55mm me thinks. You can pick them up on ebay for about £20 but you will need a 3/4" drive socket wrench.
55mm om both sides Chass. Same torque to.......230nm. Watch the eBay stuff. They tend to be alloy and crack. Get a proper socket and skim the lead in off to get a good purchase on the nut.
Thanks Niel I haven't got the bike here so I can't measure it.. sorry Cris916 I stand corrected, I just didn't want to buy the wrong socket