I've been thinking of replacing the steel spring on my shock with a TI one, and an acquaintance offered an unused (old) Progressive Suspension spring for a good price.

Problem is, that the spring is rated at 2.25×350 while I need a 2.75×350. He said it should be fine up to 2.85 (I guess that's fox for 2.75), but it still sounds scary to me. Supposidly the coil is very sparse, and he measured the gaps in between the coil add up to 3.5" (it is also long enough).

Am I asking for trouble if I buy it? Is there a way (other then measuring the gaps) to make sure if it would fit?

it's the wrong spring.

Don't use that spring the stroke 2.25 is too short, it may bottom out before the shock, damaging the shock.

So even if it can compress over 3" there could still be a problem?

I called tftuned and they figured that if I draw a line along the side of the spring and the gaps add up to clearly more then the stroke (3.5" vs 2.75" in this case) then it should work, if I can get the preload right that is. They figured this spring was probably a longer one marked down actually…

Put on the new spring, and it seems to fit ok (did not try yet). The weight saving was quite massive, old spring was 480g, new one is 148g.