As BRR said in it's conclusion: "The current generation has moved to Schwalbe's Super casings with a Super Ground and Super Race version available in several sizes. As the name suggests, the Super Race should be a bit faster than the Super Ground, while the Super Ground offers a bit more protection"
"...It looks like the Super Race version of the Thunder Burt is racking up quite a few votes and has a good chance of being tested in the near future as well."
Sadly though, the Super Race version of the Thunder Burt never made it to the top of the voting list and it expired from the list last month. I was a little disappointed by this, but I decided to buy a pair of those tyres anyway, particularly as I have an upcoming beach race in April that the Thunder Burt tread is perfect for. However, I wanted to test them first, to check how they performed against the Continental Race King Protection that I already own and have installed on the back of my MTB.
Equipment and test setup
The testing wasn't particularly straight-forward though, because my mountain bike doesn't have a power meter. I only have power meters on my road bike, my cyclocross/gravel bike and my time trial bike. Those are all Shimano Stages left hand crank-based power meters. My mountain bike has a SRAM GXP mountain bike chainset, so the chainset isn't at all compatible with those power meters.
This meant the chainset axle was too long for the Stages 105 left-hand crank arm that I tried to fit on it. It did fit on the hollowtech tech splined axle, both having the same diameter and splines, but it left a gap between the crank arm and the bottom bracket cups. I needed a 5-6mm spacer or washer to fill the gap. I found that a spare set of axle cartridge bearings filled the gap perfectly (see photo above). This was a bodge, but it worked really well. As a result, I got my Shimano 105 power meter successfully working on the left hand side of my Shimano SLX chainset.
A bit more faffing was required to do the testing though: I had to remove my SKS mudguards, which rubbed on the large knobbly mountain bike tyres, and I changed the pedals to my good clipless SPDs too. All in all, it took a fair amount of time before I could get started.
I chose to do the testing with a lightweight (150g) butyl inner tube, just to save the time and mess associated with a tubeless set up. Since I was interested in which tyre was fastest, this approach was fine, because both tyres would be subject to the same additional losses from having the inner tube installed. Furthermore, doing the testing with an inner tube allowed a better comparison with the BRR data, which also used a butyl inner tube for their testing, albeit a heavier-weight inner tube.
Results
The plot below show how the the two tyres compare. I had enough time to repeat the testing for the Thunder Burts, after testing the Continental Race King, to confirm that Thunder Burts really does give lower CRR numbers. Since the two blocks of testing with the Thunder Burts were before and after the testing with the Race King, then I can be fairly confident the Thunder Burts are a better tyre, despite the imperfect repeatability seen in the plot below.
The differences aren't massive, and correspond to only 2-3 Watts at 25 kph, but it's a benefit worth having. Something to be noted is that the Thunder Burts were slightly larger than the Race King, at 2.35" width versus 2.2". In addition, the Thunder Burt was brand new, whereas the Race King was one or two years old and has some Stans sealant residue on the inside. This latter point might be a source of additional losses, I'm not sure, but in any case, the purpose of this exercise was to compare these two tyres ahead of my upcoming race, so these old and used tyres are the ones I would have chosen from anyway.
Also torn between these tires. What's your anecdotal experience been, especially off road?
ReplyDeleteHi Logan, They certainly feel fast off road, and feel faster than my old tyre combination. To be honest though, I don't really trust my perceptions as I think the rolling resistance margins are quite small. Also, I've been dropping pressures for my MTB, on the basis of the testing I've done, from around 25psi for my old tyres down to the 17-18psi, so it's a bit difficult to judge because I've changed two things at once. I've got a couple of KOMs with the Thunder Burt tyres, but that's also not a particularly reliable indicator of anything. The one thing I have been really pleased with though, is that the grip seems to be good, in view of the light tread on the Thunder Burts (albeit only tested in dry conditions). Until now I've always ran a slightly knobbier front tyre, to give me more confidence in the front end, but with hindsight, that might have been unnecessary.
ReplyDeleteAppreciate the thoughts. Very tempting, especially as I'd prefer the 2.35" size vs. 2.2" on the Race Kings for bikepacking. Are they noticeably bigger, or is it negligible?
ReplyDeleteAlso assume pavement performance between them is similar, given the results in the post, but let me know if you notice a difference there, too.
I think for pavement performance, testing like I did here using rollers, or drum testing like is done by bicyclerollingresistance.com guy, is a good indicator of performance on pavement. That is, assuming the pressures are lower than the so-called break-point pressure, above which suspension losses start to dominate. The Thunder Burts certainly feel fast on the road, and qualitatively feel faster (although I only every had a Race King on the back with my old tyre combo, and paired it with a Schwalbe Rocket Ron on the front. So, the switch to 2 x Thunder Burts should be noticeably faster and they do feel it.
ReplyDeleteI did measure the width of both tyres, the Race King and the Thunder Burt. I've lost the measurements though unfortunately, but from what I remember the Thunder Burt was wider, and wider by an amount that was consistent the 2.2" versus 2.35" claimed width difference - which I know is not always a given, especially for tyres from two different brands. I'm the same, and prefer wider tyres around that width.
