BROOKLINEBIKER

Hi everyone,
I'm having problems with a Topeak Road Morph G Mini Pump and/or my Kenda tubes with presta valves. I bought in 2013 but hardly used it much until recently. I've had a run of flats over the past 6 months and am alarmed with the amount of bent plungers in the valve cores that I've been suffering. This happened today. I tried to blow up the tube (which was low but not flat) & the following happened: 1) initially the tube held air but every time I disconnected the head of the pump hose the tire mostly deflated through the valve in a second or two, 2) I reattached the head (firmly but not roughly I thought) & tried to repump the tire, and 3) bent the plunger to the point the tire wouldn't take air. This only happens rarely with my Specialized floor pump. any recommendations? Is the problem the tubes? The pump? Me?

2_i 

I used Morph at some point regularly, but not recently, and do not recall any particular problems with the chuck. Your 1) seems to indicate a problem in the valve, not the pump. Regarding the pump, you can change the grip by tightening or loosening the washer. Are both the washer and rigid element directions in the chuck consistent with Presta?

BROOKLINEBIKER

Thanks for responding. I'm confused by your answer. What is the "rigid element"? Is the washer you reference an internal part on the pump?

SkyDog75

Try not pushing the pump head all the way onto the stem. With a presta valve, there's no mechanical contact needed to depress the valve's core; it's done by air pressure, so you don't need to 'bottom out' the pump head like you would for a schrader valve.

2_i 

In the chuck you have two pieces secured with a nut, a rigid piece that goes deeper and a washer in the outer position. When you switch from Schraeder to Presta you reverse the orientation of both but still the washer needs to stay in the outer position. As you screw the nut on, you compress the washer and the more compressed it gets the tighter will be the grip on the valve. When you move the lever on the chuck, you likely additionally compress the washer - would need to check.

BobbyG

When I acquired my first presta-valved bike I bent the plunger and funked up the valve core a few times using the presta head on my pump. I bought a couple of presta to schrader adapters for convenience as my original floor pumps (home & office) were schrader only.

Since using presta to shrader adapters (09 years) I haven't had any bent plungers or ruined core valves.

BROOKLINEBIKER

Thanks

BROOKLINEBIKER

Thanks!