Bike Forums - Pump options

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Quote:

Originally Posted by neurocop (Post 13471177)

I don't think the highlighted comment is true. When you pump up a tire, you are increasing the pressure in the tire, pump hose, and of course the pump cylinder. The air may be "expanding" insofar as the tire volume is expanding as you pump it full of air, but the pressure is increasing in the tire and the attached hose. This leads to increased temperature. Sure, the tire "expands" a bit as you pump it up, but you are not letting the air expand freely forever. Expansion is limited by the fixed volume of the tire inner tube. Eventually the pressure in the tire build up (to 100+psi for road tires).

I've already conducted an experiment to check this out, and you can check it yourself. I've used a gadget in my shop (a "Fieldpiece" refrigerant thermometer) to check the temperature of my bicycle pump under two different scenarios. Scenario 1: pumping with the pump connected to open air; and 2: pumping into a tire.

In both scenarios there was a temperature increase, which was greater when pumping up a tire. The only way to explain the increase in scenario 1 is that the heat was generated by friction in the pump cylinder. If what you claim is true, the temperature should havedecreased due to gas expansion.

Just my 2 cents. Correct me if I'm wrong.

there are lots of factors at play - the piston friction, heat generated by air compression, the composition of the pump itself (metal will conduct heat more efficiently, enabling the surface where you’re perceiving “heat” to get hotter. Plastic will be relatively insulating, therefore cooler), the mass of the pump - the more massive it is, the less the pump temperature will rise for a given amount of heat generated by gas compression. The relatively small hose will have the opposite effect, except that the air in the hose is already compressed - compressed gas doesn’t stay hot, so it will be cooling immediately, and giving off heat perceived as increased hose surface temperature. However, the hose itself is likely made of rubber with some sort of outer layer, so relatively insulating, which will slow down surface temperature rise. All this to say - there’s no way to know what’s going on in a complex system, and using detected surface temperature as a proxy for generated heat in the system is very flawed

Jkretsch, The post you pulled up is 12 years old. You may want to start a new post.

Quote:

Originally Posted by Outrider1 (Post 23085554)

Jkretsch, The post you pulled up is 12 years old. You may want to start a new post.

I’m terrible for not looking at thread dates 🙄. If it shows up on the first page, I’ll respond. I keep reminding myself to pay more attention but the reminder never sticks😟

Pump choice has been a good discussion for at least 50 years. My choice has al;ways been and still is a Zefal frame pump, on the seat tube. The current incarnation is the Zefal HPx, which is available short enough for modern compact frames. A bit fiddly compared to my all-time favorite, the Zefal Competition, but it works so well that I ignore my floor pump. It has put a lot of other riders back on the road, too, some of them very surprised at its effectiveness but most just grateful.

For a time I used a Blackburn compact pump on my commuter but was never happy with it. I found some inexpensive plastic Zefals (REV-something) that work fine and now do not worry about loosing a pump to theft.

The seat tube is the safest place for your frame pump, it is least likely to get accidently knocked off from there. A stray pump is no fun on a group ride!

oldschoolbike

The biggest advantage in my opinion to traditional steel framed bikes is how well they accommodate full size frame pumps. For multi day rides frame pumps are the way to go.

[QUOTE=Jeff Wills;13466503]Fiddlesticks. If you're that worried about weight, take a laxative the night before you go for a ride. The difference in weight is the same as filling a water bottle 3/4 full, i.e. negligible.

Fiddlesticks? There's a word I haven't heard in a while.

I own one of those Topeak pumps, and quite frankly, I don't like it! It does have some heft, but that's not why I don't like it, I don't like it because it's very awkward looking, and it will make any bike look ugly; mine is about 6 or 7 years old, and the mount that came with mine would not hold the pump well at all. My touring is the only bike I ride that I decided not to go with a mini pump, instead I use the Zefal HPX-4 frame pump, it looks a lot better on a bike, and it actually puts more air faster into my tires than the Topeak. And the Zefal weighs less.

That's not to say that the Road Morphis a bad pump, it works and gets the job done, I personally don't like it.