Aprilia steering wobble

[lancialulu]

Hi again

On my list to try to resolve is the manic steering wheel wooble that occurs at around 35mph. While a bit frightening at first the car stays true and it goes away above that speed to be fine steering wise.

I have checked the silent block which appear fine, but have detected a small bit of play in the steering box. I mean a small amount (less than 1mm at the drop arm). This lost motion is not apparent when turning the steering wheel. The top adjuster has no play in it so am at a bit of a loss to work out if there is another adjustment by shims internally. The box seems otherwise in good order and does not leak oil.

Alternatively I wondered how critical is the wheel balance. They have been refurbished and balanced on the car (by Omicron I think), but both the front wheels do have a slight "heavy point".

Dont want to fiddle with the box if consensus is balancing. My previous experience (with sliding pillars is ziltch but with Macpherson strut cars (fords in a past life) wheel balance was quite critical but the wobble was at c 55mph.

Cant get the car out to drive it at the mo as am part way through going over it....

Tim

PS more issues to discuss in de course....

[ColinMarr]

I am sure current Aprilia owners will also have experienced this, but yes proper balancing of the front wheels is absolutely crucial! Also worth checking that the wheels/ tyres also run true, again any small irregularity is likely to cause a wobble. My memory is that the wobble set in at about 40mph and you could drive through it at about 60. The small silent-bloc bush at the bottom of the drop arm could also be a problem area.

This was a bigger issue in the 1960s when very few tyre fitters had dynamic balancing machines, or if the did they often didn’t know how to use them. On my first trip to Italy in an Aprilia I had terrible wheel tremor all the way south until the Lancia agent at Mestre balanced all the wheels on their super machine – it was free of charge, with lots of goodwill and the car ran smoother than it ever had before.

Colin

[Scarpia]

Tim,
check all the silent blocks,(4) unless recently replaced (last 10 years or so...)  the collective wear can create lot's of play.Two larger and two smaller ones.they are smaller on series 1 than series 2 so be clear when ordering otherwise they don't fit.They don't cost so much so better to replace the set (€15/piece.)
the  pin on the eccentric adjustment for the toe in can shear and if the steering arm nuts are then not tight enough you get some interesting shimmying also....wheel balance is also an obvious thing to check.  
avoid opening the steering box at all costs from beneath, you have been warned.....
William

[nistri]

I don't own an Aprilia (unfortunately) but my experience with sliding pillar wobble is that, if everything is mechanically correct after all the checks suggested in the previous messages, it does help to refit the two front wheels at 90 degree with respect to the former installation. Paint one stud, label the corresponding hole with a felt pen and refit it to the next hole. I suspect that after many years the wheels are far from perfect. Andrea

[lancialulu]

Thanks for all the input.

Have had a close look at the silent blocks which haven't brocken down.

I assume these should be "locked on the inner trunnion by doing the cam bolts up tight??

Is there any special sequence for setting the three cams?

I noted their positions but as one silent block pin was loose and a cam pin sheared on another I will be checking the tracking (which I understand to be parallel to i deg toe in for Radials - is this correct?).

Is it advisable to smear cooper grease on the cam pins to protect the pin from rusting more than anything??

Sorry for asking all these Q's

Tim

Tim

[Dilambdaman]

I've had excellent service recently from Vibration Free with a similar problem on Modestine. See Dilambda section.

http://www.vibrationfree.co.uk/index.html

Robin.

[ben]

Not sure what you mean by the three(?) cams. There should be eccentrics on the pins at the two ends of the track-rod for toe in adjustment and various sources suggest from zero to 7mm. I go for 1/8th of an inch!! If the little pin or pins that go through the flange to lock them in position are broken this will be because the central bolt is not clamping the silentbloc inner sleeves tightly. If yours were loose I think that was your problem. I dont think the order of tightening is significant but you should have the steering at the straight ahead position when you nip them up. This applies to all four bushes. It is certainly essential that the bushes are not worn and in my experience the drag link ones wear out quickest. This is for an early S1 car however.
   The trouble with wheel ballancing is that they dont always stay that way. For example if a tyre loses pressure it may shift a bit on the rim when you blow it back up. Speed humps dont help, especially if you don't see them coming! The tyres dont sit so tightly on the rims as modern tubeless ones do. Also if the wheels are ballanced on the car then you must mark them as "nistri" suggests but in order that you can keep them in the same position. If you have them balanced off the car it may then be worth trying them on different stud positions to find the best with respect to evidence of a "heavy" spot. ie check with the wheel jacked up to see if it always stops spinning with the valve (as a point of reference) in the same position then turn the wheel a quarter turn and see how quickly it moves back again.            Ben

