Talk me down!

[pooks]

Pooks,
I've had 2 bike computers installed by LBS - both were set up wrong.
So, what to do:
Line the bike up on a seam in your driveway (if you've got one), lay out a tape measure and start rolling the bike. Use the valve as your start point. roll one revolution and measure the distance. Do this 3 times to make sure it's accurate. Multiply the inches by 25.4 to convert to mm and program that in as your wheel size.
The roll out method is much more accurate than any of the calculations. Also, try to make sure your tires have the air you usually run in them, and if you sit on it while you roll it out that will help even more.
This is better than using tables etc because every wheel has a slightly different depth, regardless of the size (700, 26", whatever are not all equal within a class).

Guess what! The guy at REI told me that's what he's going to do, and he's glad I'm bringing it back because he wants to demonstrate that method to the other guys in the shop!

Pooks

ETA: I don't have the manual. It has disappeared. My husband threw out a bunch of magazines over the weekend, and the instructions to install the Astrale must have gone with them -- which is why I gave up and took it to REI to install yesterday. They did say they'd photocopy the instructions for me so I'd have them. I forgot to do that while I was there yesterday. Must remember today!