Moisture

What do you guys prefer on your gravel bike, and why?that the tire widths are the same?

mstateglfr 

Why would the tire widths be the same? That largely removes the point of going 650b.
A 650b in a narrower width(typical 700c width range) could be useful for shorter riders.



But to play your game, I would go 700c. I have no desire to drop my bike 19mm closer to the ground and the 700c wheels look better on my frame size.

tdilf

700

sloppy12

27.5

ClydeClydeson

675((b+c)/2)

Moisture

mstateglfr

They wouldn't.. well. They usually are.

Reason being, I'm curious to hear the difference between the two from perspective of diameter and how it affects handling or frame geometry.

Going 650b for wider tires is a widely established idea.

sloppy12

I think his point is generally it would make zero sense to stay with the same width tire if its even possible on the same frame. a 650bx38 on a bike that came with a 700x38 would be a pretty decent drop on the bottom bracket. Now if its a entire different frame with different geo any way whats the point of the comparison?

tdilf

Maybe a visual would help

mstateglfr 

You edited your initial post after I responded. My response made sense for what you initially asked.
Between your initial questions and your edited, I really dont know what you want to know because they arent close to similar questions.

But going off your now edited questions- I prefer 700c. I like the look of larger wheels with the larger frame, I have always used that size, that size feels fine to me for spinning up to speed, I dont want to spend many hundreds for a 650b wheelset and tires just to experiment, and the tire width I use right now is perfectly fine for how/where I ride.

Polaris OBark

If you just want to know what the effect of a slightly smaller wheel is, all other things being the same (like tire width), that is a reasonable question, so I will try answer that one.

It will change the handling of the bike in such a way that it will feel a bit more responsive or twitchier with respect to steering, and perhaps slightly more responsive to initial acceleration. It will also increase your propensity to have pedal or crank-arm strikes.

Polaris OBark

The idea in tdilf 's figure is that ideally you want the outside diameter of the tire to be the same, as this preserves the handling properties of your bike while enabling you to use wider tires. So if you normally run 700c x 28mm tires, you would want to run 650b x 48mm tires to preserve the handling properties of the bike.

On the other hand, you can use wheel diameter to tweak ride quality. If you have something like a heavy-duty touring bike, which is built around the assumption that you will ride it fully loaded, you might want to use smaller wheels and tires to make the bike more responsive when unloaded.

unterhausen

my next gravel bike will take 650bx48 or 700x40.

650b might allow bigger tires than that. I was going to go with 700x2.1", but that's a pretty big tire.

tangerineowl

Last two years been back and forth.
Main observation is a similar-width 700c rolls a bit faster, and has a better 'attack' angle across rough stuff to take down the hits a little.
This is using 1200gm wheelsets for both sizes, and a preference for lighter+fast-rolling tyres.

Saying that, if just cruising/exploring around at a slower pace, the wider [frameset max 2.4] 27.5 is a lot of fun, with its float and cushion.

At the moment am seriously considering a custom frame that will allow 29x2.2 [designed around 44mm-2.2], but still have the same trail figure and bb height as the current ride with 27.5x2.2.
Chainstay a little shorter also [kinked seat tube]. This will have more toe overlap, but am fine with that.
Basically looking around a 430cs. 285bb. 72hta. Same reach and stack.

rdecredico

29+

pbass

I like both, and have both, but for my size and frame size (small-ish) I like how 650b handles offroad. Navigating through techy stuff, switchbacks, etc--way better for me with the smaller wheel size. The extra cushion from bigger tires and low psi is also nice of course. That said, on pavement or any dirt that's really smooth, I don't really find an advantage with one over the other.

Moisture

mstateglfr sorry for the confusion. Allow me to re iterate.

I see lots of options out there with 700c x 45 as well as 650b x 45 . Im trying to understand why one would make more sense over another?

Also, I see 700c gravel bikes out there which claim to also fit a 650b wheelset without offering enough tire clearance to fully compensate in diameter. Would such a change not throw off geometry figures enough to avoid doing so?

mstateglfr 

Very few gravel bikes that come stock with 700c tires cant fit a wider 650b. It exists, I think All City Cosmic Stallion is an example(or used to be), but its hardly common. Usually the 700c maxes out at 40 or 42 or 45 and the 650b goes to 48. Some max out at 50mm for 700c and 2.1" for 65b.
But having the 650 max the same as 700 max isnt exactly typical.

And while you are the posterchild for Dunning Kruger, even you know that geometry would change if a smaller wheel with smaller tire were put on a bike designed for a larger wheel and tire combo. That doesnt necessarily mean the geometry is ruined now as the user may like the changed geometry. Who knows.

chas58

Correct. As a generalization, its gonna screw up the handling to do that on the same frame. You can't make that big a difference without affecting stability, trail, bottom bracket height, etc.

So, when going to a smaller wheel you should always use a larger tire to keep the overall diameter the same.

In my experience, increasing the diameter adds more stability, more ground clearance and makes the bike better off road. Smaller diameter can make the bike more agile, less stable, increase pedal strike, and reduce toe overlap.

But again, the goal is to keep the diameter the same.

I'm not sure what you are getting at. AFAIK, the only OEMs that make a 650x45 and 700x45 wheel options on the same bike do that on different frames. They use 650b wheels on their smaller frames so that they can keep the angles, geometry, and handling the same as their larger frames. Toe overlap is also an issue with 700c & with a short wheelbase agile bike in a small frame size. Maybe this is what you were referring to - doing this on different frames?

rourkefan

650b is good for us short kings tho

Moisture

Actually, my Trek Verve Ebike has 700x45 wheels. I feel like they are too big for me. I dont think 650b would be a good idea geometry wise, but the bottom bracket is unnecessarily high on this bike so it could be worth a try just for experimentation sake.

I

Moisture

I found a wheelset to play around with that looks like it may fit my e bike- https://www.trekbikes.com/ca/en_CA/b...rve-2/p/28299/

can anyone confirm that the hubs and brakes etc will all fit? Tire clearance could be an issue. Otherwise, if I can get this guy to ship from US, would it work ?

https://www.pinkbike.com/buysell/3245170/

fishyfishy123

My road bikes are 700C, so for my gravel bike I thought it would be fun to get one that came with 650B wheels and 47c tires. Nice to have some contrast, and I love all the cushion I can get with tubeless setup.

chas58

Even better if your OEM uses 650b in their small sizes and 700c in their larger sizes

Clipped_in

OP, I run 700c primarily for two reasons. First, nearly all of my gravel riding is mixed-surface (pavement and offroad). Secondly, tire and parts availability. While 650b is now quite common, is doesn't compare with the availability of options with 700c.

sloppy12

Looks like it should work.