Re: [CR]Tubulars..valve stem tilted

(Example: Framebuilders:Pino Morroni)

From: "dddd" <dddd@pacbell.net>
To: "Classic Rendezvous" <classicrendezvous@bikelist.org>
References: <000801c6d601$bea9d3b0$58910d54@049306920171>
Subject: Re: [CR]Tubulars..valve stem tilted
Date: Wed, 13 Sep 2006 14:09:01 -0700
reply-type=original

I have adopted the practice of dragging the front brake while riding freshly mounted tubies if valve stem tilt correction is needed. Reversing the front wheel will allow tilt correction in the opposite direction. I think this also helps improve contact between the tire and a lumpy glue-encrusted rim surface.

One thing to note is that the Tg, (the transition temperature of the partially-cured glue) is somewhat abrupt, meaning that as the rim heats up the movement of tire on rim tends to occur suddenly if the rim heats up too fast, yet this can be managed. I usually get a pretty good workout just getting the rim warmed up. I ride slowly down a steep long hill near my house for this, checking the valve at frequent intervals. Trial and error for sure.

I've had no problems with the aligned tire tread moving off-center when doing this, but this too can be easily corrected (by hand) to perfection while the rim is still warm. I use a little WD40 on a rag to quickly remove glue from the rim and tire sidewalls, and this doesn't hamper braking if the stuff is wiped off with a dry rag.

I was surprised to find how easily is is to reach the Tg temperature of even fully-cured common mastiks when riding in the local foothills. Together with my bike I'm still under 200lbs, yet I sometimes find a freshly-leaning valve stem after hilly canyon rides, and this has me concerned.

David Snyder
riding clinchers of late in and about
Auburn, CA


----- Original Message -----
From: Norris Lockley
Subject: [CR]Tubulars..



> In his last Contri about mounting tubs on to rims, Ted Ernst touched
> upon the problem of making sure that the valve does not move, or lean
> etc.
>
> This has always been a problem, but the associated problem arises from
> the difficilty, often of ensuring that the base of the tub, in those
> points immediately adjacent to the valve, sticks down to the
> rim...otherwise you end up with a little hump in the tub, which doesn't
> lead to very smooth riding.
>
> This was a real problem in the 50/60s when valve seatings within the
> tubular were not as compact as in recent years.
> The way I learned to overcome this problem was simplicity itself.
>
> As soon as you place the valve through the hole in the rim, you strap
> the tub down to the rim with a couple of old two straps..or four - two
> each side if you have them. Alternatively you can use a strong shsoe
> lace such as that from a soccer boot that is both long and quite broad.
> With this you simply wrap the lace/cord around the tub and rim for a few
> inches each side of the hole.
>
> If you do this you will never have the tub "creeping" or the valve
> twisting or tilting as youn strain in other parts of the wheel to get
> the tub on.
>
> Finally when you remove the straps/ laces, when the adhesive has set,
> the tub will be well and accurately bonded to the rim..and the valve
> perfectly upright.
>
> Norris Lockley...Settle UK