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Radius arm bush replacement - Suspension/Brakes/Wheels/Hubs/Steering/Geo - The Lotus Forums #ForTheOwners Jump to content


Radius arm bush replacement


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I think the knock is coming from the radius arm bush but worried about how to replace with taking apart the whole rear suspension. Has anyone done this before and have any useful tips. Also, when replacing the bushes can I use the same shims or do I have to get the rear end set up realigned.

thanks in anticipation

martin

 

 

 

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  • Gold FFM

You will need the geo resetting. Fitting the shims back as it come apart is a good start point. 

Just drop the arm and do it 👍

Only here once

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A beneficial procedure is to secure the springs in the compressed state with many large zip-ties (if you don't have a spring compressor).

If you are replacing that lower arm bushes, be sure to check the upper arm bushes too. The one closest to the exhaust (left side, inner) typically fails from exhaust heat.

Atwell Haines

'88 Esprit

Succasunna, NJ USA

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3 hours ago, CarBuff said:

A beneficial procedure is to secure the springs in the compressed state with many large zip-ties (if you don't have a spring compressor).

If you are replacing that lower arm bushes, be sure to check the upper arm bushes too. The one closest to the exhaust (left side, inner) typically fails from exhaust heat.

I too can vouch for using zip-ties as spring restraint and would add they must be high spec material rather than the cheap variety, commonly of a translucent white appearance. Better grade ties I've used are opaque black or grey with stainless steel tang insert for the retention function. Do use them in multitudes, as Atwell has emphasized.

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its probably worth being clear what you mean by radius arm. Certainly to change the bushes in the top transverse link (top wishbone on S3) or what I would call the radius arm (the box section running forward from the upright to the chassis) you do not need to compress the springs. I know this as did exactly this job a few weeks ago. However if you mean the bottom wishbone then perhaps you do (I did not have to disconnect this). 

 

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Yes, unless you want to redo the surface on the radius arm itself, no need to take apart the whole suspension.

Have a variety of shims ready. Old model are split, newer are one piece.

If it resembles the Stevens cars, the bracket and the shims can be had in stainless if one so wish.

Shims can be changed when doing the geo, without taking everything apart again.

Note: When Lotus did their Lotac bush program, they changed the inner diameter from 7/16" to 12mm, demanding a 12mm bolt, and the tube in the radius arms to be reamed up to 12mm. I did so, and it works fine.

If you prefer the rubber bushings, they still are made for the old slightly thinner bolt system.

I just though it would be worth mentioning, before you take it apart.

Kind regards,

Jacques

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Nobody does it better - than Lotus ;)

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Thanks for the comments. The bush I need to get at is the radius arm pivot point bush- the one with the shims.  I have done the others a while ago.   Thank martin

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  • 4 months later...
  • Gold FFM

I have a question regarding the adjustment of the radius arm pivot and the mix of shim plates and shim washers to achieve the correct spacing.

It would seem that items 46 and 39+40 are doing the same job, moving the arm closer or further away from the chassis, adjusting toe-in of the rear wheel.

However 39+40 are also moving the bush and can be fitted with all bolts in place (just loosened) whereas the 46 shims seem to be a fit and forget affair during installation of the suspension arm.

I am assuming then that some steps should be taken to get the toe-in setting as close to optimal using the 46 shim washers and adjust this over the lifetime of the vehicle with 39+40.

The question (if the above is correct), how do you set about getting toe-in close to correct while the body is off the car and nothing is at final ride height? I'm wondering if I need to install a temporary adjustable rod in place of the spring/damper unit so I can set ride height and get the geometry correct before popping the body back on or am I over thinking this? 🤔 

image.png.26d274173aacea98be425ab02e152f9d.png

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  • Gold FFM

I think this depends on the alignment method. The guy who did mine said it would have been easier had I given him the rolling chassis first as these can be tricky with the body on. I’ll be taking the tvr upto him as a chassis once that’s back together.

I’d assumed he would just whack some weights on it to get it roughly correct and do the final tweaks once it’s built.

Only here once

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  • Gold FFM

If it were mine, I’d put the same shims back in that came out when I took it apart, and then have the geo corrected when it’s finished and roadworthy.

 

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Margate Exotics.

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I set mine correct when it was a rolling chassis and then as the weight went in it was at least even either side. Tell the truth I am not sure it changed that much (although I can't remember for sure, I think it increased toe by 2mm each side going from a rolling chassis to a fully built up car but I could be wrong). Too much toe in is not a big issue (increased tyre wear and mid corner understeer), too much toe out can make the rear unstable and should be avoided IMO. Whilst it was a rolling chassis I did take the chance to fit adjustable top links as my turbo S3 did not have them. 

BTW you could fit captive nuts to the two bolts holding the shims / radius arm bush in place. I did not and it did take some fiddling to undo them but actually not as bad as I feared.

I have attached a picture of the rear suspension on mine for no good reason other than I think it looks really cool, sorry!

IMG_1409.JPG

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On the one hand the Esprit has such a superlative chassis design it often masks deficiencies in components or settings, on the other it's among the finer instruments for the exploration of roadways when in sharp condition. The latter persuasively makes the argument for maintaining top fettle of parts and settings. Though toe-in is less problematic than toe-out in general, it can be troublesome when excessive, even worse when uneven across one axle.

Cheers

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