Will this pump (if measured correctly) fit within the seat tube triangle , ie bottom bracket to underside of top tube , of my Kona Honky Tonk frame. Or should i use the dimple on the back of my head tube to the top of my seat tube ie carry it under my toptube .
Top 500 Contributor
OK, here goes. As you read this explanation you will probably realise why so many buyers return their pumps as being TOO SHORT!!! Short answer (sorry) is if you want to fit the pump to the SEAT TUBE, you should be OK.
This is because Topeak's "headline" pump sizes quoted on the Topeak packaging #and on the Wiggle website# are based upon Seat Tube length #the centre distance between bb and top tube centre# NOT Top Tube length.
These days, most riders wouldn't want to sacrifice a second bottle cage on the seat tube by fitting a pump between the bb and top tube, now that we know more about hydration and energy usage. MTB riders will choose a hydration pack, so fitting the pump to the seat tube makes sense when you may need to shoulder the bike over obstacles.
Neither do Road riders need to worry much about climbing obstacles, so often choose to fit a pump under the top tube #as most are when two bottle cages are used#. In this position, Topeak's "frame size" needs to be between 2 to 4cm LONGER than the classic "frame size" dimension, which assumes bb to top tube centres.
The diagram on the packaging clearly shows the pump fitted in this more practical "road" position UNDER the top tube. The diagram shows a horizontal top tube #NOT the sloping compact geometry often used today#. Only when you have the packaging for the pump do you realise that their diagram ALSO states the equivalent #greater# length between the seat tube and head-tube, which is the position which most #road# riders now choose.
So the answer is to use your top tube centres on a road bike as your "frame size" IF that's where you want the pump to fit. Good news is that due to the generous compression spring length in the pump handle, by measuring the "fitted length" under the top tube, it has only to match the mid-size of Topeak's equivalent seat tube length within a centimetre or so to give a good fit.
Anyone need a Master Blaster pump that's too short?