If Rene Herse 32s were tubeless, I’d give them a go, but I’m reluctant to go back to light/thin tyres with tubes, especially as we move towards winter here in the UK.
Thinking logically about it, I should probably save the speed focus for the TT bike, and just fit out the groad for long-distance comfort, which would lead me to the 35s. Mentally, though, that seems a step too far. The commuter would be an ideal place to experiment, but a) the max clearance is 28 and b) I’d rather not deal with a puncture on the way to work!
I will ponder until the current rubber has seen better days…
Thanks for the reply!
1500g is a nice weight too.
Do you feel tangible aero gains at high gravel speed (30 to 45km/h) with the 105% tire rule ?
Or it is quite marginal compared to let say a standard-wide/30mm external and 40-45mm deep carbon wheels. Thanks!
This is a question in which I’m interested and to which I’ve never found a really definitive answer. How much do you lose from breaking the rule of 105, and at what speed? It would be really helpful if anyone knew, for example, if you were running 32mm width tyres on 27mm external width rims, that would cost you x watts at y kph. My own sense is that the loss is probably pretty marginal at typical long ride speed (27-29 kph average) but it would be useful to know.
Hi Julien,
If someone can say he feels tangible aero gains on a round tubed bike, with maybe even a bikepacking pack or two on the bike (even when riding on aerobars) and that even specific for the tire and rim combo and even more specific on aero rims (which may be of current profile but not really wide enough) vs aero rims which are wide enough… I guess this person ist lying.
“Feeling” Aero is hard. There has to be a whole package in place that you can feel - “yep, this is a fast bike”, even when you are not doing 1 to 1 and back and forth comparisons between setups on the same day.
But that’s not to say that the effects are not there. It’s just so, that you can’t say “oh yeah, I’m riding 35 km/h with x watts, that is faster than yesterday on the other wheels…” That’s nonsense, even if you are riding on the same course, on the same bike, with the same tires but just different wheels. Because of the wind. Which is always there, even if you swear “it was nearly windstill…”
Having said that - there were situations on my recent 1900 bikepacking trip over mixed terrain and quite some flat tarmac also - where I thought… “Ok, that feels nice and probably sails a bit”. But this is purely anectdotaly.
I’m still in the process of honing my abilities to use the aerotune test (https://aerotune.com/) to the fullest and reducing the error margin on this. Needs practice, the right testing venue, patience and many test runs. But is very interesting indeed! And also the aerotune test still needs more improvements (especially in regards to discerning tire crr). But I and aerotune are getting at it…
Thanks for the detailed answer.
Oh nice, keep us updated on your Aerotune experimentations!
I am/we are really interested in knowing more on the subject.
I did run Soma 700x48 on my Lynskey but didn’t keep them on for very long since I threw on knobbies for a few gravel events. I think I’m going to put them back on this weekend
Sometimes stiffer carbon rims actually would cause more of an issue with this. Because the rim doesn’t deform as much at the road it then shifts out of plane more. It also can cause some issue with brake rub in rim brake bikes. Not sure this would cause much issue at the chainstay though.
When I’m riding off-road I pair these with 40mm WTB Raddler tires.
But on-road I run the same wheels with 28mm Conti GP5000 which come up at ~30mm owing to the 25mm internal rim width of the Rovals. They’re incredibly comfortable in the road configuration (60/65 psi front/rear).
I can only achieve the same level of comfort with my Enve 3.4 SES wheels on my road bike by pairing with 27mm tubeless tires and running them at 50/55 psi front/rear.
Wider tires seem waaaaay more comfortable to me. I don’t think there’s any noticeable difference in speed, at least not the speeds I ride at (25-35 km/h depending on how lumpy it is).
A better option than the hypothetical tubeless Rene Herse 32s are the tubeless Conti 5000 32s. I’ve been using these exclusively for my road setup on my gravel bike and have been very durable. I use them on a mixture of pavement and gravel and haven’t had any flats with thousands of km (actually on my second set). They roll very fast and seal perfectly.
That Flo test, if valid, don’t make the case for aero wheels at all.
They are saying that the difference between their 49mm wheel and their 77mm wheel is negligible. Even the difference between 49mm and 77mm + disc is hardly anything.
And 25mm tire on the 49mm rim versus the 32mm tire is about 1/2 watt. So 105% rule is meaningless?
Their chart shows only 1m20s to 1m30s savings over a Mavic Open Pro on a 40km TT.
Those figures sound, intuitively, about right to me.
I’ve just listened to Chris Boardman commentating on the world TT champs for the BBC, noting that 80% of all air resistance was down to body position, with clothing coming in next, followed by wheels and helmet. As an aside, he noted the shaping of the actual bike was almost an irrelevance until you’re looking for those last few seconds at the highest level.
If we (generously) proportion say 10% of air resistance to wheels, then a 90s difference over a 50 minute event (not for me lol), or 3%, seems about right.
Much less scientifically, over a long, steady ride I notice perhaps a 0.3-0.4kph average speed difference between my bike with alloys and my bike with mid-section carbon rims. Now, there are dozens of differences between the bikes, so this is hardly a robust finding, but a just over 1% difference at ‘cruising’ speed likewise seems to make sense to me.
I just expected there to be a much bigger difference between 49mm wheels and 77mm wheels or 77mm+disc. I also expected there to be a larger difference between 25mm and 32mm non-aero optimized. That’s all.
If they don’t factor in yaw at all, then maybe that is the issue. I know Zipp was famous for their “time saved in a 40km TT” charts but they probably always used the 15 degree part of the chart to make their claim.
I have 50mm wheels on my bike. They seemed to have made a good bit of difference. It’s hard to quantify but I set a lot of new PRs and got KOMs after I got the wheels.
I think about safety too. How well your bike deals with road anomalies will depend on the size of the tire relative to the anomaly. Larger tires are thus a benefit. I don’t want to rely on constant attention for my safety, because I know that isn’t possible (whether due to fatigue, or getting distracted by a car, or having the sun pop into your eyes, or being in a group and left with no option but forward). I use 650b with Rene Herse 48mm tires. I have no problems keeping up in group rides. If I have 48mm Rene Herse knobbies instead of slicks on the bike, then it feels like I have to pedal a bit harder.
Do you think it applies to say an aero road bike vs. a traditional steel bike? Or do you think TT bikes are fast because of position and not so much tube shape?
The reason I ask is my 2020 Domane is so much slower than my 2011 Shiv…but there is a huge position difference that is hard to quantify. It’s literally like 18mph vs. 20mph with the same effort. My 40K bike (Premier Tactical) with the skin suit and aero helmet is another mph faster FWIW.
Also, when it comes to actual rides on actual roads…the domane is my go-to. I can take evasive action with aplomb, it has great brakes, and I feel the bike will take care of me. Vs. the TT bikes who don’t really care about me at all and don’t even slow down much less stop.
Well I think this too (that position and frame make a difference but position more) but Boardman…who probably knows a thing or two about going fast…apparently doesn’t.
How can that even be true? I mean…he rode the Lotus! Not some round tube steel job, right?
Well it’s almost an irrelevance for me and probably 95% of this board, but if you’re going for the hour record or world title, then the very small gains attributable directly to the frame are relevant. I think Xavier Disley puts it well:
So for some people, 2,3,5w gains make all the difference in the world, but for most of us, they don’t, and that’s what I think Boardman was getting at.
