Depends on the distance of the tri's your doing.
Olympic distance in say 2hrs would not be too bad. However, Ironman distance...say 10 - 11 hours then Clenbuterol may not be ideal as it raises the bodies core temperature and may possibly lead to dehydration and / or Sodium depletion. The latter is particularly dangerous for ultra endurace athletes.
If you come off it a week or so before, you may be OK. Beware its half life time.
True, Clenbuterol opens the lungs and helps to reduce muscle loss at the end of a cycle
. It also strips fat, but it does have its down side.
Never really used Winstrol - stanozolol dep on its own for that long. Usually as part of a stack.
Try this link - good info http://www.clenbuterol.com/