Mrs has bought a dh bike and rear spring is 400×3.0. She weighs about 136lbs in her gear. Would a 200 spring be good and get better results out the shock.. or just bottom out. Not shops open to ask. And no pictures!

Have a look here:

http://www.tftuned.com/spring-calculator

How much sag does she get at the moment and how much do you want? The maths is easy from there as springs are so linear.

Turn preload to zero and measure sag. You don’t want too many turns of preload as you will bind the spring. A 400 lb spring with 3 turns gives me roughly the same sag as a 450lb spring with no preload. I prefer the 450

And thats all doubls dutch. Wheres the idiot guide for me

It’s in the very first response

Spring calculator was piss poor for me

And me.

What’s the stroke of the shock and how much sag do you get on the 400lbs spring?

A 200lbs spring will double that sag.

Spring Calc, call TF speak to them and order the spring from them. Had great advice especially when I’m on the borderline of the spring weights.
Edit you are also better knowing what bike, what suspension style etc.