Caster angle adjustment

[rfs1957]

Hi Steve,

Yes, the Gunson is deducing caster from camber measurement changes - but don't all gauges do that, even the "good ones" ?

I'm intrigued as to how the monkeys set my caster as they appear to have moved to a pretty extreme position - the photo is of the RHS and the top wishbone is moved backwards to the point it is beginning to overlap the flats on the spindle.

How does that compare with yours ?

[mgcjag]

Hi Rory, Mine is a S2....but was told by a good E engineer that a good starting point is to have 1/2 in of thread showing at the picture frame end.....just looked at mine and its about that.....by the adjusting flat you mention i have aporox 2 threads showing.........the key to setting this up is good slip plated under the front wheels so the wheels can turn really easy, 2 sheets of thin steel on top of each other with a bit of wd40 between is ok

[abowie]

My gauge looks just like the one in Steve's picture.
I drew a parallel line next to the side of the tyre with the wheels centred. I then drew the 25 degree line outward on both sides of the car from the centre of the tyre. I assumed that if one wheel turns out 25 degrees then the other would be turned in 25 degrees.
If you were sure your steering rack was properly centred you could probably just measure in the full lock position on both sides as the wheel should turn out the same amount on both sides. The actual angle you choose doesn't matter as long as it is the same one turning in and turning out.

[abowie]

could someone confirm that it is indeed necessary to undo the (inaccessible) catellated nuts and split-pins in order to rotate the spindles ?

It was possible to turn one spindle without removing the split pins but took a lot of effort. With the castellated nuts backed off it was really easy. The left hand rear nut is easy enough to get at. The right hand one is accessible once you remove the air filter canister.
I have just replaced my upper wishbones and bushes and so everything was clean and well greased which may have made it a bit easier.

[abowie]

Hi Steve,

I'm intrigued as to how the monkeys set my caster as they appear to have moved to a pretty extreme position - the photo is of the RHS and the top wishbone is moved backwards to the point it is beginning to overlap the flats on the spindle.

How does that compare with yours ?

Yours is further back than mine. Mine still has a couple of threads visible at the rear.

It is possible to set caster by having an unequal number of shims front and rear on the top wishbone. This is how my monkeys had done it. Maybe yours had this done in the past, resulting in the need to wind the spindle right back to correct for it. Or you might just have too much caster. Or it might be what your car needs.

[Gfhug]

I've spent the day setting up (ok, trying to set up ) my front suspension. Sort of getting there, but a question or two.

By luck, I seem to have the camber correct first off at +0.4 degrees both sides. This is by using a digital level and a bar similar to Steve's (mgcjag). Digital level was cheaper than the Gunson and seemed better for getting to the small angle of +1/4 degree +/- 1/2 degree.
Track has been set roughly correct.

Now the question(s) and this is because there seem to be several contradictory bits of 'advice' out on the web.
Turned (road) wheels left and right 20 degrees from straight ahead.
For the left wheel the two figures are +0.5 deg (wheel to right) and +2.1 deg (wheel to left).
Some suggestions are the difference +1.6 deg is the castor, some say double that number (castor=+3.2deg) and others even say multiply by 1.5

Reading one of the comments above about the Gunson would make me think the answer is +1.6.
But what say you, please?

Also will tightening the nuts on the wishbones alter the figures? Kind of think they could if tightening pulls the upper wishbone either forwards or backwards.

BTW, tried the plumb line, and got a figure different to any of above answers.

My plan is to leave things as is, drive a bit to get all fully settled then re-check the numbers.

Many thanks as always for any answers or help

Geoff

[mgcjag]

Hi Geoff......dont know about the guage you have but i think that you put the guage on a front wheel..turn 20deg out and set horizontal and to 0..turn back 40deg and take your reading....yes tightening up anything will alter settings...as will altering one setting will change the others....most quick fit tyre centers now have alignment machines..for about £40 they can check all measurements...just dont let them adjust anything.. Steve

[Gfhug]

Hi Steve, my gauge is not a camber gauge where you set to zero as with the Gunson. It is a digital 'spirit level' giving degrees absolute from vertical or horizontal. However, simply taking one number from the other is the same as setting to zero and then reading the second number as the castor.
If so, my castor/caster is +1.6 LH wheel (and +1.8 RH) so within the +2 +/- 0.5.

Time to tighten it all up, go for a drive and then re-check everything.

Thanks

Geoff

[abowie]

.

Reading one of the comments above about the Gunson would make me think the answer is +1.6.
But what say you, please?

Also will tightening the nuts on the wishbones alter the figures?

Geoff

I think you have 1.6 degrees of castor which should be good. See how it feels when you drive it. It should give you a positive self centering effect when driving at say 100kph without making the steering unacceptably heavy at low speeds.
I don't think that tightening nuts should change anything, but it would be interesting to do a before and after caster measurement to confirm.

[Gfhug]

Tightening the nuts on the end of the wishbones didn't seem to make any difference to the before and after readings. Driven about 50 miles and re-checked, all fine. Drives nicely at speed and not too heavy manoeuvring at slow speeds.

One thing that had me worried was the height to the lower wishbone, some 2 inches higher than it should have been despite checking the torsion bar correctly with setting links. New bushes, dampers, etc. No tightening of any nuts until full weight on the suspension, yet still stubbornly sitting high.

I could have ended up re-checking the torsion bars ad infinitum and tearing all my hair out, then Angus advised me to drive the car and see if that would make the difference, it did, thanks Angus.

This discussion and the advice has been very beneficial in getting the car set up nicely.
Another example of the value of this forum

Geoff

[abowie]

at would make the difference, it did, thanks Angus.

This discussion and the advice has been very beneficial in getting the car set up nicely.
Another example of the value of this forum

Geoff

I agree, especially with "black art" stuff like wheel alignment. It's nice to have advice that gives you the confidence to do the job yourself. In my case it took my silver car from being just about undrivable to being the joy that it is now.
I just wish that my dear friend Rob, from whom I bought the car, was alive today to experience it.