Steering shudder

[Spittybug]

I decided to tackle the ~70 mph steering wheel "shudder" that I experience. I've begun to notice it more lately, but that could be just because everything else is running nicer and I'm going faster! It's definitely steering column related as I can keep one hand on the wheel and one hand just barely touching other parts of the car (door, center console, dash...) and while the steering is vibrating, the rest of the car isn't.

I removed the steering rack and pulled it apart. While the end bushing didn't have much play in it, what play there was, was in one axis but not the other. Closer examination showed that there was a little bit more wear on 2 of the 4 surfaces that touch the rack. Another D owner that I just met this weekend told me about a brass bushing that ACE carries that fits perfectly (Hillman, 7/8" #882999 looks like HomeDepot has it too: http://www.homedepot.com/p/The-Hillman-Group-7-8-in-x-1-in-x-1-1-4-in-x-1-in-Bronze-Sleeve-Bearing-882999/202242848#.UkNCr9Ksh8E). True enough, it is a beautiful fit for the ID. It is a flanged bushing and the flange is actually spot on for the OD. That mean all I had to do was create some kind of extra diameter for the rest of the bushing and slide it in. I took a 3/4" PVC pipe union fitting and shortened it. In the middle of the union is a stop (a ridge around the inside) that is a perfect fit for the bushing. So, all i now needed to do was reduce the diameter of my PVC/Brass bushing to be equal to the ID of the steering rack tube. Thank god for benchtop belt sanders. Letting it spin up to speed and then gradually skewing it diagonally started taking the diameter down in a very uniform manner. The only thing better would have been turning it on the lathe, which I considered. After several iterations of sanding and checking, I was able to hammer it in. That PVC ain't coming out until I want it to! The brass bushing however would move in the PVC a bit when turning the pinion..... I solved this by inserting a couple of lock pins through the rack tube and into the flange of the brass bushing. Voila, no movement. For anyone else that goes this route (since you can't buy the replacement bushing from DMCH) I would suggest epoxying the brass bushing into the PVC sleeve first so you don't have this problem. I changed the fluid, checked the ball bearings and races and put it all back together again.

The worst part about this job is getting the driver's side rubber block mount in place! What a PITA and tough on the hands. I found levering a long screwdriver from the front of the car while reaching in and manually rotating it from the driver side wheel well is what actually ended up working. My hands still hurt. BTW, I never even loosened the tie rod end jam nuts, so my alignment *should* be exactly as it was.

I took it out for a test run and the steering feels very nice and tight and smooth. But the shudder is still there, albeit maybe reduced a bit!!!!! Aaaarggghhhh! Charlie Brown. Again, its in the shaft, not the car vibrating. The U joint looks fine and isn't sloppy. All bolts tight. I have never replaced the firewall bushing, but I was not of the understanding that these symptoms would indicate it as the problem.

Any suggestions? Thanks.

[Bitsyncmaster]

If you lift one front tire, you should be able to feel if any play is there (do both sides). Not finding any play, I would swap the front wheels and see if that changes anything.

[kobachi]

Any suggestions? Thanks.

I had significant shudder in my steering due to alignment problems which were not detected during the normal alignment procedure. I was several degrees out of caster, which is not supposed to be adjustable on a DeLorean and was only detected by the fancy laser machine at Les Schwab. More info in my comment here (http://dmctalk.org/showthread.php?7603-Power-Steering-in-a-Delorean&p=118010#post118010).

[Spittybug]

I had significant shudder in my steering due to alignment problems which were not detected during the normal alignment procedure. I was several degrees out of caster, which is not supposed to be adjustable on a DeLorean and was only detected by the fancy laser machine at Les Schwab. More info in my comment here (http://dmctalk.org/showthread.php?7603-Power-Steering-in-a-Delorean&p=118010#post118010).

Hummmmm... a definite possibility. If my LCA brace isn't exactly the right "angle" fully loaded, it could be changing the caster. I'm not having any steering issues other than the shudder. An easy test will be to simply remove them and see if the problem goes away. I don't recall this problem being coincidentally timed with the LCA brace addition, but it's possible.

Thanks.

