Gravel tire rolling resistance tested

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rjich
Posts: 108
Joined: Sun Apr 11, 2021 11:38 am
Location: NYC, NY

by rjich

jromano89 wrote:
Mon Dec 27, 2021 6:10 pm
The VeloNews gravel tire test is very interesting because they use the same protocol as their roubaix tire test. The gap between a fast gravel tire and a GP5000 TL is smaller than I expected.

Does anyone have experience with both the 38mm and 42mm sizes in the Pathfinder Pros? I'm currently running the 42mm which are great overall, but feel a hair slower than my old Terra Speeds. However, according to these results, the 38mm version is considerably faster.
The 38mm version felt a bit slower than terra speed 40(which appear slim for a 40mm width) in my usage. But could very well be placebo. The rolling resistance site has them pretty high up the list

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tanhalt
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Joined: Wed Dec 27, 2006 6:36 pm

by tanhalt

mathias720 wrote:
Thu Dec 30, 2021 8:16 am
yinzerniner wrote:
Tue Dec 21, 2021 6:06 pm
mathias720 wrote:
Tue Dec 21, 2021 7:29 am
I am currently looking at a new set of tire for my crux.
currently running gravelking SS 38. Looking at changing to Terra speed 40mm or RH steilacoom(extra lite)
both should give more grip, but cant figure about the rolling resistance, of the steilacoom in extralite casing vs. GK SS? anyone tried both.
currently leaning to RH because of the weight.
all the test i find of Reneherse is of the endurance casing.
riding will be gravel with maybe 10-20% asphalt.

also for the reneherse steilacoom.
is the extralite Tan lighter than Extralite black.
i know for some companies(most) the tan version is lighter than black even though they always state same weight for both colors on their sites
Terra Speed has been tested throughout as the fastest or second fastest tire, with very low weight but also very high wear and little puncture protection. Modest tread, and with little asphalt should last a decently long time.
Gravel King SS has very little tread, and will roll slower but most likely have better flat protection. Also last longer and cost less.
RH is VERY high priced with great looks and ride feel but won't roll as fast as Terra Speed, poor flat protection and high cost. The variations in manufacturing will account for more weight difference than black vs tan sidewalls.

So to break down the three choices:
-Brain says Terra Speed
-Wallet says Gravelking
-Heart says RH
Problem with test of RH is it all the regular og endurance casing. i cant find any test on the extralite casing?
A while back I roller tested both a regular and EL casing Snoqualmie Pass. The casing difference was predicted to "cost" ~2.5W per tire at 30kph for an 85 kg rider+bike load (on pavement).

tanhalt
Posts: 410
Joined: Wed Dec 27, 2006 6:36 pm

by tanhalt

tritiltheend wrote:
Thu Dec 30, 2021 6:00 pm
yinzerniner wrote:
Mon Dec 27, 2021 10:42 pm
jromano89 wrote:
Mon Dec 27, 2021 6:10 pm
The VeloNews gravel tire test is very interesting because they use the same protocol as their roubaix tire test. The gap between a fast gravel tire and a GP5000 TL is smaller than I expected.

Does anyone have experience with both the 38mm and 42mm sizes in the Pathfinder Pros? I'm currently running the 42mm which are great overall, but feel a hair slower than my old Terra Speeds. However, according to these results, the 38mm version is considerably faster.
Yeah they rank the tires and include numbers on PSI and rolling resistance but don't exactly go much deeper into why certain tires are ranked faster than others. Case in point (last four colums are RR at 2, 2.5, 3, 3.5bar pressure)
#2 Specialized Pathfinder Pro TLR 38mm 38mm 492g 32.0w 28.3w 23.2w 18.9w
#5 Schwalbe G-One R Evo Super Race TLE 40mm 40mm 500g 31.0w 28.2w 25.8w 21.8w
Based on the numbers above it seems like the G-One should be ranked just about the same if not higher than the Pathfinder, as it's a larger tire and it rolls just as fast if not faster in the 2-3bar pressure range where these tires will live.

One thing of note from the VN tests is that their results rank the tires but the numbers are tough to correlate. Also they don't state how they normalize for tire drop/casing tension/comfort level on the different sized tires - eg a ~36mm tire at ~50psi should have the same casing tension as a ~40mm tire at ~42psi, or thereabouts.

