Steering shakes severely over bumps
10-04-2005, 08:49 PM
#1
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Steering shakes severely over bumps
Once again I seek the wisdom of those who know things that I don't. And I already tried a search - couldn't find much on this.
A few months ago I got new tires, and the steering and handling felt great. A month ago, I noticed a new problem: any time I go over a rough part of asphalt, over a pot hole, or even those reflective lane divider bubbles, the steering wheel (and the whole car) shakes badly. When I'm on a nice smooth part of fresh asphalt, the car feels fine. When I hit a curve, the car feels fine, even when I'm going through the turn pretty fast. The steering feels fine at low or high speed exept it goes crazy when I hit a bump of some kind. When I do hit a bump, it doesn't really matter how fast I'm going.
I had not left the car sitting for a long time, if anyone's thinking of a flat spot on a tire. It felt great for like 6,000 miles with new tires. I just changed the wheel bearings and used fresh moly grease. I also changed the rotors while I was in there. This shaking is the same with or without pushing the brake pedal. The car won't shake if the rear wheels go over a bump. All 4 front sway bar bushings are ok. As for the rest of the bushings and stuff, I must confess ignorance. What could this be? What should I investigate? I think everything in the front suspension is original except one new sway bar bushing and those new bearings. Thanks everyone,
Arash
85.1 944
EDIT (3/15/06):
The problem was just fixed by replacing the front strut inserts with new Boge units.
A few months ago I got new tires, and the steering and handling felt great. A month ago, I noticed a new problem: any time I go over a rough part of asphalt, over a pot hole, or even those reflective lane divider bubbles, the steering wheel (and the whole car) shakes badly. When I'm on a nice smooth part of fresh asphalt, the car feels fine. When I hit a curve, the car feels fine, even when I'm going through the turn pretty fast. The steering feels fine at low or high speed exept it goes crazy when I hit a bump of some kind. When I do hit a bump, it doesn't really matter how fast I'm going.
I had not left the car sitting for a long time, if anyone's thinking of a flat spot on a tire. It felt great for like 6,000 miles with new tires. I just changed the wheel bearings and used fresh moly grease. I also changed the rotors while I was in there. This shaking is the same with or without pushing the brake pedal. The car won't shake if the rear wheels go over a bump. All 4 front sway bar bushings are ok. As for the rest of the bushings and stuff, I must confess ignorance. What could this be? What should I investigate? I think everything in the front suspension is original except one new sway bar bushing and those new bearings. Thanks everyone,
Arash
85.1 944
EDIT (3/15/06):
The problem was just fixed by replacing the front strut inserts with new Boge units.
Last edited by FRporscheman; 03-16-2006 at 03:58 AM.
10-04-2005, 09:05 PM
#2
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I might as well ask about another problem.
One of my old rotors had a groove in it. I changed the brake pads twice. One of my new rotors (same side and face) is developing a groove in the exact same place. The pads in there are the second new set I've put in since buying the car. These pads were used with the old rotors for a few months. I've heard bad pads can score rotors, but this seems like something else if it's in the same place as the OLD groove, which was made before the new pads went in...
Arash
One of my old rotors had a groove in it. I changed the brake pads twice. One of my new rotors (same side and face) is developing a groove in the exact same place. The pads in there are the second new set I've put in since buying the car. These pads were used with the old rotors for a few months. I've heard bad pads can score rotors, but this seems like something else if it's in the same place as the OLD groove, which was made before the new pads went in...
Arash
10-04-2005, 09:50 PM
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Arash: I had a similar problem and I'm currently in the process of swapping out my suspension and putting in new koni yellows and 968 springs (back is already done, just waiting to finish up the front). I'll let ya know if it changes anything.
Another thing you might want to try if you have a manual rack is playing with the steering rack tightening bolt -- see the factory workshop manual for more info on this.
Another thing you might want to try if you have a manual rack is playing with the steering rack tightening bolt -- see the factory workshop manual for more info on this.
10-04-2005, 09:59 PM
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To me it sounds like a loose component of the front suspension or the steering, e.g. ball joint in the A-arm, tie rod, etc. Lift one wheel at a time, and wiggle everything (use a pry bar, etc).
10-05-2005, 10:09 AM
#7
Three Wheelin'
Loose wheel bearings, bad ball joints, bad shocks.