[kobachi]

Hummmmm... a definite possibility. If my LCA brace isn't exactly the right "angle" fully loaded, it could be changing the caster. I'm not having any steering issues other than the shudder. An easy test will be to simply remove them and see if the problem goes away. I don't recall this problem being coincidentally timed with the LCA brace addition, but it's possible.

Thanks.

Sure. N.B. I wouldn't say my shudder is totally eliminated, but what's left is what I would imagine is natural for a manual steering car. Whereas before it took actual muscle effort to keep it steady, now I can steady it with just my left hand.

[Spittybug]

Just found this...
Vehicles usually have some positive caster specified since this promotes directional stability, however, excessive positive caster can cause two problems. The first is that excessive caster will cause a high level of road shock to be transmitted to the driver when the vehicle hits a bump, etc. The second problem is that a tire/wheel assembly with positive caster has a tendency to toe inward when the vehicle is being driven. If one side has more positive caster than the other, this causes it to toe inward with more force than the other side. This will cause a lead or pull to the side with least amount of positive caster.

Looks like I need to check this.

[David T]

Just found this...

Looks like I need to check this.

You may well be in need of an alignment but before you can do that you MUST replace any loose or worn parts. Check the bushings for the sway bar and have the wheels balanced too. Any "good" shop checks for bad parts before attempting an alignment.

[Ryan King]

Sure. N.B. I wouldn't say my shudder is totally eliminated, but what's left is what I would imagine is natural for a manual steering car. Whereas before it took actual muscle effort to keep it steady, now I can steady it with just my left hand.

So what exactly is the washer about that you speak of? I too have bad wheel vibration in my DeLorean.

[Doogie]

So what exactly is the washer about that you speak of? I too have bad wheel vibration in my DeLorean.
me three. I have a steering wheel vibration above 65mph. New Tires, balanced, but that's about it. I might have original Ball joints and whatnot too..

curious...

Doogie

[Spittybug]

Looks like I've opened a can of worms....

To reply to David T, new parts, correctly balanced wheels and a meticulous alignment (I hovered and engaged the tech who was so joyful to be doing a Delorean he nearly wet himself).

Since my brace fits between the lower shock bolt and the pivot bolt on the frame (a dimension that does not change at any point in the travel of the LCA), the other thing I need to check is the "angle" of the brace. I believe the solution to be relatively simple; shimming either the pivot bolt end with washers between the body and the brace (thus moving the brace rearward, bringing the lower ball joint slightly rearward or more negative camber) or shimming the lower shock bolt in the same manner (thus moving the brace forward giving slightly positive camber).

The challenge is that the stabilizer bar or control arm (whatever it's called...) is sufficiently flexible (the main problem) that the camber can be slightly different with the wheels hanging off a lift versus loaded on the ground. As the fore/aft movement of the LCA lower ball joint end changes the camber (lower ball joint's fore/aft position relative to upper ball joint position) it is also minimally changing the camber axis as well since it is creating an arc. Too much positive caster (moving ball joint end forward) will tend to make the tires ride more on their inner treads, too much negative, on their outer treads. There's a little impact on toe as well, adding to that wear.

My outer treads would appear to be somewhat more worn than my inners. That would, by this logic, indicate too much positive caster, which jibes with what I've read about extra transmission of road vibration under too much positive.

Test 1, remove LCA brace from lower shock mount (I think I can safely let it dangle from the pivot bolt end) and test. See if I still get the vibration at speed.
Test 2, add a small shim (washer) between the pivot mount and the brace's bushing to force the LCA ball joint end rearward a bit and road test again.

Without having access to an alignment machine to continually check on the numbers, testing will have to do until I can detect a difference.

[Spittybug]

I just loosened everything up and dropped the car. After rolling up and down the driveway a bit, I checked where the braces want to be on the two bolts, fully loaded. I rationalized that rolling the car back and forth would equilibrate the suspension. With the brace up against the body mount (on the pivot bolt), the shock tower bolt has about 1/4" space between the brace's bushing and the side of the LCA.

I think this means therefore that I need to add a spacer on the shock tower bolt to prevent the arm from being pulled too far back. So I am adding + camber. Too many angles to visualize! Hard to argue with trial and error though. Easy enough to add a spacer and go for a drive. THANK GOD I BOUGHT A LIFT!

