Bicycle pump.

[ChrisF]

I find it odd that there is a thread about pumps , with three pages of posts, without a mention of different types of pumps for different tyres. The OP was about trying to inflate a MTB tyre to 40-45 psi. MTB tyres need lots of air but at a much lower pressure than a road bike tyre at 100 psi or similar. When pumping a tyre, you can only get air from the pump into the tyre if the air in the pump is at a higher pressure than in the tyre. Now, the units are psi or 'pounds per square inch' (or metric equivalent). Assuming that a given rider can exert a certain number of pounds force (albeit more with a floor-based pump) the cross-section of the pump is important. For a MTB you should go for a wider barrel (more air per stroke, but lower psi because more square inches); for a road bike the narrower the barrel the better if you want to get 100psi, because your limited amount of pounds pressure is divided over a much smaller cross-sectional area. Simple physics, isn't it?

[pwa]

I find it odd that there is a thread about pumps , with three pages of posts, without a mention of different types of pumps for different tyres. The OP was about trying to inflate a MTB tyre to 40-45 psi. MTB tyres need lots of air but at a much lower pressure than a road bike tyre at 100 psi or similar. When pumping a tyre, you can only get air from the pump into the tyre if the air in the pump is at a higher pressure than in the tyre. Now, the units are psi or 'pounds per square inch' (or metric equivalent). Assuming that a given rider can exert a certain number of pounds force (albeit more with a floor-based pump) the cross-section of the pump is important. For a MTB you should go for a wider barrel (more air per stroke, but lower psi because more square inches); for a road bike the narrower the barrel the better if you want to get 100psi, because your limited amount of pounds pressure is divided over a much smaller cross-sectional area. Simple physics, isn't it?

And the OP talked of using an inappropriate road tyre pump. True.

[Samuel D]

The Zefal HPX, unfortunately doesn't fit the frame I intended it for, too long and also too large a diameter for the pump peg below the top tube. In use this pump was ok but took a lot of force with both hands required, one pushing and the other needing a lot of effort to resist the force. Twice the head slipped off the valve.

Thanks for your comparison test, Des49.

Regarding the quote above, what method do you use to pump?

To reduce the force required by my supporting left hand, I brace my left wrist against the inside of my left knee while crouching. Then I pump with my right arm, additionally swivelling my back into it as the pressure rises.

Some initial care is required to suitably position the bicycle or wheel with the valve at knee height and at an angle that doesn’t stress the valve.

This method is much easier than any other one I have tried. I often see people flailing about with the pump practically at arm’s length and the valve taking a lot of punishment. No wonder they find pumping hard! I know you’re not doing that but wondered if you knew about bracing the supporting hand against the inside of your knee.

[gxaustin]

My Phaart Rumbler is good for pressure because the barrel is quite narrow. It has a flexible connection and foot stirrup. Needs quite a few strokes though. I use 25mm tyres and it works OK for them.
My very cheap Air Supply pump of similar layout to the Phaart has also got me (and several others) home on reasonably inflated tyres.
Graham

[Samuel D]

Having now used my Zéfal HPX to pump up a 25 mm tyre to 100 PSI (higher than I normally use), I cannot relate to Des49’s characterisation of the pumping effort as “hard to very hard”. I’d go as far as calling it easy!

The impression given is that there is very little dead space in the chamber and that therefore the pump continues to reward effort with air in the tyre as the pressure rises – something that many pumps with short barrels do not achieve (this is why I bought the longest Lezyne Road Drive model). By dead space I mean the volume of air not pumped into the tyre at the end of the stroke.

With a pump with a small ratio of total volume to dead space, you spend a lot of effort repeatedly increasing the pressure in the barrel for no gain, since much of the high-pressure air on each stroke doesn’t squeeze past the valve into the tyre.

On this topic of dead space, I have sometimes thought a flexible hose does you no favours when using a mini-pump, since the volume in the hose and any additional fittings, though small, may amount to a significant portion of the total dead space. Any thoughts on this?

