Overview of Pumps

Generally all pumps fall into one of three types, floor pump (track), frame pump or mini pump. Floor pumps, sometimes called track pumps are pumps which use the floor or ground as a surface to press against on the down stroke.

Frame pumps are any pump which is carried on the bike frame with a length generally over 12 inches. They are sometimes held onto the frame using "pegs" which protrude from a frame tube, or more frequently held in place on the frame between two tubes using an internal spring which expands the length of the pump to hold it in place on the frame.

Mini pumps are small pumps that mount on the frame using clips which bolt beneath or in place of a water bottle cage. Some of these are small enough to carry in a seat pack or fanny pack.

Lets go on to the parts to the pump, we'll work through the pump from human touch to bike touch. The "handle" will always be the part of the pump that moves while clenched in your hand. Some pumps have hand grip areas on a part of the pump that doesn't move, that isn't a handle. Connected to the handle is a metal rod or tube we refer to as the "plunger shaft", which moves within the "compression tube" which some call the "cylinder" or "barrel". At the end of the plunger shaft is an air tight fitting assembly made of plastic, leather or rubber which is referred to as the piston. There is usually one or more washers or plastic or metal and a cup shaped piece of thick leather or sometimes these days it's rubber, that is held in place inverted at the end of the shaft. The inner walls of the compression tube are greased so the inverted cupped leather or rubber seal slides smoothly up the inner wall and on the compression stage forces all the air smoothly out of the tube.

The tradition is to make this compression seal of thick leather and still the best pumps have this replaceable seal made from leather today. Some floor pumps have an area of compressed air storage in or near their base as though it were a regulated tank on a compressor. The storage area is referred to as a "reservoir" and its purpose is to equalize and give an even rate of exit to the air the pump is compressing. By equalizing the rate of exit, the inner tube and tire are inflated at an even rate which gives them both time settle into one another on the rim or "seat" to one another, which avoids the tire blowing off the rim unexpectedly.

Some pumps have small valves built into them at the air exit point from either the compression tube or the reservoir. These valves permit the air to travel in one direction, out of the pump but not but back from the inner tube into the pump if the inner pressure of the tube is higher than that in the compression tube. This one way valve is known as a "check valve" and makes using a pump less work because you don't have to continue to compress air back into the tube again. If you think about the valve in the stem of the inner tube is supposed to do this, and generally, almost always... it does, but sometimes a Presta valve during inflation gets stuck "open" (remember Presta valves rely on the inner tubes inner pressure being higher than the outer pressure to actively close the valve). When a Presta valve gets stuck "open" the second stage of the pump stroke is much harder with out a check valve, all floor pumps do and most frame and mini pumps have one built into either the air chuck or pump body.

The fixture of the pump that contacts the inner tube valve which delivers air to inflate it is called an "air chuck", (really, we didn't make it up). The air chuck may be a part of a head that screws onto a pump, or the end fitting of the air hose, or attached to the frame or mini pump itself. The air chuck may accommodate either Presta or Schraeder valves, or have reversible inner fittings to accommodate both. Some air chucks have a "thumb lock" on them. The thumb lock is a rotating lever with a concentric cam that compresses a cylindrical rubber seal in the air chuck to make an outrageously air tight seal between the air chuck and the valve stem. If you look at one our description will make sense.

Please try to remember, when needed, that you can always use a Presta to Schraeder valve adapter. Single or Double Action - There are two stages or strokes to one complete pump stroke and they have several names. The first is the "out" stage/stroke (frame pumps) or "up" stage/stroke (floor pumps). The second is the "in" (frame), or "down" (floor) stroke.

Pumps have historically been what is now being referred to as "single action", meaning air is drawn into the pump during the first stage and compressed under pressure during the second stage. In the early 1990's "double action" pumps made their appearance as a way for pump makers to differentiate themselves from competitors who were more "low tech". In a double action pump there are two compression cylinders, one inside the other, during what would be the draw or intake stage the inner compression cylinder compress and forces air out of the pump. During the "compression" stage the outer compression tube is used to force air out of the pump.

Although the concept of a "double action" pump sounds appealing because you are left with the impression that it will take half the time, the truth is more brutal than that.

The inner compression tube is both smaller in diameter and length than the second tube it must fit into, so it displaces or compresses a much smaller volume of air. The truth is, double action pumps compress about a quarter of the air during the draw compression stage that they compress during the second compression stage. Making a double action pump introduces so many unnecessary complexities into the design, in both parts count and the added number of inner seals and check valves that may require delicate treatment.

We wanted to know what volume of air one full pump stroke of each pump delivered so we measured the volume of water in milliliters (ml) one full pump stroke would displace, then converted that figure from ml to cubic inches and to cubic centimeters so that you get a sense of efficiency in air output from each of the pumps with a single full stroke. The ml displacement figure can be converted to cubic inches by multiplying the figure times .06102 The ml displacement figure was converted to cubic centimeters by multiplying the figure times 1.000027

All frame and mini pumps should be considered an emergency pump. Notice how many full strokes it takes to fill a Panaracer Dart HC to just 40 PSI on a Mavic 231 for mountain bike riders, and how many strokes is takes to fill a Continental SuperSport Ultra 700 x 25c on a Mavic Open 4 CD to just 90 PSI. The pump stroke count is so high it will clearly take many minutes to fill a tire for only modest applications. We modified a Silca Impero to become a Vacuum pump, and extracted all the air from the inner tube prior to each stroke count test.