Setting up the front wishbones and have set camber to near as I can to zero using the
machined face of the upright as a reference.

But, how the piggin-ell do I get an accurate centre line to set the caster ?
With the upright on things stick out and get in the way, so thought about rotating them
180 deg so the stub axle point inwards but even then the casting has quite a radius, still
tricky to find the c/l.

So is it upright off and try to align the machined part of the ball joints ?

Considered turning a length of bar with an internal taper either end to fit the ball joints
but don't have a suitable lathe tool.

It is difficult which is why castor is usually set by some dynamic gauge which involves built in spirit levels (?solid state digital these days) and turntables under the front wheels. Turn 20 degrees left, zero everything, turn 20 degrees right, measure stuff et voila, a castor reading.

I have a digital protractor with built in spirit level from the bay and need to set up caster, camber and toe.

Can someone explain this 20deg caster measure method. i was just going to measure the line from verticle created by middle of ball joint to middle of ball joint.

Any other advice welcome.

soz to hijack but some good answers may come of it.

quote:

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Originally posted by bi22le
I have a digital protractor with built in spirit level from the bay and need to set up caster, camber and toe.

Can someone explain this 20deg caster measure method. i was just going to measure the line from verticle created by middle of ball joint to middle of ball joint.

Any other advice welcome.

soz to hijack but some good answers may come of it.

---

quote:

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Originally posted by bi22le
i was just going to measure the line from verticle created by middle of ball joint to middle of ball joint.

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Is it not as simple as standing a vertical spirit level behind the upright (with the wheel off) and measuring horiziontially from that to the estimated centre of the upper and lower joints. The difference between the 2 measurments, the vertical distance between the 2 measuring points and some trig will give you the angle.

if you are really serious about finding the exact centre of the joints you could cut some scrap ones vertically in half and mock up the assembly with them

Cheers

Fred W B

[Edited on 20/10/11 by Fred W B]

Chassis Engineering By Herb Adams
Caster.
Caster is the inclination of the front spindle. Positive caster – the rearward tilt of the spindle – is essential for high speed stability.
A fairly accurate measurement of caster can be made by taking two camber readings. First, record the camber when the wheels are turning full right, then repeat the measurement when turning full left.
The difference between the two readings closely approximates the caster angle.
For the left - front wheel, positive caster when more negative camber is produced when the wheels are turned right.
For the right - front wheel, positive caster when more negative camber is produced when the wheels are turned left.
To Increase caster, tilt the upper control arm rearward in the car.

Not my words just from his book.

quote:

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Originally posted by Fred W B
if you are really serious about finding the exact centre of the joints you could cut some scrap ones vertically in half and mock up the assembly with them

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quote:

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Originally posted by Myke 2463
A fairly accurate measurement of caster can be made by taking two camber readings. First, record the camber when the wheels are turning full right, then repeat the measurement when turning full left.

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Plenty of videos on YouTube showing how to measure castor with the +/-20 degree method.

quote:

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Originally posted by Myke 2463
Chassis Engineering By Herb Adams
Caster.
Caster is the inclination of the front spindle. Positive caster – the rearward tilt of the spindle – is essential for high speed stability.
A fairly accurate measurement of caster can be made by taking two camber readings. First, record the camber when the wheels are turning full right, then repeat the measurement when turning full left.
The difference between the two readings closely approximates the caster angle.
For the left - front wheel, positive caster when more negative camber is produced when the wheels are turned right.
For the right - front wheel, positive caster when more negative camber is produced when the wheels are turned left.
To Increase caster, tilt the upper control arm rearward in the car.

Not my words just from his book.

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I removed the upright from the car and stripped off the caliper and hub.

I then put a piece of straight bar through both ball joint mounting holes and and rested the bar on two equal sized blocks so the hub was hanging on the bar.

I then packed the stub axle until the face of the upright was square to the bench with the caliper mounting holes to the bottom.

I then measured very accurately down to the bench from each caliper mounting hole.

I used these measurements on a short piece of angle iron which when bolted on to the calper mounting holes is now perfectly parallel with the piece of bar. Mount it and check it on the bench.

Refit upright and hub and use magnetic angle guage on angle iron to set caster.

You need to measure very accurately and bore the holes to the dead size and use bolts with a shoulder if you want to remove and reift without setting it up on the bench everytime.

I did this before I joind LCB or thought of using the net.

Davie