Bicycle Rolling Resistance tests gravel

30 replies · 2,765 views

Volsung
878 posts
#1Jun 30, 2020, 10:20 AM
https://www.bicyclerollingresistance.com/cx-gravel-reviews?fbclid=IwAR0myLZFSzkyf5NSQOzdciwBZYNqxMuzj_YakO2Y2B2jrUJMgL-HlNxkFRU

Yeah yeah yeah testing on a drum isnt realistic because gravel is gravel and not a knobby steel drum. Jim Heinie also pointed out that the curvature of the drum is more than that of the Earth which is a useful observation.

He tests all his tires consistently so it's a good comparison. He just started testing gravel tires and more tires are coming.
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Volsung
878 posts
#2Jun 30, 2020, 2:35 PM
According to their numbers, GK slicks have LOWER rolling resistance than Reen Hers Jon Bon Pass. The GKs are 2mm wider and the pressures were measured differently, but still.
2
dangle
465 posts
#3Jun 30, 2020, 4:06 PM
Wow, that's a HUGE addition to the gravel community.
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dangle
465 posts
#4Jun 30, 2020, 4:21 PMedited
Volsung wrote:According to their numbers, GK slicks have LOWER rolling resistance than Reen Hers Jon Bon Pass. The GKs are 2mm wider and the pressures were measured differently, but still.

It's tough to say if it's fair to measure those across two slightly different tests. Seems like a similar inner tube used and both right around 30 psi though. I don't understand why Compass/Rene Herse tires are so popular around this forum anyways, but that's for another thread.

What really surprises me is that the 35 (measuring 33 mm wide) Terra Speed is identical to the Panaracer 40 (measuring 37 mm wide) for rolling resistance at the 'low' and 'extra low' pressures most likely being used. That means the Terra Speed 40 (mine measure 40.0 mm at 30 psi on i23 rims) should be even faster (or at the top of the rolling resistance charts). I'm super happy with those tires, but it looks like several others are about to jump on to that as well.
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EBG18T
53 posts
#5Jun 30, 2020, 5:49 PMedited
I really like the Bicycie RR site but I find the details kinda quirky.

I ‘feel’ that my fatbike tires are more than 2x the RR of my much narrower gravel rubbers. What am I missing?

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dangle
465 posts
#6Jun 30, 2020, 7:42 PM
Keep in mind that the BRR numbers are for a single tire at 19 mph. The fat bike tires at 8 psi are as high as I will ever ride a fat bike tire, while the 'low' pressure of the gravel tires is closer to what I use. If you compare those with each other amongst the top tires in each category, it's more like 20-25 watts per tire making it 40-50 watts in rolling resistance alone at 19 mph using the BRR methods. [RR (Watts) = CRR * speed (m/s) * load (N) using 42.5 kg / 94 lbs for their N.]

If somebody told me that I needed an extra 50 watts to push my fat bike at the same speed (of 19 mph) I think that sounds reasonable. I probably need somewhere in the neighborhood of 225 watts on smooth, flat ground on my gravel set-up. 275 plus whatever is needed to overcome the aero penalties of the fat bike would make the fat bike seem waaaay less efficient.

Maybe over extrapolating a bit, but I think what you're 'feeling' makes sense on the surface.
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zen_
110 posts
#7Jun 30, 2020, 7:57 PM
Interesting that the smooth center Overide is middle of the pack, and that the GravelKing Slick vs. Maxxis Re-Fuse, which look like a very similar tire, are first and last.
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EBG18T
53 posts
#8Jun 30, 2020, 8:24 PM
@dangle- when you present it like that, it makes more sense. Thanks!
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Slim
300 posts
#9Jul 1, 2020, 9:39 AM
https://docs.google.com/spreadsheets/d/1TP2UiAIyAbK7iR2X0mlGWWB7aJkbOecfrCmimqwcdGk/edit#gid=133566871
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mosinglespeeder
46 posts
#10Jul 1, 2020, 12:05 PM
zen_ wrote:Interesting that the smooth center Overide is middle of the pack, and that the GravelKing Slick vs. Maxxis Re-Fuse, which look like a very similar tire, are first and last.

True, but consider the weight comparison, and whereas the tread may be similar the rotational weight is exponential intertia at speed. It doesn't sound like much but 100-130grams difference per tire makes a huge difference.

