04-03-12, 09:14 AM
yes 27mm nut...when checking for slack push the chain up and down and adjust for 30-40mm of slack..dont forget to find the tightest part of the chain as you may have a tight spot,if thats the case adjust the chain with the 30/40mm measured at this point....also a good time to lubricate the chain and to make sure the wheels are aligned....these simple measures can transform the way the bike handles and also prolond the life of the chain 
One, is never going to be enough.....