BVC-CHAT Tires, spokes, irons, and tandems...

[Jeff Ackerman]

At 02:32 PM 9/26/2007, you wrote:
>Before Rob at Aggieland built up my rear tandem wheel on the Surly, 
>I was popping several spokes a week.  Since then, no problems at all...
>
>Tom


Doesn't surprise me at all. That's why I learned to do my own wheel 
building - precisely because I was breaking spokes on a tandem using 
factory wheels (even with a heavy 48 spoke tandem 
wheel).  ...designed my own light-weight tool to remove the cog set 
on the rear wheel to permit spoke replacement on the rear drive side 
on the road (assuming a custom frame with a spoke holder - or as some 
do, tape a few extra spokes to the outside or inside of the seat 
tube). If you search under my name (and hypercracker) on the web site 
below, you'll see someone mentioning my name with a photo of the tool.

http://ohmelovelo.dnsalias.org/tools/tools.html

For that matter, if you want to see that tandem that was always 
breaking spokes until I rebuilt the wheels, check/search under 
"Bushnell" on the German web page below. I have no idea how they came 
to have a photo of my bike on that page, but they do (one of a kind 
paint job, and you don't often see a tandem with campy record components).

http://www.sudibe.de/renntandem_fotos.html

...you can see the spoke holder if you look closely at the last photo 
on the bottom right on my tamu page below. ...doubles as a chainstay 
guard. Those spoke holders used to be more common on higher-end 
touring bikes, but I haven't seen any in years.

http://jma.tamu.edu/personal/Biking/Default.aspx

...back to tire removal,
For what it's worth, being the admittedly anal person I am, I checked 
in Brandt's book - one that every good wheelbuilder will recognize. 
On page 126, he also says that a wheel will shrink in diameter by up 
to 2mm after the spokes are tensioned and the spokes will stretch up 
to 1mm. I just checked a spare continental clincher of mine and the 
wire bead area is 4.3 mm high (happen to own a digital caliper). So 
if you started with a tire sized so as to just properly seat on a rim 
without spokes, then if you tensioned the spokes to where the rim 
shrank by 4.3 mm, it would completely fall of one side of the rim 
with no help what-so-ever. What Brandt (and I) are mentioning is that 
the 2mm is half way to that point, and even if the shrinkage isn't 
that much and even if the spokes did have some initial tension, only 
a small amount of shrinkage is enough to make the difference between 
allowing the tire to be removed without an iron and requiring an iron 
for removal.

The bottom line is that if you don't have any problems with your 
wheels, I certainly wouldn't bother paying to have them re-tensioned 
just to save you from carrying a tire iron, but if you have had 
problems, then it would certainly be worthwhile to find a good 
wheelbuilder to tension the things optimally and you might end up 
killing two birds with one stone.