In rec.bicycles.tech Peter Cole wrote:
:On 4/17/2011 9:54 AM, David Scheidt wrote:
: In rec.bicycles.tech Peter wrote:
: :On 4/17/2011 5:01 AM, Tosspot wrote:
: : On 17/04/11 09:27, Blue Heeler wrote:
: :
: : snip
: :
: : Cost to treat 4 tubes - about $26 made up of $20 green slime sealant,
: : $2 scalpel $4 for 8 large tube patches. I guess there is also some glue
: : in there too, but I buy my patch glue in bulk and still working my way
: : through the 100 tubes I bought 5 years ago.
: :
: : Doesn't that stuff go off after a while? I tend to 'collect' glue tubes
: : and have had a couple of *unopened* ones reveal themselves to be a solid
: : rubbery block.
: :
: : Although, thinking about it, I've had some 5 year old ones be fine on
: : first opening. Maybe it's in the manufacturing process.
:
: :The problem is that the tubes are often not gas-tight. Since they
:
unopened) are sealed at the screw top end, the only place for them to
:
ass gas is at the bottom crimped end. What I do, even with new,
: :unopened ones, is make another fold at the crimp. That seems to help. I
: :also carry 2 glue tubes in my patch kit. In a gas-tight container the
: :glue will last indefinitely.
:
: You're repeating Jobst's 'this is how they did things in the dark
: ages' spiel. Modern cement tubes are heat crimped. They're normally a
: multi-layer sandwhich. It's not perfectly gas impermable, and some
: are just defective, so there is a shelf life.
:Perhaps, but my experience has been that some even recently purchased
:tubes dry out for whatever reason. There's usually enough slack to
:double over the tube at the crimp. I haven't had one dry out after doing
:that, but I haven't exhaustively tested, either. When still-sealed tubes
:dry out, it's obvious that it's the crimp that's at fault, either by
:design or manufacture, doubling it up can only help.
: For those who patch at the work bench, cement is available in larger
: containers. An 8 oz jar with a brush in the lid costs a few bucks,
: and lasts a long time[1], as ong as the cap is screwed on after use. If
: it dries out, the usual cause is the solvent has evaporated; it can be
: thinned with hexane. If it's over heated, it can vulcanize itself
: into a blob.
:
: [1] the tubes in a patch kit are 5 grams, so about 50 of them.
:
:Unlike Jobst, I don't patch at the bench. I just don't have enough
:flats. I've had perfectly good luck just patching on the trail/roadside,
:which is my usual practice, weather and conditions permitting. I always
My usual practice is to carry a spare tube and a patch kit. If I flat
(which happens very rarely around here), i put the spare tube in. The
tube with a hole doesn't go back in the saddle bag, it's strapped to
the rack. That's a clue I need to fix it, which I do prety much
immediately. I think that I've only got one spare tube at the moment,
so I don't let them pile up. I only get flats in the rain, so
patching on the roadside is no fun.
:carry an extra tube or two and a patch kit with 2 tubes of cement. The
:belt and suspenders approach takes little extra effort. I've found that
:if I don't patch a flat immediately, I'll forget about it only to
:rediscover it when my next one happens and the "good tube" happens to be
:no so good. I haven't had Jobst's problems with failures of freshly
atched tubes, I just patch 'em and ride 'em.
JObst's failures are from refusing to properly use cement, and a
refusal to admit there are things he doesn't know anything about.
It really does need to dry before the patch is put on.
--
sig 6