Harsh Vibration full lock

[lynns hubby]

Thanks for the replies, I had read one of your earlier posts on the centralising issue so was extremely careful to get this right. I turned rack full lock to lock on the floor and as you say it is 3.5 turns. I set the rack 1.75 before fitting. I also made sure the steering wheel was in the centre position. The lower UJ will only fit the rack in one position due to the shape and position of the clamping bolt. It fitted fine with the steering wheel in the central position so I am confident the rack is set in relation to the steering wheel. I have drained and flushed the system previously and as I had to disconnect the supply and return pipes from the old rack to fit to the new It drained all the fluid again so I am sure that the fluid is good. Just thinking now, the vibration through the steering wheel had stopped for a while but has now got worse again, this could be air still as I have disturbed the whole system, hopefully it will go over the next day or two. What concerns me is the skipping bit on full lock reversing out of the drive, it's as if the front wheels are being dragged rather than steering the car. It even does it going forwards on full lock now and again. As if the car is pushing the wheels !!!

[Laird Scooby]

Originally Posted by lynns hubby

What concerns me is the skipping bit on full lock reversing out of the drive, it's as if the front wheels are being dragged rather than steering the car. It even does it going forwards on full lock now and again. As if the car is pushing the wheels !!!

That's almost certainly down to wheel alignment/tracking. I had mine set by a national chain who i can't name but their initials are ATS and it made it worse.

After buying a DIY laser tracking device, i discovered they had in fact set the tracking to 7 degrees toe out on each wheel!

Considering it should be 0 deg 18' toe in TOTAL on mine it was miles out!!! To give you an idea of what my wheels would have looked like from above, put your feet together then move them to the "five to one" position - a slight exaggeration to demonstrate but not that much.

Without going into the principles of Ackermann angles etc, suffice it to say the steering is designed so that on full lock, the innermost front wheel turns tighter than the outer wheel so the correct turning radii are maintained. If the wheel alignment is out, the inner wheel will either turn more or less than it should. Due to weight transfer, the car will follow the line of the outer wheel which may mean dragging the inner wheel against its will across the imaginary arc it describes on the ground as it travels. That is the "skipping" sensation you feel.

I think the reason people notice it most on Volvo 7/9xx models is because of their incredibly tight turning circle. Where i live there is a place where i can turn round easily in the road (traffic permitting of course) in the 760, much to the annoyance of owners of things like Fiestas, Corsas etc that are much smaller. When i do it there is usually at least one face that is showing amazement.
With that kind of tight turning circle, if something is out, even slightly, we're going to notice it!

[lynns hubby]

Thanks for the reply, it sounds encouraging. I must admit, I never got the tracking checked on the old rack, reason being that I had to have both front tyres changed about a month ago,(inner sidewalls cracked ) and I specifically asked the tyre company if there was any signs of unusual wear as I have been suffering this problem for some time now. I feel sure they would have suggested spending more of my cash if they thought so. I know it is important to get it checked once a new rack is fitted. I measured the distance from lock nut to the end of the threads on the old rack and fitted the track rod ends on the same distance when I fitted the new rack to give me a chance of getting close.
As I said earlier, not going to a quick fit centre, I have booked in with a performance and tuning garage in Norwich. Been quoted a reasonable price for check and adjust as necessary the complete front geometry.

[jpliddy]

hi my 940 has done the " skipping tyre thing " on full lock but not recently . still thinking the problem is caused by air in system !

[TheLeeds]

I noticed my R reg 940 steering was heavy and occasionally vibrated on a lock. Someone on here suggested replacing the PAS fluid with synthetic ATF, so I did, and it's a lot better.

https://www.ebay.co.uk/itm/Carlube-A...72.m2749.l2649

* disclaimer. I can't guarantee it's correct for the car, but it's good so far on mine.

[Laird Scooby]

Originally Posted by TheLeeds

I noticed my R reg 940 steering was heavy and occasionally vibrated on a lock. Someone on here suggested replacing the PAS fluid with synthetic ATF, so I did, and it's a lot better.

https://www.ebay.co.uk/itm/Carlube-A...72.m2749.l2649

* disclaimer. I can't guarantee it's correct for the car, but it's good so far on mine.

It's backwards compatible with all the fluids recommended by Volvo for what is essentially either a Burmann, CamGears or ZF rack (think there was one other option but can't remember it now) that are fitted to dozens of other cars and happily run on Dexron II-D which ATF-U covers (and is much better than) and works very well in my PAS with no ill effects.

[lynns hubby]

Just a question on this fluid Laird, Its fully synthetic, I have seen that you recommend adding .5 Ltr during engine oil changes to rejuvenate seals etc, does the MINERAL ATF have the same effect?

[Laird Scooby]

Yes and no is the answer.

That sounds like a cop-out but it isn't. The molecules in the synthetic fluid are smaller so it has a better chance of getting into places that the mineral ATF may not (it's beginning to sound like a well-known lager! ) and has a better cleaning action as a result.

Feel free to use mineral ATF but the effects will take longer to happen. That said if you add some ATF at each oil change, you probably won't notice the difference between the two types.

Both contain "Seal-Swell" so will help to revive any weak seals but neither will repair a damaged seal.

[lynns hubby]

Thanks for that, I may well get some of the fully synthetic oil as you suggest as running older cars may help.

[lynns hubby]

Back to the skipping tyre issue. Had every thing looked at yesterday. The whole front steering geometry, the Castor and Camber angles were spot on but there was a need to adjust the N/S tracking as it was out slightly.
Car drove home fine maybe a little better than before. However today, backing out of our drive, it still skips. The front wheels are being dragged rather than following the line of the steering.
I have spoken to the garage that checked and adjusted everything and they are now puzzled but assure me there is nothing dangerous with the steering or suspension. They said it sounds like too much full lock which I would agree with, but there is no adjustment, 3.5 turns full lock to lock is what got with the rack before I fitted it!!!!!