What size and offset wheels are you running? Wheels with larger offsets will amplify "tramlining", or jerking in the steering when the front end goes over a bump or through ruts in the road.
Check these out: http://autospeed.drive.com.au/cms/A_879/article.html
http://www.tirerack.com/tires/tirete....jsp?techid=47
What size and offset wheels are you running? Wheels with larger offsets will amplify "tramlining", or jerking in the steering when the front end goes over a bump or through ruts in the road.
Check these out: http://autospeed.drive.com.au/cms/A_879/article.html
http://www.tirerack.com/tires/tirete....jsp?techid=47
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10-05-2005, 11:09 AM
#8
Race Car
Could also be the steering rack bushings, or tie rod ends...
I chased down an intermittant pull I had while going over bumps, and I found worn out steering rack bushings, bad outer tie rod ends, bad ball joints, and finally loose wheel bearings. I fixed all of the above, and now it doesn't pull at all going over bumps. Perhaps your problem is similar?
I chased down an intermittant pull I had while going over bumps, and I found worn out steering rack bushings, bad outer tie rod ends, bad ball joints, and finally loose wheel bearings. I fixed all of the above, and now it doesn't pull at all going over bumps. Perhaps your problem is similar?
10-05-2005, 12:40 PM
#9
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Sounds like pretty much everything in the front end is suspect. Geoff, I tightened the wheel bearing play as per the factory workshop manual (while turning rotor, i should be able to barely move the crush washer with a screwdriver). Is this right? I do believe the front struts are due for replacement, since they're abnormally wet.
CK, I'm eager to know if new struts will help - I hope not, they cost a lot. Btw, the pics of your 83 on your website won't load
How would I diagnose whether it's a shock/strut, ball joint, A-arm, tie rod ends, certain bushing, etc. I have power steering, and it works fine, only leaks a tiny bit. I'm running stock Fuchs rims, 15"x7" on the front, an inch wider on the back. This is an '85 with the early offset, so I don't think it's an offset issue. The tires are 225/60/15 unidirectional, and they are on the correct way. I understand pretty much every other part of a car, but front suspension has always been the trickiest thing for me, so I really appreciate you guys' help.
Edit: Forgot to mention about tramlining: My mom's 84 944 has the exact same rims and tires, and she got the tires when I got mine so they are worn out about the same too. Her car drives like it's brand new (drool). I don't know if this thing is tramlining, when I go over a rough patch of asphalt (those spots where they tried to patch the road with new asphalt but it has worn away and now it looks like the asphalt giant has sneezed there), or even if I just go over a railroad crossing, the steering wheel vibrates horribly. The wheel actually turns left and right a few degrees really fast. It feels a little like when the lateral shock absorber failed on our mercedes (connecting left and right knuckles).
Arash
CK, I'm eager to know if new struts will help - I hope not, they cost a lot. Btw, the pics of your 83 on your website won't load
How would I diagnose whether it's a shock/strut, ball joint, A-arm, tie rod ends, certain bushing, etc. I have power steering, and it works fine, only leaks a tiny bit. I'm running stock Fuchs rims, 15"x7" on the front, an inch wider on the back. This is an '85 with the early offset, so I don't think it's an offset issue. The tires are 225/60/15 unidirectional, and they are on the correct way. I understand pretty much every other part of a car, but front suspension has always been the trickiest thing for me, so I really appreciate you guys' help.
Edit: Forgot to mention about tramlining: My mom's 84 944 has the exact same rims and tires, and she got the tires when I got mine so they are worn out about the same too. Her car drives like it's brand new (drool). I don't know if this thing is tramlining, when I go over a rough patch of asphalt (those spots where they tried to patch the road with new asphalt but it has worn away and now it looks like the asphalt giant has sneezed there), or even if I just go over a railroad crossing, the steering wheel vibrates horribly. The wheel actually turns left and right a few degrees really fast. It feels a little like when the lateral shock absorber failed on our mercedes (connecting left and right knuckles).
Arash
Last edited by FRporscheman; 10-05-2005 at 01:07 PM.
10-05-2005, 01:18 PM
#10
Race Car
Wet front struts. Start there. I was just re-reading it, you said it's shaking, not pulling. I'd bet that's the natural resonance frequency of your front springs under load that you are feeling, and that you are feeling it because the shocks inside of the front struts have virtually no dampening ability.
If they're wet and oily around the seals on them, then they're leaking.