[BlueSky]

Just to follow on from Ben's comments. My car has about 4mm toe in, that's the best I can get, and runs fine with that. If you do get new silent bloc bushes, beware that one of them, p/no 49601 (1 in the tav), you get from a well know English supplier have slightly oversize id holes, they are supposed to 14mm and are around 14.6mm. The small pins are easily turned up on a lathe if you have access to one.
Noel

[lancialulu]

Not sure what you mean by the three(?) cams.

I looked again at the cam parts and there are clearly three cams and I have double checked with the Tav 41. I assume the cam on the steering arm and drag link pins are to centre the steering wheel for straight ahead???

Will return to play when normal weather returns!!!
 Any ideas of tourque settings for nipping up these silent blocks??

Tim

[ben]

You are quite correct there are three eccentrics but only the two on the track-rod ends affect the tracking. I can only think as you suggest that the eccentric at the drag-link/drop-arm bush is for fine adjustment of the steering wheel position.It is not something I have ever found to be necessary since the wheel is on a 48 tooth spline which enables it to be positioned to within an inch at the rim anyway!
As a matter of interest (to an Aprilia anorak) the above mentioned bush is the one that wears out first because it operates at a shorter radius than the other three (110mm cf 134mm approx) and therefore is subjected to more twist for a given input steering angle. The maximum twist on full lock is about 45 degrees which is I think more than the rubber in the silent-bloc can handle so it shears at the bond with the inner steel sleeve early in its life and thenceforth sliding occurs at this interface causing wear and a short service life. If the sleeve isn't clamped up tight then it may slide on the central pin and the danger is then that the pin(eccentric or cam) will wear which is more difficult to rectify. As I said before my experience is with S1 where bush OD and ID are  26mm and 12mm. (Do the S2 cars maybe have a slightly bigger bush? The S1 track-rod bushes are 14mm/30mm.)
On further thought the outer drag-link bush needs to be out of the way to access the locking pin when the tracking is being set so the lower nut holding the track-rod bush should then be tightened before the drag-link bush is refitted (on the near-side). I am not sure if copper-slip is a good idea as it may make it harder to keep the sleeves clamped tight.

[lancialulu]

Ben

S2 are same as S1 silent blocks od/id. There is quite a bit variability in the current remanufactured ones in the UK with some being a nice tight fit and others are not variation c 0.5mm. I note the some ids are not circular either being a bit oval (hence tight fit..). Interestingly my n/s track rod pin diameter is 14.0mm and the n/s 13.75 plus minus .05mm. I might smear some grease on the pins to slow down any rusting.

[davidwheeler]

The solid nylon blocks I made up and fitted to my track rod ends are still going fine with no apparent wear.  The are pinched into the track rod end and rotate on old inners from the silentbocs, which I have polished up and which are clamped tight by the nut on the eccentrics.  I had trouble with silentblocs shearing.  There seems to be enough flexibility in the nylon to take up the change in angle with the suspension movement (or perhaps the track rod bends???).  Large (?original) washers preclude the possibility of the track rod end coming off.

[Scarpia]

I supect also that the track rods bend with nylon.(or at least experience more flexing)
Steel has a good capacity to flex and recover before failure but not unlimited. Titanium track rods may be the way to go......

[lancialulu]

I heard a story from Elizabeth at Omicron yesterday of an Aurelia track rod breaking in the middle of the Australian outback which shot the car through 180 degrees - luckly no other cars (well it was deserted). The owner apparently lashed it together with a hose clip and fence wire and limped home. Not something you want to happen on the M25.

Tim

[davidwheeler]

Eeeh, scary!  I only had one nylon bearing fitted but it was on the end of the steering arm.  I have removed it and fitted a silentblock instaed and will see how long it lasts.
The Aurelia limped home.  No more than 70mph then I presume,