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650b wheels on 700c gravel bike

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Cyclocross and Gravelbiking (Recreational) This has to be the most physically intense sport ever invented. It's high speed bicycle racing on a short off road course or riding the off pavement rides on gravel like :The Dirty Kanza". We also have a dedicated Racing forum for the Cyclocross Hard Core Racers.

650b wheels on 700c gravel bike

Old 07-02-16, 02:55 PM
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trail_monkey
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650b wheels on 700c gravel bike

I got a fisticuff 700c drop bar gravel machine sporting 700x32 knobbies at the moment. I just read an article from Ted on the Riding Gravel site about some new 650b offerings in the tire world and putting them in place of his 700c wheels. This got me to thinking. I went to the garage and removed my 650b wheels from my Jamis and installed them on my fisticuff for fun. With the 27.5x42 straight treads, it was comparable in bb drop and spindle clearance to ground. While my fisticuff has the ability to handle wider tires than a standard road bike, doing so on my 700c rims will just raise my bb drop that much higher which can have negative effects on geometry. I thought about building some new 650b wheels and an extra cassette and just swapping wheels depending on what I intended to ride. Maybe put road tires on my 700c grail rims and use my 650b set with larger 42+ tires when I ride gravel. I had thought about getting larger tires when I wear out my 32s (which won't be long) to give me a smoother ride on rough gravel but haven't been sure about the increased overall wheel diameter adding to the bb drop and standover height. Does anyone have an opinion on this?

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Old 07-02-16, 07:03 PM
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ehhh...I wouldn't go as far as swapping wheelsets on a per-ride basis, you'd need to mess with the brakes and have to worry about uneven chain/cassette wear. Seems like a pain.

Better to just have one wheelset and use that for everything. I think you should experiment with bigger 700c tires first. Some people like them and some prefer the smaller 650b size for anything wider than 32/35mm. I found 700cx40mm sluggish without any improvement (on gravel) compared to 650bx42.

I'm not sold on bigger tires and the higher bb having a non-zero effect on geometry, but that might be for another thread.
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Old 07-02-16, 07:15 PM
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Originally Posted by Spoonrobot View Post
ehhh...I wouldn't go as far as swapping wheelsets on a per-ride basis, you'd need to mess with the brakes and have to worry about uneven chain/cassette wear. Seems like a pain.

Better to just have one wheelset and use that for everything. I think you should experiment with bigger 700c tires first. Some people like them and some prefer the smaller 650b size for anything wider than 32/35mm. I found 700cx40mm sluggish without any improvement (on gravel) compared to 650bx42.

I'm not sold on bigger tires and the higher bb having a non-zero effect on geometry, but that might be for another thread.
I got discs so brakes are no issue. So you are saying that 650b with 40+ size tire is noticeable improvement but same size/width tire on a 700c is going backward? Or am I misunderstanding what you're saying?
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Old 07-02-16, 07:38 PM
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Hmm. It's not strictly a step backwards as you do get a minor improvement (see below) but IME the same width tire is going to feel more sluggish in 700c compared to 650b. This really depends on your riding style and if you do any competitive riding. I like to chase PRs on strava and do the occasional group ride so the sluggishness of the 700cx40 was obvious compared to the 35s I had been riding and very obvious when compared to the smaller 650b wheelsize.

You do gain a slight improvement in rollover ability with the larger wheelsize but this seems to only really matter in mountain biking where you encounter a lot of oblique obstacles (roots, natural ledges and large rocks) to ride over.
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Old 07-03-16, 07:21 AM
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Originally Posted by Spoonrobot View Post
Hmm. It's not strictly a step backwards as you do get a minor improvement (see below) but IME the same width tire is going to feel more sluggish in 700c compared to 650b. This really depends on your riding style and if you do any competitive riding. I like to chase PRs on strava and do the occasional group ride so the sluggishness of the 700cx40 was obvious compared to the 35s I had been riding and very obvious when compared to the smaller 650b wheelsize.

You do gain a slight improvement in rollover ability with the larger wheelsize but this seems to only really matter in mountain biking where you encounter a lot of oblique obstacles (roots, natural ledges and large rocks) to ride over.
I understand what you're saying. When the time comes to replace my existing, I will probably just look at the various 700x40/42 tires out there. I don't race. I like the way my 32s roll but on a bumpy gravel road they beat you up quite a bit. I had been thinking for some time of replacing them with a considerably bigger tire. But I am not sure going up a few mm is going to be that noticeable so I am contemplating making a bigger jump to anything 40 or above. Maybe something like this Nano 40c | WTB

You never did say whether u were running 650b or 700c? Which do you actually prefer and use?

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Old 07-03-16, 08:25 AM
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But I am not sure going up a few mm is going to be that noticeable
Oh ya, I barely noticed the difference from 32 to 35 but going from 32 to 40 was quite obvious and a huge improvement. I upgraded for more comfort as well, the races/rides I was doing were very technical and the 32s/35s just weren't cutting it for me.

Compass is coming out with a 44 smooth tread tire in 700c:

and there are the Bruce Gordon Rock N' Road in 700cx43 if you want another option for knobbies:
Rock n' Road Tires 700c x 43mm ? Nothing is better than a bike that fits

My regular road bike is 650b running 42mm Hetres, I ride this mainly on pavement but do a bit of dirt and gravel as well. I also have a dedicated gravel/cross bike that I run 700c 40mm WTB Nanos like you linked above. I prefer the second option for our rainy season and any sort of competitive riding as the knobs give better traction than the smooth tread Hetres.

If I could only have the one bike I'd run the 650b and swap tires when the wet season hits but I've got the luxury to have multiple bikes right now so I've been indulging.
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Old 07-03-16, 09:00 AM
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Originally Posted by Spoonrobot
If I could only have the one bike I'd run the 650b and swap tires when the wet season hits
The thing that scared me away from building a gravel bike on a 650b chassis was the limited availability of tires for anything other than MTB tires. I know there is several but not near as many as 700c plus some of the ones that were out there (like the Soma cazadaro) were not tubeless ready so that narrowed the field even more. But that being said I think I might prefer the 650b size with a 42+ size tire over the 700c wheel. I think ,as you already stated, the "roll over obstacles easier" advantage has no bearing in anything except mountain biking and even then I myself am running a 650B mountain bike so............ Honestly if I don't pursue anything in 650b beyond this thread and our conversation, it will simply be a money issue. If I was to build a set of wheels up I would have 400-600 dollars in them and I would want to be damm sure that I really wanted it and that it was not just an impulse buy and then 6 months later switch back lol. I have been known to change things on an impulse lol. I must be the manufacturers dream
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