Gravel bike - 650b or 700?

Both

Actually that's not a bad shout - I have a spare set of non-boost 650b wheels in the garage!!
So I can order with 700's and swap out as needed.

You know it makes sense 😜

yep, ive currently got a 700x38 and a 650x47 bike and makes next to no difference in real world use on the road, IMHO. but id feel way happier with the 650 tyres off road with no suspension
you'll need a 15-12mm sleeve for the front wheel 😉

If you want wide tyres then 650b lets you use reasonably-priced full 700c mudguards if you also use the bike for winter commutes like I do.
Optional 700c and narrower tyres also fit under the same 'guards. I just stuck with 650b tho

I have 35mm 700c and 650b 47mm

If I had to choose one it would be 650b. Way better off road not much worse on road

On the other hand you can run 50mm tyres in 700c and I can’t

Yes both, I got a Free Ranger with 700 x 43’s then got some nice used 650 x 50’s.
Don’t worry about gearing as someone mentioned once. The circumference of the fatter tyre is only a midges dick away from the 700.

You cAn go wide on 700s on the Camino
I got 650b alpha wheels on my Camino it’s bloody great off-road but I stuck a cheeky rockshox on ,
My friends just got one with 700 wheels and it also feels great, ive just bought a set of 700 wheels so can’t comment on difference as yet

I’ve ordered mine with the 700s because I think it’ll help me keep up with my wife 😁

If I really get in to gravel riding then I wouldn’t be against getting another set of 650s but before that I think I’d put a wider tyre on the 700.

If it gets rough enough to need a 650 x 50 tyre then I should probably take my other bike.

But this is a new venture for me so I don’t really know how it’ll work out yet & was a bit torn between which to go for.

Mine *should* be getting built this week assuming my C2Work voucher goes through OK 😃

If only one set of wheels I'd say...

Mostly off road and more than easy fire roads - 650b
More road work/easier fire roads type riding - 700c

Ideally I'd have two sets but I'm running 700s (PX Free Ranger) and while they're capable on all sorts they're sub optimal once things start getting into rooty single-track/bigger bumps.

Totally agree with garage-dweller.

Early days with mine, but I'm finding 650b with 2.1" tires is waaay more comfortable when things get bumpy than the 700c wheelset with 40mm tires and it's a bit quicker on singletrack I think. But it's definitely draggier on tarmac and slower on fireroads. You will be happy with either but it's a compromise and you need to work out what kind of riding you are going to be doing.

I'd probably go with 700c if I had to choose one. You can get 50mm tire on there if you need it

700c frame that can take up to 50mm tyres, best of all worlds/most options

if you are riding with a group of mates all on 700 and you have 650x 47+ you will notice it's more effort to keep up on the hardpack/tarmac bits. if you are on your own it's fine

if I'm out with the UKGRAVELCO gravel gang i wouldn't use the cascade with 29x2.3, It's a blast downhill but a chore to keep up with the skinnier tyres on the flat/uphill. solo rides/bike packing I'm mostly on the cotic though as it's so comfy and forgiving
what I thought about the cotic https://ukgravelco.com/cotic-cascade-review/
and for comparison the Fustle Causeway https://ukgravelco.com/fustle-causeway-gr1-review/
Fearless warlock https://ukgravelco.com/fearless-warlock-frameset-review/

Both here. 700 has GravelKing Semi slicks and the 650 has WRB Senderos. It’s a sort of Summer/ Winter setup for me.

Had a bike with 700x38 and now have one with 650x50. Preferred the 700c tbh and plan to buy a pair for the Trig.

Saying that, I also have a rigid Whippet so have both bases covered I guess? There's not a lot in it.

So about to pull the trigger

Do people really talk like this in real life?

To answer the question, 700c for me on my Fugio. My riding is a mix of canal towpath, gravel tracks and bridleways. No real need for the extra cushioning of wider tyres on 650b wheels.

Do people really talk like this in real life?

Yes.

I’ve both, a nice set of 650b Chris King/carbon wheels with 47 Senderos and the budget 700c Fulcrums that came with the bike on 42 Resolutes.

Rides far better 90% of the time on the budget 700s. If you’ve clearance for bigger tyres on adult sized wheels then go with those - much better all rounders.

All personal preferences but I don't like bigger tyres. Went up to 40c recently and while they were better on rough off road they didn't feel much better on gravel roads and felt a lot worse on the road.
They just feel cumbersome, making steering heavier, and generally feel more tank like. Aware that they may all be positives for many people but I like a lively feeling bike and 33c gives me that.
I don't think they are actually any slower, they just feel it so therefore not as enjoyable for me.

Camino al v1 owner here.
I originally built some 650b wheels for it, but found it too much like my rigid hardtail in character on 50mm tyres.
I now ride solely 700c, 40mm in summer for mostly offroad and 35mm in winter for much higher proportion of road riding when the gloop sets in.
So my answer to OP is 700c unless your commute is proper hard going.

650 for me, road and off-road now I think. I've just got a Warroad 650b with WTB Byways and any loss on road compared to my old Scott CR1-SL (itself a roubaix style bike) is balanced out by the comfort and speed over the really shoddy country lanes around here.

I have had a few of each, a couple of Crox Fe Fer on 700, then a Fugio 30 on 650's and now a Topstone Lefty an 650 x 47 wtb ventures (had a byway on rear but it was lethal on wet trails). For me, 650 x 47 seems the sweet spot for a mixture of road, windfarm tracks and off road exploring on natural paths. It is definitely slower than my road bikes, but not so much it bothers me and I am usually on my own, so pace not an issue.

Both!
Order the bike with 700c and adapt the spare 650b wheels you have in the garage.

I run 700x38 (Panaracer Gravel King SK) on my gravel bike if mainly road riding but swap to 650x47 (WTB Sendero) for more gravely rides. The 650's obviously have more drag on tarmac but pump them up and they're not too bad.

700c and buy a RedShift stem to take some shock out of the front wheel.....

RedShift stem will be cheaper than another set of wheels and tyres....

I'd buy a bike with clearance for big volume 700. 45-50mm capability ideally. Gives scope to size down for smoother faster rides, and size up for fun stuff.

I’d buy a bike with clearance for big volume 700

That's what I've just done. 700x45s are plush 🙂

Completely agree, large frame clearance is really important.
I'm currently riding on 700Cx38 and plan to change to 42's or 45's

I'd love to go up from 38s to 42s or 45s but Panaracer don't make the GravelKing EXT Plus TLC in a wider size than 38 and I need the mud capability in the winter (and I can't be bothered to switch tires from winter/summer).

Anyone got any suitable alternatives?

Thanks all.
Will order the 700 and get some 650 tyres and axle adapter for my spare wheels.