Bilstein Dillemma...

[dre]

Ok, here's my dillema,
I upgraded my dead boges on the front of my 79sc targa and got to work on the rear. Alas, i found that they are already bilsteins!

I took one out to see what shape it was in. It looks kind of old but still rebounds when compressed. I squished it as hard as I could and it behaved like a used shock. Probably about 1/3 faster than the new one. I'm thinking much of this difference would dissipate with a few thousand miles of breakin.

The last number on the serial says 92 so I'm thinking perhaps that is when it was made so its kind of middle aged. Either way, most references say a bilstein will last the life of the car.

So, here's my dillema, do I switch the shocks and move on or return them and get perhaps a front strut tower brace?

Opinions greatly appreciated.

DRE

[autobonrun]

Did you buy HD or Sport shocks and can you tell what are on there now?

Regardless however, shocks do have a finite life and usually degrade gradually rather than a total failure. Since you already have new shocks available and have gone through the labor to remove the old ones, I'd put the new shocks on now.

At least you will know the status of the shocks on the car. No telling how long the existing ones have been on. You could call Bilstein, give them the numbers on the old shocks and they can tell you the type and when they were manufactured. If they are indeed 1992 model, definitely replace them.

[Cookie Porsche]

You cannot test a gas shock simply by pressing it down. The mono-tube Bilstein contains both gas and oil, and it is dificult to see if bump and rebound is OK without a dyna.

A gas shock will rebound slowly if you compress it with weak human power!

Bilsteins are "lifetime", however they need to be serviced. If you send your shocks to a repair shop they can also be re-valved to match your front shocks. (Whether it is cheaper simply to buy new is another story).

I recommend you first sort out the shocks. Besides your tires the shocks are the single most important setup on the car and no bars, braces or similar can compensate for dead shocks.

A seal and regas/oil service should be quite cheap - re-valving is more expensive.

I recommend that you valve the rear shox 'a little' stiffer than the front (relative) because this will improve the handling and feedback.

Tom

[dre]

Hmm,
Tom, your statment that the rear should be stiffer than the front is the opposite of what I have now with the softer old in the back. Drat.

It appears revalving is 65$ per shock. I'm thinking it will be more like 80 after everything is said and done. Hmm. Perhaps I should switch them and sell the old ones on ebay. If I could get 40 each, that would get me almost all the way to the stiffener bar.

Wow, those new front ones make a huge difference even with the old ones in the back. Definetly one of the best xmas presents to myself in recent memory.

autobonrun,
I'm nearly sure that everything is just sport, not hd.

DRE

[Cookie Porsche]

dre,

Ideally shocks are matched as a set. Unfortunately not all Bilstein (or other) agents list bump/rebound specs and thus you'll have to match your rears to your new fronts.

What I was reffering to is the rear setting - relative to the front (the rears will always have a 'stiffer' setting due to the 911s inherent weight bias).

I like to specify the rear with a slightly harder bump / faster rebound (around 15%) because it helps settle the rear, especially when you later fit upgraded torsion bars, stabilisers, etc. I leave the front a little softer when the car is used for road as it helps the nose when turning and braking.

Now you can upgrade to say F22 / R20 stabilisers and you'll have a car that turns in and is easy to handle.

Of course this is just the begining...

Tom