Hello. I've been riding Speciallized Armadillos since I started cycling four years ago. Never had a problem (using the same pump) pumping up a presta tube until today.

i purchased a set of armadillo elites (lighter and foldable w/ no beads). Now the presta valve will "spit" out the end of the pump when i get to around 60 or 80 psi (going for 125psi here).

the pump still works great on all of my other bikes with armadillos/presta, and worked earlier on the all condition 'dills just fine.

What's the deal?!?! did i pinch and twist around the tubes or something? why would it suddenly be impossible to pump up my tubes??!?!! (same tubes, same pump, and plenty of other dillos to test that are pumping perfectly to 125)..

help!!!! i don't think pumping these tires should be a 2 man job right?!?!!?

thanks all!

(the goat, a 2008 trek 2.3)

Try switching tubes?

so unfortunately the problem is with both the front and rear tires, and these are the very same tubes that i've been using at 125psi for a month or two without issue. really frustrated here, as i have no one to help me hold the pump onto the valve and can't get my front wheel pumped up enough to go ride agggh!

Since your pump obviously doesn't have a one-way valve to prevent this, the valving duty is passed on the to presta valve itself, which of course has no spring to assist a positive closure.

Firstly, such valves and pumps should always be used with the valve stem near the 12-0-clock position, so that gravity can assist the rapid closure of the valve, once incoming air comes to a stop and the air then wants to exit the tube.

Secondly, it sounds like something may be impinging on the free movement of the Presta valve core, such that the valve does not readily blow shut when the pressure stroke is reversed. Perhaps the pump head is not being held straight on the valve, or there is too much motion between the pump head and the valve?

Perhaps also, the pump head is being pushed too far onto the Presta valve.
Little-known fact here, but all Presta pump heads are designed to only fit over the small-diameter portion of the valve stem.
That comes as a surprise to many who have for years forced their often hogged-out pump head gaskets and O-rings over the larger-diameter shank of the valve, and once that has been done a few times, the gasket/ring may no longer seal over the smaller reduced section of the valve stem any longer.
Sometimes, the pump head has a knurled ring that can be tightened to re-compress the gasket/ring packing, so as to tighten the fit on the valve stem, but other times the gasket needs replacement or internal shimming (with appropriate washer) to restore a good seal on the minor OD of the valve stem.

I have heard stories of rebounding pump handles blowing completely out of a pump barrel, and of a rebounding handle hitting someone's genitals. So, potentially, this could be dangerous!

I have occasionally loaned out my good floor pump to kids who need a shot of air into their BMX bike Shraeder valves (my floor pump has an over/under style twin head), but I am somewhat loathe to loan out my pump to knowledgeable cyclists who ignorantly abuse the Presta end of the pump head by forcing it over the larger-diameter step of their valve stem.

hahaha ok thanks for the responses guys.. So I am doing the 12 o'clock positioning, and i just tried to pump it up with the valve not so deep into the pump head.. still no luck. if i don't hold the pump head on, it'll blast right off without even trying to pump! so confused!

so weird. same pump, same tubes, never had this problem, and all of my other wheels/armadillos/tubes are working just fine with this pump. i am literally screaming in my apartment. maybe i should just take these tires off and try with new tubes, but it's pretty hard to believe that both tubes would suddenly change at the same time. nothing to do with these tires i suppose? jeez i guess thats all i can do huh.

The foldable tires still have tire beads - it's just that they're made out of Kevlar cords instead of steel cords and can therefore be folded.

But there's no way for either your pump or the Presta valve stem on your tubes to know that one tire has a Kevlar bead and another tire has a steel bead. So any problem with the security of the connection between the pump head and the valve stem has some other cause and is independent of the bead material.

thanks for all your help everyone.. i just had someone hold it on while i pumped them up and they seem ok so far. If they continue to give me this problem i'll certainly swap out the tubes.. thought it might be user (installer) error since i'm not used to the kevlar cords, i was just confused that it happened on both at once.

What kind of pump do you have?