Need help deciding on a new carbon wheels for my gravel bike. I’ve got a 3T Exploro Racemax. I can fit up to 46mm on 700c or 61mm on 650b.
Plan on using this bike for unbound again and some other rougher races where I ran the 2.2 in race kings. However, I am also using it for all other gravel races where I would probably run 40-45s.
I don’t think I lose any speed with the 650bs but worry a little bit with 650b and smaller tires closer to 40mm.
Any recommendations? Appreciate any help!
700c. Almost no one, certainly at the front, is on 650b and there’s a reason for that. Don’t chase the why, just stick with 700c.
I was in a similar situation before Unbound this year…was debating 650b’s w/ 2.1 ThunderBurts vs. 700c with Pathfinder 47’s (measured out at 45).
Initial test rides with the 650b’s down in Bentonville had me convinced that was the right answer…they were awesome on really chunky stuff and descents.
But after a few more rides (including group rides and some road sections), I think they were just too sluggish. And I also figured there was a reason no one was doing it on any scale.
I opted for the 700c with the Pathfinder 47’s and they were great. Never felt like I needed anything wider / fatter and they were plenty fast on the smoother, faster sections of gravel.
I would also opt for the 700c 
40-45s are more than enough width and with the correct thread you should be good to go.
I’ve always liked the Nano’s WTB for gravel events.
Thank you! Any thoughts on hooked vs hookless?
For gravel, I wouldn’t worry about…either is fine with those size tires and PSI.
Hookless often has a wider rim wall at the tire interface, which can help reduce pinch flats. It’s not really a hookless thing, just most of the newer hookless rims have gone this way. If buying new offroad wheels, there is really no downside to hookless in my opinion. At road pressures, it’s a bit more of a debate.
40-45 are more than enough? not sure i would go that far. Adequate yes, more? no
From personal experience, on a gravel bike, I think 40-45s are perfect 
But of course everyone has their preferences and what works for them. No right or wrong answer here.
I’d also go with 700c for the same reason that I ride 29" MTB wheels instead of 27.5".
Another plus of the 700c is that with a 25mm inner width, you can run anything from a road tire to an XC MTB tire depending on what fits in your frame. I’ve run 650x2.4" in the past and they felt slower than my 29x2.4" tires. 
There was a noticeable difference in rollover too.
Another thing to consider is BB height. If you ever want to run a smaller tire, it’s going to be harder to find something nice that’s smaller than 47mm in 650b and your BB height will start to get pretty low too.
@BillyWaldman to each their own. I’d have no issue running 45s in the conditions where I’d take a gravel bike. The original post mentions that their frame can only fit 700x46, so I think this is a valid point here.
I rode 650B wheels for a while, and I think they were most useful for getting a wide tire before bike companies started making frames that could take 700x45c and larger tires.
Four or five years ago, you were frequently looking at running either 700x40c (or 700x42c at most), so being able to run a 650Bx47c was a pretty large improvement. But with any new gravel frame starting at 700x45c minimum, there’s just no real advantage to riding 650B. The 700c wheels roll much better over irregular gravel terrain like potholes, washboards, etc.
I’ve got an exploro racemax which i bought pretty much exclusively because I wanted to have two wheelsets - 650b and 700c - and swap between them.
Realistically - the 650b wheelset with super fat tires never gets used.
In situations where i do use them - I wish i was on a mountain bike.