It's pretty crazy cause no matter what I do it still slips... I've had someone hold the front of the bike while I pull the wheel back and tighten. I've tried going side to side while pulling the wheel tight.

Even if I hand tighten the nuts...I'll have the tension nice and tight, but then when I get to the final rotation of the wrench is when the chain goes loose. I wouldn't even care so much, but I've popped my chain a couple times and busted my ass hard last week.