In simple language, offset is the distance from centre that the rim sits in relation to the spoke flanges on the hub.
On the front wheel, I would imagine that the rim sits centrally as the distance either side of the hub would be the same (I have a disk braked/wire wheel bike. A disk can be fitted to either side and the disk goes into a caliper mounted on forks which have the same bolts/spacers etc. Logically (though not in reality) you could take the wheel out, turn it around and refit it). The only thing thats stops this is the speedo drive.
On the rear wheel, there is probably an offset (but not necessarily, as spacers are fitted to each end of the axle) as the hub has different things happening at each end (cush drive / sprocket carrier one side, brake plate the other). Unless youre geared up to set it up and measure it accurately, I'd take them to a wheelbuilder to meaure before you strip and after you rebuild (well, actually I'd pay a wheelbuilder to do the job!) but then you may be more confident in these things!
wheel rim offset
Thanks for that Stuart. I'm getting the rims rechromed, so need to calculate any offset before I cut them off the wheels. There's no way I'm going to try and lace spokes and true up a wheel, so I'm leaving that part to the professionals!
As far as I can work out, what is needed is a reference point to determine where the rim sits in relation to the hub. So, a straight-edge laid across either face of the hub can be used to measure the distance from that plane to the edge of the rim. As long as the wheel builder knows where you took the measurements from, they can work out where the rim needs to be, as long as the new rim is the same width as the old one.
If I've got that wrong, someone please let me know!
Mark
As far as I can work out, what is needed is a reference point to determine where the rim sits in relation to the hub. So, a straight-edge laid across either face of the hub can be used to measure the distance from that plane to the edge of the rim. As long as the wheel builder knows where you took the measurements from, they can work out where the rim needs to be, as long as the new rim is the same width as the old one.
If I've got that wrong, someone please let me know!
Mark
"I'll have a V please, Bob."