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Rear adjustable lower link - Suspension/Brakes/Wheels/Hubs/Steering/Geo - The Lotus Forums Jump to content
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Rear adjustable lower link

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Just a thought, but has anyone ever considered modifying the rear lower link, to the turnbuckle style used on the upper link? :(

I imagine that it would be a damn sight easier to make toe-in adjustment, rather that having to add and remover shims and washers.

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Those are the upper links Giorgio

I don't see the point in the lower links being done, also with both the upper and lowr links being adjustable you'd need to be VERY careful about the track on the rear. With the lower links being one piece you have a factory tollerance reference point to work around for your toe in/out and camber.

Once set the rear toe should never go out and it really isnt that difficult to do the shims, especially on later cars as the shims can be slotted in and out with only loosening the mounting bolts.

Only my opinion but I don't see the point :(


Chunky Lover

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It has come up before, and at the time I was considering it in order to overcome an issue of the wheels rubbing the body, but now I think that may have been the bad alignment by the firm that set it up.

My only concerns is that it would move the centre line of the drive train relative to the centre line of the mass of the vehicle. Would this alter handling? Don't think so, but for the sake of moving a few washers I doubt it's worth the hassle of having them made.

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Lower link wont alter toe settings, only the camber - I know they had them on the race car Esprits, its one thing I have considered on mine but I bought the adjustable uppers instead.

Once the settings are done, they should be safe for a few years espeially the shimming for the castor / toe and so on.

Again mine is up at Lotus next month for the geo - I will write a report on it for anyone with interest about it, might put some minds at rest.


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I'll agreew ith Jonathan re shimming being pretty constant (unless you're experiencing initial spring settle as I am) for a long while, thus it's not a etting that has to change often. However I'll disagree with teh comment on no impact to toe.

The adjustable lower links on their own would adjust camber, and toe. Shoren the lower link and it will give a more +ve camber, and by bringing the centre of the wheel in to the vehicle it will give more positive toe out.

Use adjustable lower and upper and you could control the camber correctly (bring both in/ both out without impacting camber) and adjust the toe, by bringing the bottom and top of the hub carrier (and thus wheel) in further it would give ore positive toe out on that wheel.

But...... by shortening both uppper and lower together (so giving more toe out but leaving camber untouched) it will also alter the rate of camber change. The camber becomes more negative (in at the top) the further the wheel moved up vertically relative to the chassis, but if both links are shortened the wheel top will move in even further for a given vertical movement. And that could adversely impact handling.

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In that case adjusting the top link would adjust toe as well.

By adjusting a single link alone you will only rotate the wheel on 1 axis - to change toe you'd need to use 2 adjustable links and wind them in and out at the same rate to push/pull the whole wheel in/out.

The way I understand toe is that it is the angle between the true forward direction of the chassis and the wheel angle when looking doown on top of the car.

Personally I wouldn't use 2 adjustable links at all without knowing exactly what I was doing !

Apart from the geometry mess you'll create, if you set it too low or too high on certain bumps and deflections of the suspension will damage the drive shaft / hub bearing which (imo) is the main reason why only one of the links are adjustable - at best you'll sheer to roll pins - at worsst you could crack the hub carrier and lose a wheel.


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"In that case adjusting the top link would adjust toe as well."

It does, but only slightly.

Think of the three points for the wheel as a triangle, arm swing point, bottom link hub mount and top link hub mount.

The toe line is from approximately half way between the top and bottom link points to the arm swing point. If you move one of the link points towards the mid line of the car, you move the point that is between the two link pints in towards the mid line of the car, thus the toe has altered.

However, the top and bottom link points on the hub are much closer together (30mm or so) than those and the arm swing point (900mm or so). So if you move one link point enough to alter the camber by 1 degree, you move the mid point half that amount, and the arm swing point is 3 times as far away for the toe only alters by 1/6th of a degree.

"The way I understand toe is that it is the angle between the true forward direction of the chassis and the wheel angle when looking doown on top of the car"

Yes.

"Personally I wouldn't use 2 adjustable links at all without knowing exactly what I was doing !

Apart from the geometry mess you'll create, if you set it too low or too high on certain bumps and deflections of the suspension will damage the drive shaft / hub bearing which (imo) is the main reason why only one of the links are adjustable - at best you'll sheer to roll pins - at worsst you could crack the hub carrier and lose a wheel."

I agree, I looked at doing it, but then considered what it would do to the thrust line of the car (move it out of line with the chassis and so create setback on one front wheel), it would remove the impact asbsorbtion provided by the bushes (the ride will get even more prone to vibration from the road and possibly fatigue the chassis too much), and finally, the top and botton link mpivot bolts are not in line with the links, there is a reason for that, the bushes provide an amount of resistance to wheel movement, so in effect dampen the suspension more than the oil filled dampers alone.

Having looked at the manual for the later cars, Lotus introduced a solution to this. Split bush plates. The earlier cars had a rectangular plate with two small holes for the arm mounting bush bolts to go through and a large hole for the rubber bush to go through, so to fit or remove thes you had to seperate the bush and arm from the chassis. Later cars used the same part modified, cut the plate in alonmg it's short axis and elongate the bolt holes so that the plate can be slipped on with only losening the bolts.

Knowing this, why would we want to alter the bottom links at all? to fit an additional plate would take circa 3 mins, if removal of one of these plates was necessary it would be about the same, so there's only the initial time to swap from old style to new style plates to take account of, and if somebody is doing a major re-build my suggestion is to swap to new style plates at that time.

Andy

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I suppose when you change toe you alter 1 point of a triangle so any point could alter it technically.

OK, just done a test with a pair of scissors lol, it does work.


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