Hi. I have an old Silca Floor pump that has a head that I do not see anywhere. It can be changed from Presta to Schraeder by reversing which side of the central barrel is facing "out". Top cap is unscrewed, barrel flipped, cap screwed back on. My problem is that it is leaking at that "O"-ring which seats into the "bottom" cap. I cannot find mention of this part anywhere including Silca's Site, and it feels like it will crumble apart if I try to remove it to match it up.to a new one.....where??
Can anyone point me in the right direction towards a fix for this? I would really not want to buy a new head if I can get away with either a rubber ring or that whole ring-hose-fitting bit.
Thanks!

Yeah, this probably is a Silca article 24.4 chuck or pump head, they varied a bit in details over the years but doesn't seem to be something the NEW Silca owners offer in their catalog (in stainless steel let alone brass). But as BG says the o-ring is probably something you'll find a workable replacement for in a hardware store with a good plumbing section. It may be originally metric but chances are you can find a good enough match.
TIP: daubing a little silicone grease on neoprene parts makes them last a lot longer but don't go overboard with the grease!

Thanks for the suggestions. That ring seems like it's going to fall apart if I try to remove it to match up to a new one but I might have to try.

Hardware store tip: leave the original o-ring on its brass mount and bring _all_ the parts with you to the hardware store.

Ask for assistance in finding a proper replacement.

You will likely be pleased with the result.

This is some of the best advice I have ever seen on ANY forum. I can testify first person that following it WILL save a ton of grief.

Not to offend anyone I hope but, if the O ring is shot, it hardly matters if you leave it in place and take the whole works into
the hardware store, or not. The helpful clerk will not be able to find you an exact match, or near exact, with the O ring in place.
You can measure the outside diameter as it is, but not the cross section. This is a seal that has to withstand some pretty good
pressure, so fit is important.

If it were me, I'd carefully cut the O ring in one place , with a sharp razor blade, and then remove it, and measure it.
You need the diameter, and the cross section. Or you can compare with available rings at the store. If they have them,
I'd get one as close as I can find, and one slightly larger in cross section.

I was able to get the replacement O-ring and it works perfectly! In case anyone else ever needs one for this particular Silca head, I got it at Lowe's plumbing section - had to get a 10-pack for around $2.
5/16" O.D x 3/16" I.D. x 1/16". I tried doing a reverse Challeger-hearing and had the part in hot water for a while but it still split getting it off; it was intact enough to match up.

...and you're good for another couple decades, with a 10-pack probably a century! Ain't it nice when somebody makes a product with planned NON-obsolescence?