Tyre Pressures

V

Vince

Hero member
I always check my tyre pressures before a ride and they are usually down a bit from the 2 weeks or a month since they were last checked. I am talking rear good at 40psi and when checked down to 35 on my 3c typically. I am doing a quick trip tomorrow on the Atlas and just checked it. That's a brand new front tyre and tube that was set at 37psi a month ago and was at 28psi today. Seems like excessive leaking. What's typical out there in Laverda World? That is taken with a Michilin Digital Gauge, that cost $40 or so
 
I was surprised at how much it lost in a short time, especially having only done maybe 100ks with a brand-new tyre tube and valve. I guess I better do the spit test on the valve.
 
Always check with spit. It has always been the case, most biked coming in for service had low tyre pressures, some dangerously low and I warned people to check regularly, not a new phenomenon.
 
Vince said:
I always check my tyre pressures before a ride and they are usually down a bit from the 2 weeks or a month since they were last checked. I am talking rear good at 40psi and when checked down to 35 on my 3c typically. I am doing a quick trip tomorrow on the Atlas and just checked it. That's a brand new front tyre and tube that was set at 37psi a month ago and was at 28psi today. Seems like excessive leaking. What's typical out there in Laverda World? That is taken with a Michilin Digital Gauge, that cost $40 or so
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I do the same Vince, regardless whether its been a week or a month. After about a month have similar pressure loss.
 
Heard once that the best tubes are porous and need checking often, the reason they are considered better is because in case of a puncture the tube doesn't tear and deflates more slowly whereas the cheaper ones rip and can deflate much quicker.
Could all be an urban myth of course.
Always check tyre pressure, along with headlight, indicators, tail light and stop light before each ride.
 
Legs said:
Heard once that the best tubes are porous and need checking often, the reason they are considered better is because in case of a puncture the tube doesn't tear and deflates more slowly whereas the cheaper ones rip and can deflate much quicker.
Could all be an urban myth of course.
Always check tyre pressure, along with headlight, indicators, tail light and stop light before each ride.
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That’s because they have a higher rubber content instead of synthetic- Barum tubes were real rubber ( pinky colour) and were fantastic- cheapo synthetic tubes seem to split along radial mold marks they have formed in them.
 
Depending on the weather/ambient temperatures where the bike is stored will also account for some variation.
I've noticed it more on my lady's car as I'm away at sea, on my return I check her car over.
Always do the tyres first thing in the morning before the sun gets on the car.
In winter I seem to need to 'top up' the tyres. As summer kicks in I deflate them.

I admit to being, possibly, somewhat over zealous on tyre pressures.
I worked in a motorcycle shop years ago and we had a client who was an accident investigation office for the local constabulary.
I forget the figures quoted but it was a surprisingly high percentage of accidents, cars and motorcycles, where incorrect tyre pressure
were a contributory factor.
Not the cause, but a contributory factor.
 
Exmoor beast said:
That’s because they have a higher rubber content instead of synthetic- Barum tubes were real rubber ( pinky colour) and were fantastic- cheapo synthetic tubes seem to split along radial mold marks they have formed in them.
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Modern tubes are crap. I've had a valve tear out recently.
I now systematically use enduro or Mx type tubes, 3 or 4mm thick.

Paul
 
The atmosphere contains 78% Nitrogen and 21% oxygen, oxygen molecules are minute in size and can easily work their way through most rubber materials, tube and tubeless causing pressures to drop over a period of time.
Racing vehicles use pure nitrogen to inflate their wheels, but this is to reduce pressures from raising due to heat, normal compressed air also contains moisture which when temperatures increase expand quickly to increase tyre pressures.
Nitrogen molecules are larger and so less likely to penetrate the tubes and tyres.
The morel of the story is to regularly check tyre pressures.
 
Reunited Chris said:
The atmosphere contains 78% Nitrogen and 21% oxygen, oxygen molecules are minute in size and can easily work their way through most rubber materials, tube and tubeless causing pressures to drop over a period of time.
Racing vehicles use pure nitrogen to inflate their wheels, but this is to reduce pressures from raising due to heat, normal compressed air also contains moisture which when temperatures increase expand quickly to increase tyre pressures.
Nitrogen molecules are larger and so less likely to penetrate the tubes and tyres.
The morel of the story is to regularly check tyre pressures.
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All car garages over here use nitrogen.
I have nitrogen in the tyres of my Moroccan built Dacia. Not a race car by any means.
Paul
 
Reunited Chris said:
The atmosphere contains 78% Nitrogen and 21% oxygen, oxygen molecules are minute in size and can easily work their way through most rubber materials, tube and tubeless causing pressures to drop over a period of time.
Racing vehicles use pure nitrogen to inflate their wheels, but this is to reduce pressures from raising due to heat, normal compressed air also contains moisture which when temperatures increase expand quickly to increase tyre pressures.
Nitrogen molecules are larger and so less likely to penetrate the tubes and tyres.
The morel of the story is to regularly check tyre pressures.
Click to expand...
Sorry to be pedantic, but the above contains a couple of errors:
All gases, including water vapour, expand at the same rate with temperature rise, Boyle's Law.
It was as a corollary of this that William Thomson, later Lord Kelvin, was able to extrapolate 'Absolute Zero'. Probably, my favourite piece of scientific deduction.
The problem for aviation/racing would be the presence of liquid water or ice in a tyre which, upon vaporisation would greatly raise tyre pressures.
 
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