Measured width is 40mm. The Strada Bianca Pro HTLR 40 is nearly there as well and faster than the 36. What’s even more impressive is that the pressure is lower… The pressure is relative to the size of the tire:
Really, that suggests that the tire gets increasingly more delicate as it gets larger, because in theory a larger contact patch at the same pressure as a smaller contact patch should have lower rolling resistance. 'Course lots of other factors come into play as well, not least of all aero, but my feelings are that not discernible for most at anything below around 18mph.
This distinction becomes apparent when riding something really big with really low rolling resistance. I have a set of Conti Rake King RaceSport Tubeless 2.2 which have 15.5W rolling resistance at 25PSI, roughly half the pressure of my gp5k and nearly the same rolling resistance. There’s a 40 mile flat loop that I do most Sundays that’s mixed gravel and pavement and if there’s no wind, they’re roughly about as fast and way, way more comfortable. Also fun to ride around the streets of Oakland because one can just roll through and over all the potholes and curbs and whatever.
Yeah it’s okay if they don’t come, I had a similar experience with some tires from BTD coming like 6 months late. If they aren’t here by April I will get some Challenges
Hmm Silca is telling me 56/56 PSI roughly for tire pressure on a 34 mm tire, 180 total system weight (bike + rider), road bike weight distribution, and “moderate group ride” and “worn pavement, some cracks” setting. Does this seem high?
Regarding the 32-35mm tire chat and specifically GP5kSTR vs GP5kASTR…
As it has been explained to me, aero does factor into this chat a bit if we are talking efficiency. Part of the reason things have settled on 30mm for pro-tour rather than 32s that technically roll faster is that 30 seems to be the sweet spot where you get the best rolling resistance and give up the least drag. In the case of the ASTR tire, the real-world difference is more than just the rolling resistance. Aero difference between the 35 and 32 is going to be extremely small, but not to be completely ignored. Nobody is actually going to be able to physically parse the differences between the two tires in the real world, but if we’re talking efficiency over a 200km ride, it’s something to consider.
After feeling the two tires in my hands, the ASTR is noticeably heavier. I need to actually weigh them, I might get a chance to do that today.
After putting a full year on the 32 GP5kSTR on 200km rides, crits, and just general road riding… I definitely will be going down in size to the 30s for summer time racing as no matter where I had the pressure there was some give and take in races between what felt best cornering vs what didn’t seem to lag accelerating. My hope is that the 30s will be just a bit better in this regard. Time will tell.
Circling back to the Challenge tires… my mixed feelings regarding the SB in 36 continue. The are absolutely “fast enough” for long road rides (especially ones with some light gravel or dirt road). My experience has been opposite of Heath’s in that the handmade casings from Challenge have been very durable. Only one cut that had to be plugged and that was on a 40mmm Getaway that hit some shale at a high speed. Anecdotal ride quality puts them better than the GP5k and they seem more tolerant of a wide range of pressures go get a good feel on pavement.
Anyway… all are great, but each has it’s subtle advantages and disadvantages.
seconding this. found the same thing not only with the GP 5k TR 30 vs 32 mm but the Vittoria Corsa Pro 30 vs 32 mm. 28 and 30 mm seem to be the sweet spot for those tires. haven’t tried the AS TR tires or the Corsa Pro Control tires unfortunately.
I’ve really liked the Schwalbe G-One RS 35 mm, and y’all gonna hate me for this, I’ve only had good experiences with the 35 mm gravelking. the above recommendations look great too
STR is the road racing tire. It’s got less puncture resistance, is slightly lighter and has less wet group than the ASTR. The ASTR is the “all season” road racing tire which comes in the larger size, has better wet grip and slightly better puncture resistance.
In testing, the various sizes of ASTR vary in terms of tread thickness, puncture resistance and wet grip, oddly, with the 35mm having the best wet grip. There’s some speculation about the various compounds being used.
I’ve no expectation that my experience with punctures should extend out to others. I ride rough glass-strewn streets every day with tires more delicate than I oughta. Something about the combination of wet and glass didn’t work for the Challenge SB. I loved it for a summer tire, but the Conti is faster still in the summer and nearly as nice.
I’m going to have to interject some caveats into this. For protour bikes riding at protour speeds on protour wheels, aero is going to make a measurable difference. Drag is proportional to the square of the speed of the object. This year at the tdf Jonas Vingegaard averaged over 25mph for the whole goddamned race. That means he spent lots of time at way over 25mph.
For other speeds on other bikes with other wheels in other conditions, YMMV. I’ve seen lots of testing for gravel races that aero absolutely matters, but that the time lost with the much bigger tires is outweighed by the benefit of the bigger tires. Any given tire is going to perform better or worse depending on the width of the rim it’s mounted to, wider rims being better. The dude at Silca did a bunch of testing that suggested that a smooth tire/rim interface was more critical than tire size.
That’s a long winded way of saying that for the riding I do, which is mostly comprised of flat mixed terrain in various wind conditions going 18mph on average, I don’t give up a noticeable amount of wattage on aero between the 32 or the 35. When I was doing the local practice crit, I’d hit the front going 28-30mph and pushing something like 350W for not very long. I don’t do that any more, but if I did, I’d probably want to be on a 30, which is what I have on my road bike that I hardly ride anymore.
If anything, riding solo vs in a group (like a pro tour rider) makes aero even more of a factor. Sure, at higher speeds there’s more aero counter forces to overcome, but it matters quite a bit at low/lower speeds too.
