Does 650B still make sense when you can fit 700x45 tyres?

Especially for light weight issues concerning cyclocross / touring bikes & parts.

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gorkypl
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by gorkypl

As noted in some other thread, I am in process of designing custom frame allroad/gravel frame. My current bike cannot take more than 38mm of rubber, and this is one of the improvements I am looking forward to - I am targeting 45mm 700C tyres as max in the new frame.
I am wondering if with such capacity it still makes sense to maintain 650B tyres compatibility?

The ability to run 700C and 650B tyres on the same bike requires certain assumptions on BB drop. To accomodate 47mm 650B tyres with enough pedal to ground clearance, BB drop cannot be greater than ~70mm. On the other hand, for 700C tyres between 35 and 45mm, the optimal BB drop is between 75 and 85mm. Everything in between (like 72mm) will be a compromise of some kind.

Based on my current experiences I plan to switch between 36mm slicks for allroad touring and something like WTB Byway 44mm for all the mixed terrain.
So, do you think I could see any benefits from going even wider on 650B? Does it make any sense at all if I can run very wide tyres on 700C?

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spdntrxi
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by spdntrxi

700x45 will probably give you 650x50 atleast maybe 2.1
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jemima
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by jemima

Perhaps a more personal feel/preference than just benefit.
I've settled on a 2.2 (measuring 54/55) in a 650b as I just like that extra width/cush and tyre rolling feel.
Started on a 42mm, but then went through 48mm, 2.1, now 2.2.

When riding with the 700x45 on I've often thought what it would be like on a 700x2-2.2, if the frame was designed to have a similar 27.5x2.2 trail figure and a lower bb to suit, like you mentioned.

Main thing standing out there to me is the tyre weight that size.
I'd only be wanting to ride lightweight options on a low weight wheelset, so the spin-up and slow maneuvering isn't too bad.

Am aware of more toe overlap in that case also, but it doesn't bother me.
Would rather have a frame to suit with more of a 'road' like feel, than a long front-to-centre + short stem setup.
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emotive
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by emotive

I would say it depends what terrain you will ride. Based on you planning on 2 sets of tyres it sounds like you plan to ride a wide variety of terrain. If you want one tyre to do everything I think 700x 45 is a good choice. If you have two wheel sets you can optimize the the tyre to match to the route more.

I’ve ridden both 700x44 slicks and 650bx2.2 on my gravel bike with a 68mm BB drop. The larger diameter 700x44 has much slower steering than the 650b. Off road the slower steering makes for stable handling, but on tarmac it feels slow to turn.

650b x 2.1 has the same diameter as 700 x 35. If you choose 700x 36 for road and light gravel then 650b x 2.1 for rougher off-road routes then the steering will be agile both on and off road.

650b x 2.1 gives you a lot more air volume (suspension) than 700 x 45mm. Depending on your weight and how rough terrain you want to be able to ride will determine whether or not you want that extra suspension.

BB clearance with 650b is rarely an issue for gravel tracks, fire trails etc. it’s only singletrack routes where BB clearance becomes a factor for me, but that makes up less than 1% of my riding.

Marin
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by Marin

I'm running Conti Race King 2.2 in 27,5" so it makes sense for me

Karvalo
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by Karvalo

gorkypl wrote:
Fri Oct 08, 2021 9:10 pm
As noted in some other thread, I am in process of designing custom frame allroad/gravel frame. My current bike cannot take more than 38mm of rubber, and this is one of the improvements I am looking forward to - I am targeting 45mm 700C tyres as max in the new frame.
I am wondering if with such capacity it still makes sense to maintain 650B tyres compatibility?

The ability to run 700C and 650B tyres on the same bike requires certain assumptions on BB drop. To accomodate 47mm 650B tyres with enough pedal to ground clearance, BB drop cannot be greater than ~70mm.
If that's as big as you want to run, then no. There's no point going 650x47 if you can run 700x45.

As with the other replies, the question will be do you want to have clearance to run 650x2.1" or 2.2" MTB tyres?

gorkypl
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by gorkypl

Karvalo wrote:
Sat Oct 09, 2021 12:35 pm
As with the other replies, the question will be do you want to have clearance to run 650x2.1" or 2.2" MTB tyres?
Yeah, good point. I don't know, but probably not... I was thinking more about potential advantages of 650x47 vs 700x45 - but without intention to go wider.

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Karvalo
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by Karvalo

gorkypl wrote:
Sat Oct 09, 2021 1:58 pm
Karvalo wrote:
Sat Oct 09, 2021 12:35 pm
As with the other replies, the question will be do you want to have clearance to run 650x2.1" or 2.2" MTB tyres?
Yeah, good point. I don't know, but probably not... I was thinking more about potential advantages of 650x47 vs 700x45 - but without intention to go wider.
Cool. I think 650x47 is only relevant if you've got a bike that is clearance limited on height and can only fit a 700x40 ish or a 650x47. Again I can't see any reason to bother with 650x47 if you can run 700x45.

