N15 Pulsar Steering not self centering

I've got an N15 Pulsar, dedicated track car running XYZ coil overs. I've noticed that the steering doesn't self centre. If I turn the wheel around a corner and let go of the wheel it will keep steering that way. I think it's always been like this (or has for a long time) but I haven't taken much notice of it. (I've only driven the car 3 times in the last 18 months)

It's been quite a while since it's last wheel alignment so I can't remember the exact specs but it's running about 3 degrees of camber in the front, 0.5mm toe out and is lowered approx 25mm than standard.

Apart from not enough castor is there anything else that could be causing this issue?

Thanks

I hope you made an editting error - castor is THE main method used for self centring steering. Some modern vehicles with electronic power steering may also use a sensor in the steering column which the servo motor uses as it's 'centre' position, either with or instead of castor - this can cause problems when it isn't correct as the servo will try and 'correct' it.

What is "spec'" for the castor? I mean, the OEM setting is for a rather different suspension, wheel/tyre and use application that you're using the vehicle for.

I can't make any real recommendation to you but, if it were me, I'd probably start with around 2 degrees and see how that worked.

Something to bear in mind is that increased castor will increase the effective negative camber on the outside tyre on turns as the steering angle is increased, so it should be balanced with the nominal camber.

Many, many years ago, I would set my car (large American) up with 2 1/2 negative camber in the straight ahead position, and also 2 1/2 degrees wheel camber, relative to and perpendicular to the ground with the wheel turned in 20 degrees on a 'plate. It worked very well for THAT application, no idea what the actual castor was.

Adam, before checking the alignment, I suggest checking for binding. Friction in the steering mechanism will cause failue to self-centre. The most likely culprit is the steer bearing in the strut top. If you jack the front off the ground, it is easy to check if the steering moves freely without any binding or strange noises.

Hi Adam,

Both Gord and James have made good contributions here already. It is not normal to not feel any self-centering feedback through the wheel so it warrants some investigation. Start by checking for binding or friction in the system as James says. Sources can include steering rack, column, or even the joints themselves in extreme cases.

If you have no excessive friction in the system, the castor setting is going to be the most important wheel alignment parameter that affects the self-centering feedback. The stock setting is a good starting point, increasing this 1-2 degrees over stock is reasonable in some applications too. For a start, I'd just make sure you have at least the stock castor.