At 11/10/2006 05:43 PM -0500, Joseph Bender-Zanoni wrote:
> The first is that they are heavy. If you want a heavy strong rim,
> use a Mod. 58. The second is that for all the weight, the alloy is
> a bit soft and they are not all that strong. No eyelets.
They apparently had one advantage that a tiny minority of riders needed.
Back when the Concaves were in production, I knew several people who went on some very "Ian Hibell" type tours. Minnesota to Point Barrow to Patagonia or "circumnavigate the lower 48 and include the Canadian Rockies on a tandem" type stuff.
After using the Mod 58s (still my favorite rim) they switched to Concaves. If you whacked a big honkin' blip into the more malleable Concave, you could remove the spokes in that area, wrap several layers of rope around the rim and a signpost or such and straighten the rim out enough to carry on. Might work on a Mod 58 or the rim might crack.
OTOH the 58s were probably less likely to deform in the 1st place. But experience taught them that the Concaves were less likely to leave them stranded.
They were also stiffer, so spokes were less likely to fatigue.
I used the wider version of the 26" (559mm) Concave on the back of our recumbent tandem for about 8 years. Despite heavy loads, a lot of unpaved roads and only 36 spokes we never broke a spoke, due to the stiffness of the rim.
Mark Stonich;
Minneapolis Minnesota
http://mnhpva.org
http://bikesmithdesign.com