That was half the info I was looking for. What size tires do the professional time trial racers use?

Indeed.

I have shown you the path. It is up to you to follow it.

The correct one. At least the teams with a grasp of the science behind equipment choices. Others do what they’ve always done because they’ve always done it that way.

I did some quick Googlage. It looks like the pro time trial riders haven't got the memo that fatter is faster. I didn't do a deep enough dive to be completely confident though.

Yeah, there are many factors that can matter. I wore out a pair of Compass (pre-RH) Rat Trap Pass 26er tires. They are the fastest rolling 26ers I’ve ridden and probably the fastest around. I’ve since replaced them with Continental Contact Speed 26x2.0 for my smooth tires (and also use 26x2.2 Race King Protection in mud, where the RTP is worthless.)

The choice to use the Contact Speed is based on their advantages: 1) about 1000x easier to get on and off the rim and seated properly, 2) flat protection layer, 3) less than half the price, 4) seem to handle better on pavement, 5) reflective stripe. There isn’t a large difference in rolling resistance. Really not obvious so not enough to outweigh the advantages of the Contact Speed.

So I would still say the RTP is an amazing tire but it happens not to be the best choice for my rides.

Otto

if the TT road is smooth (like most), then they're using 23c. Nobody is using 28c. But of course weekend warriors say their fat Rene Herse allow them to dominate strava sphere. So there you have it.

I'm not surprised.

I think those events tend to be on roads with good surfaces.

I'm a new convert to fat tires. After decades of 25s, then maybe 5+ year s of 28s on some bikes, I now have 38s on new gravel bike. I can't tell the difference speed/effort wise, but the comfort on crappy urban roads and MUPs with uneven transitions is night and day. Also loving the 1x. 11 cogs with a 40 is way more than enough for me in the area I live. Finally embracing reality over fantasy (my abilities, needs), may lose the drop bars next.

If you do, look into trying out a swept back touring bar like the Nitto Albatross. With standard grips, MTB levers and standard cork bar tape forward of the levers to the stem clamp, you have a great range of riding positions and postures available. You can put the shifters in bar ends and clear the entire bar surface for various sitting and standing positions.

I mostly rode drop bars for the last 50 years but last year’s experiment with the touring bars seems to work better for me. Particularly helpful since I’ve been back to riding single speed for almost a year now, because they give a better range of positions for riding while standing than drop bars do. YMMV.

Oh, yeah. You will probably want a long stem with this type of bar. Mine puts the center of the stem clamp almost 120mm forward from the steering axis.

Otto

So you’re saying the disc brake issue is settled? What about chain lube?

I personally think that 28s are perfect for road cycling. And as that's the only kind of cycling I do, that's the size of tire I've used on my bike for years.

I have spent thousands on his tires and have tested tires in many ways. I currently use a coast down somewhat similar to Jan's method and I also use Rchung application to tease out the real world Crr. One aspect of Jan's testing clearly biases his results towards fat tires-the speed of his tests. The fastest that he tests is 18 mph and usually much slower around 15 mph. Most of my riding is closer to 30 mph. This data is a full year of riding including PBP, posted for those who will call BS. I mount a 23 mm on the front wheel and a 25 mm on the rear, GP5000 with latex tubes.

One myth is the assumption that Crr is a constant. It is not. If anyone does careful testing at higher speeds, it becomes quite apparent.

Another myth is the rolling resistance tests on a drum are close to real world values, although at 20 mph the relative rankings match my testing. In other words, if tire A is better than tire B on the drum, those results are consistent but these rankings can swap at higher speeds.

Since the average speed of of a Tour de France time trial is around 46kph you fall into a unique category given your speeds. Since I am lucky if I average 28 kph on a solo ride, tire width is not as critical for myself and most riders with normal capabilities Jans test parameters fall within my sweetspot.

Is there really enjoyment to be had making up straw man arguments just to knock them down? No knowledable person believes rollers replicate on-road Crr values. Further, how could they given Crr depends on road surface roughness and the range seen in that? It's like saying I'm correcting the myth that a stopped watch tells the correct time.

Gotta disagree with you there. People take these tests pretty seriously, which is why they come up in all these discussions 😝