Another strut/shock question

5495bb · 5495bb's Garage

I just got an '87 Coupe this summer and have decided that it needs new shocks and struts ( I feel every little crack in the road). It has 60K miles on it and is totally stock with the original Boges all around. It's got brand new Dunlop Sport Signatures on it (205/55 -16 and 225/50-16) that give it a ride height of 25" front and 24 1/4" rear. I think that the car is pretty light with no tail, sunroof or cruise but I don't know the exact weight. I'll never track it but will use it well into the Canadian winter ( my commute is about 5 miles). I guess my question is should I go with the Boges again or should I switch to the Bilstein HD front and Sport rear combination. My main concerns are quality of product, handling and ride. Thanks for any suggestions.

wildcat077 · wildcat077's Garage

I have an 89 Coupe on which i replaced the original Boges that had 123,000 kms this summer and installed Bilstein HD's on the front and Sports on the back and it made a whole world of difference. Didn't change the ride height,by the way...

As for the road noise i also replaced my Michelin Pilots 205/55/16 and 225/50/16 which were on the original Fuchs rims with TOYO Proxes T1R's on 8 inch 951 offset fronts and 9 inch rears with 225/50/16 and 245/45/16.. My Michelins only had 600 kms on them and i can honestly tell you that the TOYO's are WAY smoother and quieter than the Michelins !
The road noise you hear might be caused by the particular design of your tires, and as far as the shocks go,you can't go wrong with Bilsteins !!!
I'm glad i made those changes on my car

Rot 911 · 09-18-2009, 05:26 AM

The Bilstein HD front and sport rear is a pretty popular combination for good road feel. That is what I am running and am quite happy with the set up. My concern is that maybe you don't like a firm suspension as you state "I feel every little crack in the road). Even stock Boges are going to give your 911 a firm ride. Sport cars are supposed to have a firm ride.

Nine9six · Nine9six's Garage

Quote:

Originally Posted by Kurt V

The Bilstein HD front and sport rear is a pretty popular combination for good road feel. That is what I am running and am quite happy with the set up. My concern is that maybe you don't like a firm suspension as you state "I feel every little crack in the road). Even stock Boges are going to give your 911 a firm ride. Sport cars are supposed to have a firm ride.

+1 on what Kurt said. Some in this group may believe that feeling the road is what is commonly refered to as feed back.

5495bb · 5495bb's Garage

Well I've driven and worked on a lot of sport cars (still have two Brit 1959's) over the years but none felt like a skate board over a sidewalk crack. I don't expect the 911 to ride like my old 928 but I think that I can reasonably conclude that the shocks are gone when they don't dampen out the little air hose that triggers the overhead parking lot doors.

burgermeister · burgermeister's Garage

You may also have two other problems:
1) your car is quite low (probably around 50 - 60 mm lower than stock). You're almost certainly hitting the jounce stops (are canada roads like Michigan's?). It makes for a very rough ride.
2) If you haven't looked, the front A-arm and rear spring plate bushings have probably become eccentric with age, and you're riding on the front torsion bars and rear torsion bar cover, essentially short-circuiting the bushings.

You can swap spring plates side to side, and rotate the rear bushing on the front A-arm by carefully applying heat to the arm, rotating the bushing & can, and then heating the can & rotating it back. Or get new rubber replacement pieces. Either one will make a huge improvement in ride.

I doubt your ride is caused by your shocks - worn shocks cause a wallowy ride, not a harsh ride. Unless they have run out of fluid, of course ...

RWebb · RWebb's Garage

yes, it is 22 years old and - no matter how low th emileage - likely needs new rubber bushings all over

do that first - shocks are probably fine

moneymanager · 09-18-2009, 02:30 PM

Amen. I'd do all the bushings and reevaluate the need for shocks. You may find they are just fine.

5495bb · 5495bb's Garage

Thanks you guys. That's just the kind of advice I needed. I'll check the bushings right away.

5495bb · 5495bb's Garage

Just wanted to let the guys know that the call on the bushings was right. I checked last night and found the rear torsion bars with minimal clearance to the spring plates ( drivers might be metal to metal). I've just ordered the ELR bushings from our host. The front a-arm bushings don't look as bad. I'll pull the a-arms out this weekend for a closer look and may end up just doing Burgermeisters rotation for now. Thanks again for the help.

moneymanager · 09-23-2009, 11:06 AM

Good. This may well do the trick. Shot rear spring plates will have a 911 riding like an overloaded truck!

burgermeister · burgermeister's Garage

A thread on the fronts:

Front LCA Rubber Bushing

RWebb · RWebb's Garage

re: rotation

considering the trouble involved, I'd just replace them.

Question is do you want new factory type rubber or Elph. Racing Poly-bronze. I have the latter.

5495bb · 5495bb's Garage

Thanks for all the feedback. I couldn't wait for the weekend so I tore into the front end last night. The job went smoothly with absolutely no snags. I rotated the the passenger side and reassembled it. The drivers a-arm is out, cleaned up, and waiting rotation and reassembly tonight. My concern is that the front bushings were a lot better than the rear ones on the spring plates and yet the torsion bars still showed some sign of wear (just on the outer coating). My question to the Pelicans is should I anticipate needing new rear torsion bars given that the torsion bar covers are basically riding on the spring plates ie. completely off center?

moneymanager · 09-24-2009, 07:59 AM

It may happen but I haven't seen it on my two Porsches.

burgermeister · burgermeister's Garage

Rear bars will be fine - lots more clearance, plus the bar moves along with the spring plate. In the front, because of the torsion bar adjuster arm, it tends to wander in the opposite direction of the A-arm, compounding the problem.

If you have slop between your adjuster and front xmbr (over time, the adjuster will wear a bit into the crossmember), you can epoxy some aluminum in place to space it up a bit.

5495bb · 5495bb's Garage

OK that's great news. I won't worry about rear torsion bars. Burgermeister your rotation instructions and technique are nothing short of genius. I hope changing the rear bushings will go as smooth. Oh yeah, and by the way, in Calgary the roads are torture on suspensions and mufflers.

RWebb · RWebb's Garage

scratches in the t bar outer coating will promote stress crevices, and eventually the bar will fail catastrophically

burgermeister · burgermeister's Garage

Glad the bushing rotation thing worked for you.

Scratches in the t-bar coating will promote unsightly appearance of a part you never see. Glop some paint over them, lightly grease the bar, & re-use. A wear pattern & grooves in the metal are a different issue, and I'd get new bars sooner or later. The a-arm is much softer than the t-bars, so it can't scratch the t-bar, but it can wear it down quite nicely.

In an excessive celebration of geekdom, some pelicans did a finite element analysis to evaluate the stress concentration of a wear pattern in the torsion bar ... it's out there somewhere (though probably not worth searching for)

RWebb · RWebb's Garage

I do NOT agree. A scratch in the torsion bar is the start of a process that will have a bad ending -- it will start a stress "crack" - fissure, crevasse - or whatever you want to call it. It will fail (break).

I do agree re paint or grease.