PT1029 wrote:
Still SKS for me, but not the single hole smart head which is the rare time I use the term "rubbish" - usually doesn't push the SV core in to let the air in, so it becomes 6 bar to start inflating a flat tube, and 10 bar to inflate to 4 bar.....
Generally I find smart heads eventualy get a sticky ball in and stop switching from SV to PV when you want it to. A dismantle and clean usually sorts it. I gave up at work and use separate pumps for SV and PV.
I agree that the single hole 'smart head' design is a bit crap but not for the reason you give; good track pump chucks do not push presta valves open or hold them open. What you are meant to do is to let a little air out of a presta valve just before you start pumping. This both unsticks the valve and makes sure that there is no crud, small furry animals etc in the valve mechanism. Pumping is easy after that. The smarthead will screw itself up though; bound to really.
I think there ought to be a special place in hell reserved for designers of track pump chucks. Most of them are 100% lousy; badly designed
and badly executed. The amazing thing is that every year someone comes up with a new design and there appears to be no end to the new ways they find of making chucks that are lousy.
Some simple observations;
Anything with two holes side by side is liable to be crap; there is usually a see-saw valve inside which needs only the slightest excuse to jam in the wrong place and let all the air out of your tyre. Either that or a slider: Ugh.
Anything that screws onto anything else where one or more of the parts is aluminium is bound to cause trouble.
Anything where you have a single hole for presta and schrader (with no adaptor) is a stupid idea.
Anything which is entirely made of plastic should be viewed with suspicion.
Anything where you can't buy new seals is likely to be a problem, sooner or later.
The Topeak Twinhead deserves a special mention; one of the few standard track pump heads that works OK. Despite having numerous plastic parts it is saved by having good spare parts availability. Decathlon sell a replacement chuck which is based on the same idea; it is an OK replacement for the usual dross you get.
Dunlop (and others) worked out how to make a simple and reliable schrader valve chuck for tyres about a hundred years ago; a simple lever action design, with all the working parts made in brass, adjustable tension (to allow for seal wear) and a simple seal that is easily replaced . You can make a chuck with a similar layout work perfectly with presta valves too. My favourite version of the SKS Rennkompressor has a lever action schrader chuck (which is more cheaply made using plastic and zinc castings but still works OK) and a screw-on brass adaptor for presta/woods. It would suit me slightly better if it had a lever action chuck for presta with screw-on adaptors for the other valve types, but I'm quibbling really.
The lever action chuck on a Zefal HPX is another masterpiece; again good enough as it is, but could be even better if it were made in different materials. Even the lever action chuck that is built into a £1 pump from the pound shop is a better made thing than what you get with most cheap track pumps; one of my mad ideas is that next time I have a failed track pump chuck I shall adapt one of these to fit.
The utterly baffling thing is that no track pump designer thinks 'ooh that's good, I'll make it like that' when they see a lever action chuck. No, they all think 'Oh, I can do
better than that' just before foisting yet another horrific turd onto an unsuspecting public.
cheers
