OK so don’t laugh. Gravel setup is the e thirteen piedmont wheels with a 2.1" thunder burt super ground addix speed rear and 45mm vittoria strada bianchi (the handmade one) in front. I rode this setup in big sugar. Inserts on both ends. On the road setup it’s the bontrager Aeolus pro 3v wheels with a 32mm conti 5000 in back and a pirelli p zero up front, both tubeless with an insert in the rear. So a mishmash but, in general, your typical fast-ish road setup and fast gravel setup.
“Challenging at best, deeply problematic at worst” LOL, I hear you!
This was on new smooth pavement so we didn’t have the “line in gravel” issues but there was some wind and the temp probably varied a little (test took about an hour so maybe not too bad on temp). I haven’t seen tires get faster when they warm up but it’s something to watch for (hadn’t considered it).
As far as where is the power delivered during the lap, that seems to make surprisingly little difference. And I like time trials so the concept of “push a little on the hills and back off a little on the descents for a faster time than a steady power” is taken as truth. But I haven’t been able to prove it matters much…if at all. I think if you run a lap a whole bunch of times going for consistency you’ll end up putting down the power similarly run-to-run. I try to keep it steady and keep an eye on ave power as the lap progresses but I’m sure there is plenty of variability there. I’m just not convinced either way about it mattering (maybe it does…maybe not?)
OMG triggering! You run a lot of laps and look at the data and it’s like…“if we take lap 4 and 9 then these setups are the same but if we look at laps 2 and 7 then A is way faster than B” so when you see a youtube video with one trial for each setup…even if they are using power to measure the effort…it’s like…wow that told us nothing.
It’s good that you’re aware of that. I’m sure a lot of people that do testing, targeting a fixed average power per run, don’t realise that by pushing a bit harder in the ‘right’ places, on the uphills, in an effort to bring the average back up towards the target power, it affects their overall times/average speeds, even though their average powers are spot on their target.
There’s a lot of potential pitfalls with testing, but the fairly small variations seen in your lap-to-lap times, and also the stint-to-stint time variation, provide some really good insights into the precision of the test method.
Regarding temperature, I remember than Tom Anhalt derived a relationship between temperature and CRR (see plot in this blog post), albeit it with a fairly limited number of test points. It would be good to know if there’s any other data out there. Intuitively, it seem right that a warmer tyre would be more supple and have less hysteresis losses (like a squash ball, once it becomes warm).
Just fitted the new Schwalbe G-One RS 50mm on my Checkpoint SLR 9 (2023 model). Looks like it’s going to be a great tire and fit. Excited to give it a go coming from the older version 45mm.
I see that you weighed at least one of them. Did you weigh both? I just got a set and they are 587 and 604 grams. Spec says 585 so I’m wondering how we have such a variance between us. I know we’re not supposed to care about weight anymore, but I’m also worried about quality control at Schwalbe.
I’ve had the same experience with Maxxis, Vittoria and Perelli. The weights will always vary and I wouldn’t worry about it, but I understand the feeling.
Interesting finding while checking RC 2.2 fit on my bike. There is quite a bit of difference with similar internal width rims. I have tried the tires with 3 different rims (IR 23 mm, 24mm and 24.5 mm ) and one of them provides 4-5 mm more clearance than the other two
I forgot that BRR did a test too, thanks. It looks like BRR measured approximately 1% change in CRR per 1 degree C change in temperature, which is a bit less than Tom Anhalt’s 1.36% per degree C sensitivity. It’s broadly similar though, and it might be affected by drum/roller diameter, I guess.
Curious that you have the more aggressive tyre on the back and the less aggressive on the road - Usually this would be the other way round. I run TB 2.1 front and 50mm near slick on the rear.
Front wheel bite in the corners is v nice, back just follows.
If some wants to read German, it’s in this section of my article:
Umgebungstemperatur und Einfluss auf den Rollwiderstandsbeiwert
From these 3 sources I found
crr diff a 1,36 % per degree Celsius from Tom, 1 % / °C from Recumbents.com and 1,1 % / °C from the Automotive Journal article. So all in the same ball park. Which makes sense since all compounds differ a bit, too.
Dylan Johnson has a rebuttal of sorts to the Nathan Haas podcast bit above. Starts at 56:20 and gets a little convoluted but raises some of the same points as here with some more info on testing he’s done and others as well.
I was looking at gravel/XC tires in the 2.0"-2.1" range, that have yet to be tested on BRR (i.e. large tires for those that can’t quite fit Race Kings). There are a lot out there but very few that have the potential to be fast. So far, the only ones I could find are
Schwalbe G-One RS/RX Pro 50 (RS is next in line on BRR, RX is the knobbier version)
From the post above, these come in below 50mm, which is probably too narrow.
Vittoria Terreno XC Race 2.1 (Lachlan ran one of these in the front at Unbound)
According to Vittoria, the Terreno XC is their fastest XC tire, the ranking goes Terreno>Peyote>Mezcal>Barzo. I would like to see how this one performs. I found an old review that said they measured up to 54mm which would be pushing it clearance wise for me.
I’m currently running 2.1 Thunder Burts. Any other tires to be aware of?
I had the Terreno XC Race 2.1 - it is a terrible tire. Very slow, side knobs for whatever reason make it stubborn to lean. I took it off after a hundred miles.
It has the same basic issue as the Terreno Dry gravel tire - the tread is very thick, probably twice as thick as a Mezcal. I have a picture somewhere of the two tires cut apart showing the difference I’ll see if I can find it.
Maybe consider the Rene Herse Extralight Oracle Ridge or Fleecer Ridge - 48mm/55mm but the RH sizing is inconsistent. I’ve head the 48mm is large and the 55mm is small. BRR has only tested the Endurance casing and based on it’s performance the EL casing should be around as fast as the E25 Race Kings.