Air Pressure Gone Missing - Cause?

Pilotdave

Pilotdave

Well-known member
We keep slowly losing air pressure in all 5 tires on our Tudor. As an example, 35 psi leaked down to less than 10 over about 5 months; the drop is less if the elapsed time between checks is shorter. I installed new tires ("Firestones") and tubes (integrated valve stems) about a year ago. There was no evidence of any punctures or other damage at that time. The tires and tubes came from a local Model A parts store which, I am quite certain, gets them from the usual common source.

I'd like to fix this but first am curious as to the cause. Do these modern tubes leak air because the rubber is porous? Could I have very slow leaking valves? (This I have tried to check with soapy water - no evidence of leaks, but maybe the leaks are so slow this method doesn't work.)

I'd be grateful for any suggestions/input as to the potential causes and whether this is a common issue! Thanks much.
 
I don't know of any quality inner tubes for bikes or cars, but sure wish they were made with the same quality they had in the old days. You'd think the companies would use the same rubber formula when they move overseas, but they must not because the rubber is junk compared to what it was in the 50's and 60's.

That much loss of air should easily show with a drop of water on the valve core, so I'd guess a porous rubber seam in the tube, or the rubber itself.
 
Pilotdave,

you might dry submersing the pressurized tube in a tube of water and watching for air bubbles. Typcially not porousity in the rubber.
 
At work I have been working on a BMW Isetta, 4 new tubes, 3 leaking after a month at the bond area between the rubber part of the stem where it should be bonded to the metal, I expect the other to leak soon, 2 old stock tubes came with car---no problem
 
Thanks, Tom and brum1, both of you, for your suggestions. I will double-check the valves - if faulty, that would be an easy fix. Checking the tubes in a water bath would mean disassembling the tires/tubes....I think that may fall into the last resort category. :) As long as the air pressure loss is slow. But I could check the inflated tire in a water bath - if the tubes are faulty, the air pressure has to be escaping though the tube and the tire.

Kurt - evidence of Tom's complaint. Thanks.
 
brum1 said:
Pilotdave,

you might dry submersing the pressurized tube in a tube of water and watching for air bubbles. Typcially not porousity in the rubber.
Click to expand...

I have an inner tube on my Cub Cadet that leaks quickly when installed, but when I stick the tube in a sink of soapy water I'm unable to find any bubbles. It's been inflated all winter and still looks full leaning against the kitchen wall, but I know what will happen if I install it again.
 
Pilotdave, I had a couple of slow leakers on one of my tractors wasn't enough to warrant a teardown, I put 8oz of Tire Slime in each one and presto no more air loss. That stuff worked for me. Good luck on whatever you choose to do......Clyde
 
I do not know if I should say this as it is not the best thing to do.... however if you get the green slime tire seal for car tires, NOT the type for atv or lawn mowers. and put it in the tubes it should seal all small leaks. This is a band aid method, the stuff works, a good tube is a better idea, but sometimes you have to take short cuts.
 
My new Firestones all had the same problem. I eventually threw up my hands and just started draggng my compressor out once a week and pumping them up as a part
of my routine maintenance. It's a pain in the butt, but it's the only thing that seems
to work for me. All the valve stems passed the leak test, and all mounted tires pased
the water/air bubble test. I'm sorry that I can't offer the solution you were looking
for, but just wanted you to know that you are not alone.

Jack
 
Pilotdave ....................
After I had four new tires and tubes installed, two tires went flat. I took them back to the shop that installed them and the owner showed me where the seams, in the foriegn made tubes, were faulty.
This was on 16" tires/tubes from Coker Tires.
MIKE :)
 
Thanks, guys. Helpful to hear that I am not alone.

I had not thought of the green slime fix - that might do the job. Else I will have to continue to use Jack's method....I'm not as disciplined as he is, though!
 
On the off chance that it might be a v-e-r-y s-l-o-w valve leak not easily detectable by the soap solution method, put a dime-store balloon as far over the valve stem as possible, tape (or rubber band) it at the base and see what happens over a week or two.
 
My new ones don't leak much. But they do leak, thus before a big run I always check mytires. The volume of lair ina Model a tire is much less that fatter ones.

Maybe I carries too many womens
 
Seems to be a common problem now days with this new rubber used in tires, Have been told by more than one source that the air permiates through the rubber very slowly and to inflate tires with nitrogen at an extra cost. what will they think of next to get that extra dollar out of you? I've been filling my tires wrong all these years, but I hate buy into this theory, but it seems to have some merit.
 
I had troubles with the valves that came with the metal stems I got from A&L.

I had one that just would not seal. It was visually not mating right. All the others were clearly not much better.

The rubber valves stems I cut off used a better valve so I just switched them in to the metal valve stem. Problem solved.
 
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