I have open bath Float 32 RLs and was wondering about changing the shims to increase the compression damping a bit. However, that’s relatively complicated… On the other hand, I have my rebound damping set towards the slowest end of the adjustment (because I run my air pressure quite high), so if I had higher viscosity oil then that would increase the compression damping and bring my rebound control’s default more towards the centre of the range.

Seems a good idea but I’m probably missing something!

This would work. I once contemplated doing the opposite (a lighter oil) in some Marzocchi’s but never got round to it.

I would only go up by 2.5wt to start with though. Oh, and if you do a search online, it seems that not all oils are comparable. So one brand of 7.5wt might be more like someone else’s 10wt.

Incidentally, I’ll glad I finally understand how shimmed dampers work! I remember building a Tamiya R/C car when I was about 10 and liking how you could change the pistons and oil to get the damping you wanted but I wasn’t sure what all this shim-stack malarkey was about. Seems by placing shims one side or t’other of the piston, the shims act as one way valves which can open to become two way valves under high loads, so you can have different damping rates in either direction, which then change again depending upon applied forces. Very cunning.

Your theory is sound and it should work if you spec oil in centi-strokes rather than by wt.