Rookie mistake with Mini-Pump.........

[chappers1983]

Hi all,

Made what can only be described as some kind of novice mistake with my Mini-Pump on a sportive this morning.

Got a flat, so changed it no problem (I was quite proud of myself as normally I am terrible at getting the tyre back on the rim), but when I went to pump it up with my Topeak Race Rocket it all went wrong.

Basically I screwed it on and pumped the tyre up OK, but when it came to unscrewing it it took the whole valve out with it. So I tried it again, and this time the valve got jammed in the pump. So I'm left roadside with a tyre without a valve, and a pump with a valve jammed in it which isn't moving. Cue a sheepish call to the event support team to help me out.............

So where did I go wrong? This hasn't happened before, but then I've been lucky enough to not have a roadside puncture in nearly two years. Did I just simply screw the pump on too tight, or does it suggest that my new inner tube had a loose valve in the first place?

Also, as I now have to get a new pump does anyone have any recommendations?

Thanks in advance

 

[Racing roadkill]

Don't use 2 piece valves. They suck. A lot of pump manufacturers have a pressure release button now, but it doesn't help a lot. I use Specialized 1 piece valve tubes, and steer clear of Continental 2 piece numbers.

 

[youngoldbloke]

If you carry a spoke key you might find that one of the slots (No 12) fits the flats on the valve core so that you can tighten it before your 2nd attempt.

 

[screenman]

CO2

 

[Racing roadkill]

CO2

Exactly, CO2 saved my backside a couple of weeks ago, when I suffered 2 punctures inside 10 miles ( one front, one back) and all I had left was a Conti 2 piece valved tube.

 

[mjr]

I can't see how unscrewing the pump would remove the valve core unless the core threads were slightly larger than they should have been, so either way, it sounds like a dud tube.

I prefer pumps with push on hoses for the roadside, but I've seen one of those pull a dud Continental valve apart too, so I doubt it would have helped! It's a shame really, as Continental's touring tubes are really rather good but this is quite off putting if their race tubes often do this.

 

[mjr]

Exactly, CO2 saved my backside a couple of weeks ago, when I suffered 2 punctures inside 10 miles ( one front, one back) and all I had left was a Conti 2 piece valved tube.

How? Didn't you run out of gas?

 

[youngoldbloke]

I can't see how unscrewing the pump would remove the valve core unless the core threads were slightly larger than they should have been, so either way, it sounds like a dud tube.

I prefer pumps with push on hoses for the roadside, but I've seen one of those pull a dud Continental valve apart too, so I doubt it would have helped! It's a shame really, as Continental's touring tubes are really rather good but this is quite off putting if their race tubes often do this.

If the valve core is already loose, and you have screwed on the pump hose firmly, the core will unscrew along with the hose. Easily done. If you have tubes with screw in valve cores just make sure you tighten them up well when you fit the tube, and carry a suitable core spanner or spoke key (see my tip above).

 

[mjr]

If the valve core is already loose, and you have screwed on the pump hose firmly, the core will unscrew along with the hose.

Why? The pump screws onto the stem thread, not the core thread.

 

[youngoldbloke]

Why? The pump screws onto the stem thread, not the core thread.

? My pump hose screws onto the core thread - the same thread the dustcap screws onto. Most of my inner tubes are Michelin - they have no thread on the stem. The hose screws onto the core thread (these are Presta valves we are talking about, of course).

 

[mjr]

I'll go look at a Continental at lunchtime, but they never used to be like that and it sounds like a daft design!

 

[youngoldbloke]

I'll go look at a Continental at lunchtime, but they never used to be like that and it sounds like a daft design!

- they've been like that for at least 55 years in my personal experience, and probably a lot, lot longer than that !

 

[mjr]

- they've been like that for at least 55 years in my personal experience, and probably a lot, lot longer than that !

I'm not quite as old as you, but I'm sure I remember being unable to screw a pump onto a valve with no stem thread!

Well I went out ( ) and checked and it seems like the Continental core threads are about 5mm across (not the flats) and the stem thread is 1mm wider. The tubes currently in my road bike (Vavert I think) have the same two threads but the core isn't removable. I also checked some 10+ year old tubes (which I really ought to take the tip ) but they measured about the same.

So then I thought to check the pump heads. The modern pumps (both push-on and screw-on) are just over 4mm ID so are probably using the core threads... but an old frame pump had a Presta hose which is quite deep and measures a little wider which seems to slide completely over the core thread and attach to the stem thread. Maybe those pumps used to be more common?

 

[BikeCurious]

I've had the same problem with Continental inner tubes. A year or two ago I had to fix a flat on the side of the road. Got the new inner tube in, pumped it up with my minipump that has a screw on hose. As I was unscrewing the minipump I had the head at a slight angle and it was enough to grip the valve core threads and unscrewed it! I didn't even know I had removable valve cores until then. To make matters worse I then managed to lose the core as all the air rushed out of the inner tube I'd just replaced. Luckily I had a second spare and took the core out of that. Lesson learned, I now always make sure the hose comes off straight and stop turning if it looks like it's catching the threads on the core.

 

[mark c]

I had the same problem with Continental inner tubes i solved it by using Loctite thread Adhesive.