You're a goldmine of knowledge. Thank you, sir!
ReplyDeleteI believe the discrepancy between Your test result (“The Thunder Burt is slightly faster than the Race Kings”) and that presented by BRB (“The Race King is slightly faster than the Thunder Burt”) is mainly caused by the significant difference in the diameter of the used rollers/drum. While You used two rollers with a diameter of no more than 8.x cm (based on the photo in Your article https://www.morespeedlesspower.com/2022/02/testing-of-tyre-rolling-resistance_19.html), BRB used 77 cm drum (https://www.bicyclerollingresistance.com/the-test). Please note that Thunder Burt’s contact patch knobs are only 1.4 mm high (https://www.bicyclerollingresistance.com/mtb-reviews/schwalbe-thunder-burt-super-race), while Race King’s contact patch knobs are 2.7 mm high (https://www.bicyclerollingresistance.com/mtb-reviews/continental-race-king-protection-e25). In other words, the Race King’s center knobs are almost exactly two times higher than those of the Thunder Burt. Now, having this in mind, consider these Jan Heine’s words: “The problem of the convex drum applies even more to knobby tires, since the drum concentrates the pressure on a small area of the tire tread, rather than spread it over multiple knobs. /… / A small drum will penalize supple tires and knobbies more than a large drum. From what I’ve heard from tire engineers, you need a drum that’s at least 1.8 m (6 ft) in diameter if you want to reduce this effect to the point where it’s no longer a problem” (https://www.renehersecycles.com/tire-testing-lab-vs-real-road/). My point is, that Your very small two “drums” penalize a tire with reltively higher knobs (such as the Race King) more than they penalize a tire with reltively lower knobs (such as the Thunder Burt).
ReplyDeleteIf this is true, then using rollers with even smaller diameter than 8.x cm, or using only one 8.x cm roller instead, would make hysteretic difference between the two tested tires bigger. On the other hand, increasing rollers’/drum’s diameter would minimize the difference and, at a certain point, eventually make the difference disappear. Based on Your and BRB’s testing I’m pretty sure that on the aforequoted as-close-as-possible-to-the real life-conditions 1.8 m (6 ft) drum the Race King would outperform the Thunder Burt even more.
The conclusion is very clear: in real life conditions, the Race King is faster tire than the Thunder Burt.
Thanks for your comments. I think what you describe makes sense. I can see how the smaller diameter rollers might penalise tyres with taller knobs to greater extent than tyres having shorter knobs. However, it's still slightly speculative in my opinion. Your final statement confidently concludes that in real life conditions the Race King is faster than the Thunder Burt. However, unless you actually have real life data for both tyres, you can't make that assertion. You might be right, you might be wrong, but we need real life data to be sure - and real life good quality test data is very diffcult to obtain with good quality, precise test protocols. As a final word of caution, I would be careful about believing what's written by Jan Heine. I'm not a tyre or rolling resistance expert, so I'm not in a position to critique his blog posts about tyres. However, I am an aerodynamics expert, have nearly 30 years of aerodynamics experience, and when I read his blogs posts on gravel bike aerodynamics there is a lot nonsense and misinformation in what he has written. For me, that puts a big question mark over his credibility.
DeleteI agree with you totally about the speculative nature of my final conclusion because yes, only real life good quality test data can proof or disproof it. In that sense my final conclusion was clearly overconfident - thank you for reminding me of that!
ReplyDeleteI am not a tyre or rolling resistance expert either. I don't even have a background in natural sciences. Still, that doesn't prevent me from critical thinking, and as a critical reader I can't swallow many claims made by Jan Heine. I only quoted him, because the idea of »penalizing rollers« he published in one of his blogs made perfect sense to me (as it does to You as I gladly see!). If the idea had been published by You or anyone else instead, I would have quoted if for the same reason.
I also think I'm in a position to express gratitude to You for performing rolling resistance (and other) tests and kindly sharing valuable data with us who might not all be as qualified as you are in this field. Thank you very much and keep up the good job!
Thanks, that's very nice of you to say. You're absolutely right about the merits of being a critical reader, and it sounds you're like me, that we're able to think about problems like this, think about how they could be solved and what the potential pitfalls could be of certain approaches. Despite what I said about Jan's aerodynamics credentials, I think his comments in that tyre testing article seem valid to me. I still have some doubts about his test data because I know some rolling resistance experts have expressed big reservations about his rolldown test techniques, but what he says in that article is a very good explanation. Thanks again for your comments though, I really do appreciate it. A lot of testers I've talked to on internet forums tend to react negatively and defensively when people question their test techniques, but I try to be avoid that reacting that way. I think it's a healthy aspect of science in general, that studies are published, researchers are transparent with their data, and the strengths and weakness can then be discussed by the wider community. In this case, the observations you made about the possibility of roller size affecting one tyre more than another tyre is something I hadn't considered previously. Maybe that is indeed why the results seems to be slightly different to the Bicycle Rolling Resistance results. I would love to do a real world tests at some point in the future, to get real world data, but I need to find the time and enthusiasm to do a difficult test like that.
Delete