Well, a 27" rim is 630mm diameter, 650B 584mm, a 46 mm difference. With the same tire profile, the standover height would be lowered by half of that, or 23mm which is damn near an inch. Granted, 650B tires are traditionally quite fat, but Rivendell are selling some which aren't a lot fatter than a wide 700C tire one would commonly find on a tandem, as their new Saluki uses 650B wheels. Not sure I think the Saluki is going to be a profitable project, but I sure am happy it has caused Rivendell to make 650B rims and tire more easily available.
Regards,
Jerry Moos
hersefan@comcast.net wrote: I'm not sure the math is correct - a large 650b tire and a 700c tire have very similar diameter - not as much difference as the post suggests I believe.
Also, be sure you're not going by "modern" conventions regarding standover. In my experience, not nearly as much standover is needed as is often suggested. But if you take my advice and your singing soprano, forget you ever read this post!
Mike Kone in Boulder CO
> At 6/5/2005 10:58 PM -0400, Roy H. Drinkwater wrote:
\r?\n> >Jerry Moos asked:
\r?\n> >>Anyone ever installed 650B wheels on a bike designed fot 27"? I'm
\r?\n> >>looking at a tandem which is very attractive except that the standover
\r?\n> >>height is 1/2" to 1" too high with 27" wheels. 700C wheels will only
\r?\n> >>lower it 4mm, so I'm considering 650B. That should lower it nearly an
\r?\n> >>inch, but will the rims then be too low for the brake pads? (It has MAFAC
\r?\n> >>cantilevers). Anyone ever done this?
\r?\n> >
\r?\n> > Just finished one up tonight, I had a pair of DiaCompe 750's but
\r?\n> > they were still too short for the rear. I had to make a Sheldon drop
\r?\n> > bolt, see .
\r?\n>
\r?\n> Might work, but the brake arms *may* foul the existing canti pivots.
\r?\n>
\r?\n>
\r?\n> Mark Stonich;
\r?\n> Minneapolis Minnesota
\r?\n> http://mnhpva.org
\r?\n> http://bikesmithdesign.com