And for those who haven't seen the full results yet, remember that "reader mode" is your friend :thumbup:
The "reader mode" is a great tip, thanks!

I count seven tires that based on a straight ranking from wattage at a given pressure should rank ahead of the tire that's above them. If there is some hidden adjustment they are making to normalize for varying tire size it isn't apparent, as I don't see any consistent logic. Really somewhat baffling.

The Wheel Energy lab supposedly uses a hydraulic shock and a drum with a rough surface to better determine the optimum pressure. But it appears you have to go to extremely high pressures before they identify a break point, much higher than is reasonable. Therefore it does not appear that this test protocol properly identifies the proper pressure for gravel riding, something they only acknowledge in passing.
Actually, as I understand it, the Wheel Energy rig uses a PNEUMATIC cylinder to apply the wheel load, and thus has some measure of damping inherent in the system. Unfortunately, it's only about 1/10 of the damping one would expect from the energy being absorbed by human tissue.

So...because there's at least SOME damping, the test should reveal "A" breakpoint pressure (as one would see in riding outside), but because the damping is so low, the breakpoint pressure will appear to be quite high for the roller roughness and speed. The good news is it confirms the concept as is seen in careful, well-designed field testing of tires (i.e. methods that can separate out aero and rolling drag, not lump them together). It also shows that for pressures BELOW breakpoint, roller testing is a valid, and useful, way of evaluating the hysteresis loss properties of tires, despite what some folks decry about it not being "like the real world". Just don't overinflate your tires and roller tests results are COMPLETELY valid and useful. <rant mode off> :lol:

tritiltheend
Posts: 83
Joined: Sat Jun 02, 2012 2:42 am

by tritiltheend

tanhalt wrote:
Sun Jan 02, 2022 12:06 am
Actually, as I understand it, the Wheel Energy rig uses a PNEUMATIC cylinder to apply the wheel load, and thus has some measure of damping inherent in the system. Unfortunately, it's only about 1/10 of the damping one would expect from the energy being absorbed by human tissue.

So...because there's at least SOME damping, the test should reveal "A" breakpoint pressure (as one would see in riding outside), but because the damping is so low, the breakpoint pressure will appear to be quite high for the roller roughness and speed. The good news is it confirms the concept as is seen in careful, well-designed field testing of tires (i.e. methods that can separate out aero and rolling drag, not lump them together). It also shows that for pressures BELOW breakpoint, roller testing is a valid, and useful, way of evaluating the hysteresis loss properties of tires, despite what some folks decry about it not being "like the real world". Just don't overinflate your tires and roller tests results are COMPLETELY valid and useful. <rant mode off> :lol:
Good info, thanks for the correction, and explains the very high "breakpoint" that the VN tests show. I can't help but think that the use of a rough drum and some damping just kind of clouds the picture and will be misinterpreted by a lot of people. Thanks to the efforts of people like yourself and Josh Poertner, many more people are becoming properly educated about all this stuff, but there's still a lot of misinformation out there. I'd estimate about half the people on average that I run into on a day-to-day basis are still overinflating their tires, some of them by large margins.

req110
Posts: 867
Joined: Thu Nov 22, 2018 10:23 am

by req110

Gents, i am looking for SLICK tire which will be fastest on tarmac, but able to not get punctured from small stones in first gravel section.

Optimally 38mm or so. Ideally tubeless.

I see that even fastest tires on BRR are around 23W :/
SW SL8 RTP 56cm @ 9270 / CLX II / CS OSPW / CEMA BB
S Epic 8 L @ XX T-Type / Berg Ratheberg 30 / Quarq / Fox Transfer SL 100mm / 3p

Singular
Posts: 537
Joined: Mon Jul 27, 2020 8:59 am

by Singular

Bog standard Gravel King in the 38/40 size?

I guess that the equivalent Rene Herse (name escapes me...) would be a fine choice too.

I've used the discontinued Vittoria Voyager Hyper in 38mm as a very, very fast slick tire (essentially a supersized mid-range road tire) that did work very well as tubeless too (although not rated as TL).

