string selection
 

what do you guys use for drop c tuning for 4 string bass?
hard to choose between

Ernie Ball 2831 Nickel Wound Power Slinky Bass String Set (55 - 110)

DR Strings DDT-55 Stainless Steel Bass Guitar Strings, Heavy
55-115

or

DR Strings DDT-55 Stainless Steel Bass Guitar Strings, extra Heavy
65-125

Might help if you told us what strings you are using now, and what you like/don't like about them? Maybe what kind of bass you have, what kind of amp/cab, what genre of music, etc.? :)

I personally use Thomasic Infeld Jazz Flats (.100/.070/.056/.042) and Acousticore (.086/.068/.053/.041) for Drop D and Drop C. YMMV.

For Drop C I use gauges .125 .085 .065 .045, if you want more tension for this tuning I'd recommend .130 .090 .070 .050. I put together singles to achieve this, or purchase 5 string sets and throw out the "E" string.

For Drop C you would go with Tylerwylie's suggestion...

Those sets are better for C Standard.

How long is it?
 

What's the scale length of your bass? If it's 34" or 35", then I agree with tylerwylie's reco. You CAN go as high as .145 for the low C if you want to tighten it up. Tension increments are small with fat strings so don't be afraid to go BIG.

my bass is ltd 1004 phoenix
playing metal
ampeg cl head 410hlf
the string right now is stock string

For drop tunings I've always found getting single strings for custom gauges more useful.

I use Ernie Balls 45 65 80 110 for a Drop Db Ab Db Gb.

The power slinky's are equally a heavier gauge across all the strings and i find tensions across the neck uneven.. both in sound and feel