With the caveat that it’s ~5W slower on nearly smooth steel drum. So ~5W slower on tarmac. Now clear at all to me how the steel drum rolling resistance tests carry over to actual dirt. And just talking about non-technical dirt, not situations where you’re actually using the side knobs to avoid sliding out.
I ride the same singletrack trails using low RR tires on my gravel bike and “very high RR” tires on my MTB (Maxxis Minions) and anecdotally I reach higher speeds without pedalling on my MTB on non-technical descents. Though that could entirely be from the dual suspension being far more efficient reducing unsprung mass. Though part of that unsprung mass reduction is also being able to run 2.3" tires at far lower pressures than most gravel tires can safely be run.
Just overall I think we have a vacuum of information about real world RR on actual dirt. Which I get because there’s a huge range of types of dirt and gravel out there, and it’s super useful to use just the same steel drum as a common baseline.
It’s been covered in this forum before by the RR wonks. Steel drum tests correlate well to all surfaces.
Source?
FWIW, While I do believe Josh’s experience at Roubaix are relevant, I do not believe they are entirely descriptive to the conversation at hand.
Back when I raced CX, I lived in KC so never knew whether the conditions would be dry and dusty or on the other end of spectrum peanut butter mud (funniest race ever) and always raced on (now) Donnelly PDX tires f/r. I never once felt I was slowed down or at a disadvantage in dry conditions or stretches of pavement.
Based on what I’ve read, drum testing correlates well to one facet of rolling resistance, the capability of the rubber compound.
You have additional losses which are a function of casing tension, road surface, rider weight, etc; these do not correlates well to drum testing, although they are more a function of tire pressure, tire dimensions, and maybe the suppleness of the casing. That second source of rolling resistance is going to greatly outweigh the first on rough terrain, i.e. mountain bike tires, which would explain the situation presented in an earlier comment.
I strongly suspect the first is still a majorly contributing factor to rolling resistance on smooth dirt roads, simply because there’s not much reason they’d be all that different from pavement.
Tldr, on relatively hard packed dirt roads, with appropriate pressures, the gravel tire that tests faster on a drum will likely be faster on the road. As the road surface gets softer and/or chunkier, the tire composition matters less, tire pressure gets much more important, and less easily quantifiable characteristics like traction due to knob shapes will matter more as well.
Based on what I’ve read, drum testing correlates well to one facet of rolling resistance, the capability of the rubber compound.
Drum testing is a way of characterizing hysteresis, which depends on much more than just the compound(s). How much rubber, how it’s distributed and shaped, what the casing fabric is like, how it’s all laid up, ditto for cut/puncture protection layers, etc. Any part of the tire that flexes as it rolls against the ground. It’s worth noting that these things can be sensitive to influences such as the temperature of the tire.
(Obviously it’s also dependent on PSI and load.)
Fluid movement also affects this sort of testing, although the impact is typically minor. For example, adding sealant to a tire can increase the reported power to spin.
Tldr, on relatively hard packed dirt roads, with appropriate pressures, the gravel tire that tests faster on a drum will likely be faster on the road. As the road surface gets softer and/or chunkier, the tire composition matters less, tire pressure gets much more important, and less easily quantifiable characteristics like traction due to knob shapes will matter more as well.
That would be my guess.
And the need for grip is so context dependent. If you’re racing on fire roads without any technical descending (like Mohoric’s awesome flat turns at gravel Worlds), picking near-road tires file tread tires that roll fast is probably a good bet. Much more than that I’ve come to adhere more to xtrpickels maxim about grip. For technical gravel/MTB I might still check where the tire is on the BRR site (or elsewhere), but it’s no longer the first thing I check.
It’s been covered in this forum before by the RR wonks. Steel drum tests correlate well to all surfaces.
Source?
FWIW, While I do believe Josh’s experience at Roubaix are relevant, I do not believe they are entirely descriptive to the conversation at hand.
Try the search box for this forum.
Considering that you seem to have a specific conversation in mind, I find it a bit of a cop-out to just refer me to the search which returns hundreds of results.
Considering that you seem to have a specific conversation in mind, I find it a bit of a cop-out to just refer me to the search which returns hundreds of results.
Nope. I’m just not gonna spend my time looking.
I’m not your research assistant.
Considering that you seem to have a specific conversation in mind, I find it a bit of a cop-out to just refer me to the search which returns hundreds of results.
Nope. I’m just not gonna spend my time looking.
I’m not your research assistant.
I’ll write this…
The higher the tire pressure, the lower the rolling resistance until an inflection point where rolling resistance goes up.
