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Ideally you would want to install the grab bars onto wood studs, whether there is tile or not. However, most grab bars are not sized to precisely span the standard 16" center-to-center spacing of wall studs. Some installers will purchase longer bars... 18" or 24"... and install them at an angle so that each end aligns with a stud. However, all homeowners do not want this "askew" installation.
Using toggle bolts, the folding fasteners commonly used on drywall... is an acceptable alternative for one or both ends as long as you use 3/16" or (ideally) 1/4" toggles. You do not need to use toggles in every hole... two 3/16" toggles per side (top and bottom holes) is more than adequate for most installations. If you can locate the studs (sometimes difficult through ceramic tile, even with a "stud finder"), try to attach at least one end of the grab bar to a stud.
(NOTE: Though toggles can hold hundreds of pounds, they obviously are not as strong as mounting the bar into solid wood. However, mounting in wood might require extensive carpentry and tile work, in some situations, to add the necessary supports within the wall. The expected use of the grab bar is critical in determining whether such an installation is necessary.
For example, if this grab bar must support the full weight of a heavy person over and over again and act as a critical safety device, toggles might not be adequate. Also, for commercial and medial situations, there are building code regulations that may apply.)
Ceramic tile can be drilled with either sharp masonry bits or with special ceramic tile bits. I emphasize sharp... buy a new one for this job! To help start the hole where you want it, put a piece of masking tape on the tile to keep the business end of the drill bit from slipping until it makes a dimple in the tile. Fortunately, the location of the hole is not micrometer critical, since it will be covered by the grab bar mount.
I like to drill the smallest hole possible, so I use a unique toggle bolt called the "Toggler". It is a specially designed toggle that uses a solid bar instead of a folding toggle and is held in place on the wall with a vinyl harness. The advantages of the Toggler are two-fold. First, you do not need to drill as large a hole to get the same strength... important when drilling through ceramic tile. Second, the toggle bar stays in place when installed. This means that, unlike a standard hinged toggle that drops into the wall when you remove the bolt, the Toggler's bolt can be unscrewed and rescrewed numerous times.
You can get more information on the Toggler at www.toggler.com.
You can probably buy them locally but you may have to do a little hunting.
A final note... with standard toggles, part of the hole in the wall may appear around the edge of the grab bar if the holes in the grab bar are close to the edge. To prevent this, offset the hole for the toggle towards the center of the grab bar mount. Just make sure that the desired location of the bolt is within the offset hole. Have fun!