Ok. I haven't had the time to get my suspension upgrades installed yet and am second guessing some of my choices. I have Koni yellows, NM springs and both a 19mm and a 22mm rsb to install. (I'll probably use the 22mm)
However as I read about axle alignment vibrations I'm thinking of going with a set of JCW springs instead. I already have the Sport suspension under my 2009 r56 JCW. How much difference will I see changing out to those springs?

Thanks

It depends on what you are looking for. If you want the aesthetics of a lowering spring, you will likely be disappointed with the JCW. They only drop 10 mm, where the NM is 25-30 mm lower than stock.

I don't know for sure, but I would expect that the spring rates are slightly stiffer on the JCW than what you have now.

I personally think the biggest benefits will come from the Yellows and RSB. I'd put the 22mm on in the middle setting, and see how you like it. I ran yellows on my 08 for several years, and was happy with them. I had them set on full soft, and was really happy for a daily driver.

Said a different way: The springs will be for ride height, the shocks will determine the ride harshness/handling trade off, and the RSB will allow you to tune the response of the car to your preference.

Have fun,
Mike