And ill add my long standing comment, its not 100% about straight line speed, tech downhill and twisty singletrack do appear on gravel courses and can create gaps if you have the wrong tires.
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The video is somewhat confusing.
It is said that BRR and Silverstone both overstate the wattage difference between tires.
BRR has the 40mm Cinturato & 50mm Cinturato at 1.5w difference.
Silverstone has them at 13w difference.
This doesnāt seem to follow?
The pedaling efficiency rig seems like it requires itās own evaluation and right now doesnāt seem very useful in comparison to BRR and perhaps virtual elevation testing.
The advantage or penalty for using Race Kings at 36kph, compared to 35mm Cinturatos, is -40w or +33w depending on surface?
Race Kings have a 32.6w rolling resistance (exclusive CRR not factoring aero) penalty over 35mm Cinturatos on pavement? This seems an order of magnitude greater than expected based on real world/real surface testing.
Cinturatos arenāt even fast tires, what would be the Race King pavement penalty compared to the Hutchinson Caracal Race? or GP5K AS TR? Iāve done long paved rides on all three and I cannot imagine or see a 30w+ difference.
Donāt take this the wrong way, I think this is useful and interesting. I wish there was more information on the pedaling efficiency rig, it seems at odds with everything else.
It it humorous that this debate has entered a phase where discussion is between two types of roller testing.
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If BRR āinflatesā the differences between tests of tires because their roller is too small of a diameter, the 5 fastest 40mm labeled tires are only 3.4w apart. In reality they would be expected to be closer?
Agree, without any data on correlation of the SSE rig to real world I am having a hard time believing any of that. At least with BRR we have quite a bit of evidence that it correlates well to pavement Crr from Chung testing. I donāt think those numbers would hold up when testing those same tires on pavement or gravel outside.
Not only that, but you donāt know for sure what the ādecisiveā moment will beā¦is it a road section, is it a descent, is it a climb? Or is it when a counter-attack forms that ends up chasing someone down and then winning the race?
Tactics play a huge role in what becomes ādecisiveā and you canāt necessarily plan for that.
Outside of professionalsā¦ Who is averaging 22-25 mph in a gravel race?
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Thatās just semantics though.
No it isnātā¦.it is a complete reversal in approach.
Which ever direction you go at it, you settle on the tyre that is most appropriate for the race youāre doing (in your opinion). The starting point is irrelevant.
No because the āoptimalā is now viewed diametrically different than before. Previously it was essentially ānarrow as possibleā while now it is āwide as possibleā
Your assumption that they reach the same point is flawed.
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Also, since the closer you get to āoptimalā, the smaller the differences you can notice (or measure), the reversal of approach means you land on the widest tire that isnāt super slow, vs the narrowest.
E.g.based on DJās testing, you might have ended up with a 40 for race going smallest to largest, but now youāll end up with the 50 for the same race.
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Where is everyone seeing specific rolling resistance for tires on comparable surfaces? I.e. pavement vs category 1,2,3 etc. I generally look at bicycle rolling resistance (donāt have a subscription) and just see a general value it gives.
This is why I donāt find the data to be overly applicable to gravel. Plus, they still only use a 17ID wheel which doesnāt represent where gravel or road wheels are at right now. ID influences tire size which in turn impacts rolling resistance. And not all tires respond to a wider ID as others. Maybe Iām wrongā¦it happens from time to timeā¦most of the time.
Thatās a very strange way of thinking rather than simply trying to work out the fastest tyre for your specific situation, but whatever, you do you.
Interesting. How would āsimply trying to work out the fastest tire for your specific situationā work, exactly? I donāt understand what youāre sayingā¦
It also influence tire shape, squaring the tire a bit more, which I would imagine could have some impact on rolling resistance.
so BRR - smaller drum, but act as a pavement simulation -
RaceKing 2.2 @1.7 bar , tubeless 18.2W
RaceKing 2.2@3.1 bar tubeless 15.7W
Pirelli Cinturato 40mm @1.9 bar tubeless 23.2W (tube: 28.2)
Pirelli Cinturato 40mm @3.1 bar tubeless 17.1W (tube: 20.3)
I know its not possible to compare two test methods, at least absolute numbersā¦ BUT! BRR states the RaceKing is faster (highly doubt that) on pavement (drum is kinda smooth surface, but not completly) while Dylanās test shows the complete oppositeā¦ and with a huge difference!
Chung testing is pretty straightforward to run.
If you are serious about tire choice and your āaā race has a mix of surfaces it is worthwhile imo to go spend some time running a test on 2-3 different tires on a few different surfaces to dial in which suits the conditions the best, and that is not necessarily the fastest.
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The point I think weāve all aligned on is that there isnāt a ācorrectā answer, so the way I would do it is look at the course characteristics - what sort of gravel? Gravel on key sectors? How much pavement?
If it was entirely extremely rough rocky gravel / cobbles, I would go as wide as possible. Conversely, if it was all tightly packed smooth stuff, Iād be looking at circa 32mm. Then across that spectrum, I would decide where the sweetspot sits for the particular course, where one would expect across all courses, the average sits somewhere towards the middle. Of course there are some other factors to help the case for leaning towards wider when unsure - comfort, grip etc.