I am a careful worker and have never broken a valve by using a pump without a hose, though the hose on my Lezyne Road Drive certainly makes holding the pump more relaxing. But it’s clear the Zéfal HPX is easier to use at high pressures. Of course it’s also bigger and heavier.

I’m impressed by this Zéfal, now that I’ve got it working.

[samsbike]

I have ordered one of those nice Lezyne micro floor pumps (high pressure version with gauge) for my wife to use on her commute, so when it arrives I will do a comparison test with one of my Zefal HPX frame fit pumps. I will count the strokes to get to a specified pressure, and offer some subjective impressions about ease of use and build quality.

(I will ensure valve cores are nice and tight before testing because I understand the screw-on Lezyne attachment can cause loose cores to unscrew)

I have this pump and the one time I used it, it took 100 pumps to get to a 100psi. I know this as I was working in tens and swapping hands as its not the most easy to cup into your hand.

There is also a lezyne mtb pump with a similar function.

[Brucey]

Having now used my Zéfal HPX to pump up a 25 mm tyre to 100 PSI (higher than I normally use), I cannot relate to Des49’s characterisation of the pumping effort as “hard to very hard”. I’d go as far as calling it easy!

The impression given is that there is very little dead space in the chamber and that therefore the pump continues to reward effort with air in the tyre as the pressure rises ....

I’m impressed by this Zéfal, now that I’ve got it working.

yup, that is the way with a pump like that; the best pumps have almost no deadspace inside them. Mind you if there is no grease on the plunger it can be somewhat harder work, maybe Des49's pump has run dry...?

BTW I have the older Zefal HP pump which is the same as the HPX except in the last inch of the stroke; in the HP pump the spring that holds it in the frame has to be worked against before the plunger will bottom out; in the HPX the spring is already defeated by a clever mechanism in the handle, which doesn't add a lot of weight. The difference in pumping effort is ~4lbs as the piston bottoms.

cheers

[Drake]

After reading the replies on here, I'm perhaps not being fair to the " pocket rocket "

Pump maintenance. Never done that. In fact never considered it. Obviously wrong there. Can't blame the pump if it's not maintained. But I still feel that something is not right with my " pocket rocket ".

Pump capacity. Never considered that one either. I mean, a pump is a pump is a pump, innit. Obviously not. So wrong again. So I'll be looking for a pump that's more mtb orientated.

Problem with my " pocket rocket " ? Well when you pull back the plunger to fill the air chamber, the plunger just wants to return to closed position. It's just as though there is a valve sticking and won't allow air to enter the chamber.

[Brucey]

After reading the replies on here, I'm perhaps not being fair to the " pocket rocket "...

Problem with my " pocket rocket " ? Well when you pull back the plunger to fill the air chamber, the plunger just wants to return to closed position. It's just as though there is a valve sticking and won't allow air to enter the chamber.

that is a bit weird. I've not taken a pump like yours apart but usually the incoming air either bypasses the main piston seal or (less often) there is a separate air admission valve. [In some pumps the air admission port is in the handle grip area, so you can block it off whilst trying to use the pump.... ]

It does sound as if you have a sticky valve or something...?

cheers

[Des49]

The Zefal HPX, unfortunately doesn't fit the frame I intended it for, too long and also too large a diameter for the pump peg below the top tube. In use this pump was ok but took a lot of force with both hands required, one pushing and the other needing a lot of effort to resist the force. Twice the head slipped off the valve.

Thanks for your comparison test, Des49.

Regarding the quote above, what method do you use to pump?

To reduce the force required by my supporting left hand, I brace my left wrist against the inside of my left knee while crouching. Then I pump with my right arm, additionally swivelling my back into it as the pressure rises.

Some initial care is required to suitably position the bicycle or wheel with the valve at knee height and at an angle that doesn’t stress the valve.

This method is much easier than any other one I have tried. I often see people flailing about with the pump practically at arm’s length and the valve taking a lot of punishment. No wonder they find pumping hard! I know you’re not doing that but wondered if you knew about bracing the supporting hand against the inside of your knee.

