Pump Adaption

[pickerd1]

Hi there,
I have a couple of Topeak pumps that fit directly onto the inner tube valve (presta). I find that these are difficult to use and often bend / damage the valve on the tube.
I also have a Topeak Turbo Morph that has a hose and I find to be very good.

Rather than discarding these direct fit pumps is there a way of attaching a hose to the non-hose pumps?
I have tried the cheap / traditional pump hoses but their threaded attachment falls out of the pump too easily.

Any ideas?

Thanks

[[XAP]Bob]

Can you attach an old presta valve onto the 'pump' end of a hose?

[gaz]

That sounds like a good idea.

In the garage I have the hose from a broken Topeak Mini-Morph. Time to see if it can be used to "upgrade" a more basic mini-pump.

[Brucey]

Hi there,
I have a couple of Topeak pumps that fit directly onto the inner tube valve (presta). I find that these are difficult to use and often bend / damage the valve on the tube....

strictly speaking it is more likely the case that you bend the valve stems etc using the pump to do it...?

With any direct fit hand pump (which has fewer seals, valves, parts to go wrong and therefore should be more reliable), technique is everything. There are two main methods;

1. with a loose wheel; it is OK to hold the pump only (eg using your left hand, if you are right handed and use your right hand to work the piston)

2. with a wheel in the frame; it is best if you react the main piston load through the forefinger of your left hand, wrapped around the end of the pump. Use your thumb on /around the tyre to check/ensure that the pump is not moving around too much in relation to the wheel (which is what can bend the valve stem).

If you go at it gangbusters with any pump, the pump will flap about and this will damage the pump, the valve, everything. Using a pump with a hose mitigates this to some extent rather than eliminates the problem entirely; if you are clumsy enough you can pull the valve out using a pump with a hose, too....

Using a direct fit pump is (like many things in life) a skill that it is useful to acquire. I grew up with (at first) pumps with connectors and they were all junk; too many parts to go wrong. However my first forays with a direct fit pump were no better, and there were plenty of opportunities for rookie mistakes; back then a silca frame fit pump would have no check valve in the base, and if it moved when you were pumping and the (presta of course) valve jammed open, the result would be that the pump piston would be launched like a small mortar shell, often going fifty yards through the air, to the consternation (or more often great amusement) of any onlookers.

Not all direct fit pumps are any good of course, but as a breed they ought to be more reliable than those with hoses. As you have discovered, any flaw in the sealing is usually a bigger problem with a hose type pump than a direct fit one; if the hose leaks down between pump strokes the pumping action becomes catastrophically inefficient, and the larger the connection volume (in the hose), the worse this is. A direct fit pump has near enough zero connection volume, so will tolerate small leaks rather better.

Perhaps you can find a connector hose that will work for you here;

http://www.sjscycles.co.uk/pumps-spares-dept963_pg1/

cheers

[[XAP]Bob]

A valve at each end of those should help that of course, drops the dead volume of the compression.

[Brucey]

sure, but if there is a small leak it doesn't help any, and if the check valves need a pressure differential to open or don't flow easily, the whole process just becomes even harder work.

To this day the least net work in inflating a tyre is had when using a fairly basic frame-fit pump and presta valves IME, and that is the reason why.

cheers

[pickerd]

Would a valve extender and old style hose do the trick?

[Brucey]

it might do, but only if the hose/connector doesn't leak. Mostly, they leak, IME.

cheers

[[XAP]Bob]

sure, but if there is a small leak it doesn't help any, and if the check valves need a pressure differential to open or don't flow easily, the whole process just becomes even harder work.

To this day the least net work in inflating a tyre is had when using a fairly basic frame-fit pump and presta valves IME, and that is the reason why.

cheers

The valves do need to be well constructed.

Although with two valves you have a chance of overcoming a small leak - but only a very small one, since you can actually keep feeding in reasonably high pressure air. If you can pump faster than the leak then the tyre will get the difference. The leak of course will accelerate as the hose pressure increases, so you're fighting a losing battle.

It always surprises me that there aren't valves at the base of track stands.

[Brucey]

most track pumps (and all with gauges) have check valves in the base; they are large, and flow easily.

this hose -of the inexpensive ones- looks a good bet provided the presta adapter has a seal in it.

http://www.sjscycles.co.uk/zefal-zefal-flexi-schrader-connector-prod20256/

cheers

[pickerd1]

Thanks for all the help.
The hose suggested looks good and is cheap enough. The problem I have found with this sort of hose is that the pump end fitting, whilst great for screw in type pumps, does not fit well enough into push / direct fit pumps. This seems to be due to the length of the threaded part being too short compared to a tube presta valve - hence my idea of fitting a valve extender to this type of hose.

[Brucey]

sure; I think it will work best with a valve extender too.

cheers