Bicycle Mechanics - how much pressure from a Zefal HPX?

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Fat Hack
07-28-04, 07:25 AM
Their web site suggests a max of 135psi, but I've seen 160psi written on the box they come in.
http://www.zefal.com/AAA/page.php?nom=produits&sousFamille=pompesHautePression&langue=an

I managed to BLOW UP two 20mm Continental Ultras that are rated to 150psi using the HPX.

Does it depend how strong you are?

So, in my opinion, me, being such a big fat hack, can easily get 170psi (yes, 170) out of one.

RAAAAH!! :D

Retro Grouch
07-28-04, 11:47 AM
Well, I haven't measured, but I'd guess the Zefal HPX has a piston cross section of about 1/2 sq/in. If that's the case, you'd have to push the plunger with 80 lbs. of force to get 160psi. That's a good amount of force for one arm, but I wouldn't think it impossible for lots of people. Of course, the real trick to doing that is not to tear off your inner tube valve stem in the process.
sch
07-28-04, 06:52 PM
The HPX is one of the few frame mounted pumps that will take a tire upto 120# without undue strain on the part of the pumper. The last 10# is a sum*****, but
compared to the foldup minipumps getting above 80-90# a piece of cake. You
would have to have considerably more upperbody development than Lance to go
much higher. Steve

Fat Hack
07-28-04, 07:06 PM
Well, I did have a Bullworker :D
ewitz
07-28-04, 07:53 PM
from experience......enough to bolw the tube off the rim.

Atleast 160lbs, just be careful not to pull the valve out of the rim.
OldsCOOL
07-30-04, 08:52 PM
I just purchased a mini-pump from Nashbar (their Nashbar "special" w/guage 14.95). Tonite while mounting the new tires I thought I'd do a practice drill for having a flat. With a fair amount of oomph (if you work leverages correctly) I was able to generate 105lbs rather quickly. The 12v compressor was used to top-off at 120lbs.

Impressive little pump.


Olds