Talk about stumbling at the first hurdle.

According to wheelpro's spoke length calculator, I need 270 mm spokes.

Which is fine, but CRC only go to 268, Wiggle want to sell me 100 at a time and don't list 270 either, is there anywhere else?

Just go to a bike shop and ask for the number you need they will probably have the right length.

seems quite long for a MTB wheel?

try dtswiss.com

a bike shop will probably charge around £1 per spoke! mine does, and 2mm will make bugger all difference anyway

Daft, I didn't think about asking LBS, doh!

nickc, it's an old Hope XC hub with a Mavic xm819 rim

cycle basket
uk bike store
spa cycles

HTH

mmb I did wonder if 2mm would make a difference, it's my first go so being careful.

a bike shop will probably charge around £1 per spoke! mine does, and 2mm will make bugger all difference anyway

change shops, the one i used is 50p inc nipple for one silver sapim race

OK, feeling really dumb now, thinking I was wrong somewhere I put the rim and hub back into the calculator and come up with 259mm.

Skulking away now in shame at my general dimness.

2mm makes a lot of difference if its 2mm the wrong way. ie you run out of thread.

Don't forget you'll need the mavic tool for the spoke insets on an 819 rim. Not the easiest rim for your first build

Not the easiest, but IMHO the best wheel, well components anyway 😯
and it's the rim that features in the wheelpro book.

The way my brain is functioning at the moment this could be a challenge 😆