Hi all, car is pulling to the left and outside of left tyre shows wear as well as shoulder where it has worn through the arch liner at the front. Have jacked it up and cannot feel play but maybe not got the knack. Is it the wishbone and bushes that are responsible for this. Believe there are two types 18mm or 21mm if you guys reckon it is the wishbone then will get on with ordering 🙂 thanks in advance 🙂

Plus the rear anti-roll bar bolt had snapped on the same side. Starting to think driver thinking it is a f1 car rather than a 1.6 focus 🙂

That's an odd mix of symptoms tbh.  Soft wishbone bushes allow the wheel to move backwards under acceleration.  I'm struggling to see how that could allow it to scrape the front liner!

You can check the bushes fairly easily while it's on the ground.  With the handbrake on hard, and a trusted assistant in the drivers seat, get them to 'bump' the clutch up to bite point with a few revs so it doesn't stall and you should see the wheel moving back in the arch, while the rest of the suspension remains stationary.

Does the car have standard wheels?  And is the arch liner secure or is it flapping about at the bottom?

Must admit, with pulling to the left, a snapped drop link and a worn liner, that sounds more like something's bent from accident damage than anything else!  Is the driver a fan of hitting kerbs?  

 

1 hour ago, TomsFocus said:

Soft wishbone bushes allow the wheel to move backwards under acceleration.

Assuming you're referring to the front wheel that doesn't sound right Tom. Surely the wheel will move forward under acceleration on a FWD car? It must be moving a heck of a long way to do that to the liner though, so not surprising it's pulling badly.

3 minutes ago, mjt said:

Assuming you're referring to the front wheel that doesn't sound right Tom. Surely the wheel will move forward under acceleration on a FWD car? It must be moving a heck of a long way to do that to the liner though, so not surprising it's pulling badly.

Hmm, have I got my physics wrong here? 🤔

When cruising, the wheels naturally pull back a bit, due to the resistance of the road, which is why we set tracking to toe inwards slightly, so that they're perfectly straight on a fast road (motorways for example, to reduce tyre wear over long distances).

I'm not sure about acceleration now...where does the greatest amount of force come from in that scenario...

The stationary test still works either way!

The way to think of it is that the wheel is moving forwards trying to pull the car with it. The mass of the car is trying to stand still so the wheel will move forwards until it's taken out all the play in the suspension.

It will still be moving forwards during cruise but not so much as it only needs to counteract the air drag. Rolling resistance will cause it to move backwards under deceleration as the mass of the car is then trying to continue at the same speed (Newton's Laws).

Rolling resistance doesn't come into it during forward motion under power, it just adds to the load on the engine.

52 minutes ago, mjt said:

The way to think of it is that the wheel is moving forwards trying to pull the car with it. The mass of the car is trying to stand still so the wheel will move forwards until it's taken out all the play in the suspension.

It will still be moving forwards during cruise but not so much as it only needs to counteract the air drag. Rolling resistance will cause it to move backwards under deceleration as the mass of the car is then trying to continue at the same speed (Newton's Laws).

Rolling resistance doesn't come into it during forward motion under power, it just adds to the load on the engine.

The wheel isn't powering itself though.*  It takes drive through the driveshafts from the diff.  That drive is always being resisted by the rubber on the road.  So the diff is constantly trying to 'roll' forwards (path of least resistance), and overtake the wheel while cruising, it is only stopped by the weight of the car that it's bolted to.  The diff doesn't suffer air resistance, it can move forwards minutely on the rubber mounts compared to the chassis, leaving the wheel very slightly behind the centre point.

*With a wheel powered by direct electric motor, the forces would be much more simple to calculate!

You're forgetting that the driveshaft UJs decouple the wheel from the diff so the wheel can move independently, just as if it was an electric motor in the hub.

35 minutes ago, mjt said:

You're forgetting that the driveshaft UJs decouple the wheel from the diff so the wheel can move independently, just as if it was an electric motor in the hub.

The wheel can move independently laterally, but not rotationally.  

(PS - It's nice to have an intellectual debate on here, even if I am wrong!  )

Hi assume these are standard focus wheels? Tyres are 205 55 16. Will perform the test described. Looks like original WB on there and car has done 146k. Liner was not best secured towards the rear of the car but everything else seems in order. Have ordered a new liner and obviously rear ARB bush and bolt. Will report back thanks

Yes, wheels & tyres are correct.

Which part of the ARB is loose?  I thought you meant the drop link at the front.  But it now sounds like one of the actual ARB brackets has come off?  

 

Hi, it is the rear ARB bush that has snapped the bottom Hex nut off and obviously lost the bottom part of the bush. Did read that track cars suffer from wearing the liner. Car hasn't  been on track 😉

2 hours ago, TomsFocus said:

The wheel can move independently laterally, but not rotationally.

Well, it is lateral motion we're discussing . . . .

24 minutes ago, mjt said:

Well, it is lateral motion we're discussing . . . .

Sort of...  It's the rotational force that I'm assuming to be creating this movement though.  Similar effect to a torsion bar.  It doesn't matter how many CV joints are in the system, the rotational force at the output end will be the same, and be creating the same amount of resistance at the input end.

I may be overthinking this now.  But it was a well trusted tutor that explained the reason for toe-in to me.  I don't think he'd have got it wrong.  (Unlike someone at a chain garage trying to sell me a geometry adjustment lol!).

42 minutes ago, scoobydo123 said:

Hi, it is the rear ARB bush that has snapped the bottom Hex nut off and obviously lost the bottom part of the bush. Did read that track cars suffer from wearing the liner. Car hasn't  been on track 😉

Ah ok, thanks.  Hopefully two separate issues there then!  (Although that does suggest some abuse lol!)

I've bought a couple of cars with liners worn like that.  Both times due to excessively large wheels having been fitted.

 

OK so MOT failed with off side  and near side spy Bush. Have removed the wishbones and used a piece of paper to "print' the receptacle for the taper. The print is 18mm ie the bit on the hub. Assume the measurement  of either 18mm or 21mm is measured like that? So is that the 18mm required? 

 

Tks

I would agree with your 18mm size. 👍

 

OK but I found this and measured what came off and it is the same as the description for the biggest on the attached. However it could be that the wrong part was fitted by someone amd if the maximum on the taper is 18mm on the smaller one then I can't see that working?

New wishbones fitted and rear ARB link and now have a years mot 🙂 wishbones not too bad a job one side the nut on the balljoint took a lot of persuading to remove the initial release of torque was easy but the removal up the thread was a challenge. New liner also fitted and wheel alignment.