Technical & Reference Section > Tech and Restoration

What keeps the pressure in tyres?

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McQUEEN:
I've got a set of Panaracer Freestyle tyres, NOS before I fitted them, and the front way stay pumped up, but the rear loses its pressure after a week or so.

I've checked, there's no puncture in the tube and the valve isn't letting air by.....The tyre looks fine, it was a little dry, but I made them a little more supple by treating with Autogym Vinyl and rubber care treatment.

The tube has been changed over as well, and the originally installed one is fine in another tyre....

The question is, can a tyre get old and not support / hold the inner tube and / or has anyone get an ideas??

hokuspokus74:
Did you try the tubes in water,that happened me,when i had the tubes in water there was very small holes and the valve was letting some air out. are the tubes dozed?

Jon The Bassist:
It's not the tyre. Normal (butyl) inner tubes leak air very slowly. Some other types of rubber (eg latex) leak a lot faster. Old butyl tubes can leak a lot faster. IME a lot of tubes without punctures start to leak around where the valve joins the rest of the tube.

Gnarlyscoots:
Where do you keep the bike? If it's kept in a warm room, the tubes lose pressure too, especially if they were blown up using a high pressure or electric pump  :)

griff:
If they're 80s tyres then you really shouldn't be using modern air to pump them up - this can be very dangerous (remember the cross ply / radial public service films?*

Get yourself some NOS air - available from reputable retailers and the internets







* here's that radial/cross ply film for anyone too young to remember  :2gunsfiring_v1:

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