Post Bilstein HDs blues.
06-06-2007, 03:09 PM
#16
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Thanks for the help guys.
I'll have a go at reducing the tyre pressures, and get the ball joint replaced so that the castor angle can be brought within tolerance. I'll also check the ride height measurements as per Jeff's DIY.
I have to say I was always sceptical that new shocks would make a "night and day" difference. I was more inclined to believe it was the post-HD-install re-alignment that made the biggest diffrence i.e. people had been driving around for years with cars whose alignment had gone out of spec. over time. Maybe I was right to be sceptical???
Anyway, on the bright side, I took the opportunity of having a 3 spoke 996 steering wheel fitted when the suspension was done - and at least I'm pleased with that!
I'll have a go at reducing the tyre pressures, and get the ball joint replaced so that the castor angle can be brought within tolerance. I'll also check the ride height measurements as per Jeff's DIY.
I have to say I was always sceptical that new shocks would make a "night and day" difference. I was more inclined to believe it was the post-HD-install re-alignment that made the biggest diffrence i.e. people had been driving around for years with cars whose alignment had gone out of spec. over time. Maybe I was right to be sceptical???
Anyway, on the bright side, I took the opportunity of having a 3 spoke 996 steering wheel fitted when the suspension was done - and at least I'm pleased with that!
06-06-2007, 03:19 PM
#17
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Originally Posted by SJB993
I have to say I was always sceptical that new shocks would make a "night and day" difference
06-06-2007, 03:40 PM
#18
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Hi Arnaud, I take your point - however, a mate of mine on this side of the pond with a 993 also convinced me it would be "night and day" - it was for him.
I'm not too bothered by the expense, my 11 year old factory shocks were probably due for replacement anyway. I just don't feel as safe as I think I should in a high performance sports car when I'm taking a spirited drive around our country lanes!
Thanks to you guys I've got a few things to try and/or check. I'm confident I'll get to the bottom of the problem before too much longer (I just hope the impact on my bank balance isn't too great).
I'm not too bothered by the expense, my 11 year old factory shocks were probably due for replacement anyway. I just don't feel as safe as I think I should in a high performance sports car when I'm taking a spirited drive around our country lanes!
Thanks to you guys I've got a few things to try and/or check. I'm confident I'll get to the bottom of the problem before too much longer (I just hope the impact on my bank balance isn't too great).
06-06-2007, 04:22 PM
#19
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Chiming in too, tire pressures (I use 32.5f/35r), alignment and shocks all make a significant difference on these cars. I have a C2, so even less weight over the front end than yours, and my car is rock solid at speed. I do feel that since the front end is light that it needs additional damping than the rear. As I'm running pss9's, I have my fronts at full stiff and rears at one click less than full stiff. Maybe you should've gotten pss9's. Kidding, I'm sure you'll get it right.
Further note, I don't think the rake has much effect on things. I've had the fronts a little higher than the rears and now, as you may be able to see in my avatar, I'm about the same f/r (as measured at the fenders) and the car was equally stable either way.
Kidding, I'm sure you'll get it right.Further note, I don't think the rake has much effect on things. I've had the fronts a little higher than the rears and now, as you may be able to see in my avatar, I'm about the same f/r (as measured at the fenders) and the car was equally stable either way.
06-06-2007, 06:40 PM
#20
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In addition to checking the a-arms, do not forget to check the tie-rod ends. They seem to start to fail as early as 60k miles for some and they fail very gradually, so you hardly notice it at first. The front just seems to be very vague and spongy.
Best of luck sorting it out.
Best of luck sorting it out.
06-06-2007, 07:02 PM
#21
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Originally Posted by SJB993
Louis - do you have the same size tryes/wheels as me? I'll give the lower rear pressure a try.
06-06-2007, 08:03 PM
#22
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I suspect that the measures Gert supplied to you were intended to initially set the adjuster/locknut correctly on the shock itself. This 'best approximation' is to allow the initial install be (nearly) correct for the specified heights at the chassis measuring points: final heights require some tweaking of the adjusters, as each car is somewhat different.
06-07-2007, 02:55 AM
#23
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Thanks for the continuing suggestions guys.
Tom - how would I establish if there is wear in the control arm bushes or tie rod ends?
Louis - the tank was full, and I made sure it was (as per the instruction in the workshop manual) that it was full when the alignment was done.
Thanks.
Tom - how would I establish if there is wear in the control arm bushes or tie rod ends?
Louis - the tank was full, and I made sure it was (as per the instruction in the workshop manual) that it was full when the alignment was done.
Thanks.
