TubaForum.net

What size rotor would you use for a 5th valve add on and does anyone have one??? I’m receiving a used 186 this week, and if it plays like I hope it will, I would like to add a 5th on it in the near future. The horn is an early 70’s late 60’s…….

Miraphone claims a .772" bore, but probably/actually a three-plus thousandths smaller bore.

Moot, if ordered from Miraphone, because it will be theirs - so it will be the correct bore size.
For B-FLAT tuba, I would recommend an adjusted SEMI-tone with a 5-inch-or-so pull, and well-aligned.
5-4 can be used to play low E spot-on in tune and (assuming 4th valve C is flatter than 4th valve low F) 5-1-3 can be used to play B-natural spot-on in tune.
With the recommended set-up, 5-2-4 (pulling the 5th slide out about 4 inches) offers a spot-on low E-flat, and then your D (2-3-4) doesn't involve the 5th valve.

Hopefully, you have enough straight pipe (in the mouthpipe tube - above the 1st rotor) to add a 5th rotor without having to change up anything.

(The reason I don't believe that you do not need an adjusted WHOLE tone length is because a B-flat tuba ALREADY offers a very nice low F - which is the main reason for that length on a C instrument, so you can then move on to the NEXT-worse/worst problem - using the length I suggest - which is the sharp 2-4 combination...which - with an adjusted WHOLE-tone 5th valve - is FLAT...ie. 5-2-3 would be FLAT.)

I have no idea how busy I'm going to be this winter, and I have no idea what your opinion might be of this advice I'm offering, but I think it would be fun to install that on a 186.

I just received the instrument and it is fantastic. It is a 1970 model 186. It plays well with the lead pipe that has been rigged upon it. But I think I definitely would like to replace it with a Truman Mirafone lead pipe. Where would you recommend? I begin looking for a lead pipe with a receiver on it? Is that a direct to Miraphone thing or should I try Badger?