I had to think hard about your description as I am left handed! But seems like a good method. I tend to lean the wheel against something to help stablise the valve end and this stops me waving the wheel around and risk damaging the valve.

Having now used my Zéfal HPX to pump up a 25 mm tyre to 100 PSI (higher than I normally use), I cannot relate to Des49’s characterisation of the pumping effort as “hard to very hard”. I’d go as far as calling it easy!

My reference was against my Lezyne track pump and I compared everything against that as a base level effort. I do agree the Zefal is a nice pump and seems well made. I would ride with it if it fitted my bike. But it doesn't, and for me the Lezyne Micro Floor Drive is easier to use even though it takes a bit longer, plus it clips alongside a bottle cage or can be thrown into a pannier.

Regarding dead space in hoses, I can't say I notice this. The Lezyne Micro Floor pump doesn't seem to have any noticeable dead space, even with the hose. While my Lezyne track pump has a very handy extra long hose, again no noticeable drawbacks from this in use. My Joe Blow track pump needs a bit more effort to ensure that that important last bit of squeeze is given and seems to have more dead space even though the hose is shorter.

[Samuel D]

Thanks for reminding us that you were comparing the effort to a track pump, which had slipped my mind. I’d agree one of those (I use a Silca Super Pista) is considerably easier than the Zéfal HPX.

Sheldon Brown described a pumping technique similar to mine here, under the “Pumping Technique” heading. When I was a young child I had no choice but to devise such methods to inflate my tires, since I lacked the strength to pump with bad technique. But even today I think technique is more important than brute strength when pumping up tyres.

It helps to have a good pump!

[Des49]

I will practice with that technique and try it out on my daughter to see if she manages. Previously I have never had to worry about this too much as brute force was in adequate supply, nowadays I am getting to the point I need to think a bit more!

[pwa]

The portable bicycle pump is unusual in that you generally go out and buy what you hope will be a nice one, then hope you never have to use it.

For anyone who doesn't know, the Zefal HPX comes in four sizes to fit different frames. Unfortunately a lot of modern frames don't have a place where such a pump can fit.

[Sweep]

Edinburgh Bicycle co-op do a Revolution which is like a mini track pump, I've had one for years and i use it for all my pumping, I have found that I just don't need a full size track pump anymore. It's probably about £20 but sometimes they have a sale. As for any kind of pump failing to get up to pressure try taking the gromits apart and apply literally a drop oil, it acts as a sealant and prevents air under pressure escaping.

I agree that with a decent mini track pump it is possible to get by without a full size track pump. I have a pump from edinburgh bike co-op which is probably the one you are talking about. One with a metal foot? Nice pump though the guage is a pig to read and - it's biggest flaw if it's the same as mine - it cannot be opened up or serviced in any way, let alone spares sourced. So when it misbehaves it will have to be thrown away. A good first pump, or a spare, particularly if bought in a sale, but a Topeak Morph is better.

[Brucey]

re dead space in hoses; with a 'traditional bike pump' with the screw-on adaptor hose this was a real problem. But more modern track pumps / pumps with hoses generally either have one check valve, in the base of the pump (if they are presta only) or more usually these days, two check valves (if they are for Presta and Schrader).

Provided the connection to the valve is airtight, the hose stays at tyre pressure between strokes and there is no 'dead space loss' in the hose.

However such valves are not without penalty; you have to work some to get air through them at all, and this effort is (more or less) balanced against the chances of them leaking. It doesn't need much crud inside the pump to cause these valves to leak IME, though having said this, the Zefal HP/HPX has a check valve in the base (which is a little restrictive IMHO) but it has never leaked on me.

BTW to get 100psi with a Zefal HP/HPX, I think you need to push with a force of about 50lbs in the final strokes. I think that most club cyclists can manage this OK but anyone who doesn't have reasonable upper body strength is liable to struggle.

cheers