can see it's a flat surface and therefore the readings are accurate for asphalt or hardpack.in other testresults i have they did 2 tests with different pressure settings: 2.5 bar and 3.5 bar with the result that about all tires had around 2-3 watts less rollingresistance. see this other test below!



 

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Interesting stuff but it really doesnt tell you how the tire is going to roll during a race and how good the traction is. I am running a set of Specialized Rockster Pro's and in my opinion little or no rolling resistance. The traction isnt good either. I also have Panaracer Fire XC in which the resistance is very high but so is the traction. I still find the tire unsuitable for racing. I am more interested in a tire that has great traction and low rolling resistance, for the most part I am not concerned about pinch flats, I try to stay close to the ground. The Fast Fred or the Nokian NBX look like interesting race tires because of their low rolling resistance.
 

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Discussion Starter · #11 · (Edited)
i posted just the numbers...

i posted just the numbers but they also tested each tire in the "real life" and gave comments on cornering/braking traction as well as other inputs...

i can only say that i have tried the fastest tire of last years test (the Nokian NBX Lite 2.0 at 21.2 watts) and would never go back! the difference in speed is simply too much.if i see the Michelin Wildgripper Comp S leading this years test i have to say i don't like this tire too much.it has too little knobs that make for a soft and spongy feeling when cornering and it is lost once things turn humid or wet. it has more cushion as it is really wide for a 2.1" tire but i still prefer the Nokian :faster and better grip everywhere !

i already repeated several times that the Nokian NBX Lite 2.0" improved my "lap" times by 5% compared to the Explorer Supersonic i used before. that's 3 minutes per hour less. i was able to measure this a few times on different standard routes i do for years now. now i hear those who say different power input or different temperatures or whatsoever...the heartrate was even lower on that faster runs too. i log down each and every ride with heartrates etc. and i was really faster with this tire. and no, it's not the grip as the downhill parts aren't so long and the seconds i gained because of better grip were maybe 5 or so. i also watch my stopwatch when entering the downhill sections and know how long it takes from top to bottom. i'm usually within 10 seconds each time.

Conti Explorer Supersonic: 31.3 watts
Nokian NBX Lite 2.0": 21.2 watts

so my homemade mathematics tell me:
31.3 (Conti) - 21.2 (Nokian) = 10.1 watts = 5% savings

so each 2 watts results in a saving of 1% riding time on a given distance. that's 36 seconds per hour FOR FREE!

now don't forget to enter the Tubelkesskit as it also saves 2 watts over the fastest inner tube and 4 watts compared with regular butyl tubes.

i'm curious to hear your input on my simple example....
 

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borregokid said:
Interesting stuff but it really doesnt tell you how the tire is going to roll during a race and how good the traction is. I am running a set of Specialized Rockster Pro's and in my opinion little or no rolling resistance. The traction isnt good either. I also have Panaracer Fire XC in which the resistance is very high but so is the traction. I still find the tire unsuitable for racing. I am more interested in a tire that has great traction and low rolling resistance, for the most part I am not concerned about pinch flats, I try to stay close to the ground. The Fast Fred or the Nokian NBX look like interesting race tires because of their low rolling resistance.
OK, now if you can explain what was said here that would be super!!!
 

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Discussion Starter · #13 ·
correction...

nino said:
Conti Explorer Supersonic: 31.3 watts
Nokian NBX Lite 2.0": 21.2 watts

so my homemade mathematics tell me:
31.3 (Conti) - 21.2 (Nokian) = 10.1 watts = 5% savings

so each 2 watts results in a saving of 1% riding time on a given distance. that's 36 seconds per hour FOR FREE!

now don't forget to enter the Tubelkesskit as it also saves 2 watts over the fastest inner tube and 4 watts compared with regular butyl tubes.

i'm curious to hear your input on my simple example....
i guess i have to take both tires into account for the 5% savings.
so it's

62.6 - 42.4 = 20.2 watts = 5%

so it's 4 watts that save 1%
 

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Hey here's some more data:

This is analysis of performance improvement due to change in weight and rolling resistance for a track I ride. It takes ~10:30 min per lap average across a XC race distance.

First case is for getting some Eclipse tublesskit instead of tubes which saves 4.4 W:


Second case is for getting some Nokian NBX lites over some Conti Explorers, saving 10.1 W:


Third case is getting some Nokian NBX lites with Eclipse over Conti Explorers with tubes, saving 14.5 W:


So in the best case of getting some NBX lites with Eclipse over Explorers with tubes Icould expect to save ~3 min 12 seconds on this track for a XC race distance just through some saved rolling resistance. In general more flat the terrain is the more prominent the savings of time thanks to rolling resistance become. Sorry for the big images.
 

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Discussion Starter · #15 ·
oops - looks complicated....

but in the end it's the same result - cool!

it's hard to believe a simple tire swap can actually make you so much faster.to be 3 minutes faster you usually have to train quite a bit, don't you? these savings on the other hand can be had FOR FREE.
 

