TheBlackPumpkin

Looking for a good set of tubes for some 650bs I had made. 18.6 mm internal width so I bought some grand prix 5000s for tires at 25 mm. Now, I found some tubes that are 18-25mm, but kind of worried about stretching to the top end. Should the ones I bought be fine or does anyone else have further recommendations? I had it recommended to me that I look for some 25-30s or 32s but finding anything in that width range on a 650b is very difficult. Hell, finding something like I did was a miracle it feels like. Has to be a presta if possible. Thanks in advance.

Rolla

I routinely run tubes whose upper limit is the same as my tire width. You'll be fine.

TheBlackPumpkin

Roger that. I suspected as much but, I've had so many issues getting my bike to a ridable state recently just wanted to make sure.

ThermionicScott 

The Schwalbe SV12B would seem to be perfect for what you're doing. It can be ordered directly from their site if you have trouble finding another distributor: https://www.schwalbetires.com/bike_tires/tubes/finder

TheBlackPumpkin

Thanks I'll check them out if the ones I ordered fail on me.

Camilo

Just a big FWIW and YMMV... I always use a tube that is rated for a size smaller than the tire. Your tire is 25mm. The tube is 18-25. I would not hesitate to use that tube, but even more so, tend to use a tube in which the higher number is less than that, whatever happens to be available as the next size smaller. I do this with all my bikes - road, gravel, mountain. To me, they are easier to install (less bulk to get folded and pinch) and I haven't experienced any increase in fragility that I can point to. Plus, for carrying a spare, they fold up smaller into the seat pack. I have gone so far as to use a tube from my road bike supply (23-25mm tires) with my gravel bike tires (35-37mm). I normally wouldn't go that far, but they never failed.

I use 26" tubes in a 650B/27.5 tire.

70sSanO

In the past 6/8 years I’ve moved to the 25-32 tube in a 25mm tire. It might be a result of my own expectation, but the tubes seem to hold air better. But I rarely get flats.

The downside is trying to literally stuff the larger tube into the tire without folds.

Note: These are 700c tires/tubes.

John

ThermionicScott 

+1. My preference is for a tube that has to stretch the least to fill the tire. And then a thin/lightweight tube in that size. That way, I get light weight, but a very consistent wall thickness in use.

My experience is that when you put the minimum amount of air into a tube so that it takes on a round shape (usually about as much as you can put into a Presta tube with your mouth), it's still narrower than the size of the tires it's rated for, so it's not that hard to stuff into a tire at that point. (You can get a crude estimate for this width by measuring how wide the tube is when rolled up flat, then applying some simple math.)

Some examples:
CST 700x25-32C tube, used in a 28mm tire. 26mm flat, ~18mm round.
Schwalbe SV14A 559x40-54mm tube, used in a 38mm tire. 37mm flat, ~25mm round.

Is this overthinking things? Oh, probably.

Camilo

Nah, there's no such thing as overthinking the minutia of bike stuff. Could you post your spreadsheet?

ThermionicScott 

Haha, I would, but my notes are on paper, and pretty soon into it I figured out that I could do much of it in my head.

I noticed after a while that my preferred tubes were about the same width (when rolled flat) as the tires they were going into, so that has become my crude rule of thumb for minimum size. Another benefit of sizing up the tube is that a patch doesn't constrict as much of its circumference as a skinny tube...

I'll probably have to break that rule when I size up to 50mm tires on one bike -- I'm not aware of superlight tubes that are also 50mm+ wide when flat. Oh well.

BlazingPedals

OK, I have to ask. What is the point of having a 650B x 25 tire? I thought the advantage of 650B was to fit fatter tires in a road frame, which then morphed into mountain bikes getting them.

Rolla

650b wheels have been around since LONG before the wide tire thing caught on. Some touring frames, road frames, smaller frame sizes, women's frames, etc., are made for 650b, but don't have the clearance for wider tires, and/or their caliper rim brakes require narrower rims and tires.

BlazingPedals

Are you sure you're not talking about 650C?

Rolla

The same is true of those as well, but 650B was pioneered on French randonneur bikes of the 1920s and 30s, then was later used on women's bikes like the Motobecane women's mixte in the 60s and the Raleigh Portage, a touring model from the 80s. They didn't have especially wide tires, although some frames could accommodate 38s with fenders. Point being, 650B X 25 may not have the same advantages that we use 650B for these days, but it still might suit someone's purposes.

Rolla

Same post in every thread. Nothing suspicious here.