Lotus Elan

Strange "jerk" in the steering

PostPost by: chris_uk » Tue Feb 19, 2013 12:53 am

and no I don't just mean the one behind the wheel! The symptoms are that I back out of the drive and head off down the road. After a couple of miles when the speed reaches around 60 the car gives a little jerk to the right. This is sufficient to alarm both driver and passenger. My theory is that backing out the drive puts something (probably in drivers side steering - RHD UK car) into one configuration and then this is pushed into another configuration when speed reaches a certain point. I've jacked the front up and had a pull and push at various bits to no avail. Anyone solved something similar or know where I should look? My guess is I need to look at the driver's side track rod end but before I lie on the drive in the rain to dismantle it it would be good to have the benefit of other's knowledge/experience and know if there are parts I should buy in.
Thanks!
Chris
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PostPost by: pharriso » Tue Feb 19, 2013 1:18 am

Rack clamps? Sounds very disconcerting! :shock:
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PostPost by: robertverhey » Tue Feb 19, 2013 5:52 am

Don' t forget to check the back end as well
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PostPost by: stugilmour » Tue Feb 19, 2013 6:19 am

Check bearing runout front & rear? I had jerking about when I has a bearing failure.
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PostPost by: UAB807F » Tue Feb 19, 2013 7:01 am

As an oddball suggestion but how about the brakes ? a caliper slightly sticking ? If you're going so fast you might not see the smoke :)

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PostPost by: oldelanman » Tue Feb 19, 2013 7:41 am

Also check the steering column U/J and the trunnions (may need lubricating). Try jacking the front of the car up and see if the steering moves freely to full lock on both sides.
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PostPost by: 512BB » Tue Feb 19, 2013 8:46 am

But whatever you do Chris, do not drive the car until you have found and sorted the problem, at least, not very fast. Accidents happen very quickly at 60 mph, and if it steering related, as seems likely, you could be in the wall sooner than you know it, or are able to react.

Good luck, and let us all know what you find.

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PostPost by: chris_uk » Wed Feb 20, 2013 1:02 am

Gentlepersons,

Thanks for the comments so far. Jacking it up and playing with the steering all seems fine. And the "jerk" only happens once per trip which makes me think that the backing out of the drive (on full lock) is significant and that sufficient force is required to "reconfigure" whatever it is. Rack clamps sound like the sort of thing I was expecting so I'll have a look at these and the other suggestions also and report back (won't be for a while as it will have to wait for a suitable weekend). Oh and I don't think it will pitch me into a wall (there aren't many in North Northumberland where the car is based) but it might into the oncoming traffic ! For information the care is relatively new to me and came via a 5 year stay in a garage post a bereavement sale where the owner died before the mechanical restoration was finished (a common story?) so past history is a bit obscure! Pictured here:
lotus-elan-f19/anyone-know-oyj40-t26619.html

All the best.
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PostPost by: JJDraper » Thu Feb 21, 2013 10:14 pm

I had a similar symptom early in my ownership of my +2. Car seemed to be fine, but at a specific bend on my journey to work, the suspension seemed to lurch slightly and take a 'set'. It got worse and started doing it more frequently. Long story short, it turned out to be that the front lower wishbone holes had worn oval and the upright moved slightly under load. Just pulling at the suspension didn't show up any play initially. Worth checking... Easy to prove, easy to cure.

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PostPost by: MickG » Thu Feb 21, 2013 11:06 pm

Sounds like a very plausible explanation. Check all front wishbones and bushes.
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PostPost by: ricarbo » Mon Feb 25, 2013 8:47 pm

I've been told that the highest loads in the steering are at very low speed. Think of the effort you put into the steering wheel when the car is not moving. Perhaps this points to the rack moving when you reverse out of your drive?
Does the steering wheel take up a different 'set' for straight running, after the jerk?
I'm also told you should check for movement in the suspension when it is normally loaded, i.e, the car is not jacked up with the wheels hanging down. I suppose this is most easily down by putting the front on ramps.
Regards
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PostPost by: chris_uk » Sun Mar 03, 2013 11:42 pm

well I had time to take a closer look and follow up these suggestions and, good though they were.... no real progress!
The rack clamps sounded promising, and on inspection, well they were not loose, but then they were not very tight either, so I tightened these up and felt good about the prospect of an improvement - but no, just as before - one "jerk" per journey!

So I looked more closely at all the front suspension with a particular view to the wishbone holes, bushes, loose joints, etc. The wishbone holes seemed fine, but again there were a few nuts thay needed tightening and I thought that tightening them might improve matters, but again a test drive after doing so revealed the same problem.

One thing I pondered was the anti-roll bar to suspension joint. I was surprised at how big the hole is in the bar where it bolts onto the lower wish bones and trunnion. It seemed to me that there was room for the roll bar to move around on this fitting even with the nuts done up tight (as they were) - but at the same time its not clear that this would create the "jerk" I was getting. Anyone feel it might?

Anyway, it seems I am going to have to do a bit more thinking and poking around to get to the bottom of this.

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PostPost by: innesw » Mon Mar 04, 2013 12:21 am

Checked the rear yet? Only other suggestion I can think of is two pairs of eyes and plenty of light while manipulating the suspension and steering, helps catch things you might miss out of human nature.

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PostPost by: fatboyoz » Mon Mar 04, 2013 3:54 am

Chris,
Two things.
Firstly, the anti-roll bar should have four special cup washers that fit to the top and bottom of the two rubber/urethane cushions at both ends. These are designed to fit into the large hole of the ARB and centre it so that there is no slop. I think these are the same items fitted to the diff' torque rods.

Secondly, it might be worthwhile removing the outer steering ball joints and rack gaitors and checking the rack, inner ball joints for condition/stiffness. The book basically says that the tie rod should only just support it's own weight plus the weight of the outer ball joint.
Regards,
Colin.


chris_uk wrote:well I had time to take a closer look and follow up these suggestions and, good though they were.... no real progress!
The rack clamps sounded promising, and on inspection, well they were not loose, but then they were not very tight either, so I tightened these up and felt good about the prospect of an improvement - but no, just as before - one "jerk" per journey!

So I looked more closely at all the front suspension with a particular view to the wishbone holes, bushes, loose joints, etc. The wishbone holes seemed fine, but again there were a few nuts thay needed tightening and I thought that tightening them might improve matters, but again a test drive after doing so revealed the same problem.

One thing I pondered was the anti-roll bar to suspension joint. I was surprised at how big the hole is in the bar where it bolts onto the lower wish bones and trunnion. It seemed to me that there was room for the roll bar to move around on this fitting even with the nuts done up tight (as they were) - but at the same time its not clear that this would create the "jerk" I was getting. Anyone feel it might?

Anyway, it seems I am going to have to do a bit more thinking and poking around to get to the bottom of this.

Chris
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PostPost by: chris_uk » Mon Mar 04, 2013 11:57 pm

Innes, Colin,

Thanks for these additional comments. I have not looked at the back end yet. Largely because I have been proccupied with the fron as the noise and the action when it goes "jerk" seem to point to the front and the way it seems to "set" in one way by reversing on full lock and resets some time later in forward drive all see to suggest the front - you're right I should not overlook the back.

Yes the ARB has the washers and the rubber doughnuts, but I can't believe they are very effective in holding it in place and on one side the bolt/stud is clearly not centre in the ARB so the washers don't seem able to seat properly (and given the robust nature of the ARB and the tolerances these cars were built to it's somewhat surprising the ARB can ever be well fitted.

And yes you are right the next thing at the front is to peer at the joints hidden under the rubber gaitors.

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