Sidemount VS Backmount

Have seen many posts from SM divers talking about which tanks they use: but wondering what the consensus is about which tanks "carry" the best and what measures if any divers use to make them better.

For dives where I'm not taking tanks off... LP95s work great, for my body type. I've not dived with anything smaller that didn't ride just fine.

I used to dive with HP130s, but when they were full, they put me a little foot heavy. I had room to adjust the bands further back, but the valves would be way too far forward and they'd be well below where I'd like.

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Originally Posted by SuPrBuGmAn

For dives where I'm not taking tanks off... LP95s work great, for my body type. I've not dived with anything smaller that didn't ride just fine.

I used to dive with HP130s, but when they were full, they put me a little foot heavy. I had room to adjust the bands further back, but the valves would be way too far forward and they'd be well below where I'd like.

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Body type is important. I am 5'4" and I and a lot of women might not fit your size. What size are you?

5'10"

Rent tanks from Edd and give a few sets a whirl, or borrow? There's a ton of people in Wakulla/Tally sidemounting.

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Originally Posted by Puttzer

Have seen many posts from SM divers talking about which tanks they use: but wondering what the consensus is about which tanks "carry" the best and what measures if any divers use to make them better.

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I'm curious about this as well. As a newbie SM diver, I've only had the opportunity to dive AL80s in fresh water and HP100s in salt water.

While both were stable platforms, I really liked the rotational freedom that the AL80s provided. The HP100s, being only a few pounds more weight in the water, ended up like ballasts on each side of my body. Very stable in the water, but every time I rotated out of horizontal trim, it'd snap me back in place.

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Originally Posted by Gary

but there is no "best system" they are all systems with different advantages and disadvantages and different areas of weaknesses and strengths - plus a lot of personal preference, experience and expectation to boot.

If you want to spend 98% of your dive horizontal and like it SM may be good for that - it's also good for variable geometries and low passages. No-mount is good for smaller passages yet. Backmount is very easy to learn, maintain and very adaptable to a lot of diving. If you want redundant systems lots of independent tanks are good for that. If you want buddy system air-tracking/sharing simplicity manifolds are good for that. Strait bar manifolds are simple use no-problems with valve alignments or fill mix-ups.

But for all the argument that goes into "proving" (theorizing why) one system superior to another there are almost NO real life death counts to indicate that any of this is a problem. Even when diving a "single-tank, single reg and solo" people aren't being found dead due to equipment failure. Out of air accidents are traced back to bad planning, silt outs, not running lines getting lost or confused. Gas mixtures are far more dangerous than tank configuration.

There are a lot of bad ways to set up equipment but no one way that is inherently superior for all needs. Different set ups have advantages in different areas of endeavor. Different people, different types of diving, different conditions and no way to put 100% money and effort into every method all at once.

There are things that are similar for each but not all experiences cross over. An experienced rebreather diver is not inherently ready for a complex sidemount dive (or vice-versa). A diver used to independents but diving on a manifold may think they are out of air on both tanks when they simply had a roll off on one with the pressure gauge. Trying to learn "all configurations" doesn't prepare one as well as concentrating on one or two that best meet your needs.


Even experience with a particular system may not prepare one for the unexpected enough - nor guarantee that one interpets the symptoms properly. Imagine diving into a deep syphon surprised to find your gas going much more quickly than expected - already below 2/3! Turning the dive and heading back (already nearing half) you discover the problem: the manifold valve is closed - you are breathing from just 1 of the 2 tanks. But cracking the isolator open doesn't fix things - instead the pressure drops from just above 1/2 to just above 1/4 - since the isolator valve was already shut when the tanks were getting filled...

