Tom Sherman wrote:

Chalo Colina wrote:

Cathy Kearns wrote:

My
husband and I needed two different stashes of tubes at home. I have 650c
wheels, and I can tell you, you don't want 650c wheels.

My wife and I often ride together, her on her bike with 700x28 tires
on 20mm wide rims, and me on my bike with 700x60 tires and 38mm wide
rims. We have to have different sized tubes with us. I might be able
to swipe one of her tubes if I were riding one of my 700x40 equipped
single-speeds, but she would have some difficulty using one of mine.

That little detail is not enough to make me want to use the same size
tire as she does.

Does not your wife weigh about 1/3 Chalo?

It wouldn't be circumspect of me to discuss that. You can draw your
own conclusions:

http://datribean.com/presskit.html

She's about 5'8" tall.

Similarly, having two similar size riders on a tandem with the same tire
sizes and inflation pressures as they use on their singles would be silly.

I was only demonstrating that using the same rim diameter does not
necessarily mean you can interchange consumables.

I used to believe that at a given pressure, tire width should be
proportional to the load (or conversely, that at a given tire width,
pressure should be proportional to load). Observation has shown me
that tire internal volume serves as a better indicator of load
capacity and/or appropriate pressure. My bike with 700x35 tires (32mm
actual) is the closest equivalent I have to my wife's bike with 700x28
tires (26mm actual). Those bikes can probably use the same tubes and
tires if the need arises.

Chalo