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Old 14 November 2016, 10:45   #1
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Tube pressure without a gauge

I do not have an air pressure measuring device for my 650 Pro.

Whilst I know exactly what the manufacturer's recommended bar/psi is, I have no way of accurately testing it. I can't obtain a pressure gauge where I live as am located on a remote island...hence this request:

How can you tell whether the tubes are inflated to more-or-less the correct pressure? Currently, I keep them inflated where if I hit them with the palm of my hand, they sound like a drum; fairly taught skinned. Am I on the right track?

Any experience advice much appreciated. Thanks.

Pete.
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Old 14 November 2016, 11:01   #2
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That's about what you're looking for.

At 240 mbar / 3.48 psi, it is extremely hard to indent the tube.
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Old 14 November 2016, 11:02   #3
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Sounds about right. Ive not seen anyone with a pressure reading. Shouldn't be much give at all when you press on it, some people have them absolutely rock hard.

Remember once in the water they'll cool down and go soft. You don't want soft tubes as in rough weather they'll flex and possibly damage them. Conversely, if you pump them up and then take it out and leave in the sun, they'll expand. If you dont have pressure release valves, be careful.
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Old 14 November 2016, 11:45   #4
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Quote:
Originally Posted by office888 View Post
That's about what you're looking for.

At 240 mbar / 3.48 psi, it is extremely hard to indent the tube.
Richard, Thanks for the reassurance. I can 'dent' the tubes if I press on them with my finger, so maybe I could pump them up a little harder.

FYI I have both a 12Vdc pump (which I use most of the time) and a mains voltage pump which I employ until they are no longer sucking air through the inlet nozzle. The back pressure in the tubes seems to limit the amount of air going in at a certain point but I have no idea what pressure is in the tubes at that moment. I also top up with my foot pump to attain more pressure if necessary but I am afraid of over-inflating with that.

Pete.
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Old 14 November 2016, 11:52   #5
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Quote:
Originally Posted by HUMBER P4VWL View Post
Sounds about right. Ive not seen anyone with a pressure reading. Shouldn't be much give at all when you press on it, some people have them absolutely rock hard.

Remember once in the water they'll cool down and go soft. You don't want soft tubes as in rough weather they'll flex and possibly damage them. Conversely, if you pump them up and then take it out and leave in the sun, they'll expand. If you dont have pressure release valves, be careful.
Thanks for the further reassurance my pressures are about right.

The sun is very hot here (Bahamas) so the air inside is invariably expanded.
In the 'cool' evenings (@~28 deg C, all relative!) I notice they go slightly softer.

Unfortunately, my tubes are not fitted with PRVs so I tend to be cautious about making them rock hard.

Pete.
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Old 14 November 2016, 13:43   #6
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I also top up with my foot pump to attain more pressure if necessary but I am afraid of over-inflating with that.
It is almost impossible to overinflate the tubes with the footpump. The pump cannot physically exceed 4.4 psi. Realistically, I don't think I've ever seen anyone excess 3.8 psi.

I am 165 lb (75kg). With the Bravo 7 and Bravo 8 foot pumps, I must jump on the pump with both feet to get the pressure up to 3.48 psi.

At ~2.5 psi, I can no longer depress the pump with one foot easily.
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Old 14 November 2016, 14:11   #7
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Quote:
Originally Posted by office888 View Post

I am 165 lb (75kg). With the Bravo 7 and Bravo 8 foot pumps, I must jump on the pump with both feet to get the pressure up to 3.48 psi.
Sadly based on this formula I can get about 7 psi in my tubes - thank the lord for PRV's
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Old 15 November 2016, 10:58   #8
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I've got something like this:

http://www.rib-shop.com/universal-rib-pressure-gauge/


Though I'm Afraid I don't use it. I just do the "ping test":

Flick it with your finger (like you used to do at school to other people's ears etc)

And if it people pings in an agreeable way it's about right


Ok not very scientific or measurable but it's always seemed ok
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