Caster Again

[Jon Bradbury]

Having got the Beast running under its own power (with brakes too), I drove it out of the garage and turned it round. When I reversed I noticed loads of self-centering force (steering wheel spun wildly) but none whilst going forward.

 

Now, the camber / toe in settings are assuredly out on my car, but I would not have expected this to happen, given that I used the RHE drill holes in the chassis to locate the arms.

 

What is going on here?

[Guest paul thompson]

Hi,

Doesn't this have more to do with castor rather than Camber, i.e. the angle the centre line between the upper and lower ball joint centres makes to the vertical. You should have negative castor (caster?) i.e. lower ball joint further forward than the upper. Positive castor i.e. lower ball joint ctr further back than upper would give you this result. Can you check this? I know I have about 5 degrees of negative catsor cause I checked while building, done on the advice of Jaguar Vehicle dynamics to give good self centreing.

[Jon Bradbury]

Yes; that is why the topic is called "Caster again" and not "camber again".

 

Camber can have a small effect on self-centering force I believe, which is why I mentioned it.

[Guest paul thompson]

Sorry, I must learn how to read!!!

[Peter Bell]

Sorry Jon, are you sure it was trying to centre or was it swinging onto full lock?

Peter

[Jon Bradbury]

Good question.

 

It seemed to me it was centering but I stopped it very quickly because I didn't want to hit the neighbor's car in an uninsured vehicle.

 

Its entirely possible that this effect is caused by drag on one side - the steering arms (track rod ends) were fitted the wrong way round so the big triangular tab on the ball joints comes into contact with the inside rim of the wheels when only a minor amount of steering input is applied.

 

I will try a little experiment tonight if I get home early enough, and let you know the result.

 

Cheers

 

JonB

[Jon Bradbury]

Yes, definitely centering in reverse but not forward.

 

Have checked suspension arms visually - it appears I have positive camber. The top arm balljoint appears to be closer to the rear of the car than the bottom. (see attached image).

 

I must say I hate driving it with no seat or mirrors.

 

Anyway, caster looks ok and there is no real drag occurring with the steering arm lugs. What next?

[Longboarder]

Don't panic. You can get a better view of castor if you want to. Measure the ground to lower arm distance, jack it up on the arm, whip off the wheel and disc, jack it back down to the original height and you can visualise the line going through the centers of the top and bottom ball joints. 5 degrees is a good starting point but its the feel when driving which counts and you may just have to be patient for a bit.

 

Nigel

 

Mine self-centres in reverse and forwards.

[Jon Bradbury]

Yes, Longboarder, I understand where you're coming from.

 

I can ignore the whole issue for now anyway as I have to get some other bits plated and some are on the front suspension so it'll have to be at least partially dismantled. I can check it properly then.

 

The camber and toe-in are nowhere near right BTW, and one of the tyres (actually, its the one in the picture) is totally bald on the inside edge. I bet this is contributing.

 

One more thing to note - the ball joints (top, bottom & steering arm ends) are all really stiff at the moment. I think this is a contributing factor too.

 

On the other hand I might expect it to demonstrate no self centering at all (reverse or forwards) if the camber was near correct and the other factors were playing their part.

 

Unfortunately I cannot take it for a spin to try it out properly because I'd really hate to be caught driving an uninsured / unregistered / untaxed bare chassis about.. might be embarrassing....