Marin
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Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

Gravel King or Strada Bianca. Both very fast

CampagYOLO
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by CampagYOLO

req110 wrote:
Mon Jan 03, 2022 10:18 am

I see that even fastest tires on BRR are around 23W :/
That's at "Extra Low" tyre pressure which according to BRR is between 25-33 psi. If you're mainly on tarmac then you'll be running higher pressures than that and hence the rolling resistance will decrease.

req110
Posts: 867
Joined: Thu Nov 22, 2018 10:23 am

by req110

That is true. Do you think that slick gravel tire 38-40c can get down to like 15W when pumped to be as hard like 25c on 6 bar?
SW SL8 RTP 56cm @ 9270 / CLX II / CS OSPW / CEMA BB
S Epic 8 L @ XX T-Type / Berg Ratheberg 30 / Quarq / Fox Transfer SL 100mm / 3p

yinzerniner
Posts: 206
Joined: Tue Jun 13, 2017 8:54 pm

by yinzerniner

req110 wrote:
Mon Jan 03, 2022 11:16 pm
That is true. Do you think that slick gravel tire 38-40c can get down to like 15W when pumped to be as hard like 25c on 6 bar?
Probably not - a 25c tire at 90 psi is roughly equivalent to a 38c tire at 50 psi for the same casing tension and the contact patch will still probably be larger and this the tire would be slower than skinnier tires at the higher pressure. Would prob be in region of 18w at that width.

Marin
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by Marin

req110 wrote:
Mon Jan 03, 2022 11:16 pm
That is true. Do you think that slick gravel tire 38-40c can get down to like 15W when pumped to be as hard like 25c on 6 bar?
Bon Jon Pass EL was right among the fastest road tires in Tour Mag, and Strada Bianca should be faster.

Don't forget that at higher speeds, you will use >200W to overcome aero resistance, so 2 or 3W difference in tires is the equivalent of lowering your head a Millimeter or 2.

Noone will drop you because they're on Turbo Cotton and you are on a fast TL gravel tire. Individual TT - different story

Image

PS 6 bar is insane for the Bon Jovi, but it won't be much slower at 4 in the real world

yinzerniner
Posts: 206
Joined: Tue Jun 13, 2017 8:54 pm

by yinzerniner

[/quote]
Don't forget that at higher speeds, you will use >200W to overcome aero resistance, so 2 or 3W difference in tires is the equivalent of lowering your head a Millimeter or 2.
PS 6 bar is insane for the Bon Jovi, but it won't be much slower at 4 in the real world
[/quote]

So there's the rub - a ~35mm tire at ~6 bar is equivalent to a ~25mm tire at ~9 bar, and also the aero penalty from 25mm to 35mm will be pretty significant - even when optimizing the rim to the tire (ie 105 rule) just the frontal area quotient of the Cda increases 40%. In an GTN clip the Aerocoach head said a 3mm width difference can account for ~5w at 45kph, and even his mortal enemy Hambini stated similar findings of 23mm vs 25mm at 30kph.
https://youtu.be/aMxP3aEgVRY
https://www.hambini.com/testing-to-find ... le-wheels/

Normalizing for casing tension 35mm Bon Jon at 4-5 bar will me likely ~5-8w slower than 25-28mm GP5K at 6-7bar.

So even with equivalent rolling resistance the aero penalty will most likely be a minimum 12-15w at 30+kph speeds with an aero optimized rim. Add in the ~5-8w RR penalty for 4 bar BJP vs 5 bar GP5K and you're at 17-23w. That's enough to get dropped over a pretty small distance.

Marin
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Location: Vienna Austria

by Marin

No, you get dropped if you can't stay in the draft or if you climb slower. Draft advantage is waaay more than 17-23w

Marin
Posts: 4035
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Location: Vienna Austria

by Marin

Anecdotal, this is on Conti 2.2" MTB tires, 42kph average over a few km:

https://www.strava.com/activities/56691 ... /8463/8779

They are Race King Racesport - should be faster than the Protection version - which are the fastest true knobbies on BRR https://www.bicyclerollingresistance.com/mtb-reviews

This bike is much faster than it looks:

Image

by Weenie


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User avatar
fa63
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Joined: Mon Feb 19, 2007 7:26 am
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by fa63

It is anecdotal, but I was down to one bike (my gravel bike) for several months and group rides where I am normally one of the strongest (we usually average around 32 kph on moderately hilly terrain), I struggled to keep up with and even got dropped twice while on Panaracer GK 38mm tires (the slick ones; ones that test as one of the fastest by BRR). I don't ride with power anymore so I don't know about difference in power.

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