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Cloxxki said:
I'd like to see the machine they test their tires on. I have a hush the roller is quite small. As long as the directional knob spacing is close, even DH tires can give low readings on it, it seems. I bet a really sliggush slick tire would still "roll good" on it, while in reality it's an anchor.
It's possible to up the pressure during a test to determin ideal tire pressure for easy rolling, but that would only make sense if the roller would similate offroad conditions with small bumps in i.e. gravel.
It would actually not be that difficult to make the machine they use for testing. All you would need is an old electric treadmill and one of those devices which measures current. You would hook up the machine so that its running at 20 kph and measure current it is drawing just by itself and then you would put on a wheel to run with a 50 kg load on the belt and power up the machine to 20 kph and then see what current it is drawing now. Difference in current between two cases is directly proportional to power the tire/tube/wheel consume (P = chanage in current x voltage).

If I ever come across a cheap old treadmill at some garage sale I'd consider making it. It'd be cool to be able to perform these tests.
 

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MBA Tire Test

Did anyone read the October MBA? They have a new tire test with interesting results. The tires to get 5-star "pedalling efficiency" were:
Nevegal Lite
Roll-X Pro
Blue Groove Lite
Karma DTC

They only gave the Nokian NBX 2.0 three stars. How can there be such a difference of opinion?
 

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Boj,

Interesting model. Just some details:

Isn't the rolling resistance coefficient equal to Proll/(mgv), and the test's power numbers given for one tire at 20 km/h and 50 kg? That would for example give those Conti Explorers approximately Cr = 35.7/(50*9.81*(20/3.6)) = 0.013 rather than 0.0353, and the pair of Eclipse Nokian 0.0078?

And isn't that 0.25 cwA a typical value for road riders in drop bars, and a typical value for MTB higher? I found a flat bars cwA value of 0.45 here: www.2peak.com/robots/bike/en (search for 'flat bar' on that page).

Then I'm waiting for your Track Time 2.0 that includes bouncing over roots and rocks, turning, braking, sliding, jumping, floating over mud, and plowing through grass :D
 

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anden said:
Isn't the rolling resistance coefficient equal to Proll/(mgv), and the test's power numbers given for one tire at 20 km/h and 50 kg? That would for example give those Conti Explorers approximately Cr = 35.7/(50*9.81*(20/3.6)) = 0.013 rather than 0.0353, and the pair of Eclipse Nokian 0.0078?
Yes, you are right. Those would be rolling resistance coeficient numbers on that smooth roller on the machine but not on the trail. What I have done is some reverse mathematics to come up with Cr ~ 0.03 for fireroad riding.

P = 0.5*Cd*S*P*V^3+m*g*Cr*V

so Cr = [P - (0.5*Cd*S*P*V^3)]/(m*g*V)

For example I average ~25kph on certain flat fireroad training rides and from similar rides on the trainer I know I make 180 W there, so Cr = 0.0283. Through several examples like that I have just come to accept Cr ~ 0.03 for fireroad riding.

How tire W values come into the equation is that they supply the difference between two coefficients. The other value for Cr in the model is just the difference between two RR tire values:

Cr2 = 0.03 + (35.7-21.2)/(50*9.81*(20/3.6)) = 0.03532

So in fact I could put in any value for tire W but just as long as the difference between them is the same result for the time saved would be the same too. The importance here is on the difference between two models (eg predicting time saved which is relatively accurate) and not on absolute accuracy of models by themselves (eg predicting lap times which is not accurate). You may wonder why I didn't get coefficients by ratios instead of difference as it would seem the more correct way:

Cr1/Cr2 = W1/W2
0.03/Cr2 = 21.2/35.7
Cr2 = 0.0505

Well as you can see it just gives too large a difference between tires in the real world and you don't save as much time as it predicts. For whatever reason times saved using the method of difference has proven inline with real world time savings from riding the tires so for the moment I have accepted it as right. Maybe one day when I get a powertap I could explain why.

anden said:
And isn't that 0.25 cwA a typical value for road riders in drop bars, and a typical value for MTB higher? I found a flat bars cwA value of 0.45 here: www.2peak.com/robots/bike/en (search for 'flat bar' on that page).
Thanks. I've included 0.45 for Cd*S for future analyses although it would be good to see some actual wind tunnel data as there are stacks of pages on the web giving vastly different values.

anden said:
Then I'm waiting for your Track Time 2.0 that includes bouncing over roots and rocks, turning, braking, sliding, jumping, floating over mud, and plowing through grass :D
In between trying to take over the world, yes, I am working on Track Time 2.0. In addition to all those features it will also come with a free 'The Making of Track Time 2.0' DVD and a 'Track Time Forever' cap and a T-shirt. :D

 

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Discussion Starter · #20 ·
MBA and adverticement...

craig said:
Did anyone read the October MBA? They have a new tire test with interesting results. The tires to get 5-star "pedalling efficiency" were:
Nevegal Lite
Roll-X Pro
Blue Groove Lite
Karma DTC

They only gave the Nokian NBX 2.0 three stars. How can there be such a difference of opinion?
i don't know what the test looks like but usually MBA has either "hot off the pants" riding impressions or is influenced big time by who is placing ads in the magazine...

maybe they didn't test the NBX light? that may be the reason for the low rating. other magazines allover the world praise the Nokian...

by just riding a tire you can't tell too much. you get inflicted by the noise it makes and tires that don't make noise usually feel faster....
MBA also rated the Roll-X as a top 10 item of the year to make you faster. it is well known that these tires are some of the slowest rolling tires on the market yet Specialized has full-page ads. any questions?

the Kharma is indeed a fast tire. have a look at last years testresults below.

 
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