steering rack mounting

[graham]

Am I right in assuming that the steering rack should be mounted parralel to the wishbone mounts. The book shows everything sitting paralel . As I have the body of and no motor or gearbox do I set up toein and bump steer on paralel axis.

[paddy]

At normal ride height, the lower wishbones will be level. However, this means that for zero bump-steer the tie-rods will not be level - they are inclined, so that the inboard ends are slightly lower than the outboard ends. (Very very approximately, think of it as the incline on the tie-rod is "half" of the incline on the upper wishbone at normal ride height.)

To set the height of the rack there are really two methods (both covered in earlier threads):

- to set the rack mounts to a specified height relative to the upper wishbone pivots;
- to set the height by measuring bump-steer explicitly (and there is a variety of more or less precise/expensive/timeconsuming methods suggested for doing this).

It is easier to do while you have the body off. Then, with the body/engine etc fitted you should have to adjust the ride height but not re-adjust the rack level.

(I assume you're setting it up for the road rather than racing - if not, ignore me completely and speak to someone who knows what they're talking about.)

Paddy

[john.p.clegg]

Sorry Paddy but tend to disagree here,maybe in theory the lower wishbones will be level but with a real world scenario?...but with the engine out and with the body off?............I much prefer to work from real ride-height with half a tank of petrol? and passengers? and use this as a centre line and set the bump steer from there...

John

[gerrym]

Recommend you do a little internet browsing and understand what bump steer actually is before diving in.

If setting bump steer via explicit measurements (of TOE-IN changes as the suspension moves through bump and rebound), you will need to remove coil-overs and ARB.

Doesn't really make any odds if this is done with body on or off. Just makes access to the rack mounting fasteners (U bolt things) just a little easier. Remember you are removing or adding shims that fit between rack mounting pads and the rack mounts themselves.

Regards

Gerry

guys, just edited my error, should have been TOE-IN not tie-in, bump steer being by definition inputs into steering geometry induced by bump or rebound changes. In turn, due to fact that steering tie-rods centres are offset to the wishbone theoretical pivot centre.

[GrUmPyBoDgEr]

Recommend you do a little internet browsing and understand what bump steer actually is before diving in.

If setting bump steer via explicit measurements (of tie-in changes as the suspension moves through bump and rebound), you will need to remove coil-overs and ARB.

Doesn't really make any odds if this is done with body on or off. Just makes access to the rack mounting fasteners (U bolt things) just a little easier. Remember you are removing or adding shims that fit between rack mounting pads and the rack mounts themselves.

Regards

Gerry

Miked covered this very well in his fairly recent Posts,
A job that requires some concentration & the will to "do the job right"

[graham]

Thanks for the replies. Ihave spent some time looking at the threads for this in the archives- very time consuming. I thought it would be easier to do when mounting rack and suspension on bare chassis. question-should the rack be parallel to the wishbone mounts therefor different shims to each side . Chassis powder coated and no sign of any shims. Have put in 5mm shims and gives a nice even curve up and down same both sides.
Thanks again
Graham

[john.p.clegg]

Graham

...all you have to do now is to make sure the "outer" point of each curve is where your hubs will be at actual ride height......so any deflection inwards is up or down from that point....on both sides...with an "average" load in the car...

John