If you don't track your car or anything, get the boge cartridges for the front, and change them yourself, ~$120 for the front end, and you don't need an alignment when you're done, since you can line them up exactly the same as the old ones were.
If they're wet and oily around the seals on them, then they're leaking.
If you don't track your car or anything, get the boge cartridges for the front, and change them yourself, ~$120 for the front end, and you don't need an alignment when you're done, since you can line them up exactly the same as the old ones were.
10-05-2005, 05:05 PM
#11
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Yeah, sounds like they're adjusted properly. One way that I tested mine when I was doing em, I put the wheel on minus the center cap, and left the dust cap off...tightened 2 lug nuts, and wiggled it... there should be very little play. when I had some, I reached in through where the center cap was, and tightened it a little more... wiggled, repeated, until I was satisfied.
10-06-2005, 12:27 PM
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Sounds like a good method for the WBs. Incidentally, I noticed wheel bearing grease on my left front rim yesterday as I washed the car 
When I was hitting the dust cap back on, I did notice some grease squeeze out of the groove in the side of the hub (for using the allen on the lock-washer). Maybe I didn't wipe up all the exuded grease, or maybe there's a grease leak?? The rotor and rear part of the hub looked dry...
The only reason I don't think it's the shocks is that the steering wheel shakes left to right. I have a merc 300td with horrible front shocks and brand new rear shocks; it feels rough when the front goes over a pothole or something, but I feel absolutely nothing through the steering wheel, no left-to-right vibration at all. If the shocks were bad and the springs were more free to oscillate, wouldn't that just make the whole front of the car bounce and/or rock side to side? That's my intuition anyway.
Arash
When I was hitting the dust cap back on, I did notice some grease squeeze out of the groove in the side of the hub (for using the allen on the lock-washer). Maybe I didn't wipe up all the exuded grease, or maybe there's a grease leak?? The rotor and rear part of the hub looked dry...The only reason I don't think it's the shocks is that the steering wheel shakes left to right. I have a merc 300td with horrible front shocks and brand new rear shocks; it feels rough when the front goes over a pothole or something, but I feel absolutely nothing through the steering wheel, no left-to-right vibration at all. If the shocks were bad and the springs were more free to oscillate, wouldn't that just make the whole front of the car bounce and/or rock side to side? That's my intuition anyway.
Arash
10-06-2005, 07:16 PM
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Devon, Tirerack doesn't have kyb for my year, just koni 
. I like their prices though, I'm bookmarking that site. I looked around and it seems kyb inserts and shocks will run me like $160. I guess if it has to be done, it has to be done... I just wish I could be more certain before I start throwing money at it. Is there some procedure for testing various suspension components? I mean, my struts are obviously shot but I think they have been shot for a long time. Can tie rods be loose but still attached (if so, I'm terrified)?
Arash
EDIT (3/15/06):
I didn't want to add a new post and "revive an old thread" so I'll just tack on my results here.
I just replaced the front strut inserts. I went to my local Porsche dismantler (EASY in emeryville) and they hooked me up with new Boge front inserts and used Koni rear shocks for $200 total. The problem with the steering is now completely gone. Not only is the steering wheel firm, but the ride is smoother, and the car handles better (I know, duh, but it's nice to feel it). I hope this helps future readers.
. I like their prices though, I'm bookmarking that site. I looked around and it seems kyb inserts and shocks will run me like $160. I guess if it has to be done, it has to be done... I just wish I could be more certain before I start throwing money at it. Is there some procedure for testing various suspension components? I mean, my struts are obviously shot but I think they have been shot for a long time. Can tie rods be loose but still attached (if so, I'm terrified)?Arash
EDIT (3/15/06):
I didn't want to add a new post and "revive an old thread" so I'll just tack on my results here.
I just replaced the front strut inserts. I went to my local Porsche dismantler (EASY in emeryville) and they hooked me up with new Boge front inserts and used Koni rear shocks for $200 total. The problem with the steering is now completely gone. Not only is the steering wheel firm, but the ride is smoother, and the car handles better (I know, duh, but it's nice to feel it). I hope this helps future readers.
Last edited by FRporscheman; 03-16-2006 at 03:54 AM.
10-06-2005, 09:33 PM
#15
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I thought 85.1 and 85.2 both had the same rear shocks?? theres like two or 3 different categories (perfoirmance, street, etc.) did you check them all? they are called KYB Gas-A-Just.