Originally Posted by
Darth_Firebolt
Depending on the maximum large cog tooth count that the current rear derailleur has, he could very well need a new one. If it's listed as 28 and someone has put a 32 in it (as many Shimano derailleurs have been known to be conservative in their max tooth count), then he is out of luck with his current equipment.
According to Surly, the Cross Check comes with a Deore mountain derailleur, so should be no problem to fit a 36 tooth cog on the back.