Depends how it was set up - if it's already as short as it will go then you'll need to add an inch i.e. one inner and one outer link, to compensate for the approximate two teeth more that the chain wraps around the chainring. To check, split the quick link and wrap the chain around the largest sprocket and the 40t chainring, not through the derailleur, so the ends overlap on the chainring - if it only overlaps 4 or 5 links you'll need to add a couple more. Rear suspension and you may need another couple more - it's important that the chain can easily shift to the largest sprocket without binding up, even in the tightest position of the swing arm.