Each shock company sets up a valve chart, and each valve chart is different form each other, and some times a shock company may have more than one set of numbers for different shocks. The best way to put this is no two numbers are the same. A guy will and say, I am running a 3 valve RR and this has very little meaning. There was a day that it meant something more than is dose today, but as you shock guy gets better it means less.
As we already know all twin tube shocks have more rebound in them than they do compression, this is something that the car manufactures did years ago and the racing community just followed that path. Just to clear that up a 3 valve twin tube shock is as such (100 lbs of compression and 150 lbs of rebound). This has confused most people for years or most did not know that it is this way. BSB shocks are the same from side to side, for example when we do a 3 valve it is 160 rebound and 160 compression, and if you want a split valve than we just do it that way. Most shock companies also do compression 1st and rebound 2nd, but BSB and a few others do it backwards, reb. 1st and comp. 2nd, as far as I know the reason for this was because the dyno’s back in the day which were like the pencil dynos of today had rebound 1st or on top. I know this makes it hard for a lot of people and that is why we do something like this for you. 7r-2c or 300r/125c. Just remember that when you tell your shock guy to just do you a 4 valve for the RR that there could be a lot more evolved in doing it than you think. Check out the cart and you can see the difference in shock companies valve codes, but remember this is the chart we use to express what we call a 4 valve for other shock companies.
Update: 4/11/2020 code extended to a 20 valve number.