As the terrain gets rougher this inflection point happens sooner.
However, as a cyclocross or MTB enthusiast will tell you, it doesn’t matter how fast the tire is if the tread can’t provide the grip needed for the course.
Rolling resistance correlates well to all surfaces, but sometimes you have to trade rolling resistance for grip.
Rolling resistance correlates well to all surfaces
…is your speculation. I’m 80% sure what you’re referring to, but refuse to cite, is road tire testing on road surfaces at road pressures and road widths. Up to very rough road surfaces.
Off-road tires at off-road sizes and pressures on fully off-road surfaces changes quite a lot in that equation. My guess is the pure non-technical rolling resistance “extrapolates” reasonably well. But that’s just reasoned assumption more than verified.
Even on the BRR site where the GP5000 TR 30mm @75PSI is the “fastest gravel tire,” I don’t think any gravel race is actually going to use that, except on one of those races that’s like 70% tarmac. And in an actual downhill test I’d speculate that 40mm Strade Bianca tires just below it in “drum testing” will roll faster down a rough downhill. Because once the surface gets rough enough, I speculate “rolling resistance” goes beyond just hysteresis of the casing and tread. The suspension effect on the sprung mass increases rolling efficiency as well. (This is why suspended mountain bikes are faster on even moderately rough terrain, even on the flat, even though they’re heavier)
So the statement that “the GP5000 TR is the fastest-rolling gravel tire” depends a lot on context, and may not be true in some cases. And not just talking about grip, but going in a perfectly straight line and on moderate grades where grip isn’t much of a factor.
Hey - long time! hope you are well. Funny you should say that about the GG’s - i found them great originally as a tubed clincher and was excited when they started making them as tubeless - man was i disappointed in the quality to the point where after wasting money on 2 sets i became and ABC’er…anything but challenge!! What did you decide to go with?
I haven’t found a suitable replacement that matches the security of side knob purchase i felt with the GGs. I’ve tried all 3 specialized options (and they are hella slow on pavement or brown pavement), Terra Speeds (not yet in conditions that would test them), original G-Ones, and Ramblers.
Still on the search for something that might get close to matching it. Going to try either the ultradynamico rose or G-One RS next.
I have stupidly signed up for Tour Trans Alps and as such need to ride though the winter (you may remember i dont do trainers) - hence my search - i have a set of Terra Speeds on currently which are not bad however also have a set of G-One RS on order!!
Never heard of that event but it looks DOPE. Have plotted a bikepacking route from Geneva to Zurich that I’d like to tackle at some point but this also is going on the list.
I also have abhorred the trainer but the partner recently got me onto zwift and oddly enough it’s made it a lot more tolerable to watch a little digital avatar going around a fairytale land.
Gravelking SS hater here. Quick tire, I find the puncture resistance terribly over stated from BRR.
Mine constantly have tiny little cuts in the center tread weeping sealant. I’m riding Umstead in Raleigh. Not your midwest sharp flint gravel or mixed in rooted single track. I may get 1000 miles on one of them, maybe if lucky. Usually around 5 to 600 miles. Which is a horrible value proposition. They just look shreded to hell on the center tread also quickly.
Considering trying the Challenge getaway pros. Similar BRR rolling resistance and slightly better puncture score and more tread. I suspect the file tread on the Gravelking SS in the middle vs some kind of real “tread” is why they get ruined in that area quicker.
Gravelking SS hater here. Quick tire, I find the puncture resistance terribly over stated from BRR.
Mine constantly have tiny little cuts in the center tread weeping sealant. I’m riding Umstead in Raleigh. Not your midwest sharp flint gravel or mixed in rooted single track. I may get 1000 miles on one of them, maybe if lucky. Usually around 5 to 600 miles. Which is a horrible value proposition. They just look shreded to hell on the center tread also quickly.
Considering trying the Challenge getaway pros. Similar BRR rolling resistance and slightly better puncture score and more tread. I suspect the file tread on the Gravelking SS in the middle vs some kind of real “tread” is why they get ruined in that area quicker.
Me and and a bunch of others I know had the casing delaminate from the tread on the GK SS.
The only indication visually was excessive weeping of sealant.
But you could heard the casing stick and unstick every tire rotation.
That was the end of Panaracers for me.
Never liked the way the side knobs felt either, squishy and sketchy on anything hard pack.
Me as well. I really don’t understand that tire: it rolls reasonably fast & well on hardpack but is useless as soon it gets more than dusty. That little file tread is for nothing more than looks, especially compared to a tire the Terra Speed, which does well in crr tests and grips well.
