Lift Capacity...

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I logged on to ask questions along just these same lines... I am replacing my BC and have stumbled into having to understand just these issues.

I dive in the Caribbean a couple of weeks each year and do several dives in the cold water of Ontario. When south I use a 3mm full wetsuit, (with 18lbs o' lead), and when diving in Ontario I use a full 7mm double-core wetsuit, (with 28lbls o' lead) - this all seems to have worked out pretty well so far but the BC is not comfortable and is not really a good fit. I am 6' and about 220lbs - relatively solid. I bought a cheap Dacor Enduro BC when I first started diving and its time to replace with a back-inflate.

I was considering a Zeagle Stilleto but my LDS is suggesting that the 34lbs of lift is inadequate for the 7mm cold water diving. I don't want to over equip here as I also want to keep the BC as low profile and light/packable as possible. It seems the next step up in lift is somewhere around the 44lb lift bladder of the conceptII/Ranger series.

I wonder if I really need all this lift - by my calcs the 34lbs seems adequate...?

I dive a Sherwood Avid, L which has 32 pounds of lift. Wearing 20 pounds while diving E7-80s in to the 75 foot range in fresh water I never seemed close to maxing anything out. You will keep adding air since the air in the bladder gets compressed, a lot of this does not translate into lift it's a combination of increasing and maintaining displacement (lift) as the surrounding pressure increases. Remember that while pressure increases with depth the density of water is essentially constant and density is what displacement plays against for buoyancy.

The Avid is a very common cold water BC around here.

44 pounds is a lot for single tank diving. Especially since being in Ontario for your cold water dives you may end up in a drysuit which can/will contribute lift relative to your starting condition.