cmat

I was tweaking tire pressures on my car after its winter hibernation (I do drive it some when roads are dry so I don't pump them up high to avoid flat spots) and had a thought. My pressures seem to have stayed more constant over time compared to other cars. Could that be because the total volume of air in the tire includes the hollow spoke volume so it is greater for the same size tire than with a normal wheel? If this is not the case, wouldn't it be a good idea if it did? ......just wondering.

VNTGSPD

IIRC, the hollow spokes do not share air with the tire. The spokes may be hollow, but they are also completely enclosed.

cmat

Thanks. I guess is there was a good reason to connect the air in the hollow spokes to the tire, Porsche would have done it.

DanQ

This is true. I had an intersting experience when i pulled the valve stems out of my hollow spokes the other day. When I unscrewed the nut on the stem, and disturbed the rubber gasket, a tiny amount of air escaped. I wonder if there isn't some porosity that allows air pressure in the spokes? Or there was just different barometric pressures when the valve stems were installed from when I removed them. Obviously there was no tire on the rim at the time, but there was pressure in the wheel itself

Canyon56

That's right, no air from the tires in the spokes themselves. You don't want them open because you don't want water (condensation) and any crud getting in the spokes. The crud would spin around in the spokes and get stuck, throwing off wheel balance making the wheel useless. I have a set from a 996TT that was refinished and crud somehow got inside the valve stem opening on one of them during the refinishing; the wheel had to be replaced as it was impossible to balance it.

H.H.Chinn

Porsche hollow spokes are filled with exotische luft von Leipzig making them extra light.

cmat

I'll bet that Porsche looked into that.

vincer77

Now I remember long ago reading that the 959 hollow spoke wheels did actually have hollow spokes opening through the rim. Is this not true?

cmat

I did a little search on the 959 and you are correct sir. There was indeed extra air in the spokes for the tires. This must be where I got the idea. You can read about it here: http://auto.howstuffworks.com/porsche-959-history.htm

Augustus Davies

That tiny amount of air you heard escaping was actually helium. Porsche does this at the factory...after it leaks out it can't be filled again...

Boston911fan

I have hollow spokes on my VW New Beetle Cabriolet and find that you almost never have to add air because they seal so well with the tire.

nippy

I also recently refinished my hollows and when I pulled the valve stems ,allot of air came out of the wheels.

LOl,just realized how old this post is,oh well.