Plus, I am guessing the tire carcass/construction has a lot to do with both the above and the ride quality/speed
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ljsmith
762 posts
#11Jul 1, 2020, 4:22 PM
Its awesome to see gravel tires getting tested. However I would like to be able to compare some of the tires on the mountain bike list with these, but I think the differences in testing protocol make that hard, specifically the pressures. For instance the Schwalbe Big One (this was renamed to G-One Speed a few years ago) seem to have ridiculously low rolling resistance if directly compared to any of these tires. But the pressures in that test are pretty high for a 2.35 width tire. It also seems Thunderburts would be a better choice than many of these tires, but again differences in testing make it hard to know for sure.
1
EBG18T
53 posts
#12Jul 1, 2020, 6:13 PM
ljsmith wrote:But the pressures in that test are pretty high for a 2.35 width tire. It also seems Thunderburts would be a better choice than many of these tires, but again differences in testing make it hard to know for sure.

Very True. I’m not sure who runs a 2.35 at 55 psi. its rare that I go beyond 28psi..
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ccand51997
265 posts
#13Jul 1, 2020, 6:43 PM
ljsmith wrote:Its awesome to see gravel tires getting tested. However I would like to be able to compare some of the tires on the mountain bike list with these, but I think the differences in testing protocol make that hard, specifically the pressures. For instance the Schwalbe Big One (this was renamed to G-One Speed a few years ago) seem to have ridiculously low rolling resistance if directly compared to any of these tires. But the pressures in that test are pretty high for a 2.35 width tire. It also seems Thunderburts would be a better choice than many of these tires, but again differences in testing make it hard to know for sure.

My takeaway from this list is something I have already suspected from my own power meter testing; that gravel tires are not really any faster than the current generation of mtb tires, which is good for me because 35-42mm tires just kill me in the summer sand around here. I need the float of 50+mm tires and other than the increased wind resistance at higher road speeds, it does not seem that there is a disadvantage.

I think BRR tests at a lot of pressures out of curiosity lists the most practical pressure on it its "main" list. In my own testing, I can't tease out ANY difference in speed when I vary pressure, so I wonder if the smooth drum accentuates the pressure differences. Another blog to keep in mind is run by Tom A. called Blather about bikes. He also roller tested a large number of gravel tires and he is pretty good at it, as well. He had the Terra Speed at the top of his list, other than the Slick-ish Reine Herse tires.
I like to run the Thunder Burt as my front tire with a Conti Raceking Protection 2.2 on the rear.
BRR has both those tires pretty close in RR which is interesting to me because the TB (not snakeskin) seems a more supple tire. It makes me wonder if the Black Chili really does make the Conti tires faster.
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thumper88
198 posts
#14Jul 2, 2020, 8:19 AMedited▲ Top
Im pretty disappointed. Basic issues: 1) he’s using 17.8mm rims. 2) he’s testing only 33-40mm tires and frankly seems more interested in the CX stuff he’s lumping together with gravel.
I had been hoping for a couple years he would do this. It was a no-brainer for him, the big gaping hole in his web site... reliable tire data is hard to come by for many types and gravel tire performance data in particular is the Wild West ... I start to get quesy every time I see some reviewer saying a tire “rolls fast.” They almost always say that... and enough have said it about tires that are clearly bricks that the phrase has lost all credibility.
Anyway.
Despite some quirks, like using really narrow wheels even by modern road standards, Bike Tire Rolling Resistance is the gold standard for road tire RR data. His numbers seem properly derived and dovetail well with smaller and less sophisticated tests elsewhere. In short, the numbers feel pretty reliable.
But my sense is he doesn’t understand the world of gravel equipment, or much about it generally, and has little interest in it, and this translated to some bad decisions.
For starters, OK, I can live with him lumping CX and gravel together, though there’s not much more overlap than with MTB. whatever. I understand his need to hold down what must be a lot of labor to a dull roar but...And understand Im talking only 700c here. 650b is a whole different issue.
But ... testing only 32mm to 40mm. REALLY? The sport keeps edging toward slightly larger tires and few serious gravel bikes come with anything smaller than 38mm now, and every new generation of frames accommodates larger and larger tires.... at least 40 was the loose standard for awhile, then 42, 44.... now you’re seeing numbers like 47 (diverge), 50 (routt) and these are NOT bikes aimed at bike packing.
The best gravel tires in 700c are now often most popular in 40mm and up. 42-43 is the standard for DK for example and lots of other major gravel races too.
So the top of HIS limit is barely hitting the bottom of the scale for gravel.
Also...he is just using rims that measure 17.8. It’s just not right. It’s hard to know how that is affecting the testing, but it surely will. Gravel wheels are still trending wider and 23-25mm internal is the current standard, with a few narrower and a few wider.
But now, like road, he has started down a certain path, and changing that would render those first 10 tests outliers....

