FORD ESCORT STEERING SHAKE

[Mike Bell]

OK, story so far- before Silverstone last w/end I found during test that there was a front wheel balance type vibration on my RS2000. After a visit to local tyre place with wheels, perfect.

Checking car on the road today, found nasty steering shake (as in trying to tear wheel out of my hands), so whipped the wheels back to tyre place to see if out of balance. Hardly. Refitted and shake still apparent, but not quite as scary. Removed Dunlop tyred wheels and fitted Yoko set, thinking crap D'lop the problem. WRONG. Shake now so bad that daren't try and drive through it!

So apart from having Yokos rebalanced, what should I be looking for? Steering all feels tight, I tweaked the hub bearing clearance just in case, dampers feel OK........

[VIVA GT]

A bent hub or something else making the wheel not sit flat? You could check for hub run out using a DTI?

[GORDON STREETER]

Mike has it only just started ? think back to when it was ok, have you done anything at all since or has it always had a slight tendency to get the dreaded ford wheel wobble. On my car I found that too much castor or a castor imbalance caused all sorts of wheel wobble especially at low speeds.
Having worked on Fords for 50+ years they have all suffered from the problem ever since they fitted the simple McPherson strut front suspension/steering system in the 50s to the 100E models.

[bauble]

Check the Nut that holds the wheel.

[terence]

Mike,are they stick on or knocked on weights? Think I would get the wheels balanced on the car if possible just to check.Are both ends of the rack tight(inside the boots)?

[zefarelly]

Check the rack joints. Track rod ends, rack mounting, bottom ball joints on TCA's, usual stuff you've already done I'm sure.

[Mike Bell]

Thanks for the suggestions- even Bob's.....

I well remember the problems we had with the first 3 litre Capris, caused by their 185/70x13 tyres and 5.5J rims. Customers having wheels balanced almost weekly!

The Escort problem is well beyond a simple vibration, though. Nothing has changed since the race, but will look at all the suspension mountings first. Then dampers......

[terence]

No big kerbs at slitherstone either.

[Neil Duke]

Originally Posted by Mike Bell

Thanks for the suggestions- even Bob's.....

I well remember the problems we had with the first 3 litre Capris, caused by their 185/70x13 tyres and 5.5J rims. Customers having wheels balanced almost weekly!

The Escort problem is well beyond a simple vibration, though. Nothing has changed since the race, but will look at all the suspension mountings first. Then dampers......

Most Capri's had to have 'on car'balancing,only way to cure it.

[GORDON STREETER]

Back in the day most of the problems used to start at about 30/40mph and then disappear as you got faster, balancing them at high speed didn't cure it but did if you could use a slow spinning balance machine.
I know what you mean regarding "serious vibration" Mike as I have been approached on the grid after the formation lap after marshals had reported that they thought a wheel was loose and about to fall off !

[Tel 911S]

Might seem silly , but have a look at the tracking . If you have almost parallel on the front it might be causing a "flapping " when the steering is straight ahead .

Try about 6 mm toe in & see if that changes it .

[Mike Bell]

Interesting, I will check the toe. Had time this afternoon to check all joints and mounts. Nothing found. Removed 5mm spacers (reqd for Dunlops to clear struts) and ran car on Yokos up the road again. Small shake experienced, slowed down, then accelerated through it holding wheel very firmly in case. Rest of journey perfect, until after slowing down for junction and then accelerating, severe shake again!!! Grrrr........

Will also have that set of wheels rebalanced, just to be certain.

[morninggents]

Are the inner wheel faces and hub faces flat?
Are the wheel nuts holding wheels tightly?

[Tel 911S]

It is possible that you might have a bit of bump steer .
Enough to go from a mm or so of toe in to a mm or so of toe out with suspension movement , even if your suspension is very stiff .

That could be enough to cause your steering shake . Which might be exaggerated if your scrub radius has changed with different heights of the tyres or offset of the wheels .

So putting a bit more toe in might damp that out , or might point you in the direction of what is happening .

[Paul D]

Probably a stupid question Mike, but the wheels have been balanced dynamically, as opposed to statically?

You should have weights both on the outside and inside edges of the rim if they're dynamically balanced - if you only have weights stuck inside the rim near the middle, then it's only balanced statically and this doesn't always eliminate wheel wobble if your car is particularly susceptible to it.

Might be worth checking as you seem to have ruled out most of the usual culprits!

[GORDON STREETER]

In the end I never cured it completely and learnt to live with it as it would only develop (in my case) under braking for a slow corner. I found that having the discs plough ground made a difference for a while as well, Some wheels are difficult to get stick on weights 0n the inner rim because of small diameter wheels and huge brake callipers/discs that limit space, knock on weights don't always work well because of the profile of the edge of the rims (especially on alloy wheels). Obviously if they could be balanced actually on the car it would be better as you are then balancing the complete revolving mass.

[Mike Bell]

I keep wondering what could have changed on the car. Could be that all the moving parts are now 'bedded in', so any small imbalance shows up more.

Front wheel alignment is spot on, not changed, and as the problem occurs driving on a flat surface with no bumps or undulations, doubt anything to do with bump steer. The front geometry is more or less as per factory- maybe a bit more camber, but that's about it!

Will refit wheels that are being balanced again and see what occurs. Have asked the guys not to hide the weights behind the spokes! I also marked the previous weights and locations, to see if different this time.....

Could be it has to be lived with Gordon, but vibration is one thing, severe shake another!

[SidewaysFeltham]

When I worked for Ford Europe in the mid-to later 1960s, this was a classic service problem. The Ford technical description for the problem was "Steering Shimmy".

