Dodgy Steering

[Scouse Lee]

Hi guys......the steering on my 1986 SJ413 feels a bit dodgy, (to say the least), it's not too bad off road obviously with all the bumps and that but on tarmac it feels really loose and the car goes from side to side somewhat although when it's stationary and I turn the wheel slightly the tyres turn so it doesn't seem like a problem with play if you know what I mean. I will try and look at the ps box tomorrow to see if it needs tightening but is there anything else it could be?
cheers
Lee

[Edweird]

It could be that the toe or caster angles have been changed. Are you running standard suspension?

[Scouse Lee]

spring over axle conversion/extended shackles & body lift

[Jordi]

spring over axle conversion/extended shackles & body lift

That could be the cause. Is it running a Z bar steering arm or over the top steering conversion?

[Scouse Lee]

ya got me there.......new to this SJ game so wouldn't have a clue, what do I need to look for exactly

[Jordi]

If you can take a photo of the front axle and steering arms.

Sounds like it will have a Z bar fitted. If you look at the steering it'll be obvious, runs from the steeing box to the passenger side hub and is z shaped.

A lot of people run these but they are known for appalling handling. Check for wear in the steering damper too.

[Scouse Lee]

cheers Jordi I'll get on to that later, just off to the docs

[ScottieJ]

I would check the caster angle as well, loads of people tilt the diff up to point at the tbox when doing spoa and this gives you negative caster and trolley like handling.

Easiest way to check this is to use an angle finder on the face of the front diff flange, it should measure 10* off vertical, slightly pointing up at the tbox.

[Edweird]

I would check the caster angle as well, loads of people tilt the diff up to point at the tbox when doing spoa and this gives you positive caster and trolley like handling.

Rotating the diff to point at the T-box reduces your caster angle towards negative.



The extended shackles will defiantly mess with your caster angle, which will make your SJ wander a lot more. The other lifts mess with the connection between the steering box and the axle.

I've read a lot about this guff for Formula Student. I broke this down for a guy a few weeks ago. The caster angle is basically the angle between the axis on which your front wheels turn and vertical. Almost every vehicle you'll come across has a positive caster, which helps the vehicle drive in a straight line.
Because SJs front shackles are in front of the axle, extending the shackles reduces the caster angle closer to zero and possibly even making it negative which'll make your SJ actively try and turn rather than go in a straight line.
Your front wheels should be toeing in a bit too (the front of the tyre should be a tiny bit closer together than the rear) and this helps make your car more stable at speed, although this makes more difference on cars with independent suspension that live axle, though it'll make a big difference to how it feels in corners.

[ScottieJ]

That's what I meant negative not positive! Half asleep this morning

Scouse lee has shackle reverse on the front of his SJ not extended shackles so the caster will all depend on the angle that the spoa perches have been welded on.