Lotus Elan

Rear Suspension Question

PostPost by: elancoupe » Sun Mar 27, 2005 12:49 am

Posted for a friend:

"I am assembling the chassis for a series 2 Elan, body off. I have installed new struts, new a arms, and re used the stock springs. The brake rotor binds against the lower a arm on both sides. I am baffled, as all seems to be assembled correctly. Is this a function of the body and its weight not being applied? Or am I overlooking the obvious?"- Paul
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PostPost by: garyeanderson » Sun Mar 27, 2005 11:58 am

Paul/Mike

The long bolts (3.25") go through the rotor with the top hat portion of the bell facing outboard. Then through the axle stubshaft and finally into the donut. A photo would be more helpful or there is a good exploded view in the manual on page D6 of X036T0327Z Oct. 1972

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PostPost by: frearther » Sun Mar 27, 2005 12:32 pm

Does your friend have a CV joint rear suspension? Some of these seem to allow the rotor to contact the wishbone at full droop. I'm fabricating limit straps to solve this interfrence.

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PostPost by: elancoupe » Sun Mar 27, 2005 1:35 pm

I believe that he has a cv axle setup.

To the best of my knowledge, (although I have not seen it in person) the disc is fitted correctly.
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PostPost by: nebogipfel » Sun Mar 27, 2005 1:48 pm

"Does your friend have a CV joint rear suspension? Some of these seem to allow the rotor to contact the wishbone at full droop. I'm fabricating limit straps to solve this interfrence."

Art, I'm not sure I understand what you are saying here?? To move the position of the rotor/brake disc in relation to the wishbone you would have to modify the outer stub axle yoke.

The rotor/disc moves up and down with the stub axle so it has no effect on the disc position relative to the wishbone if you are on full droop or not.

I would guess if Paul's friend is having a problem with the rotor/disc to wishbone clearance then either:

He has the wrong rotors/discs

or He is trying to fit them on the wrong side of the driveshaft yoke

or The rear bearings/stub axles are not correctly fitted so the yoke is in the wrong position relative to the wishbone

Is it the same both sides?
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PostPost by: garyeanderson » Sun Mar 27, 2005 4:09 pm

CV's are irrelevant, its still brake rotor, axle shaft then CV adapter plate. I was looking at my S2 with CV's. The CV is inboard of the axle and rotor.
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PostPost by: type26owner » Sun Mar 27, 2005 4:31 pm

Realize that the donuts prevent the struts from going to full droop normally by about two inches from the bottom of travel IIRC. The tubing of the a-arm is very close to touching the rotor if all is well. I'd be asking for those missing dimensions of the a-arm which the manual fails to depict fully in Section D, page 4. Assuming nothing is correct is the best practice approach to take here.
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PostPost by: garyeanderson » Sun Mar 27, 2005 5:13 pm

I just went out to the garage and jacked up the rear, No cv's installed and suspension at full droop and it does not interfer with the rotor. They are Spyder lower arms but dimentially they arn't any different. It still brake rotor, axle shaft and then the adapter plate or donut.

LEFT Hand Side

000!
00/
*!A D

*!A D
00\
000!

* bolt
! rotor
A axle
D donut or CV

0's are just for space otherwise they just stack on the left column
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PostPost by: nebogipfel » Sun Mar 27, 2005 5:44 pm

CV's are irrelevant So is the fact that the suspension can go to full droop

Nobody (and certainly not Colin Chapman) would design a car so that the brake rotors/discs fouled the wishbone on full suspension travel!
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PostPost by: elancoupe » Sun Mar 27, 2005 11:34 pm

Lots of interesting input, thanks guys.

My curiousity was sufficiently raised that I went out and jacked up my own Elan (correctly assembled and with cv's) At full droop, the rotor hits the lower a arm on the front side near the outboard end of the diagonal tube. I guess it is moot point as to whether or not the rotor hits at droop, as the cv's would be locked anyway....

As noted by Keith, donuts limit suspension travel, so this does not occur on a stock car.

TTR sells shorter travel rear struts to stop cv lockup, my assumption is that rotor interference would be eliminated as well.
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