I'm wondering if anyone can tell me, what's the thickest possible string for a bass that will tune to A?

Mainly I use drop tunings and have the 3rd string tuned to F# but sometimes I do tune it to A, so don't wanna have to restring every time!

Any ideas/suggestions?

PS the main reason for this is that I use a .110 for my E (down-tuned to B) and it's waaaay louder than the A (F#) when I play. I think the A is a .085 at the moment

you should probably just buy a 5 string bass.
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So, you play in drop B then? By that i mean B-F♯-B-E.

One way to switch between drop B and E standard might be a 5er with light gauge strings on it so you can tune up the extra step on the E A D and G strings. but the tension would annoy me and you'd have to adjust the truss rod every time you made the change.

You should check your pickup height if you havnt yet and lower it a bit more if needed to keep the output of each string even enough.

Anyway, going from B-F♯-B-E to E-A-D-G just isnt going to be any fun the gauges needed for each tuning are just too different.
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