Rear end Bump Steer Adjustment

[GilesM]

The back of my Elise (2003 S2) is fitted with hubcarriers that are connected to the toe link with a parallel stud on the toe link ball joint, there is a spacer on this stud between the ball joint and hubcarrier that is designed to give the correct bump steer, (toe-in under compression as I understand it), at some point in the life of the S2 Lotus changed the design, and on later cars the toe link ball joint stud is now tapered, and the hub carrier is tapered to match, the original hubcarrier to match the parallet stud is no longer available. I plan to replace the hubcarriers, (the current ones have more rust than metal), therefore I will have to change to the hubcarrier with the tapered hole and obviously the new ball joint to match.
Have a look here and you'll see what I mean, the hub carriers are item 1 and the ball joints are item 34 parallel stud and 47 tapered stud.

http://www.deroure.com/diagrams.asp?TBL ... 0&ST=&SC=0

That's the back ground, now the questions are:
1. Is there anyway that bump steer is adjustable on the latest tapered version?
2. Will it make any difference, and does it matter, I'm not planning to race the car.

Thanks

Giles

[Mikie711]

The easy answer is no and yes. No you can't adjust it and yes it makes a difference if it's wrong, how much of a difference will depend on how far out it gets. The S2 elise geo is set for a ride height of 130mm IIRC so if you lower your car it will have an effect on rear bump steer. There are kits to tune this setting that come with a tapered stud for the hub carrier end and spacer to set it correctly. But to do that you need a bump steer gauge.

[GilesM]

The easy answer is no and yes. No you can't adjust it and yes it makes a difference if it's wrong, how much of a difference will depend on how far out it gets. The S2 elise geo is set for a ride height of 130mm IIRC so if you lower your car it will have an effect on rear bump steer. There are kits to tune this setting that come with a tapered stud for the hub carrier end and spacer to set it correctly. But to do that you need a bump steer gauge.

Thanks for that, the ride height is standard, and no plans to lower it, so hopefully I'll be okay, unless somebody has any other thoughts.

Cheers

Giles

[roadboy]

If you're sticking to standard ride height then the lack of adjustability is not a problem.

If you're replacing all your uprights (or even just the rears) I'd be interested in buying your old ones off you as I'm considering converting my S1.

Cheers

Dan

[Scuffers]

ride hight makes no odds to rear toe settings...... (the front is a different matter)

[robin]

Hi Simon,

Do you mean that whatever your ride height you should set the toe the same?

or

Do you mean that raising/lowering the ride height doesn't change the toe angle in the first place?

Cheers,
Robin

[Scuffers]

Hi Simon,

Do you mean that whatever your ride height you should set the toe the same?

or

Do you mean that raising/lowering the ride height doesn't change the toe angle in the first place?

Cheers,
Robin

neither!

the ride hight has (for all intent purposes) no effect on the relative bump-steer characteristics, only the start point.

[Mikie711]

Not sure I agree with you on that. If that were the case the same would be true for the front and by your own admission it isn't.

[robin]

Completely agree with you Simon that the bump steer curve is what it is and the ride height only affects where you start on it.

So to say:

"ride hight makes no odds to rear toe settings"

Is confusing to me.

To me it seems clear that changing the ride height and doing nothing else must change your toe as you moved along the bump steer curve a bit by adjusting the ride height.

What, if anything, should you do to your rear toe adjustment if you raise/lower your ride height?

Cheers,
Robin

[Scuffers]

Not sure I agree with you on that. If that were the case the same would be true for the front and by your own admission it isn't.

front is a completely different setup, don't try and relate the two.

Completely agree with you Simon that the bump steer curve is what it is and the ride height only affects where you start on it.

So to say:

"ride hight makes no odds to rear toe settings"

Is confusing to me.

To me it seems clear that changing the ride height and doing nothing else must change your toe as you moved along the bump steer curve a bit by adjusting the ride height.

What, if anything, should you do to your rear toe adjustment if you raise/lower your ride height?

Cheers,
Robin

OK, in hindsight, I should have said "ride hight makes no odds to rear toe link bump steer settings"

[Mikie711]

So, if all the above is true why did Lotus publish the bump tolerance graph and setting procedure for the early S2 ?

[robin]

Cool - I agree with that.

To answer your question Mike I think that when the bump steer is adjustable, there has to be a procedure to adjust it.

I don't know why they removed the ability to adjust the bump steer on later S2 - perhaps because they could finally build the car to a tolerance that meant it was "good enough" without adjusting it or more likely 'cos it's cheaper to make the non-adjustable version

Cheers,
Robin

[Mikie711]

The cheaper part makes sense as it isn't adjustable on my 111r nor was it on the 2-11. Guess it will make little or no difference when I lower the 111r but if what scuffers is saying that means I will still need to fit rack lowering plates for the front.

[Scuffers]

So, if all the above is true why did Lotus publish the bump tolerance graph and setting procedure for the early S2 ?

so that you can set the 'rate' of bump-steer

Look, think about it, the rear toe link shares the same pivot point as the wishbone, so follows the same arc, thus the relationship between the wishbone and toe link does not change with ride height.

the outer joint hight relative to the lower ball joint on the wishbone is what gives you the bump-steer, and this does not change with ride hight (not 100% correct, but in the context of this conversation it is).

[GilesM]

Look, think about it, the rear toe link shares the same pivot point as the wishbone, so follows the same arc, thus the relationship between the wishbone and toe link does not change with ride height.

the outer joint hight relative to the lower ball joint on the wishbone is what gives you the bump-steer, and this does not change with ride hight (not 100% correct, but in the context of this conversation it is).

That I understand, and from the posts from you and Robin I can see how the ride height does not change the shape of the bump steer curve, it just changes the position on the curve. If I fit the new style hub carrier and toe link without any possible adjustment, then am I safe to assume that new suspension set-up will have acceptable bump steer, ideally within the recommended zone, I would hope that Lotus have done their calculations and made sure the new design meets the required spec without any adjutsment, or am I being wildly optimistic.

Thanks