Re: Tubulars for Brevé?

On 6 Sep, 04:55, Stephen Bauman <sbau...@xxxxxxx> wrote:

Please re-read my post. I did not claim a 1 minute tire change. I stated
that the waiting time from the first application of glue to being able to
mount the new tire should be not be greater than 1 minute. That implies a
complete tire change in 3 minutes, which is not unreasonable.

Which I think may be possible even with the likes of Mastik 1.

Modern road glue is still the gummy, gloppy stuff it always has been,
not the shellac of old school track racing.

Only Mastik 1 is hard setting

Directions on a tube of Continental Special Rim Cement

Directions for use

1. Buff the rim base and clean with petrol or similar solvent
2. Apply Continental Special Rim Cement thinly and evenly rim base and
seam protector.

Wetting the base tape with the relevant solvent first will help to
draw in the cement.

3. Allow bonding cement to dry for at least 15 minutes

Shows that it is a volatile solvent and not water. It only needs to
dry so that the surface does not wet your finger, after pressing your
finger should come up clean and dry.

4. Then apply a second coat to the rim base .

If there is already sufficient cement then the surface just needs
reactivating by brushing on a little solvent. A lot of contact
adhesives use acetone as the solvent, a good sniff easily identifies
it. Sold as nail polish remover if you dont get it from a paint
supplies.

Fit the tyre on the rim.
Pump the tyre up, keeping it positioned in the centre of the rim.

Doesn't take too long to get it rough n ready.

My experience has been that the rim cement has no adhesive property for
those 15 minutes.

True, the solvent must evaporate for the polymer to bond to the
substrate. The solvent is effectively a lubricant to help in the
spread of the polymer.


The EU promulgated VOC (volatile organic compounds) regulations that
required the reformulation of all tubular cements. US VOC regulations
caused reformulation of Fast Track in 2005. There's been a pause that
causes brevet sew up riders to miss a control ever since.

Once the adhesive polymer is affixed to the tyre and the rim in its
dry state as a spare and a rim which has had its punctured tyre
removed, the adhesive requires 'reactivation' using a suitable solvent
to allow cohesion to take place between the two separate layers. Heat
may also be used to soften the layers enough so that they mingle and
form one. You would need to carry a plumbers propane can/torch to get
this done quick. A brush and a small bottle of solvent are all that
is needed. Probably acetone, try it.

It is air pressure that holds the things on. Glue helps, a lot. But
these glues under pressure will seat themselves. You do not need to
reglue to install a spare on the road.

This is only because riding generates the heat and massages the layers
together, this may not work in colder weather depending on the
adhesive used.

I thought the same thing 26 years ago. I was 20 kilometers from finishing
my second PBP, when I had a rear flat. I replaced the tub without gluing
because it was raining and I thought I could avoid rolling the tire by
being careful. After the tubular rolled off the rim for the third time, I
applied Clement road rim cement in a bus shelter. I did not roll the
tubular after that.

The rain kept the rim and tyre cold preventing the usual bonding to
take place. Applying the cement reactivated the existing adhesive by
introducing the solvent and permitted the cohesion to take place
without heating. Riding still helps in ensuring a complete bond.
High tyre pressure should be used until the cohesion is complete.
24hrs is the usual recommendation for a new rim and tyre but I doubt
this is necessary if judicious use of solvent and/or heat is used.
When you are forced into riding immediately you have no choice so must
make the best effort in the time permitted. Use a brush and some
solvent to reactivate the adhesive polymer. Use as little as will do
the job, you cannot do better in the short time allowed.
.

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