One topic that seems to come up frequently in online forums like thesession.org and Banjo Hangout, are what string gauges to use for Irish tenor banjo? First off, the term Irish tenor banjo is somewhat misleading. It doesn't necessarily mean you play Irish music, it just means you tune your tenor banjo GDAE - one octave lower than a mandolin or violin. This tuning is preferred by melody players who flat-pick fiddle tunes because of how it suits this type of music. It works great for old-time or any mandolin-related music actually.
Problem is, most tenor banjo string sets that you can buy are still intended for the classic jazz tuning of CGDA. These strings will be too light and floppy for GDAE. You will need heavier/thicker strings for the Irish tuning. So, what I do is buy single loop end strings in specific gauges from JustStrings.com, a retailer in Milford, NH USA that - you guessed it - specializes in strings.
Opinions vary on exactly what gauges to use. One benefit of assembling a custom set is it allows you to zero in on the best fit for your instrument. The biggest string-related debate among tenor banjoists might be over how heavy do you need to go for the "G" string? For my short scale 17-fret openback tenor banjo, I like to start with a fairly heavy G string, at either .044" or even .046", and go from there. I don't mind the thickness of the string as much as I like the tension it provides.
Here are the gauges I use:
G - .044" or .046" - Nickel Wound or Phosphor Bronze
D - .032" - Nickel Wound or Phosphor Bronze
A - .022" - Nickel Wound or Phosphor Bronze
E - .013" or .014" - Plain Steel
I don't recommend mixing and matching Nickel Wound and Phosphor Bronze - but use one or the other and see which sound you prefer. Nickel Wound is probably the most popular and durable. Phosphor Bronze can sound funny at first, but develops an interesting tone after the initial brightness wears off. For Nickel I usually get D'Addario brand and for Bronze I've been using GHS.
What gauges, string types and brands do you use?