gunlover05

I've got an 85 (90% Street driver) coupe which i bought last fall with 86k miles...very little service history. bilstien struts up front (well green anyhow) and boge shocks in back - have no idea how old. I've pushed down on the bumpers, but little or no bounce. I will do a few AXs this year, and a few trips to the "tail of the dragon" which puts some g's on a car with all the sharp curves....

How else can i check or tell if I need new shocks/inserts??

Peter Zimmermann

Why anyone would mix Boges and Bilsteins is beyond me. Get yourself a set of HD Bilsteins and go have fun. At least you have the good struts! Bad shocks on a torsion bar 911 are difficult to describe, but you'll have a general harshness in the car. Try this, have you driven a car with over-inflated, twenty-year old tires? That's what bad shocks feel like.
Pete

BRB-83-911SC

I'll join in since I have the same question. I have green Bilsteins all around. I get no bounce, but I have a generally harsh ride, and a loud bang, sometimes followed by a hollow sounding rattle, from the right rear wheel when it hits a bump. Bushings look OK and the sway bar mounts are not broken. Could that shock be dead? The 3 other wheels handle bumps with no unusual noise. I have hesitated replacing the rear shocks - wanting to make sure this is my issue. Pete - your analogy to driving on overinflated tires prompted me to get in on this thread - that's what my ride feels like, plus the noise. Any way to verify a bad shock? I will be getting under there for a look soon.

Daniel Dudley

The answer is you often don't know how bad your shocks were until you experience good shocks. Maybe you can mooch a drive at an autocross or get together...

Peter Zimmermann

Brian: It's rare for a Bilstein to fail so completely that it could make the noise that you describe, but it's possible. My first thought was sway bar mount, but you cleared that item off the table already! I've seen, a couple of times, where a rear shock dust cover separated, and the tube part slid down and rattled loudly enough to hear while driving. Bilsteins are so good that there are cars like yours out there that are still fitted with originals, and all of those cars that have passed 75 - 100K miles should have replacements. When most SCs were daily drivers we had a number of cutomers who sailed right past 100K miles and the cars felt great, but sitting for periods of time also can take its toll. If the ride height of your car is as seen in your avatar that should not be an issue. Old tires (5+ years) can also add to ride harshness, and some tires are more harsh than others. I have Bridgestone RE 750s on my '82; I intentionally stayed away from SO-2s because my car doesn't go on the track, and those tires aren't as comfortable as I thought they would be, but they're not bad. We have Michelin Pilots on our Passat, that car is stiffer than the 911! It'll be interesting to hear what you find when you replace your shocks.
Pete

ron mcatee

brb-83-911sc, check the nut on the top of the shock to make sure it is all the way tight. I had the problem you have and found the nut wasn't all the way down. Maybe yours is loose, too. I snug mine down with a 90 Degree air ratchet to make sure it is tight.

BRB-83-911SC

Pete - my car has 92k miles, and I suspect the shocks are original. I have new tires (Toyo Proxes 4). One point, that is probably important, is that when I bought the car it was lowered quite a bit, and I had it raised and aligned to the stock settings during the PPI. I did not think much about the ride quality at the time, and hadn't driven it enough or on rough enough roads to encounter the noise at that point. Since the car had previously been driven for some time in a lower setting, and is now raised, could the shocks be less effective at the new height?

Spider - A loose top shock mount is one area that I thought could cause the noise I have. I will check into that. Thanks.

madmmac

A clunk from the rear while going over bumps can also be caused by a worn/bad CV joint.

loosecannon

I'll tell you a funny thing that happened to me and my 911SC. I had stock Bilsteins all the way around and the back of the car was harsh going over bumps. I suspected bad shocks but the car wouldn't bounce when I pushed down on it. I pulled a back shock off and found that it had less than 2 inches of travel before it hit something solid inside the shock. Something inside was very broken and life was good when I put Koni yellow adjustables on the back(and now on the front, too).

Peter Zimmermann

Brian: Yes, raising a too-low car can certainly have an impact on shocks. Of course, the car being very low could have already damaged one or more shocks by simply forcing the shocks to work outside of their design range.
Pete

srf506

If its the rears the back end will feel "twitchy" in "spirited" driving as you'll be compressing them to the stops which then gives you an effective spring rate of infinity. Thus the car will lurch and bounce because it is on hard stops. I've never felt any noticeable change when the fronts are gone other than diving under hard braking.

You might think a shock is still functional after 100k miles, but the oils viscosity is gone (if there's oil left in it), the valving is probably shot, and the shock mounting rubber parts are probably gone too after being tightly compressed for some number of years. In my experience after about 65-70k miles you might as well replace them, they're gone.

Good luck and keep us posted on what you do.

Jim P.

Greg D.

15 years ago, in Europe, I remember a machine that I drove my car on, kinda like 4 scales - one for each wheel, and each corner would push up and release under each wheel, like a lift if you will but faster, and take measurements on compression, rebound etc... You knew for sure then ! Haven't seen such a machine in ages...

My 1983 Sc has 173000 on stock shocks, as far as I know ! It sure feels harsh, which I attributed to lowering, but I think it may be time because the symptoms fit to a Tee ;-) A few more months before I can afford it though !

Is bilstein HD the recommended set for an SC anyway ?

Peter Zimmermann

Greg: For me, and I've driven just about every combo of suspension and shock there is, HD Bilsteins are definitely the right choice for a stock, or Euro height stock, SC.
Pete

srf506

Greg D, its a four-post dynamic shaker that can be programmed to simulate a car traveling over a route and the suspension tuned to the optimum for that route. Most major race teams own one. In fact, they take data from their on-board data collection systems during testing and practice. Back at the shop they can then simulate whatever circuit they're going to and tune the suspension for items such as Shock valving and compression/rebound rates, springs, bars and tire pressures. Gives them a head-start on finding a good set-up right off the transporter.

Chuck Jones

I was getting a clunking sound out of my right rear area in my87 and ended up changing out the rear shocks for new ones....then noticed that I still had the clunk when I went over railroad tracks. I put it on a lift and found that the muffler was sitting too close to the frame on the corner...and a good bump would cause the muffler to hit the frame. Took a pry bar and pryed it out a bit and that fixed it. Should have done that before I put in the new shocks....would have been a lot cheaper.