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Second valve on spacesaver

Posted: Sat Nov 02, 2024 7:38 pm
by Ralph
The spare wheels that have the spacesaver collapsible tyre generally have 2 valves - a bolt in Schrader and a bolt in other type as below:

Image

I thought that this second valve was for rapid air deflation but on the wheel that I have it doesn't seem to do anything? I did read somewhere that Porsche made a special pump that could remove the air quickly to enable the collapsible tyre to return to it's un-inflated size correctly but I also read that this second valve was in fact a reverse functioning valve that prevented the spacesaver tyre from being over inflated.

Does anyone have first hand experience with the workings of these or know exactly how it works?