Correct BPM to set for a 6/8 shuffle rhythm pattern so that is sounds like a 12/8 tempo at 135 BPM?

Question

I am learning to play Tie Your Mother Down by Queen:

The song should be played at 135 BPM, the tempo is 12/8 (3 eight notes on each of the 4 quarters of the bar):

Beats: 1 ...... 2 ...... 3 ...... 4 ........
Notes: 1  2  3  4  5  6  7  8  9  10  11  12
       \     /   \    /   \    /   \      /
        \   /     \  /     \  /     \    /
       Triplet  Triplet  Triplet   Triplet (each note 1/8) -> 3 * 4 = 12 1/8 notes

My keyboard (Roland Juno DS-88) has builtin rhythm patterns which I use for the drums while playing.

The problem is that there isn't any pattern with a 12/8 tempo, so the closest one is a 6/8 shuffle tempo.

But at 135 BPM the 6/8 shuffle is too fast. How can I set the BPM accordingly so that 6/8 shuffle sounds as the 12/8 at 135? Is there a formula, a rule or something?

Thank you!

UPDATE: Right now, if I set 115 BPM and use 6/8 shuffle, it almost sounds like the speed of the original song, but I am not sure, I have just set it to this value while I was playing.

Answer 1

It makes sense that one bar at 12/8 is twice that on one bar at 6/8, so halving the time factor will be the solution. Half of 135 is 67 ish, but if you leave the bpm at 135, and treat each two bars at 6/8 as the one bar at 12/8 it should sound right.

The 12/8 is a red herring, as 135 is the timing for the four beats in the bar. If you used a straight four beat at that tempo, it fits. If you keep that same bpm and use 6/8, then two bars of that will be the same feel - almost.