[David T]

I just loosened everything up and dropped the car. After rolling up and down the driveway a bit, I checked where the braces want to be on the two bolts, fully loaded. I rationalized that rolling the car back and forth would equilibrate the suspension. With the brace up against the body mount (on the pivot bolt), the shock tower bolt has about 1/4" space between the brace's bushing and the side of the LCA.

I think this means therefore that I need to add a spacer on the shock tower bolt to prevent the arm from being pulled too far back. So I am adding + camber. Too many angles to visualize! Hard to argue with trial and error though. Easy enough to add a spacer and go for a drive. THANK GOD I BOUGHT A LIFT!


Vibration (shudder) starts by something rotating and is out of balance. It gets worse at certain speeds because of resonance and/or loose parts allowing things to move. Does it get worse during braking? Just because you put new parts in doesn't mean they can't be bad. Check the air pressure in the tires. Even though they are balanced you could have a bad one. Alignment isn't going to fix that!

[Spittybug]

Vibration (shudder) starts by something rotating and is out of balance. It gets worse at certain speeds because of resonance and/or loose parts allowing things to move. Does it get worse during braking? Just because you put new parts in doesn't mean they can't be bad. Check the air pressure in the tires. Even though they are balanced you could have a bad one. Alignment isn't going to fix that!

I definitely agree with you David. Especially when it is speed related. It does not get worse with breaking. Tire pressure is at 30 on the front. Tie rod ends have no play, nor did the new EU ball joints I put in. Bushings are new PolyU. I have not replaced the upper ball joints or bushings as I've been told by many that these just don't wear. When checked, they had no play. I'm beginning to believe that it is simply a case of the out of round rim that was "fixed" after my sheered ball joint incident not being true enough. It's good up to ~70 mph, but after that it just starts to judder. Until I can swap it out to test, I'm stuck.

FYI, I added some shimming to move the LCA nose forward, adding + caster. No noticeable difference. The steering and handling are really nice except for this damn vibration at speed! I'll leave it shimmed as is since this would appear to be closer to the right caster based on a loaded suspension rather than hanging. I'll monitor the tires.

(I erroneously said Camber two posts back.... shimming adds/subtracts caster with some secondary impact on camber...)

[David T]

I definitely agree with you David. Especially when it is speed related. It does not get worse with breaking. Tire pressure is at 30 on the front. Tie rod ends have no play, nor did the new EU ball joints I put in. Bushings are new PolyU. I have not replaced the upper ball joints or bushings as I've been told by many that these just don't wear. When checked, they had no play. I'm beginning to believe that it is simply a case of the out of round rim that was "fixed" after my sheered ball joint incident not being true enough. It's good up to ~70 mph, but after that it just starts to judder. Until I can swap it out to test, I'm stuck.

FYI, I added some shimming to move the LCA nose forward, adding + caster. No noticeable difference. The steering and handling are really nice except for this damn vibration at speed! I'll leave it shimmed as is since this would appear to be closer to the right caster based on a loaded suspension rather than hanging. I'll monitor the tires.

(I erroneously said Camber two posts back.... shimming adds/subtracts caster with some secondary impact on camber...)

You should not, under normal circumstances, have to adjust castor or camber. If they are not within spec something is bent or worn. A vibration that is speed related is definitely going to be caused by tires or rims (or both). 30 psi in the fronts is way too much. You should be closer to the recommended 23# You would see a bent rim in the machine when you are trying to balance the wheel. You won't always see a bad tire. Run your hand over the tread and each sidewall and feel for bulges, bumps or ripples.

[kobachi]

So what exactly is the washer about that you speak of? I too have bad wheel vibration in my DeLorean.

Well I wasn't trying to fix shudder, I was trying to fix the car listing to the left at any speed. It just so happened that the camber change seems to have improved the shudder, too. Remember too that the problem that was fixed was a significant /difference/ in camber between the two front wheels. We did not (intend to) adjust the overall camber.

And I still get significant shudder while braking, which suggests to me I also have some unevenly worn brake rotors, but it's not enough that it concerns me at this point.

As to how and where exactly the washer was installed, well, that's a question for Toby. Far as I remember he machined it himself to fix my car's exact problem. He's got my car fixing a jammed driver window right now, when I pick it up from him I'll ask him the details again.

[kobachi]

You should not, under normal circumstances, have to adjust castor or camber. If they are not within spec something is bent or worn.

