Front Wheel Wobble

Paul Gregory
Posts: 115
Joined: Wed Sep 24, 2008 10:20 pm

Front Wheel Wobble

Post by Paul Gregory » Mon Nov 10, 2008 10:31 pm

My car is a 1948 four light 75 and has a habit of wheel wobble if you catch a bump whilst braking, usually on a corner. It usually occurs when you are doing around 30 mph and I have to slow to almost a standstill to be able to clear it. My father has observered it whilst following me in his car and has said that when it occurs you can see the wheels wobbling from behind.

I haven't got to the bottom of the problem yet, but the car is sat in the garage at the moment with its front suspension in pieces. Inevitably the first thing seems to be to look for free play in the steering. My intention is to gradually work through the parts which have free play. As a result I have replaced the drag link from the steering drop arm to the steering relay. The original unit had a rubber joint at one end and a ball joint at the other. As the rubber joint had some play I replaced it with a new link from Mike Cauldry (Meteor Spares) which has a ball joint on each end. Sometimes I think this may have reduced the wobble occurance a little but it certainly still happens and I suspect I am just kidding myself that there has been an improvement.

My current activity is to replace the steering relay as it has some play. This was actually replaced 8 years ago as part of a major rebuild, but it has some sideways play in as well as vertical movement. The exchange unit I will be fitting shortly doesn't have any vertical motion, so I am hoping that it will have some effect. Whilst I replace the steering relay I am also replacing all of the rubber bushes as you have to dismantle most the suspension to get the relay off. If this doesn't solve the problem I will have three steps left.
1) have the front wheels rebalanced - probably should have done this long ago. This may be a long shot but I am aware that you can get horrendous vibration as a result of badly balanced wheels - I remember driving a Land Rover which nearly threw me off the road at certain speed because of this.
2) have the steering box rebuilt - I know there is considerable play in the steering box, so I probably ought to do this anyway but would prefer to leave it for now if I can.
3) check the wheel bearings - again something I should have done long ago and may well have done, but can't remember checking recently so will do as part of the current re-assembly.

So, at the moment I don't have an answer but am gradually working through the possibilities.

I recently met Ron Taylor from the North East who has a very nice 1948 6 light 75 who is also trying to get to the bottom of what seems to be a very similar problem. At times his car ends up with a considerable wheel wobble which sets in at about 30Mph. He is also working through the possibilities on his car, with the steering box or wheel bearings seeming to be the most likely culprit at the moment.

Has anyone else come across this in the past?

As far as I am concerned, however, the the good news is that it must be solvable as Stewart Devlin has never had a similar problem with his 1949 6 light 75.

Will keep you informed on progress ...when I finally manage to get back into the garage again!

Paul
RSR Post 1950 Librarian

Do you have anything which could be added to the RSR Library for the benefit of all members? Please let me know if you have.

User avatar
Phil - Nottingham
Posts: 357
Joined: Thu Oct 09, 2008 10:45 am
Location: Nottingham

Re: Front Wheel Wobble

Post by Phil - Nottingham » Mon Nov 10, 2008 10:58 pm

Its called shimmy and apart from what you have suggested can be caused by worn kingpins/too much endfloat/stiff ie semi seized, worn/unbalanced dampers as well as out of balance wheels and incorrect tracking. Unlikely to be worn box unless caused by driving too long with foregoing :oops:

Rear end problems eg loose spring U bolts and shackles or misalligned rear axle - how is the rear end bodywork has this been repaired/bodged in the past
P2/P4/P5/P5B/LR's - EXJ 8**/2**8MY & others

Dirkco
Posts: 142
Joined: Thu Oct 30, 2008 2:12 am
Location: USA
Contact:

Re: Front Wheel Wobble

Post by Dirkco » Tue Nov 11, 2008 1:43 am

Hi Paul,

I have a P3 6 light and the same problem. I have rebuilt the front end and paid particular attention to the relay arm and after discussion with Mike Couldry I decided to replace the drag link with the newer ball joint type. As this is a part of a complete restoration I have not driven it since the rebuild. However I noticed that the shake would occur when I went over a small bump. It shakes so badly I have to come to a complete halt. Mike did not seem to think it was the king pins and everything else was replaced.

I am leaning towards the steering box. as Dave Dudley Toole explains the orginal drag link as it wore was miss understood as a loose steering box. Unfortunatly people would then tighten the adjuster on the steering box. the over adjustment meant the worm would wear prematurly and in the most often used area. I am begining to think this is the porblem. If you read the article in this issue of Freewheel Dave explains this in detail and he also rebuilds the boxes as well.

