Anyone running 650b in a gravel bike?

700x40 vs 650x47 are my options too. I have Nano 40s on the 700s and Rutland 47s on the 650s. The former definitely feel faster, certainly on shorter rides. The Rutlands are way more comfy though and, especially after a long day on rougher terrain, get their own back by causing less fatigue, thereby letting me enjoy a bit more speed.

Not sure that helps much but my default is the Rutlands and it's the Nanos that are saved for particular rides.

IMHO no

My bike just feels great set up 650b

It does of course depend on what gravel riding means to you. But once I’m off road the bigger tyres always feel better and they are fine on road

My current set up is 650b for off road. Vittoria Terrano Dry in the summer. Something with more tread in the winter.

The same bike said has a set of 40mm gravel king sk on 700c rims. These are better on the road

What I don’t know is whether 50mm 700c would be better as they don’t fit

My Cervelo Aspero GRX1 came with 650b x 47mm set up which was fun for hooning off road around on. At the time also had a second road wheelset set up 700x 35mm for broken road / dusty & smooth conditions.

After 18 months I sold on the Easton EA70AX 650b wheels, got a set of Roval Terra CL Carbon 700c x 40mm now. For me that's a faster set up than 650b and considerably lighter weight which makes the bike feel pretty rapid tbh, the Aspero is the racy end of gravel as it is.

700c on Nanos for winter.

650 cannonballs for summer.

Yeah I’d probably agree the bigger tyres feel better off road, but then again going on my exp I’m comparing 47mm 650s with 35s on 700, so 40s or 42s may bridge that gap

I’d say my riding is a mix of on and off road, certainly nothing too extreme.

the only thing that’s swaying me towards the 650s right now is the carbon, but I’m not sure how much that’s going to make a difference.

Yup - 700s for road and ‘fast’ gravel (GK SKs), 650b for normal or unknown routes. Am a fan of the Rutlands - about to get the 2.1s as my frame will take them and found the 47s a bit skinny after 50mm Cinturato Ms  (which are also pretty good, just struggled a bit with the slop over the last couple of months.

With my Planet X tempest I have 650B carbon wheels with 42mm tyres. Also have both a carbon and alu set of 700cc wheels, carbon are set up for road with 38mm slicks and the alu have 42mm Scwalbe G One Ultra Bite.
I don’t really notice a huge amount of difference speed wise between 650B and 700cc, but I am running same width tyres I suppose. My riding is a mixture of road, gravel and single track. With the Tempest I could fit 48mm tyres on the 700cc rim, so I’ll probably do that towards the end of spring. When I’m on the 42mm Ultra Bite I don’t feel I need wider tyres, just interested to try it out. For this time of year, with the mud and soft conditions, the Ultra Bite work well.

Being a bit of a weight weenie, I’d probably go with what ever is lightest.

I have 700c road wheels and run 650b gravel wheels (with Vittoria Terrano Dry tyres) to make for a larger contrast in the riding experience than simply putting gravel tyres on the road wheels.  No regrets with the decision.

Nope, not tried 650b at all - I like big wheels and I cannot lie.

Gradually upped from 700x35 to 700x38, then 700x42rr/47fr. Frame swap then allowed 700x50 both ends, a big increase in volume over previous sizes and a corresponding increase in comfort off-road. No idea how compromised they are on tarmac but can’t say I care, given the comfort.

My TwinSix Rando handles so much nicer on 650x47 than 7000x40.  Maybe because that's what I'm used to on it (29er for all my other bikes).

I would have thought the only benefit of 650b is if it allows larger tyres than 700c. If you can fit 700x50 then I can't see the point of a smaller wheel

Think 650b wheels can be lighter and stronger? But a fair point about main benefit being tyre volume. Have a light set of Token 650b wheels with 50mm Cinturato's on mine, and never really felt an itch to put 700's on it that needed scratching. Really like my current set up.

 I’m comparing 47mm 650s with 35s on 700, so 40s or 42s may bridge that gap

I'd say 42-45mm 700s matches a 50mm 650 off-road in many ways but a lot depends on the tyre itself. I had 45mm 700 WTB Riddlers back to back with 47mm Byway 650s and though the named size was almost the same, the volumes were very different and the ability to use pressure that let you hit roots etc off-road at speed was better on the 650s. Volume is king off-road.

I've also found tyres like G-One Speed 50mm 650 to be really fast on road, only the overall wheel weight as a minor drawback Vs 32-40mm 700. I've used G-One 50mms for mid-distance audaxes quite happily, when riding at a steady pace and not jumping around accelerating I don't think wheel weight is an issue, yet comfort really is over a long ride.

It depends on what sort of comfort you want too. A bigger OD wheel has roll-over advantage on bigger bumps. A higher volume, lower pressure tyre has advantages on fast high frequency bumps like bad lanes at 20mph. The dynamics of all that mean there's a crossover of that amplitude and frequency thing in theory but I still found pros and cons of the 700 x 40 or 45 vs 650 x 47 or 50. Thing is, a 700 x 45 isn't that much larger OD than 650 x 50. Obvs the best could be both, 700 x 50, but then you're into longer frames and forks, heavier wheels etc.

