From a roadside in Croatia

[JohnMurray]

This is very much a noob question, but ...

I have puncture.

When I ordered my bike I asked for the rims to be drilled for Shrader (twice)..

The bike came with Presta tubes, but I thought that was just standard, and that I'd be be able to fit the Shrader tubes I carry as spares. But now it comes to the crunch, I see that I can't.

I hope that there's just a Presta insert in the hole, and that Thorn didn't forget to drill them.

***  But if it is an insert, how do I get it out? It seems to be made of metal. ***

(Yes, I can just keep trying to find the hole in my Presta tube and fix it, but that's a pain without water,)

[julk]

John,
The only metal inserts that I have press in from the tube side, so they should tap out to the tube side of the rim.
They may be a tight fit or have some alloy corrosion holding them in.

My recent presta tubes have had valve inserts which needed tightening slightly, I was getting slow puncture symptoms until I tightened the cores a bit.

Finding a puncture in a tube without water is still possible. Blow the tube up and pass it slowly and closely by your open eye.
You will feel any slight jet of air on your eyeball which is very sensitive to a cool draft of air.

Have a great trip.
Julian.

[mickeg]

You should easily be able to see if the hole in the rim is significantly larger than your Presta valve.  If not, then the Presta is the only one that will fit.

The plastic adapters look like this.  I have not used these, I assume these are inserted from the inside but can't say for sure.
https://www.sjscycles.co.uk/rims-tape/mavic-rim-valve-hole-drilling-converter-insert-schraeder-to-presta/

The metal ones look like this.  They are inserted from the inside.  You should clearly see it from the outside.
http://wheelsmfg.com/presta-stem-savers.html

[StuntPilot]

I had the same problem last year John, also in Croatia! A broken spoke required that I took off the tyre and remove the inner tube. However the metal insert was oxidised so much that the valve stem, Wheels Manufacturing metal insert and rim had all fused together as one and it took a long time with various tools to remove the metal insert and inner tube!

I looked at the plastic inserts mentioned by mickeg but currently am still using the metal ones. I avoid the oxidation now by smearing the metal insert with a little Copperease and have not had the problem again after regular checks.

Interestingly the Wheels Manufacturing site shows the metal inserts inserted from the inside of the rim. I do it the other way and insert them from the outside before the valve stem lock and cap. This prevents any dirt and dust from getting into the rim.

[mickeg]

I am planning to switch to the plastic Mavic ones, currently use the Wheels Mfg ones.  I had a flat, puncture was very close to the valve stem and a friend suggested that the metal edge on the adapter might have caused the puncture.  I bought several plastic Mavic ones a few months ago, but plan to only switch them as I remove tubes for flats or tire changes, I have them on three or four bikes.  Since I insert them from the inside, I have to remove the tubes to change them. 

[Danneaux]

I use vinyl grommets as my way of downsizing Schrader-drilled rims for use with presta valves. Currently, my only bike setup like this is my tandem. The vinyl grommets have proven good in my use over the last 30+ years, are cheap, work well, pad the area of the valve base (on single-wall rims) and nicely locate the valve against movement on double-walled rims. Being stabilized vinyl, they don't rot or break down under UV or ozone exposure like rubber can/does and they are easily removable and replaceable if you need to swap back and forth between Schrader and presta valved tubes. Best of all, they do not corrode to the rim.

Sadly, I gave up on the Wheels Mfg. aluminum spacers for the very reasons cited -- they quickly attempted to corrode into place on my rims.

Best,

Dan.

[JohnMurray]

Thanks all.

Turns out it was a much more noobish sutuation than I thought. I pumped up the tyre in the hope of making the next town with a bike shop - and it has stayed up. I think I must have not tightened the Presta locking nut enough ...

BUT how I hate Presta! *insert standard anti-presta rant, with Lezyne-pumps-screw-out-the-core topping*

[mickeg]

Thanks all.

Turns out it was a much more noobish sutuation than I thought. I pumped up the tyre in the hope of making the next town with a bike shop - and it has stayed up. I think I must have not tightened the Presta locking nut enough ...

BUT how I hate Presta! *insert standard anti-presta rant, with Lezyne-pumps-screw-out-the-core topping*

If you have removable core presta valves, yes they can stay in the Lezyne pump chuck when you take the chuck off the valve stem.  Solution is to screw that presta core into the valve stem a bit harder with a wrench or pliers.  Does not need to be really tight (don't over do it) and then do not tighten the Lezyne chuck onto it too much.

Most presta tubes do not have removable cores, so this rarely is a problem.  But I learned of it the first time on a tour.  And I learned the hard way that I had those tubes on both front AND rear. 

I still usually use the Lezyne on tours although I have another good pump that has a conventional chuck that does not thread on.

I prefer presta over shrader, but each has their own preferences.  I prefer presta because when I have used shrader, sometimes I was not quick enough to get the chuck off of the valve stem and lost some tire pressure in the process, but I can't remember that ever happening with presta.