The Crankbrothers Gem S pump is a small but wide pump which pumps efficiently at either high volume or high pressure. The pump shaft isn’t that long though so it’s a bit tiring to use, if this is really a problem though you can always buy the Gem L which is a tad longer.
Measuring just 175mm the Gem S (s for short) is pretty tiny. What it does lack in length it does make up for in width though, this at 9cm circumference is one of the largest diameter mini pumps I’ve ever used. At 128g it’s not the lightest either but it’s not that hefty and fitted into both my pack and my bum bag with ease.
The Gem S features a knob on the base which can be rotated to provide the pumper with either high volume (up to 40 PSI) or high pressure (40-100 PSI) meaning this pump is a good choice if you are a mountain biker that likes a gravel foray from time to time. There is also, thankfully, a clip on rather than screw on head although you will need to brace your valve with a knee or spare had when pumping top avoid bending or dislodging it. An extendable hose (as on this Syncros pump) would solve this problem and make the pump a little easier to use, as it is all the action needs to take place quite close to the wheel which can make it a cumbersome task.
You can convert the head between Schrader and Presta, this involves unscrewing the collar and reversing the inner rubber neck, normal for a pump at the price (£20.99).
The pumping action is smooth and the volume delivered when in the high volume mode is plentiful. The pump shaft is rather short though, but Crankbro’s do also sell a longer version of the pump if that’s a real issue. As it is this one sacrifices a bit of volume over its packability. When pumping up MTB tyres from flat, I switched to high pressure long before 40PSI (or even 20PSI) was reached in order to save some arm fatigue.
It’d be nice to see the pump head able to be secured when not in use so you can attach it to the bike and not worry about the shaft becoming exposed. I taped mine down with electrical tape before using a frame strap to secure it to my bike.
At £20.99 though this pump is good value, small enough to fit in any enduro bum bags and will provide the user with enough air to ensure they don’t have to spend too long fixing up punctures.
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