Chung testing includes all loses since you’re testing the real system in the real world. The downside is more sources for variation, more noise, less precision of measurement.
Roller drum testing can be very precise, but it’s also missing or altering important aspects of real world usage. It has a convex and improper friction surface. It only measures tire hysteresis but has no human body, frame, or suspension hysteresis.
Roller drum testing shows wider tires to be slower at equal pressure. Or at best it shows wider tires the same speed at equal pressure drop (comfort). But that ignores all other hysteresis. Overly trusting roller tests is why it took so long to prove wider tires are faster.
Chung testing is the only testing that takes into account all factors (aerodynamics, actual turbulent wind, rolling resistance, surface conditions, handling effects, etc). There’s still many ways to do it wrong, but it’s the best we’ve got.
Gotcha, curious how you can get a tire with such poor performance in casing hysteresis to perform well in Chung testing. Did you test back to back vs the raceking or dubnital?
It’s not my testing, so I can’t discuss specifics of that.
What I can say is that the human body hysteresis results in much larger power losses than occurs in the tires themselves, at least if the surface is rough. So that’s why wider high performance tires are typically faster than equivalent narrower tires, on rough enough surfaces.
Of course there’s a point where the surface gets smooth enough that the wider tire isn’t reducing suspension losses and is slower due to worse aero and losses in the tire.
The above is true for all bikes. For road bikes, it’s pretty straight forward. For mountain bikes it really depends on the course, rider and bike. Bikes with suspension really complicated everything. How does the suspension interact with the tire and rider? How does uneven, bumpy and loose terrain affect it all?
That’s why roller drum testing is especially not the full picture for MTB. Since Chung method is testing the real world, it’s telling you what’s actually faster in the exact way you rode. So does a simple stop watch, but Chung method estimates how much of your power was spent fighting aero vs rolling resistance vs gravity. It’s still not perfect, but I know of nothing better for measuring actual performance and the contributing factors.
I think the most important thing to realize with this subject is that hysterisis is a component of rolling resistance.
Ultimately, we are most concerned with the actual rolling resistance than we are with the hysteresis.
I think there is an idea that a tire’s rolling resistance is a convenient addition problem of drum testing hysteresis along with rough surface suspension losses.
It’s definitely not that simple and there is nothing to say that a tire has one set hysteresis value across many surfaces. It’s actually probably the opposite, but it also doesn’t matter since we can analyze the total rolling resistance on surfaces we commonly ride on.
These things (drum v outdoor) get discussed in current automotive tire research also, and it’s a bit ahead of that published on bike tires.
This paper covers some off road Chung method testing in regards to accuracy, reliability, etc.
Started testing this week an Aspen ST 170 in the rear (normal 170 Aspen in the front). Quite impressed so far, even surprised. Cornering traction seems to be the same as the Aspen, and, somehow, climbing traction on the dry seems to be better ? We have lots of mud spots due to all the summer storms this week and the ST survives those and clears mud like no other.
No comments on rolling resistance, as we know how “feels” work, but at least the results from John Karrasch seem to be very promising. I’ll just say that they are nearly completely silent on the road, and that’s cool.
Maybe I’ll be stating the obvious, but the sole clear con of the ST Vs the regular Aspen seems to be braking traction.
Overall, quite impressed so far, curious to see if they’re durable
Heck yeah! I as a fellow singlespeeder I held my finger over that category when I registered this year for a minute but realistically couldn’t do it as I haven’t spent much time on the SS this year at all. Ordered a Rick and TB for tires in 2.4 although considered Mez/Peyote combo as well. 36t seems ambitious for the single speed (I’m a 32t kind of gal) but who am I to judge as I’ll be running a 36t on my geared hardtail . As they say only three speeds on the singlespeed: sitting, standing, or walking. Gotta risk it for the biscuit to get out in front to get the best shot out at making it up those hills before you get stuck behind geared spinners. Good luck!
I rode the 2.4 Race Rapid Dubnitals today, and for a direct comparison the 2.4 MaxxSpeed Aspens yesterday. I don’t have calipers with me, but the Dubs were clearly a little narrower than the Aspens on the same 28i rim. At the same pressure (18.5 front 20.5 rear, 205ish bike+rider weight), the Dubs felt more damped/smoother and definitely had better traction. That pressure felt good on the Dubs but ideal pressure for me on the Aspens is probably 0.5-1 psi lower. Speed didn’t feel any worse with the Dubs on road or trail. For reference, the trail I rode with the Dubs today was typical western Wisconsin Chequamegon forest - flowy, rooty, and occasionally rocky, but not near as rocky as east coast or Colorado trails. The Dubs seem like a pretty solid choice for MN and WI racing, and I’ll probably take them to Chequamegon in September.
Have been riding with 2.4 dubs for 3 months now and overall happy, BUT got to try friends bike with 170 aspen/aspen st today and i already forgot how good these tyres are! So much more supple and comfort over rough fields, roots etc and feels you can carry more momentum through technical stuff and probably only 1-2W ( flexfitjohn chung test ) slower than dubs and ricks on the gravely stuff. Typical “cat3” gravel testing isnt probably anywhere close to bumpy mtb trails and to be honest its almost impossible to test on that kind of stuff. Probably gonna switch back to aspens for next season
i went for : Specialized Fast Trak Flex Lite T5/T7 TLR XC 29x2.35
Really curious how it compares against the Trinotal, as the Air Trak 2.35 in real life testing by John Karrasch showed it is very-very close to Dubnital, so the BRR drum could be a good comparision point…
It def looks a size bigger (and i like it) on a 30mm rim vs the Trinotal 2.4 (due to it has much round profile, while the Fast Trak is square-ish)
At the risk of completely destroying all credibility … here is the lap I’ve been testing on. Lap starts at 4:42 if you want to skip the data on Race King Protection vs. Wicked Will Super Trail on the rear wheel…how much does the WW cost you in time?
. As they say only three speeds on the singlespeed: sitting, standing, or walking. Gotta risk it for the biscuit to get out in front to get the best shot out at making it up those hills before you get stuck behind geared spinners. Good luck!