After going to and fro between rim size on a few gravel bikes for a long time starting with Col de la Vie 38mm and Panaracer 42mm 650Bs I've only got 650 on my gravel bike. A 700C wheelset would be a bit more spirited on tarmac but I have an audax bike and a road bike for that kind of thing. For rides that mix unpredictable lanes, byways and smooth open road on a bike that feels at fairly quick and at home on tarmac I'd take 650s, or I'd have the whole bike redesigned for 700 x 50 and accept the longer wheelbase handling, slower feel of the bigger wheels, etc.

If you can fit 700×50 then I can’t see the point of a smaller wheel

Only real point is the frame and fork geometry influence of the larger wheels esp if you want to fit guards (I do on bikes like this). The wheel will be up to 10% heavier but that wouldn't influence my decision, it'd just add up to make the bike feel a bit further away from a road bike.

I'd say that's the main advantage of 650B here - building a bike that can do a lot more than a road bike but at times still feels quite road bike-like.

i've run 650b x1.9 on my camino , stuck a Rudy fork on front so can be ridden hard offroad, unfortunately i dented my rear rim, so been consdering the 650b ribble carbons wheelset. currently got on dt swiss ln gravel 700 with 38mm tyres, its alot bumpier but quicker on tarmac.

think i'll go back to 650b soon, i prefer the feel of the monster truck tyres.

I have 650b on mine and they are certainly more comfy off road. Planning on getting some big wheels though as I don't use it off road that much.

After trying quite a few combos I much prefer 650b. I really like the nimble and fast accelerating feeling, and the extra volume and off road capability, plus it has acceptable speed on road (rather than optimal, so depends on your priorities). I tried 700x50 on the Camino, and while I liked the volume and capability, it felt too cumbersome and the front wheel flopped noticeably, and it wasn't as nimble. My abiding thought was that while the tyre fits, it was a little beyond the ideal geometry envelope of the frame. As Jameso said, full mudguard fitting is important, and there's no room with 700x50. I'll be trying 2.1-2.2 fast XC tyres when it gets a bit drier, and I think it'll feel good (without 'guards).

For a comparison of 700x50 and 650x47 see the pic below. Both wheels resting on the ground. Quite a big difference. EDIT - and also a decent change of BB height.

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Anyway, happy with mine...

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I'm running 3T Discus Plus on my Arkose X with Hutchinson Overide 47 in the summer and WTB Sendero 47 in the winter. The bike obviously handles better offroad but feels noticeably slower on road than even the super cheap stock wheels with Nano 40's on. As I use this bike for commuting, often in the dark, I prefer knowing I can hit stuff and not worry but my next gravel bike will be more of a 'fast and light' spec for using on roads, light gravel and summer smooth offroad - basically a hybrid! That will definitely have 700c.

I reckon a good rule of thumb on a gravel bike is: Double chainring = 700c x 40    single ring = 650b x 50

Just get the nice carbon 650b rims. I haven't got any real experience of 700c wheels on my Genesis Fugio (apart from trying a set of 700x40 wheels when I first got it, but that was just a quick spin around the block), but I have been very happy with my 650x47 & 50mm tyres. Currently running 650x50 Pirelli Gravel Ms which are great. I mainly ride forestry roads and the odd bit of XC singletrack with short road sections linking it all together.

I had 45mm 700 WTB Riddlers back to back with 47mm Byway 650s and though the named size was almost the same, the volumes were very different

I've just fit some 45mm Raddlers, they come up closer to 40mm.

I don't mind as they are my "fast" gravel tyres, but the 40mm ones I bought in the same sale went straight back.

Personally I can't get my head round 650b on a gravel bike, after we all went on the 26in to 650b to 29in journey on our MTBs. A drop bar bike intended for covering ground offroad, but it has smaller wheels and lower-volume tyres than my MTB? What's that about?

@faustus what 700x50 tyres are you running?

@dc1988 - I was running Maxxis Ramblers, which are great tyres. The ones in the picture above are Goodyear Connectors, but they both had defects in the bead which made them wobble! As I said, back to 650b now though...

I'm running Riddler's which i like but at 45c with plenty of clearance I'd like to try a bit more volume. I don't do especially gnar gravel riding so those Goodyear's look like quite a good tread pattern

The tread on them looks ideal, just check they don't have a wobble, mine were a manufacturing defect. So keep the receipt!

A drop bar bike intended for covering ground offroad, but it has smaller wheels and lower-volume tyres than my MTB? What’s that about?

The MTB should have the biggest wheels + tyres, agreed. The larger wheel size journey makes sense but that's for a bike that's only meant to be used off-road. For me / my uses a 650B drop bar is about that compromise between road and off-road where you're basically on a road-like bike but want to be able to ride byways, tracks and shortcuts etc - the larger tyre volume helps off-road, lack of tread and low overall wheel size + weight (vs a 29er) helps on road. More all-road than off-road. 650B is also better ime for carrying a load for touring/bikepacking etc. Having tried them all out on a few variations of gravel bike it makes sense for my uses, but it's such a grey area. No one answer.

It’s probably a mistake to apply logic to this stuff or justify personal choices

I love the way my gravel bike steers with 650b. One of the things i like about is that you need to steer it round things but it’s great to steer round stuff