right, so my wheels have some sanshin hubs with mavic MA 40 rims.
the rims are stickered at 650w. the tires are 700x28. what the heck
are 650w rims?

no idea about 650w (watts or width according to google) - as far as I'm aware if the tyre is 700 by X then the rim is a 622 ETRTO standard size.

https://sheldonbrown.com/tire-sizing.html#isoetrto

MA 40 should be 622mm / 700c
Maybe someone just slapped on a sticker. Don't assume everything by the sticker. They're just stickers and can be misleading if someone slaps another one on.

I have just purchased a lightly used wheelset with Mavic Factory Decals that say MA-40 650W.
I thought they were 650 wheels, but are closer to 700C. I have not tried any tires on them.
I would appreciate any information about what they are.

Thank you,

I have the same labeled wheelset on my '86 Bottecchia and it's 700c. Maybe close to 27" but definitely not 650b.

This from a Velospace page: Mavic MA40 ("EMR7" Stainless Steel Eyelet Hard Anodized Treatment 650W) https://velospace.org/node/12635
That doesn't solve the mystery.

Neither does this previous (2007) BF thread: https://www.bikeforums.net/archive/in.../t-272175.html

Please note that this current thread began in 2008 and was asleep for two years until yesterday.

I appreciate your help and it is nice to be able to revive a 2 y old thread like this when needed.
I figure better than starting another one when this one is dead on topic.
I wanted to clear up the notion that the stickers are "just slapped on".
They are on both wheels and are absolutely Mavic factory.
Thanks, Jon

Another year later. I got a set of these wheels for a mountain bike I was building into a touring setup.
Just put a tire on them for the first time, REALLY tough to get set, gave up on 2 wire beads before I nuzzled a kevlar RiBMo on there (which was actually completely painless), but anyways, seems to me from this experience, they're 26"/559, sitting pretty with a 26x1.5" on there now, though that happens to go against everything I've read about the wheels since picking them up, but thankfully it's what I was looking for.

Google shows that MA-40 rims have been available in 26" and 700 sizes. And other sizes, such as 27"???

The sticker says "EMRT Stainless steel eyelet hard anodized treatment 650W".

A search finds references to 650W with Mavic MA40 rims which are obviously 26", 700c and 27" therefore "650W" can not be a size.
I guess it is the type of hard andodising treatment: "hard anodised treatment 650W" . Confusing.

A mystery tire size would refer to a tire made for an obsolete rim.