Shaking front wheels

[gouldsborough7]

My Berli appears to be suffering more than before with shaking front wheels, echoed through the steering wheel. Immediate reaction you might say is wheel-balance! Not sure if this is the case, as the original weights are still in place, the shaking is not related to any particular speed, and the tyres/wheels have not been kerbed. The tyres/wheels are I think Sierra Cosworth type, with 205 section tyres.

I might try swapping front/back wheels over, to see if this makes any difference. Cannot see if anything on the suspension/steering rack has changed.

Being a highway engineer, I know our roads are going to pot, but this is probably not the reason for the shaking. Anybody's Berli suffered in the same way?
Cheers
Mike

[dogoncrazy]

Re: Shaking front wheels

Had a problem with those on my Cabrio at 70 ish mph. Had wheel rebalanced twice and tracking checked to no avail. Finally disappeared when new tyres purchased. Put the problem down to the crap 'Champino' tryes the car came with.

[gouldsborough7]

Re: Shaking front wheels

I think some of the problem stems from the whole idea of putting giant wheels on Cortina suspension/steering. On the couple of occasions I have taken off the wheels, they have to be the heaviest I have ever lifted, even though they are alloys. Anything slightly less than perfect I believe produces the 'shakes'.

As a no cost experiment, apart from getting backache, I'll swap the front with back wheels and see if that makes any difference at all. I know the previous owner had all the wheels balanced, and it has only done 2,500mls since. The weights haven't moved or fallen off, so it must be something else. I know our roads are crap, and the potholes & ruts don't agree with the old suspension design. On the better roads (if you can find them!)the shakes disappear. Will provide feed-back as & when OK.
Cheers
Mike

[Dane_Rescueman]

Re: Shaking front wheels

Mike,

There was a very similar story in Pitstop bsolutely yonks ago. I will try to find the relevant mag (somewhere in the loft) and let you know. My rotten memory seems to think that tyres were one of the issues. The awkward camber set up in the Cortina models cerainly did not help. The Cortina upright and bearings should cope OK with the wide wheels though. Keeping the front bearings nipped up correctly is a must though.

Good luck with it all

[macdonald.dm]

Re: Shaking front wheels

Good point by Dane.

Before you remove your wheels, try gripping each tyre at top and bottom, give it a good 'rock', and check for 'play' in your bearings. A TINY amount of movement is ok, but you should be able to sense whether it's excessive.

[gouldsborough7]

Re: Shaking front wheels

OK Guys
I'll give everything a good tug, and check for any 'play'. Failing that, I might entrust the problem to my village garage, the proprietor of which is very user-friendly towards kit-cars! For a very modest fee, I am sure he will put it up on his fancy hoist, and push & shove everything.

Will let you know the outcome for general info.
Cheers
Mike

[djj_engineer]

Re: Shaking front wheels

I agree with Alan.
I tried everthing with FMB but in the end decided it must be the tyres. A new set got rid of the wobble. There wasn't anything visable with the old ones but there must have been something strange with them. I did wonder if the two tyres were reacting with each other.

[jeremy61]

Re: Shaking front wheels

Mike, Et Al,
The problem with the front suspension on the Berlinetta is that it was designed with a large amount of positive offset ie the angle though the kingpin centres (ball joints) strikes the ground way inward of the tyre centre line. Thus every bump can be felt through the wheel. Ford got over this by the use of the rubber doughnut type of lower steering joint. Sadly the Berlinetta can not accomodate that joint and the Triumph/Rover metal one is too harsh. The upside is the terrific feel and positive control of the steering. However if all suspension joints are good and tight that is all you can do. Ironically if you fit wheels from a front wheel drive car they have much more negative offset to erradicate the torque steer. However they wont necissarily clear the wishbones and will look funny. Narrower wheels will not help as they are usually designed to give the same overall track thereby making the wheel's offset even more to the outside. I had 7" Alloys and they shook I now have 5.5" spokes and they are the same but look a lot better. I think if you could get 5.5" x 15" wheels in really lightweight with an even offset ie the wheel hub face is in the centre of the rim width it would sove the problem. If anyone has a shake free Berlinetta please let me know.

[Dane_Rescueman]

Re: Shaking front wheels

It is just possible that the problem is endemic with those cars that run a large negative camber. The tyres will wear most on the inner part thus slightly reducing the inner diameter as compared to the outer diameter. Carried to the ludicrous extent, the outer circumference of the tyre will try to cover more ground per revolution than the inner. Of course it is all glued together very firmly! If the rubber is slightly distorted, it is possible that the inside (or outside) catches up the flexibility of the rubber in little jerks. This is probably a red herring/blind alley but an expert may be able to help. I suppose that at may be a bit like a knackered supermarket trolley where the worn tyres and shabby bearings induce dreadful shimmy.
My camber is only a tiny bit negative now and I do not get any vibration (apart from the crashes into the Cornish pot holes of course. I actually suffered a broken front spring recently which I blame on the bad roads here.)

When I had the "standard" Berli negative camber my tyres did wear much more on the inner edge than outer. It is thus important to swap the tyres around fairly often.

Now your turn to shoot me down.......