As to the tires he starts with....The results generally gybe with other tests... but six of the 10 are small tires that aren’t of much interest.
Conti was slow to the game and is therefore behind the curve... and he’s happy to celebrate that ...the Terra Speed 35, at 33mm true width, is of no use to me. None. More people will buy the “40” which barely measures 39 on my wheels and is super fast in every test I’ve seen... but Conti need to build a tire will at least measure out at a true 40 and preferable 42-43. It’s the fastest proper gravel tire in the test, though I wouldn’t use it on courses with serious sharp rock.
mosinglespeeder
46 posts
#15Jul 2, 2020, 11:47 AM
very well said thumper
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bearlyfinish
49 posts
#16Jul 2, 2020, 3:42 PM
thumper88 wrote:I start to get quest every time I see some reviewer saying a tire “rolls fast.” They almost always say that... and enough have said it about tires that are clearly bricks that the phrase has lost all credibility.
Truth.

I actually don't 100% agree with Thumper about the 33-40 tire size. For some parts of the world, that is the "gravel tire" size. If you live in a place with relatively few dirt roads, every "gravel ride" is really a mixed surface ride. If I need a 47mm tire, I'm bringing my mountain bike. But running a 35-40mm tire makes a lot of sense in the mixed surface application. By BRR using the same rim diameter, I can compare a road tire to a gravel tire. So I know using my 38mm gravelking slicks I'm losing 7W (per tire) to the GP5k's. So now I can make the correct tire choice based on route knowing the %paved vs %dirt.
I think the main issue here is that gravel riding is different to everyone because there's no standard and we lumped all drop bar biking on dirt as gravel. I would say that BRR tested a lot of tires that fit the "allroad category". A lot of the new endurance road bikes fit up to 38's, so there's a lot of people re purposing their road bike as a pseudo gravel bike.

You're right though that he should at least consider tires in the 42-45 range.
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thumper88
198 posts
#17Jul 4, 2020, 2:50 PM
bearlyfinish wrote:

Truth.

I actually don't 100% agree with Thumper about the 33-40 tire size. For some parts of the world, that is the "gravel tire" size. If you live in a place with relatively few dirt roads, every "gravel ride" is really a mixed surface ride. If I need a 47mm tire, I'm bringing my mountain bike. But running a 35-40mm tire makes a lot of sense in the mixed surface application. By BRR using the same rim diameter, I can compare a road tire to a gravel tire. So I know using my 38mm gravelking slicks I'm losing 7W (per tire) to the GP5k's. So now I can make the correct tire choice based on route knowing the %paved vs %dirt.
I think the main issue here is that gravel riding is different to everyone because there's no standard and we lumped all drop bar biking on dirt as gravel. I would say that BRR tested a lot of tires that fit the "allroad category". A lot of the new endurance road bikes fit up to 38's, so there's a lot of people re purposing their road bike as a pseudo gravel bike.

You're right though that he should at least consider tires in the 42-45 range.
all that is defd fair enough... also... and I think you understood this...I meant “quesy” not quest... dumb typo on my part.
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avatar78
29 posts
#18Jul 4, 2020, 3:28 PM
While none of the tire sizes he tested are ones I would be using, I think the useful takeaway for me is that the rolling resistance generally correlates with tire weight. And it makes sense that the lighter and more supple a tire, the lower the rolling resistance. I can extrapolate that out to models and sizes I'd actually run.

Another takeaway- Conti needs to start making wider 700C tires, and 650bx47, because their tires are pretty darn good.
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widget
4 posts
#19Jul 4, 2020, 7:52 PM
EBG18T wrote:

Very True. I’m not sure who runs a 2.35 at 55 psi. its rare that I go beyond 28psi..

With the G-0ne Speeds, anyone who doesn't want the front to massively self steer!
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EBG18T
53 posts
#20Jul 5, 2020, 7:29 AM
widget wrote:

With the G-0ne Speeds, anyone who doesn't want the front to massively self steer!

i think we were talking in relation to mtb tires being tested at a higher psi. While that tire does come in a 2.35, it does have a max psi of 50 (according to the mfg). Im not sure I’d put the g-one speed in the mtb tire category.
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