I have two road bikes and usually inflate the tires to 110 psi. In each case after about four days they are down to around 70 psi. The tubes are butyl rubber, and have presta valves. Is this pressure loss normal? Is it due to diffusion of air through the tube or valve leakage? If I were to install tubes with schrader valves would they lose pressure more slowly and require pumping up less often?
Pumping up the tires twice a week is really no problem, but I cannot understand why it is necessary particularly when I consider that I only need to inflate my automobile tires about twice a year.
I have two road bikes and usually inflate the tires to 110 psi. In each case after about four days they are down to around 70 psi. The tubes are butyl rubber, and have presta valves. Is this pressure loss normal? Is it due to diffusion of air through the tube or valve leakage? If I were to install tubes with schrader valves would they lose pressure more slowly and require pumping up less often?
Pumping up the tires twice a week is really no problem, but I cannot understand why it is necessary particularly when I consider that I only need to inflate my automobile tires about twice a year.
TIA, Ernie
Dear Ernie,
My tubes hold about 120 psi easily for over a week, so I suspect that you have either leaky presta valves or else pinhole punctures.
Some soapy water may show if the valves are leaking.
If the valves aren't blowing soapy bubbles, I'd pull the front tube because it's easier, inflate it until it swells a bit, and then run it through a sink full of water, looking for tiny bubbles. If you find any leaks, look very closely at your tires for broken-off thorn tips or Michelin wires.
I have two road bikes and usually inflate the tires to 110 psi. In each case after about four days they are down to around 70 psi. The tubes are butyl rubber, and have presta valves. Is this pressure loss normal?
Sounds a bit on the high side, but not abnormal if you have very lightweight tubes.
Quoted message said:
Is it due to diffusion of air through the tube or valve leakage?
Most likely through the tube. I've had rare slow leaks from valves before (both Shraeder and Presta), but they wouldn't be consistent across the four tires.
Quoted message said:
If I were to install tubes with schrader valves would they lose pressure more slowly and require pumping up less often?
The lightest tubes (i.e. thinnest rubber) tend to come with Presta valves so you may well have less air loss if you switched. But you can also get heavier tubes with Presta valves which won't lose air so rapidly.
I have two road bikes and usually inflate the tires to 110 psi. In each case after about four days they are down to around 70 psi. The tubes are butyl rubber, and have presta valves. Is this pressure loss normal?
Sounds a bit on the high side, but not abnormal if you have very lightweight tubes.
Quoted message said:
Is it due to diffusion of air through the tube or valve leakage?
Most likely through the tube. I've had rare slow leaks from valves before (both Shraeder and Presta), but they wouldn't be consistent across the four tires.
Quoted message said:
If I were to install tubes with schrader valves would they lose pressure more slowly and require pumping up less often?
The lightest tubes (i.e. thinnest rubber) tend to come with Presta valves so you may well have less air loss if you switched. But you can also get heavier tubes with Presta valves which won't lose air so rapidly.
I have also noticed that tubes designed for thinner tire have to stretch a bit. I've been told that butyl rubber can be porous, so stretching it out can lead to faster air poss simply from its porosity. When I swiched to slightly larger tubes, my air loss problem went away (albeit to be replaced by the occasional internally folded tube!)
I have two road bikes and usually inflate the tires to 110 psi. In each case after about four days they are down to around 70 psi. The tubes are butyl rubber, and have presta valves. Is this pressure loss normal? Is it due to diffusion of air through the tube or valve leakage? If I were to install tubes with schrader valves would they lose pressure more slowly and require pumping up less often?
Pumping up the tires twice a week is really no problem, but I cannot understand why it is necessary particularly when I consider that I only need to inflate my automobile tires about twice a year.
That's a bit more than usual. The higher the pressure, the faster the air loss though.
Car tyres lose air very slowly because the rubber is thicker - tubeless tyres are better in this respect because the tyre *is* the tube. A bike tyre is not sealed and once the air escapes from the (thin) tube it easily leaks out through the spoke holes.
When I was growing up, we had tires you had to cut open, patch the tube oh-so-carefully, then sew them back together. At their best, we had to inflate them every single day, and we LIKED IT!!!
E. Willson said:
I have two road bikes and usually inflate the tires to 110 psi. In each case after about four days they are down to around 70 psi. The tubes are butyl rubber, and have presta valves. Is this pressure loss normal? Is it due to diffusion of air through the tube or valve leakage? If I were to install tubes with schrader valves would they lose pressure more slowly and require pumping up less often?
Pumping up the tires twice a week is really no problem, but I cannot understand why it is necessary particularly when I consider that I only need to inflate my automobile tires about twice a year.
"Zog The Undeniable" wrote: Car tyres lose air very slowly because the rubber is thicker(clip) ^^^^^^^^^^^^^^^ If this is too obvious, I apologize, but car tires have much more air volume, so a given size leak produces slower deflation.
there might be a leak "E. Willson" <[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
I have two road bikes and usually inflate the tires to 110 psi. In each case after about four days they are down to around 70 psi. The tubes are butyl rubber, and have presta valves. Is this pressure loss normal? Is it due to diffusion of air through the tube or valve leakage? If I were to install tubes with schrader valves would they lose pressure more slowly and require pumping up less often?
Pumping up the tires twice a week is really no problem, but I cannot understand why it is necessary particularly when I consider that I only need to inflate my automobile tires about twice a year.
What's that about? Are we trying to re-live your impoverished childhood? "richard" <[email hidden]> wrote in message news:Ws3Rc.223566$IQ4.96711@attbi_s02...
Quoted message said:
When I was growing up, we had tires you had to cut open, patch the tube oh-so-carefully, then sew them back together. At their best, we had to inflate them every single day, and we LIKED IT!!!
E. Willson said:
I have two road bikes and usually inflate the tires to 110 psi. In each case after about four days they are down to around 70 psi. The tubes are butyl rubber, and have presta valves. Is this pressure loss normal? Is it due to diffusion of air through the tube or valve leakage? If I were to install tubes with schrader valves would they lose pressure more slowly and require pumping up less often?
Pumping up the tires twice a week is really no problem, but I cannot understand why it is necessary particularly when I consider that I only need to inflate my automobile tires about twice a year.
"Zog The Undeniable" wrote: Car tyres lose air very slowly because the rubber is thicker(clip) ^^^^^^^^^^^^^^^ If this is too obvious, I apologize, but car tires have much more air volume, so a given size leak produces slower deflation.
Car tires also have much lower pressure than bikes, which means that the air inside would migrate outwards much more slowly.
Impoverished? Know how much Criterium Seta's or del Mondo's cost back in the 70's???
Lance Boyle said:
What's that about? Are we trying to re-live your impoverished childhood? "richard" <[email hidden]> wrote in message news:Ws3Rc.223566$IQ4.96711@attbi_s02...
Quoted message said:
When I was growing up, we had tires you had to cut open, patch the tube oh-so-carefully, then sew them back together. At their best, we had to inflate them every single day, and we LIKED IT!!!