Honestly my prediction would be that 650x47 fades away into a small and outdated niche as more and more new single track/adventure capable bikes will fit 700s up towards 50mm and 650s in MTB sizes. Then most new race gravel bikes will still fit 700x45 and not care about 650s.

spdntrxi
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by spdntrxi

one thing to think about is that if you use fenders... going to 650 generally will let you use wider tires and still use fenders. This is what I do in the winter.
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justRideIt
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by justRideIt

spdntrxi wrote:
Sat Oct 09, 2021 3:33 pm
one thing to think about is that if you use fenders... going to 650 generally will let you use wider tires and still use fenders. This is what I do in the winter.
Which 650 tires do you run with which fenders?
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spdntrxi
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by spdntrxi

I can run 42mm 650b with my portand design works fenders ^^^
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Jdadour
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by Jdadour

Karvalo wrote:
Sat Oct 09, 2021 2:31 pm

Honestly my prediction would be that 650x47 fades away into a small and outdated niche as more and more new single track/adventure capable bikes will fit 700s up towards 50mm and 650s in MTB sizes. Then most new race gravel bikes will still fit 700x45 and not care about 650s.
100% this. I'm new to gravel as of last year, and from what I gather, 650B got popular years back when people couldnt fit more than 700x38 or 700x40 on their bikes.

On my Carbonda 696 (which can fit up to 700x50), I recently tried out a 650bx48 wheelset to compare against my 700x40. The 650bx48 was more twitchy, less stable, and less confidence inspiring than the 700x40. It was clear and obvious. In my opinion, theres no benefit to having 650b unless you are really limited on tire clearance. 700x45 or 700x50 is just going to get even better in terms of handling and stability.
Last edited by Jdadour on Thu Oct 21, 2021 2:05 am, edited 1 time in total.

Jdadour
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by Jdadour

Karvalo wrote:
Sat Oct 09, 2021 2:31 pm

Honestly my prediction would be that 650x47 fades away into a small and outdated niche as more and more new single track/adventure capable bikes will fit 700s up towards 50mm and 650s in MTB sizes. Then most new race gravel bikes will still fit 700x45 and not care about 650s.
100% this. I'm new to gravel as of last year, and from what I gather, 650B got popular years back when people couldnt fit more than 700x38 or 700x40 on their bikes.

On my Carbonda 696 (which can fit up to 700x50), I recently tried out a 650bx48 wheelset to compare against my 700x40. The 650bx48 was more twitchy, less stable, and less confidence inspiring than the 700x40. It was clear and obvious. In my opinion, theres no benefit to having 650b unless you are really limited on tire clearance. 700x45 or 700x50 is just going to get even better in terms of handling and stability.

CampagYOLO
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by CampagYOLO

If your gravel bike is N=1 then 650x47 has roughly the same ride height as 700x28 meaning no adjustment of the seatpost each time you swap wheels.

I'm currently using 2.2" tyres on 650b wheels and loving it compared to 40mm tyres. I just roll over things like tree roots and have to be less discerning with my lines.

If you're just riding on open gravel though, I'd stick with 700c.

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FlatlandClimber
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by FlatlandClimber

My take on this is a definite: "yes".
I run my gravel bike with the following four tires:
- Specialized Pathfinder Pro 42c x 700
- Pirelli Cinturato Gravel M 45c x 700
- Contiental Race King ProTection 2.1 x 650b
- Schwalbe Rock Razor 2.35 x 650b

With my gravel bike being my go anywhere machine, and my winter bike, I want it to be capable.
The Pathfinder is a great do-it-all tire, but performs best on hard pack, road, forest paths, light gravel, and cobbles.
It doesn't perform well in Sand, deep mud (especially on climbs), and when you need more cushioning (rocky or rooty descends).
The Gravel M has a more aggressive Profile, marking it perform better on mud and muddy climbs, so when it rains a lot, I tend to use this tire. This is not nearly as good as the Pathfinders on hard pack or road, but keeps you afloat on mud and sand a little better. It doesnt add noticeable cushioning.

The Conti RaceKing, a MTB tire, is one of the best tires I know. It is actually quite fast on road and hard pack, but performs better on mud than the 700c, and has a lot more cushioning. With the added width, you can run it at super low pressure, it descends well, and floats much better on sand.

The Rock Razor is really a "speciality tire" for me. It is "okay" on the road, but slow in comparison to any of the aforementioned. However, last winter it had rained for weeks on in. The forests had super deep puddles, all the mud was extremely soft, the brooks had overflowed and it was really a mess. Then, the aggressive thread and the width was a true blessing. Otherwise I just couldn't have ridden many of the paths and trails at all.
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