This exactly. Mine was out of spec by >2.5 degrees. Bent sway-bar most likely.

[nkemp]

I had shudder/vibration in the front for a long time. I tried re-balancing the tires but no luck. The fix was going with the polyurethane bushings upgrade to the front sway bar. Nice and smooth now. I suspect the old rubber bushings were not holding the suspension rigid giving it a shudder/vibration.

This may or may not be related to your problem but others my find it helpful.

[Spittybug]

I went to Firestone today and had an alignment check. I figure it's a no-brainer to get the lifetime one with these cars. Tech was happy as hell to work on the Delorean and let me help (great for making sure things get done right!) They have the fancy schmancy Hunter laser setup, but beware, they list the toe spec as being .20* to .28* on each side. Our manual states .10* to .14* per side. Looks like they lost something in translation. All other specs in the system are correct.

If you recall, I have the lower control arm braces in place. I recently did a little bit of shimming to get them "more correct" under load rather than free hanging and I wasn't far off with my alignment.

Front
Camber: 0* and -.2* This isn't adjustable without modifying our upper control arms, so I'm happy right where it is. Spec is -.5* to 0*
Caster: 2.8* and 3.3* This is only minimally adjustable by loosening the front sway bar bushings and shifting, which we did, but got very little. Spec is 3.5* to 4*, so I'm a little negative. I can adjust this a bit by adding another shim or two to the backside of the control arm, on the lower shock bolt between the arm and the brace, thus forcing the LCA a hair forward. I'm not going to worry about it right now since this really isn't a tire wear condition. The car tracks straight.
Toe: .1* and .12* Spec is (per book), .10* to .14* This should help the most in preventing rubber wear. I was out of spec on the driver side by little bit.

Rear - nonadjustable
Camber -.8* and -.1, both a bit out of spec of -.8* to -.03, but not bad. I think older springs and shocks contribute to this and the resulting minimal "sag". Rears are wearing well though, so I'm not worried.
Toe - .23* and .34* Spec is .20* to .28* per Firestone, but I can't find that in our books. Again, out of spec by a bit, but nonadjustable.
I don't know what geometry playing with trailing arm tabs would have (toe I would suspect), but being that I'm close I'm not going to worry about it.

So, after hundreds of miles with my LCA brace, no problems I am pleased to say.

Prior to all of this I swapped my front wheels for Ian's (TexasTwister) recently re-balanced ones and went for a spin. Same shudder at the same speed! Too coincidental. When I put mine back on it *seemed* like I had a little less shudder than before, so maybe there is minor discrepancy in the wheel orientation on the hub. I don't know. Everything is tight, balanced and aligned. It must just be the spirit of JZD making itself known at ~70mph. Maybe BTTF had it wrong; it's 70 not 88?

[David T]

I went to Firestone today and had an alignment check. I figure it's a no-brainer to get the lifetime one with these cars. Tech was happy as hell to work on the Delorean and let me help (great for making sure things get done right!) They have the fancy schmancy Hunter laser setup, but beware, they list the toe spec as being .20* to .28* on each side. Our manual states .10* to .14* per side. Looks like they lost something in translation. All other specs in the system are correct.

If you recall, I have the lower control arm braces in place. I recently did a little bit of shimming to get them "more correct" under load rather than free hanging and I wasn't far off with my alignment.

Front
Camber: 0* and -.2* This isn't adjustable without modifying our upper control arms, so I'm happy right where it is. Spec is -.5* to 0*
Caster: 2.8* and 3.3* This is only minimally adjustable by loosening the front sway bar bushings and shifting, which we did, but got very little. Spec is 3.5* to 4*, so I'm a little negative. I can adjust this a bit by adding another shim or two to the backside of the control arm, on the lower shock bolt between the arm and the brace, thus forcing the LCA a hair forward. I'm not going to worry about it right now since this really isn't a tire wear condition. The car tracks straight.
Toe: .1* and .12* Spec is (per book), .10* to .14* This should help the most in preventing rubber wear. I was out of spec on the driver side by little bit.