06-09-2007, 01:29 AM
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I'll second the tie rod (both inner and outer) suggestion. I had a bit of wander at highway speeds and replaced the tie rods and was pleasantly surprised at the improvement. The outer tie rod on the driver side had the rubber bushing separated from the metal and the passenger side had a failed inner rod.
06-10-2007, 05:06 PM
#25
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I'm beginning to wonder just what difference Bilsteins actually make. It seems that most of people's problems have been down to bad alignment, worn tie rod ends, worn control arms, tire pressures, etc. etc.
Only joking (I think?).
Only joking (I think?).
06-10-2007, 05:20 PM
#26
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New shocks (HDs or otherwise) do make a difference when your current ones are as dead as mine were :-) The angels didn't sing first time I drove the car but it's lost a good deal of nervousness.
06-10-2007, 05:24 PM
#27
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I second and third checking air pressures. The factory called 44 is way too much, and unless you use hydrogen, when it heats up, you could be running close to 50 psi. I believe that Porsche decided this to be a good pressure for good MPG rating, but is it sure feels like you are ice skating when you run these pressures.
I found that the 993 is very susceptible to air pressures, more so than any other car that I have ever owned.
It took me literally a couple of months of trying different front / rear pressures until I found a combination that worked for me. Brand of tire makes a big difference too.
BTW, my magic number is 32 front and 36 rear.
I found that the 993 is very susceptible to air pressures, more so than any other car that I have ever owned.
It took me literally a couple of months of trying different front / rear pressures until I found a combination that worked for me. Brand of tire makes a big difference too.
BTW, my magic number is 32 front and 36 rear.
06-28-2007, 07:10 PM
#28
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Hi, I have similar symptom you are describing. I found and fixed one issue - the (993-343-018-00-M100) Shock Mount Flange it had some play in the bearing on and stated to click as I was pulling up the driveway. IT was hard to diagnose.
I replaced it and car got much more stable, however there is still a little bit of directional instability left. I will be replacing the right side Shock Mount Flange if this doesn't fix it - I will turn to the ball joints. Shock Mount Flanges are really easy to replace - you do not need to disconnect lower shock mounts so there is no need for alignment - cost of the part is $100.
Please let me know if you find ball joints to be a source of your issues.
Mike
I replaced it and car got much more stable, however there is still a little bit of directional instability left. I will be replacing the right side Shock Mount Flange if this doesn't fix it - I will turn to the ball joints. Shock Mount Flanges are really easy to replace - you do not need to disconnect lower shock mounts so there is no need for alignment - cost of the part is $100.
Please let me know if you find ball joints to be a source of your issues.
Mike
06-28-2007, 08:16 PM
#29
Race Director
Originally Posted by SJB993
Thanks again Geolab.
I've just read through Jeff's DIT and now I'm confused.
He shows the the measurement being taken between points on the chassis and the ground, whereas the measurements in Gert's DIY are taken between points on the shock itself (i.e. the bottom of its strut tube and the adjustable spring holder). However both sets of dimensions are the same - 144mm and 127mm.
I'm now wondering whether Gert's DIY (which is what the mechanic used to fit the shocks) is wrong?
I'll make the measurements where Jeff says (I note that his diagrams are from the workshop manual, so I guess they must be right).
BTW - Jeff's range of fender heights (25.25" - 25.75" +/- 0.4") means that my heights are about right. He does say the rear should be around 0.25" lower than the front - but given a 0.4" tolerance on the heights, maybe that isn't too important???
I've just read through Jeff's DIT and now I'm confused.
He shows the the measurement being taken between points on the chassis and the ground, whereas the measurements in Gert's DIY are taken between points on the shock itself (i.e. the bottom of its strut tube and the adjustable spring holder). However both sets of dimensions are the same - 144mm and 127mm.
I'm now wondering whether Gert's DIY (which is what the mechanic used to fit the shocks) is wrong?
I'll make the measurements where Jeff says (I note that his diagrams are from the workshop manual, so I guess they must be right).
BTW - Jeff's range of fender heights (25.25" - 25.75" +/- 0.4") means that my heights are about right. He does say the rear should be around 0.25" lower than the front - but given a 0.4" tolerance on the heights, maybe that isn't too important???
Basically, Gert's measurements are prior to installing the shock on the car, Jeff's are for after the shocks are installed. Does this clear that up?
Hope you get it worked out.
06-29-2007, 07:38 AM
#30
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Originally Posted by Jack of Hearts
I would reduce the pressure in the front as well. Play around with pressures in the 32 to 34 psi range. Remember, the car has very little weight on the front end and will never be as inherently stable as a well balanced front-engine rear-drive car.
