Camber Adjustment

[A900ss]

All,

Will lowering the ride height of a Chim give more or less negative camber? In my head, the lower it goes, the more negative camber it will have but I'd like somebody who knows what they are talking about to advise.

Thanks

[J400GED]

There are many combinations that will affect the change in camber, so without knowing the angle at which your wishbones currently sit, the effective length of each wishbone, the pivot point vertical position relative to each other, the current camber angle and by what amount you intend to change the ride height it is impossible to give a definitive answer.

Basically, it depends on the relative lengths of the wishbones and where each wishbone sits in it's rotational arc prior to the change of ride height.
For example, if the current setting is that both wishbones are horizontal and the upper wishbone is shorter than the lower, lowering the car by a given amount will have a greater effect on the upper wishbone compared to the lower wishbone and therefore it will effectively pull the top of the hub inboard, thereby reducing positive camber or increasing negative camber.
It will have a greater effect on the shorter wishbone because a set amount of vertical adjustment in the pivot point of each wishbone will push the shorter wishbone further around it's rotational arc.

[A900ss]

I 'think' what you are saying is that on a standard Chim with short rear upper wishbones in relation to the longer lower wishbones, lowering the ride height will have more effect on the top wishbones, therefore pulling the top of the wheel in and increasing negative camber.

That's assuming I haven't already already got the car too low(I havent).

Thanks for the technical response, much appreciated.

[J400GED]

What Camber do you have at the moment?
At what angle do the wishbones sit at the moment?

[J400GED]

Don't forget that dropping the ride height can also change the toe setting, and the effect on toe dynamically as well for the same reasons.
It is this change in toe that's called "Bump Steer".

Hope this helps.

[QBee]

My expert makes sure the boot is empty, I have half a tank of fuel and the right set of wheels/tyres on, then sets the ride height, then does a full geo on his Hunter machine.

Then sits me in it and corner weights it.

[bobfather]

The standard setup has the wishbones horizontal at rest, this enables the different length wishbones to alter camber differently depending whether the suspension is compressed or expanded. If you lower the body by simply altering the spring length or spring platform position you will no longer have horizontal wishbones at rest. You may still be able to adjust for correct camber at rest but the camber during suspension expansion will initially change the wrong way.

[J400GED]

bobfather said:

The standard setup has the wishbones horizontal at rest, this enables the different length wishbones to alter camber differently depending whether the suspension is compressed or expanded. If you lower the body by simply altering the spring length or spring platform position you will no longer have horizontal wishbones at rest. You may still be able to adjust for correct camber at rest but the camber during suspension expansion will initially change the wrong way.

I see what you're saying Bob, but the following hasn't been established:
1. At what angle the wishbones are sitting currently.
2. What ride height the vehicle is at currently (measured from the underside of the ends of the chassis rails as these are directly connected to the wishbones, not from the bodywork due to possible variations in mouldings).

If all the wishbones sit horizontally when at rest, the camber change will be consisitent whether in bump or rebound because all the wishbones are starting from the same point in their arcs of rotation. That is why it is ideal to have all the wishbones horizontal at rest.

[A900ss]

I'm not with the car for a couple of days so I'll get the info and come back.

Car is riding too high, about an inch over standard both ends but I'll get the wishbone angles and ride height measurements.

Edited by A900ss on Friday 3rd April 09:06

[bobfather]

I have the 5 stud conversion so my ride height for horizontal wishbones may be slightly different. Measuring to the outrigger corners isn't easy, I have two lengths of dowel cut to fit perfectly when the suspension is horizontal.

There are many different answers to the suspension set up question on PH, I think the general opinion these days is:

Rear
Height 155mm to outrigger corner
1.4 degrees neg camber
1.5mm toe in per side (12 minutes)
Front
Height 145mm to outrigger corner
3/4 of degree of neg camber
0.75mm toe in per side (6minutes)

10mm difference is very commonly quoted.

[J400GED]

A900ss said:

I'm. It with the car for a couple of days so I'll get the info and come back.

Car is riding too high, about an inch over standard both ends but I'll get the wishbone angles and ride height measurements.

Don't be too precious about measuring the wishbone angles too accurately, at this point you just need to establish whether they are pointing up or down and whether the fronts appear the same across the car and the rears appear the same across the car.
You will probably find that they can't be parralel to each other because of a difference in height in upper to lower wishbone mounts compared to the upper to lower hub fixing height.
FYI, mine sat at 174mm rear ride height (bottom of the rear of the chassis rails to the floor) and 131mm front ride height (bottom of the front of the chassis rails to the floor). Mine had half a tank of fuel, don't worry too much about what fuel you have at present, just make a note of what fuel you have. (Normally measured with half a tank of fuel because the ride height would be at mid range due to fuel level variations)

HTH
Ged

[A900ss]

All wishbones are pointing down (wishbone lower at hub/upright than at chassis). It's not a huge angle but I would suspect the chassis side is about an inch higher than the upright side (which fits with the car being an inch higher than standard).

My current camber is not within tolerance (with no further adjustment possible) and what I'd like to know is if I slacken off the coilover height to dial an inch out of the ride height, will this give me a chance of getting the car back within tolerance?

Thanks.

Edited by A900ss on Friday 3rd April 14:56

[bobfather]

Yes, but an inch of spring platform does not equal an inch of ride height. It's close and a good starting point. If you're going to the effort of setting up to stock alignment I think it's worth ensuring the ride height is correct first. Ride height adjustment must be fixed prior to aligning the camber and toe.

[J400GED]

bobfather said:

Yes, but an inch of spring platform does not equal an inch of ride height. It's close and a good starting point. If you're going to the effort of setting up to stock alignment I think it's worth ensuring the ride height is correct first. Ride height adjustment must be fixed prior to aligning the camber and toe.

What bob said.
Measure your clearance at a given point for each corner ( I would use the ends of the chassis rails as previously stated, bodywork and outriggers have more room for tolerances/error) then take an inch out of the lowest front and rear corners - with your spring seats, then match the height to that on the other side. Make notes of the before and after measurements. The car will now be sitting level across the axle and 1 inch lower than the lowest original height. Then you can set your geometry.