Rear - nonadjustable
Camber -.8* and -.1, both a bit out of spec of -.8* to -.03, but not bad. I think older springs and shocks contribute to this and the resulting minimal "sag". Rears are wearing well though, so I'm not worried.
Toe - .23* and .34* Spec is .20* to .28* per Firestone, but I can't find that in our books. Again, out of spec by a bit, but nonadjustable.
I don't know what geometry playing with trailing arm tabs would have (toe I would suspect), but being that I'm close I'm not going to worry about it.

So, after hundreds of miles with my LCA brace, no problems I am pleased to say.

Prior to all of this I swapped my front wheels for Ian's (TexasTwister) recently re-balanced ones and went for a spin. Same shudder at the same speed! Too coincidental. When I put mine back on it *seemed* like I had a little less shudder than before, so maybe there is minor discrepancy in the wheel orientation on the hub. I don't know. Everything is tight, balanced and aligned. It must just be the spirit of JZD making itself known at ~70mph. Maybe BTTF had it wrong; it's 70 not 88?


You should be referring to Service Bulletin ST-34-1/82. All specs are in mm and degrees so if there is any confusion it could be because of improper conversions. First of all you must check everything at the specified ride height. Even before checking ride height a good shop will check for anything bent, broken, or worn. You cannot do an alignment with bad parts. Being off a little is OK but both sides MUST be close if not the same. Alignment is not going to affect shudder unless it is way off and if it is way off something is very worn, bent or broken. There is a way to custom enter a setup so they can either change the settings or just enter a new setup for Deloreans. Rear toe is more properly called "Thrust Angle" and is important and needs to be set properly. Now to "shudder". Usually caused by loose, worn parts but can be caused by bad tires. Is it really vibration and you call it shudder? Does it seem to get bad at a particular speed or on a certain part of a road? If it seems speed dependent it is probably a tire problem, either a bad tire or an out of balance tire or bent rim. Is it worse when you first start out and get better or does it get worse? You should not have any shudder or vibration. If you notice it when braking it is either loose, worn parts and/or the rotors are bad and need to be cut or replaced. If the sway bar bushings are worn (on the frame AND the lower control arms) they can be a big source of the problem and will accentuate a problem with the tires. BTW the spec for front toe is 3 mm or 0.12 inch per wheel. There is no acceptable range, it is supposed to be exactly that #. Same for the rear. Check your tire pressures and you should do an alignment with 1/2 tank of fuel and sandbags or other weight in the driver's seat approximating 150 lbs. The torque setting on the rear Trailing Arm Bolts is very important. Also important is the centering adjustment so the steering wheel is straight ahead when the car is going straight. That is a sign of a good shop when they get that right and is a big red flag when they don't. Too many shops rely on their wiz-bang alignment rack with all of it's bells and whistles and not enough on the skill and expertise of the person turning the wrenches. Springs can only affect ride height, not alignment directly. Shocks have no effect on static alignment. Last point, is there any play or looseness in the steering?

[Spittybug]

In the original workbook, it says 3mm (.12) with no units. The service bulletin clarifies this as .12 inches I see. That means I've had them give me slightly less toe than that as I interpreted it as degrees. I think I'm willing to live dangerously with perhaps 2mm of toe rather than 3... I get no drift and the it drives nice and straight.

Credit to Firestone and the guy that did my car, he did all the air, steering wheel, component checking that correctly point out. I cannot say that I was spot on for weight, but not far away given the tank was near full.

My post was as much about rebutting the fear mongers who said my LCA brace would screw up my geometry and hurt my car as much as it was about the high speed steering shudder. The two are not related.
My steering is very nice and tight, symmetrical turning to both sides and no play in my front bearings. The LCAs have been boxed and are not pristine, but nor are they in bad shape. The bushings are all nice condition polyurethane except the pivot bolt bushing which is rubber and in good shape. New lower ball joints, tight uppers. Nice tight tie rod ends. This car drives like it is on rails. The "shudder" is reminiscent of your typical tire out of balance feel, but a bit amplified since we aren't power steering. It only materializes ~70mph and I can't say that it progressively gets worse with more speed. Totally unrelated to braking. It is most likely as you point out; a slightly bent rim or tire, despite them having been balanced. I have lifetime balancing on them, so it's not a big deal to have them try again. I notice the shudder more on some roads than others, despite similar speed. This has me thinking about road surface imperfections being transferred through solid metal steering assemblies and wondering if that can be mitigated.....

I am 100% confident in the overall mechanics of the steering and front suspension.