Hi James; pretty scant on supplying any info there, but I'll give a go at your query?anyway-
Yes- that is a thing.
If you are losing air pressure in a matter of minutes or hours, makes sense there is a slow leak going on somewhere, be it the body of the tube, or the stem, or the vulcanizing attaching the stem to the tube body.
This could be from faulty manufacturing.
Or the tubes may have been abraded during installation.
Also, tubes age.
Just like the carcass of the tires themselves, old tubes can present with age checking, and air passes out through the deepest of the checking, which is why generally we get new tubes with new tires.
(are those '75 tubes?)
Ditto with aging at the vulcanized connection between stem and tube, aging can have an effect here.
Valve stem inserts can develop weakened springs as they age, which means centrifugal force may open the valve, releasing air.?
(why classic racers are often careful to use metal valve caps, with good seals in them)
And the o-ring seals at the base of the stem inserts can be faulty as well.
??
Or, if losing air pressure over a week (or several) it may be that the tubes installed are natural rubber rather than synthetic, in which case that's totally normal.
Natural rubber tubes are slightly porous and do not hold air at a constant pressure indefinitely like synthetic tubes.
And they also cost two or three time as much as synthetic tubes.
But the reason many of us still prefer to use natural over synthetic is that when punctured, synthetic can tear, causing a blowout, while punctures in natural rubber tubes do not, meaning there's a slower pressure loss, as well as a highly reduced pucker factor
and so an increased safety factor.
I use natural rubber tubes for the above reason, and also because I'm lazy about checking the condition of my tires.
I know if I'm checking my tire pressure weekly (for me it's every Sunday morning: regularity) I'll also bother to scan the tire carcass for any anomalies that might also be a concern.
Best-
George
(extended answer)
A little tool philosophy.
In my home shop I have a Draeger dial-type pressure gauge in the toolbox; while onboard, for stowing convenience, I carry a Milton pencil-type pressure gauge, one of the
few American-made pencil gauges still made.?
I tried a number of Chinese pencil-types gauges, but they were varying and inconsistent when compared to the Draeger, while the Milton agreed, and continues to agree, so
I think paying $12 instead of $2 is a worthwhile investment.
Anyway, even though I check the bike's air pressure at home, I use the Milton from the bike's toolkit.
I do this for familiarity?with the toolkit.
I try to do as much of the bike's home maintenance?as?possible using the bike's toolkit, before using anything from the shop toolbox.
I do this because, while I rarely have an issue on the road, I want to be both familiar with what's in the bike's tool tray, and what I'm capable of doing with what's in
the tool tray, should I have the need while out on the road.
G.
?
Seems the tires on my '75 R90s lose air quickly - more quickly than my other BMW's. Is that a thing?
