43 replies to this topic

[S pack]

More shims on the front bolt or less shims on the rear bolt will give more positive castor, however it's not that simple, as adding or removing shims to change the castor setting also affects the camber setting. So you have to add or remove differing thicknesses of shims from both front and rear bolts so as to change the castor setting without changing the camber setting.

 

How to actually measure the castor I do not know. I opt for the easy way out and leave it to the (so called) experts with the proper equipment.

Edited by S pack, 12 October 2013 - 08:00 PM.

[Toranamat69]

Castor is a bit trickier to measure as you don't just need a gauge to measure it but you also need an acurate way to turn the wheel 20 degrees each direction to take the measurement.

[Toranamat69]

Yeah that's what I use - just a different colour and brand - probably made the same place though.

[76lxhatch]

Just make up a guide to allow reasonably accurate turning of the wheels 20 degrees either way (as mentioned above). Measure camber at 20 degrees left and 20 degrees right, then multiply the difference by 1.5 for a pretty close measurement (good enough for general wheel alignment purposes). Don't forget to allow for positive and negative numbers correctly, e.g. the difference between +1 and -1 is 2.

[Bigfella237]

Opposite sides of the same coin JAS, more (positive) caster will return to centre better but obviously make it harder to steer away from centre.

[76lxhatch]

If you're having trouble with both then I'd suggest checking/refreshing the steering components first. Its amazing how much difference a new steering column bearing or sorting out the rack can make to steering effort (when not in top shape to begin with).

[axistr]

Even with zero caster they should still return back to centre quickly due to the K.P.I (king pin inclination), if it doesn't, as above check the front end components. 

[76lxhatch]

Its a possibility, I've swapped over columns before and found a big improvement in the weight of the steering, would have been on 15s with 225s at that stage.

What specs would I set it up at...? +6.5 deg caster, -0.6 deg camber
Depends on what front end you have, how and where you drive, and what suits you. I'd suggest aiming for caster to be at least positive, maybe 2 degrees if you can get it. Camber around 1 negative maybe a touch less, don't put too much on.

[Bigfella237]

-1° camber is okay... -1.5° caster is terrible!

 

Negative caster will make the steering want to be anywhere but centre, the car must've been a handful to drive? Depending on the wheels and tyres you're running and whether you've got power steering, I'd say at least +2° caster, if it was me I'd be trying for a lot more than that but it will get real heavy to steer with a manual rack and big boots.

 

Nice looking gauge though, if it's not too rude a question, where'd ya get it and how much?

[Bigfella237]

Moving the top ball joint backward (by adding shims to the rear bolt) increases positive caster and unfortunately (as you've found) also increases negative camber.

 

I would start with no shims at all on the front UCA bolt and however many you can safely get behind the rear bolt, it's a question of balancing positive caster against negative camber and hopefully finding a happy medium.

 

Does this car have HQ spindles on it? If so you've inherited about a degree and a half of negative camber just from the stub axle change too.

[Bigfella237]

looking at the gauge above mine. the + and - are at opposite ends for caster readings ??

 

mine is for doing both but im guessing for camber the + and - are correct.

for caster do i treat the - as +???

 

Yeah, sounds like the gauge might be reading backwards, or maybe you're reading it backwards, or maybe it got messed up when they translated it from Chinese?

 

I was just thinking, it's a pity nobody has thought to build a laser pointer into these gauges so you could do toe as well, they'd sell twice as many of them I reckon!

Edited by Bigfella237, 16 March 2015 - 08:19 PM.