Abu Mahendra

This seems like the latest fad, and i have to ask, does the marginal size difference between 584 and 622 make a significant difference? Tire selection? There is no shortage of 622 gravel tires. I own 406 and 451 wheel bikes, and the size difference is marginal, and the size difference is bigger than 584-622. So, i really wonder. There may be other ancillary benefits, but size alone, come on,, folks!

prathmann

I agree that the change in diameter is pretty minimal. But if you're starting with a frame that was designed for narrow 700c (622mm) wheels and would prefer to use wider tires then converting to the 584mm rims may allow you to do that. I.e. the frame with 700c wheels may only permit tires up to 23mm in width before the tire starts to hit the rear brake bridge or front fork crown but could allow tires of up to 40mm width using the smaller 584mm wheels. Of course you also have to consider the brakes if they operate on the rims.

Spoonrobot 

Often you can get a 15-20% bigger tire by going to the smaller wheel size. The smaller wheels also ride differently and have a different feel. I much prefer 700c myself but only came to that conclusion after spending significant time on the same bike running 650b. There's also a size and physiology component. Smaller riders I've worked with almost universally prefer the smaller wheel size when using bigger tires. 40+mm tires are much easier to pedal on a smaller wheel. There are some riders who cannot tell the difference and as you noted some who cannot tell the difference even when there is an extreme disparity. It's silly to think that some people think 10mm of stem length is huge, 5mm of seat height is the difference between pain and comfort but 1.5 inches of wheel diameter is nothing. Just another option, if people don't find it useful it'll fade away like all the other ineffective bike trends.

IMO the marginal size for equal width tires is large enough to be considerable.

clasher

I've been thinking about doing it so I could put some wider tires on a couple of road bikes but now that I have a cross bike that takes wider 700c tires the justification for an expensive new wheelset has gone down a lot... the only decent rim-brake wheels would be built around the pacenti brevet rims, I can't find anything else that is similar to the open pro rims that I would be replacing, I have no desire to build up a heavier wheelset than the one I am thinking about replacing. I could also see building a 650b disc wheelset if one has a modern "endurance" bike that only runs 30mm tires... probably could fit 42mm or even wider 650b tires in it and take into some good off-road situations.

5teve

Slightly more tire/air volume in the same overall diameter, more or less, is a great thing. More comfort, more control, unless you race and every gram and second count, it's hard to find a downside to rollin' 584. I even like it better aesthetically. On the smaller frames I ride (54-ish top tube) a 650bX42-50 wheel/tire just looks less monsterous than 700c wheels with tires of similar volume. Fewer compromises to a small bike's geometry too, less toe overlap. Really, for me, there's no downside.

LesterOfPuppets

Not really the latest fad. It's been popular with randonneurs, tourers and other proto-gravellers for quite some time.

ThermionicScott 

Even when it comes to weight a case can be made for 650B -- for the same extrusion, the rim will be lighter, the spokes shorter, and you can do without a couple, leaving the tires. My 650B bike rolls on 300g tires and 100g tubes, which would not be horrible on a 700C bike, and I'm sure there are lighter options out there.

Facanh

"does the marginal size difference between 584 and 622 make a significant difference?" Yes it does, and it's not that marginal.

I've heard that for smaller riders 700C can feel a bit too big, but I can't comment on that since i'm 6 feet.

The true benefits of 650B come when you try to jam a big tyre in a drop bar bike. MTBs use a wider bottom bracket, they have longer top tubes, and slacker head angles, long forks with small headtubes. Gravel or adventure bikes are just tweaked road bikes.

Grab a road bike frame, tweak the geometry slightly, then you get a gravel/adventure frame. Now try to design it to accept a 700x47-50mm tyre. It's not going to be easy. At the back, you have the 68mm bottom bracket WITH bigger chainrings, that limits you a lot. So unless you do something like a chainstay yoke, or an asymmetrical dropped chainstay you simply have to lengthen the chainstay a lot. Then you get to the front. You're going to get a LOT of toe overlap with a big 700C tyre and something like a 71-72 degree head angle, and shorter top tubes compared to MTBs.

650B makes sense because of the smaller diameter you can easily retain the road-ish geometry with big tyres.

DarKris

When I found out about 650b conversions it was from the position of being a clyde who was having trouble with 700c wheels and having a very tight budget at the time. I'm ~350lb and I had a bike that could only comfortably fit 38mm tires on 700c rims, and said rims were constantly falling out of true/breaking spokes even at 36 spoke count. I bought a pair of Weinmann XM280 rims in 650b that were 36h for ~$140 total. Had them for about 2 years and only broke one spoke and had some minor truing/redishing done. Also my front wheel survived me falling forward on it after a failed manual attempt.

As for my bike I was lucky that it was able to fit up to a 47mm knobby and 50mm slick 650b tires. As it stands now, even though I have a spare 700c wheelset, I see myself sticking to 650b (at least until the weight goes down).

JonathanGennick 

Yes. It makes a difference. For me the move from 700c to 650b began as a way to fit a 47 mm tire onto a frame designed for 32mm. Since then I've come to appreciate the balance in proportion between frame size, tire diameter, and my own body height.

Riders distinguish between frame sizes sometimes in 2 cm increments such as from 54 cm to 56 cm. Right? So it's perfectly reasonable to choose between tire diameters in the same manner. In an ideal world, tire diameter and frame size would both change and be in proportion up and down the range of sizes.