How can I center a TV on a wall with a centered stud?

Question

I have a 60" Panasonic Plasma TV that weighs 81 lbs. I want to hang it on the wall using a full-motion wall mount made to handle 175 lbs. The wall is drywall with wood studs. I plan on using the 4 lag bolts provided on two studs. I don't know the size of the lag bolts. The Instructions say to drill 3.5" pilot holes using a .25" bit. So, my guess the lag bolts are slightly bigger like 3/8". The problem I have is with the wood studs. There is one at the center of the wall. To the right, the next one is 12-13" apart (center to center). To the left, the next one is 16" away. These are 2x4 studs.

The wall plate on the wall mount has many holes in the back for the lag bolts. Would it be safe to shift the mount off center so that the end result is the TV is centered to the wall (but not the studs).

If it is not safe, would it load be easier to the studs on 13" apart or 16" apart?

If I can do option 1 but have to give up extending out the TV, I am ok with that.
UPDATE:

Thanks for all the input so far. The TV mount has 2 arms that attach the wall mount plate to the tv mount plate (they come together like a "V") but they cannot slide or adjust. Here is a link to the TV mount, product 12280 on monoprice. You can also some of it on the box in my pictures. http://www.monoprice.com/product?c_id=109&cp_id=10828&cs_id=1082821&p_id=12280&seq=1&format=2

I want to use 2 studs (and 4 lag bolts) but do not want to add any new boards behind or on the drywall.

These two pictures represent the options I am considering.

As you can see, with Option 1 (red arrows) the TV will only be 3" off center to the Center Stud but it leaves 8" of the wall mount unsupported. Would this be an issue when I pull the TV out? Would strap toggles be necessary on the left side of wall mount? Option 2 (blue arrows) looks for secure to me, but is further from center so I would only consider it if Option 1 is not safe. Thanks!

Answer 1

Measure the side to side of the back plate. I believe that most manufacturer's will have the plate long enough to span 2 wall studs. (BTW: most wall framing is established at 16 inches on center or 14 1/2 inches in between 2 wall studs). If your plat measures at least 16 inches install it on the 2 studs closest to the center of the wall. Some TV wall mounts have 3 axis' of adjustment: one axis allows you to swivel the TV side to side. This makes it easier to orient the TV on the center if the mounting plate was not. Also, it may be possible, depending on the mounting plate type, to offset the bracket that attaches to the back of the TV so that when it is hung on the wall mounting plate it is closer to room center.

Answer 2

Sanus makes tilting wall mounts that are designed for an off-center mounting on a stud. You can adjust the television a couple of inches to the right or left of the stud so that it sits where you want it to be. Check out their website for more details. They have a model that'll hold up to a 130 pound TV, or so their engineers claim.

Answer 3

If you can offset the mount to hit two studs, that would be better, as @ojait suggests.

If you would rather leave it centered, you can. The main stress on a fixed TV wall mount attached to one stud with two lag bolts is downward. This puts a shear stress on the mounting lag bolts and compression stress on the holes in the studs. There is also some outward stress. This is a form of tension on both the lag bolts and the studs themselves.

When you use a full motion mount, the outward tension stress increases greatly as the TV is tilted, and there is also a twisting, or torsion stress on the bolts and the studs as the TV is moved from side to side.

Two well placed lag bolts can handle most of the stress, but you should supplement them with wallboard anchors at both sides of the mount. I would recommend using two on each side and would use strap toggles.

The straps are shifted so the metal toggle section is parallel, inserted into a predrilled hole in the drywall. The straps are then shifted, turning the toggle perpendicular to the strap and parallel to the inside of the drywall. The toggle is then snugged to the wall by pushing the collar to the outside surface of the drywall, and the excess straps are broken off. The bolt is then inserted through the mount and into the toggle.

These will hold the mount tightly and spread the outward and twisting stresses over a large area of drywall. The lag bolts will still carry most of the stresses. You should be fine.

Answer 4

4 lags in two studs is sufficient. The 8" mentioned is not "unsupported" it is cantilevered with plenty of support.

Answer 5

It isn't necessary to center the mount on the studs. As long as you hit the studs, you'll be fine. Make sure you locate them as accurately as possible.

UPDATE: Both of the options in your update would be fine. As long as you hit two studs, with the center of the mount between the studs, it will be solid.

If you want it right on center, you could put two lags through the center of the mount into the center stud, and a pair of Snaptoggles into the drywall on either side. The lags would bear the lion's share of the weight (and would probably be adequate by themselves) and the Snaptoggles would insure that the mount doesn't flex / stays flat.