As Gordon has already stated, it was a product of Ford's love affair with the McFearful Strut; and poor tolerances in manufacture.

If all aspects of steering and suspension are in tolerance (TCA joints are the usual suspect, particularly the bottom strut ball joint), then usually it is a wheel balance problem.

As PaulD has already suggested, the first real step is a proper dynamic balance; "on the car"! Since this balances the sideways moments of inertia induced on the wheel bearing and the steering and suspension components.

When I was setting up my tuning and diagnostic centre in 1971, a critical acquisition was a -very expensive! - Repco state-of-the-art dynamic balancer supplied in the UK by Brabham. This was so accurate we could even use it to balance prop shafts.

The pick-up head could be positioned at the bottom of the suspension, to read and then balance rotating (vertical) nodes of force; and then inside the wheel/suspension, to pick up the sideways "wobble".

The balancer was used, very successfully on a wide range of road and competition cars, from the F2 Huron; thru F3 and FF; Anglia, Escort Capri, Midgets X 3; Cooper s and even Melvyn Coon's Gregor Grant-Shellsports Clubmans Championship car.

Thus, Mike, I would commend your first step is a proper dynamic balance, on the right kit, wheels on the car.

Alternatively, you could of course, always redesign Henry's appalling cheap front suspension!

[Mike Bell]

Thanks, I'll have to search out a tyre place with on car balancer.

The shake is just as bad after having the second set of wheels balanced again. If you let go of the steering wheel and lift off, the car wobbles all over the place, and continues to do so until almost stopped.....

I will check inside the rack boots tomorrow, in case a joint has come loose- although fact that track is correct would suggest otherwise. Maybe need to order another pair of TCAs as well........

Frustrating!

[SidewaysFeltham]

Originally Posted by Mike Bell

Thanks, I'll have to search out a tyre place with on car balancer.

The shake is just as bad after having the second set of wheels balanced again. If you let go of the steering wheel and lift off, the car wobbles all over the place, and continues to do so until almost stopped.....

I will check inside the rack boots tomorrow, in case a joint has come loose- although fact that track is correct would suggest otherwise. Maybe need to order another pair of TCAs as well........

Frustrating!

Mike:

Don't throw good money away!

Checks:

1. Rack Ends and Rack itself:

Ensure rack float is not excessive; disconnect track rod end joint: check sideways movement this at lowest, middle and top angles. Then rotate 180 deg and check again.

Test TREs in a similar fashion, rotating them before loading them.

Not unknown for thrust washer to wear, remembering they are a sacrificial component and competitive usage places much more end load and thus wear on the part.

2. Bottom Ball Joint: a primary suspect! Disconnect from bottom and using a long lever, move it both up and down (Replace the nut with a much larger washer). Small amount of wear is magnified through the suspension.

3. Test the rims for rotational "wobble": can be done on the car, all provided the wheel bearings themselves are not too worn. Ideally with a Dial Gauge: however, a fixed point at the periphery of the rim can show up significant "Run Out".

Come back with results!

[Mike Bell]

All the suspension and steering parts were new when the car was put together. It's now done a max 3hrs of track work and some road miles testing, so would hope that wear in something isn't a factor! The rack and TCAs are modern repro items though, so quality could be an issue......

[Geraint Owen]

Somewhere I have an on car balancing machine with a blown bulb. Other than that it works. I looked into getting it fixed but gave up when I managed to cure the problem another way. It is quite old and the bulbs were really pricey. I suspect someone with some electrical know how could wire it up to a cheap engine timing light. You are quite welcome to borrow it if you can be arsed to fix the bulb then let me have it back when you are done

Incidentally I have known this effect on two cars and in both cases it was excessive castor

Geraint

[james s]

Are the wheels round ?

[SidewaysFeltham]

Originally Posted by Geraint Owen

Somewhere I have an on car balancing machine with a blown bulb. Other than that it works. I looked into getting it fixed but gave up when I managed to cure the problem another way. It is quite old and the bulbs were really pricey. I suspect someone with some electrical know how could wire it up to a cheap engine timing light. You are quite welcome to borrow it if you can be arsed to fix the bulb then let me have it back when you are done

Incidentally I have known this effect on two cars and in both cases it was excessive castor

Geraint

Usually, they use a Xenon Tube (Same as a photographic flash).

Critical are the circuit which provides a very high discharge voltage and the trigger modality.

A Timing Light is triggered by picking up either the LT or HT pulse from an ignition circuit. Wheel balancers are significantly different. They normally use a spring loaded plunger, which is a permanent magnet, surrounded by a coil of very fine copper wire. When the imbalance node "bounces" the rotating assembly down, this creates an EMF (Electro Motive Force - Faraday Effect) or if you like a very small electrical current. This current is amplified and triggers the Xenon flash tube.

Unlike a timing light, a dynamic wheel balancer must be capable of triggering (at full voltage) 1,400 to 1,600 times per minute; thus the voltage potential has to be pretty large and instantaneous.

Thus one needs:

1. A Signal Amplifier Circuit Module:

2. A High Tension Circuit (To raise 12V DC or mains 250 Volt AC rectified to DC to hundreds of Volts):

3. A Trigger Circuit:

Lots here:

[GORDON STREETER]

I hope that you find a cure Mike as that problem is a real pain in the a***, at least the Escort has a rack as the problem is even worse on the Fords with the steering box and can cause serious damage to the chassis rails where the box and idler fit.
We used to make up and weld 2mm plates around those areas before it caused cracks. Believe me I know the problem you have and we are not talking about a "little" steering shake !