Hi,
I’ve got a rear shock that’s 222mm long and the spring gap measures 155mm.

Could I fit a 145mm spring and wind the preload more?

Measuring 145mm along the shock would leave me with half of the remaining thread for pre loading the spring.

Anybody got any idea if I’d be entering a world of pain?

Edit, reason being I’m trying to find a Vivid Ti spring and it’s proving very hard to find the correct combination of length, weight etc
Thanks

What numbers are on the springs?
ie 450×2.75(2.8 fox), as a guide try to make sure that the second numbers are the same.
As long as the spring is weighted correctly for you and is long enough for the shock to fully compress then it’ll be ok.

thanks for the info.

One spring I’ve seen is 450 x 2.75 (which is the correct stroke length).

There’s another that’s 500 x 2.75 but I keep reading that a N’proof Ti spring should be 50gs lighter than what’s on already. I’ve currently got a 500lbs spring on my Fox Shock (that’s being replaced with the Vivid)

Either of those will be fine then.
Have you checked tftuned spring calculator?
Weigh yourself in all your riding kit(not saying you haven’t already) you may find that the 500×2.75 is correct

Yep, TFtuned says 429.

I’ve ordered a 425 spring and am tempted to grab the 500 too. Test both then sell the unwanted one.