Tuning a 5 string up to C

[SteveXFR]

I'm struggling with my P bass in C so I tried using my multi scale XL 37" scale length 5 and it plays and sounds great. I'm only using 3 strings so slackening off the other two to try to avoid over stressing the neck. Should it be OK or am I risking a broken neck?

[Cosmo Valdemar]

Do you mean tuning the strings up a semitone? It shouldn't have any adverse effects on the neck at all, although you might need to tweak the truss rod. Loosening the other strings won't help.

A good friend has his bolt-on Warwick Thumb tuned to CFBbEbAb for the past 20-odd years and it's fine.

[MichaelDean]

Should be alright. My Dingwall is in drop C all of the time at the moment. I'm using the Payson set for it. Sounds great. I've even tuned up the A# string to a C as well.

[Dan Dare]

As others point out, a semitone shouldn't drastically increase the tension. Effectively, it will be akin to changing to heavier gauge strings, so the truss rod may need a tweak. If you're worried, you could use slightly lighter gauge strings. I wouldn't slacken any, as that may stress the neck unevenly.

[BreadBin]

I often tune mine to C, when playing along with Devin Townsend songs.

I've seen no ill effects, and it's quite good exercise I feel.

[Mykesbass]

If anything, slackening off the other strings will be the bigger problem as the tension across the neck will be way off kilter. Semitone up no problem. 

[SteveXFR]

Thanks everyone.