Dave and I will be at the NEC both Saturday and Sunday if you want to discuss it with him.

Keep the post updated with what you find

Cheers
Dirk in the States

patrick hiron
Posts: 19
Joined: Mon Nov 03, 2008 4:30 am

Re: Front Wheel Wobble

Post by patrick hiron » Wed Nov 19, 2008 4:09 pm

This was a problem with the original P3 front suspension design , even when the cars were fairly new . The P3 front end was redesigned from a system similar to the Morris Minor where the top link was a huge Armstrong lever arm shock absorber , to a more conventional tubular shock absorber .This is the system shown in the Rover parts manual . The conversion is a simple swap of parts . The Armstrong shock is repaced by a fabricated mounting with pick up points for the tubular shock .
It's worth checking that the Armstrong shocks work properly and are bolted down securely . Also check the ball ends of the radius arms which locate under the gear box . On IKB the rubber ball end covers were a soggy mess after being soaked in oil for 50+ years . The aluminum sockets which bolt to the chassis were also badly corroded from galvanic action .This meant that the rear anchor points for the front suspension were sloppping around under the car !!
I was lucky enough to find a complete unworn telescopic shock front end in a junk yard.I rebuilt my front suspension using the best parts from both units and a complete new set of bushes from Scott in OZ . I also rebuilt the steering box , had the wheels balanced and added a grease nipple to the steering idler .
With this set up I had no problems with wheel wobble or anything else except the ridiculous P3 turning circle
Cheers
Patrick

davedt20
Posts: 16
Joined: Mon Nov 17, 2008 5:46 pm

Re: Front Wheel Wobble

Post by davedt20 » Thu Nov 20, 2008 11:41 am

Hello Paul, just a few tips on curing your wheel wobble.
Firstly, get both front wheels correctly balanced.
You dont mention what kind of shock absorbers you have, the lever arm type are more prone to problems, but they can be re-built, Derek at Stevson Motors in Birmingham can re-build them, although they are not cheap any more. Telescopics are much better, I have Spax adjustables on my P3, and they really do a great job.
Play in the relay, either side to side or up and down will certainly contribute towards shimmy, but its a good thing that you have gone for the twin ball joint type arm, these are 100% better than the old type with the rubber bush.
The `tennis balls` on the back end of the radius arms go very `soggy` after many years of being soaked in oil, and are well worth changing.
All of the rubber bushes in the front suspension will be suspect, I made my own bushes some years ago from Polyurethane that I bought as a stock bar from Polybush in Wales, I turned them up on the lathe and they are as good now as the day I fitted them, there is a company called Classeparts that advertises on Ebay and they are now selling these bushes.
I would pay particular attention to your front wheel bearings and king pins, any play in either of these will cause `shimmy`.
I notice you say you have `considerable play in the steering box`, all of the steering boxes on P3s and P4s are completely worn out internally, over the past 12 months or so I have stripped and re-built quite a lot, and there has not been one that I would have fitted to my own car without a full re-build, I honestly think that most owners dont realise how badly worn their steerings boxes have become over the past 60 years or so. If you put your steering on to either full lock and remove the four nuts and take off the top plate you will see that the `worm screw` will be badly damaged around the middle part of the screw, but what you can`t see, is similar damage that has been done to the upper and lower thrust bearings. Its unfortunate that over the years, when it becomes evident the the steering has developed general slackness, most owners will usually tighten up the adjuster nut on the top of the box, this is infact the worst thing to do as over time this can wear out the worm screw at an alarming rate, and in some cases so much pressure is applied to the ball bearings that they shatter and do even more damage. It is always the thrust bearings that go first, but if you think about it, P3s and P4s are very heavy at the front end, and the steering has to do an awful lot of work, and the axial load on the steering shaft and bearings is enormous.
I did a write up a couple of months ago for Freewheel and the P4DG Overdrive with further details, could be worth you having a look, hope this bit of information helps, cheers, Dave.

Paul Gregory
Posts: 115
Joined: Wed Sep 24, 2008 10:20 pm

Re: Front Wheel Wobble

Post by Paul Gregory » Mon Nov 24, 2008 5:40 pm

Thanks everyone for your replies. Sorry I haven't responded sooner but work on the P3 has stopped at the moment whilst I try to get some decorating done amongst a few other things.

