When do strut inserts need to be replaced?
 

Next stupid question: How do you know when your struts need to be replaced?

Bilstein sports front and rear. No idea if ever replaced or revalved. Car weighs about 2555 without me in it. 21-27 T-bars.

I've bottomed out a couple times recently on rough transitions at our autocross venue. Hadn't happened before. Might have been approach angle.

But, I did it again today on a moderately boogered up railroad crossing at the bottom of a dip. Took it at about 50, done that before no issues, and BUMP it felt like I hit bottom.

No obvious leakage. No bounce. Car is lowered to 24.5 to bottom of fender well in front. That's about 8 mm lower then it was before the alignment mentioned in another post. I guess that could be making the difference.

Really, the question is, how long to struts last? 82 SC, 82,000 miles.

Not since 82! The oil breaks down and the seals start to weep. I would send them in to be rebuilt and revalved. Send them either straight to Bilstein or to Delta Vee Bilstein shock rebuild service

Have somebody follow behind you on a bumpy road. If the wheel bounces up and down a bunch (as in, numerous cycles) after hitting a bump, the shock is wasted.

YOu can also disconnect the shocks (rears are easier than fronts but neither are horribly difficult) and see how much effort is required to compress them. Shocks should require a considerable amount of force to compress. For instance my scrawny 165 lbs of self needs to lean on the shock with almost all my weight to get them to compress.

I wouldn't count on a compression test to check if a shock is good. The piston can be significantly pitted from cavitation, the oil wasted, and shims worn out and you won't be able to compress them much.

If they are from '82 and have 82,000 miles on them, you'll be happy they were rebuilt.

Very good points. I'm simply basing my comments on what i've witnessed on worn out 911 shocks i've replaced on various cars. The old ones are typically super soft and have very little compression resistance.

I'd also caution people that lower the car a good amount to be wary of exceeding the travel limits on the shocks. Get it low enough and you'll be hitting the bump stops for sure. Cars that are lowered for hard track use really should have the body or shaft (whatever is applicable to the construction of the shock) to avoid bottoming them. I had a Koni single adjustable on the front of one of my cars go bad. Bump donuts were in place but it still bottomed out and jammed the adjustment.

Bilstiens with a bump stomp should be fine with hitting the stops. Their is nothing on the inside that would cause a problem.

Sure it won't cause a problem with the mechanicals of the shock. But hitting the stops will completely alter the handling of the car when you hit the stop and the spring rate effectively goes WAY up

Ain't that the truth!

OK, good suggestion on the follower. I'll tell you this, I can't compress them much with a fender push, and there is only one rebound stroke (no bouncing) of maybe 1/2 inch.