Another dim question about rear wheel Camber & Caster

[Grease Monkey]

I know, its been asked a million times, but i'm just checking.

The GD book says zero camber at the rear, ie hubs vertical when the lower wishbone is in 'driving' attitude (40mm fall inner to outer)

That i've done with two lengths of steel and some levels, and it appears fine. (see below)

http://www.cobraclub.com/crcforum/user_files/4302.jpg

My main question is:

GD says you need .25 - 1 mm of toe in on each of the back wheels. See my artistic attempt at showing what i mean below.

http://www.cobraclub.com/crcforum/user_files/4303.jpg

I presume 'A' should be 1mm smaller than 'C' at a given distance of 'B', the question is, whats 'B' ?


There ain't no replacement for displacement.. GD427 on order ... Chassis arriving May , Body in July
Cost to date (Including Tools): [font color=red]£1504.55[/font], Progress to date: Big pile of assorted jag bits in cupboard.

[Mike]

The toe angle as viewed from overhead refers to the difference between the front tread centreline to the rear tread centreline of the two tires on the same axle.

eg the measurement distance between the centres of the front of the tires is 1mm closer than the measured distance between at the rear of the tyres.
Der, I hope that made sense.
Mike

[Grease Monkey]

Bit tricky monkeying around with the whole wheels, with the rear axle on the bench, and since i dont yet have the actual wheels that are going to be fitted (i'm using some XJS donor wheels), I'm using some iron sections bolted to the hubs.

OK, so you're saying with 'B' as the radius of the fitted tyre, then A should be 1mm less to the centre line than 'C'. (or 2mm to the equivilent point on the other side of the car) for a 1mm per wheel toe in.

OK, its not exactly correct, as my bar is flat against the hub, and not 100mm out from it, but the angle is such that it makes bugger all difference.

Anyone have anything to add, or shall i go and shim my wishbone carriers ?



There ain't no replacement for displacement.. GD427 on order ... Chassis arriving May , Body in July
Cost to date (Including Tools): [font color=red]£1504.55[/font], Progress to date: Big pile of assorted jag bits in cupboard.

[craigh]

i managed to set mine up initially with spirit levels clamped to the hubs horizontally,and taking measurements at the front and back of the hubs to try to acheive the 2mm overall,i know its not great but i plan to take it to get the alignments checked properly soon

[callum]

The toe in is set by the pre-drilled GD bars that tie the inner wishbone pivots fore and aft to the chassis. The trick is to centre the toe in by measuring back to the thrust line. See http://www.familycar.com/alignment.htm
Measure off from a straight edge clamped to the hub face at say 50 cm from the axle centres to the centre of the chassis/thrust line and get the same reading from each side by shimming the inner pivot castings off the diff casting - do not simply assume the diff is itself centralised when bolted in place. The diff may be marginally out of true but your rear axle geometry will be at right angles to the line of travel, the (slight) toe in will be even on each rear side and only then can you effectively align the front wheels and avoid crabbing and tyre scrubbing. :tu