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I disagree with you Gary, again I have dived extensively in BM before switching to SM so I am coming at this SM thing after realy giving BM a run here. The kind of diving I do involves carrying tanks down sinkholes, dry caves, virgin jungle, rappeling etc.. so right from the start and before even getting in the water doubles are either very impractical or not possible at all logistically, for example there are a few dry caves that you can hardly get in but then open up for the walk down to the water, in these cases you would have to take apart your doubles and reassemble them on the other side (or dive SM) to me a much better solution. Then I mostly dive caves that have not be dived before so I have no idea what I will find, I do not want to trek for and hour, climb down a vertical sinkhole only to find that 10 mins into the dive I come upon a restriction that I cannot pass in BM, SM allows for a much greater level of flexibility that BM cannot physically provide you are limited by the space that the tanks take up on your back period. That is the kind of diving I do and BM makes absolutely no sense to me and is very limiting, it is why I state that for the kind of stuff I do SM is a much better system. Now I am not sure what rig you are using in SM but, although I do spend allot of time right side up, I find that SM is far superior when you have to wiggle your way through tight spots upside down, in BM I found that you are way too back heavy, I do not like that in SM it is much more neutral and in my view feels better upside down etc.., also if you do get "stuck" I wear my rig slightly loose as it allows me to wiggle my way out if need be.
No I am not saying that SM is better than BM I am saying that for me BM makes no sense at all as it does not have the flexibility of SM.
I can think of many situations were BM would be either a real hassle or not possible at all but I can think of none were SM would not work.
Even if SM were a bit less safe than BM I would still choose to dive SM as the system offers a far greater level of flexibility than SM.
Granted there have been many caves mapped and dived here in BM but some of them would have been so much easier and far less work and logistics had they done it SM. SM is not at all a system just for small tight restrictions, it is a simple single rig system that allows one to dive anything, anywhere with any size tanks.
But again to each his own, I just found that doubles were a real hassle and also more importantly I have way more fun diving SM than BM.

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Originally Posted by Puttzer

Have seen many posts from SM divers talking about which tanks they use: but wondering what the consensus is about which tanks "carry" the best and what measures if any divers use to make them better.

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"Carry" as in transport to dive sites or "carry" as in the way they ride through the cave?

"Carry" as in transport...that was a huge motivational factor for me to go SM. I dive out of a Mustang convertible. Pulling a set of doubles out of the trunk OR from behind the back seat involves back-wrenching that was making my chiro rich. With SM, the 85's fit easier behind the back seat, but the 95's and 108's fit, too...just less room between me and the steering wheel.

"Carry" as in, well, carrying...if I'm energetic, I can always carry both tanks down to the water at the same time. Otherwise, I have the option of taking one at a time, or conning two innocent bystanders ;) When the dive site required...lowering them one at time on rope was also easier than trying to lower doubles would have been.

which tanks "carry" the best - the one in the other persons tank bag ;)

I think putzer was referring to how they "ride" on your side during a dive. Things like bouyancy and trim.

A lot depends on the size of the diver, both height, and body weight. I am 5'9", and weight 160 lbs. I sidemount tanks from 14 cu ft, up to 104 cu ft. Smaller tanks are much easier to trim, but require me to wear weights with them. Big tanks don't need any weights, but trim is harder, because they tend to "ride" in one place. If that place is right for your body, then they are wonderful. If they ride too far back. then you will end up tail down.

Like some mentioned, borrow/rent various tanks, and see for yourself.

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Originally Posted by sskasser

"Carry" as in transport to dive sites or "carry" as in the way they ride through the cave?

"Carry" as in transport...that was a huge motivational factor for me to go SM. I dive out of a Mustang convertible. Pulling a set of doubles out of the trunk OR from behind the back seat involves back-wrenching that was making my chiro rich. With SM, the 85's fit easier behind the back seat, but the 95's and 108's fit, too...just less room between me and the steering wheel.

"Carry" as in, well, carrying...if I'm energetic, I can always carry both tanks down to the water at the same time. Otherwise, I have the option of taking one at a time, or conning two innocent bystanders ;) When the dive site required...lowering them one at time on rope was also easier than trying to lower doubles would have been.

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Originally Posted by phillip1

The kind of diving I do involves carrying tanks down sinkholes, dry caves, virgin jungle, rappeling etc.. so right from the start and before even getting in the water doubles are either very impractical or not possible at all logistically, for example there are a few dry caves that you can hardly get in but then open up for the walk down to the water, in these cases you would have to take apart your doubles and reassemble them on the other side (or dive SM) to me a much better solution.

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Sounds like a sidemount CCR driven off a pair of 14 cuft supply bottles would be perfect for you. Lots of divers diving like that with a single 40 cuft bailout (or with the 14cuft bailout). Practically unlimited bottom times. Minimal weight.

Of course any system has disadvantages. Limited bailout, reliance on electronics, durability, price, extreme commitment to equipment maintenance and preparation, lots of training, and a high, poorly understood, fatality rate...

Lots of trade offs in that range of equipment as well. New rebreathers with enhanced safety features, or even SCRs that can do without electronics. Some designs are commercially available while others can be built from kits or even designed and built from scratch.