Your responses seem to imply that I am certainly heading in the right direction. My car is a fairly early one and as a result is on lever arm dampers. I have removed them and filled them with oil as they were extremely short of it - it is interesting to know that some later cars with lever arm dampers actually have filler plugs in the shock absorber bodies which saves you taking them the car to top up, but no such luck with mine.

I will be replacing the 'tennis balls' at the ends of the radius arms because they certainly look well past their best, and I have all the rubbers for the bushes on the wishbones so they will be done as well. I recall reading in the P3 workshop manual that the aluminium sockets for the tennis balls were replaced by malleable iron ones on later cars - and that early ones ought to be similarly replaced when servicing the suspension. I wonder how many of us still have the aluminium ones rather than the replacement iron - I believe mine to be aluminium.

The Steering Relay I am fitting already has a grease nipple in it, so I hope that will help me look after it and avoid excessive wear in the future.

Once it all starts coming back together I'll check over the kingpins and wheel bearings as well - I get the impression from everyones posts that any play anywhere can end up causing the shimmey.

Dave - thank you for the comments about the steering box. I had already read your interesting article in both Freewheel and Overdrive which has certainly pushed me towards sorting out a rebuilt steering box fairly soon although that will probably have to wait a little bit longer to allow funds to recover from a very recent aquisition.

I'll let you all know when I finally get it all back together and take it for a run.
Cheers
Paul
RSR Post 1950 Librarian

Do you have anything which could be added to the RSR Library for the benefit of all members? Please let me know if you have.

lakesrally

Re: Front Wheel Wobble

Post by lakesrally » Sun Dec 21, 2008 11:56 pm

As Paul knows, my 1949 75 does not suffer from the shimmy problem and is still on the lever type shock absorbers, although it is on the slightly later ones with the small reservoir tank on the top. So whatever the cure is it cannot solely be down to fitting the telescopics.

Best of luck with the decorating!

Paul Gregory
Posts: 115
Joined: Wed Sep 24, 2008 10:20 pm

Re: Front Wheel Wobble

Post by Paul Gregory » Wed Jun 17, 2009 9:45 pm

Well, after far too long I finally managed to get enough time together and finish putting the front suspension together over the weekend. As previously mentioned I have replaced the steering relay, all the wishbone bushes and the tennis balls which are still mounted in the original aluminium housings as suspected. I haven't done anything about the steering box at the moment, I'm sure I probably ought to, so it is on the list of jobs to do but it is way past time it was back on the road again so that will have to wait.
I took it for an MoT on Monday and it passed with flying colours. Just driving to the MoT station and back, which is probably no more than a couple of miles, it was clear that the whole car felt stiffer. This is no doubt due to having new shocks on the back and refilled ones on the front. I haven't had chance to take it out since the MoT, having only got it re-taxed yesterday, so I don't know if I have cured the shimmey problem yet. I'll have to get a few miles in and see if it still occurs, here's hoping it doesn't! I'll let you know how things gone once I've got a few miles covered again.
Paul
RSR Post 1950 Librarian

Do you have anything which could be added to the RSR Library for the benefit of all members? Please let me know if you have.

User avatar
47p2
Posts: 767
Joined: Wed Sep 24, 2008 7:51 pm
Location: Scotland
Contact:

Re: Front Wheel Wobble

Post by 47p2 » Wed Jun 17, 2009 11:41 pm

The shimmy subject was brought up at the recent SARR Rally when someone was mentioning the problems he had with his P2. He tried everything and eventually discovered that the castor angle was to blame. Apparently the wedges that sit below the front springs and on top of the axle were fitted the wrong way round and should be fitted with the thickest part to the front of the car

User avatar
Phil - Nottingham
Posts: 357
Joined: Thu Oct 09, 2008 10:45 am
Location: Nottingham

Re: Front Wheel Wobble

Post by Phil - Nottingham » Thu Jun 18, 2009 5:42 pm

Wedges not really applicable on IFS there are so many more variables than with a beam axle as on P2 and even different tryes makes/trye tread depth can affect IFS paticularly the early and more primitive designs.

To tight or too slack king pins apart from weak an dunblanced dampers/tyre/wheels have far greater effect.

A bent radis arm (even slightly) with IFS can cause shimmy as will affect camber and castor
P2/P4/P5/P5B/LR's - EXJ 8**/2**8MY & others

Post Reply