Ruining wishbone bushings, possibly due to bent wishbone(s) ?

[pboedker]

During the winter, I completely refurbished the front suspension on my Europa, having the wishbones sand blasted and powder coated before fitting all new rubber bushings.

After not many miles, now the right side has developed a squeeking noise, and I find that it is because a rubber bushing has separated, and the suspension arm started to move towards the chassis. The attached photo shows the right side lower front bushing. The inner tube and the rubber is showing, the outer tube is still properly located inside the suspension arm.

I have contacted the parts supplier, who sold me the bushings, and they say that this is typical for having a bent suspension arm, and they have seen this a lot.

I didn't notice anything bent before assembling it, and I did assemble the uprights first, to make sure that the inner ends of the wishbones aligned where they should. I will disassemble the wishbone one of these days, to see how bent the wishbone is.

Has anyone seen this problem before? And was the bushing or the suspension arm the reason for the failure?

[BDA]

When you assembled the suspension, did you put it at ride height before you tightened the nuts on the shafts? The rubber in the bushing can only take some much deflection so you have to set it up in the middle of the travel. As for the bushing coming out of the A-arm, I think something similar happened to me. I'll take a look but I think I might have put a big washer on both sides of the bushings. For me, at least, it had nothing to do with a bent suspension as my uppers are adjustable ones from Richard (they're pretty beefy), and the lowers were new.

[StrawberryCheesecake]

Similar to the above, I've seen wishbone and other suspension bushes on other cars fail when they are torqued up with the car in the air. The  best method is to finger tighten, put the car back on the deck (on ramps or blocks if you need to get underneath) and then torque up.

[BDA]

To expand on Strawberry's post, I made a set of blocks to hold the front suspension at ride height when I tightened the nuts. It can be really difficult to get to them with the wheel on. Another more expensive option is to get polyurethane bushing as you don't have to worry about the ride height with those.

Theoretically, the rubber bushes contribute to the spring rate - or wheel rate - though I don't recall anybody mentioning that so I doubt it's significant.

[Grumblebuns]

Peter, I had similar failure of my front control arm bushes. During  replacement, I noticed that some of my bushes had torn rubber and that the arm had been displaced inward toward the chassis pivot point.
 
With new bushes installed in the control arm sleeve, I noticed that there is a slight gap between the outer control arm attachment point on the trunnion and the control arm hole. I'm wondering if closing the gap (~3/8" on each side) when tightening the bolt is adding undue forces on the rubber and the sleeve of the bush. Over many miles of up and down cycling of the suspension, the rubber finally fails and detaches from sleeves. I've added a few pictures of my failed bush.

Joji Tokumoto

[pboedker]

Thank you for the answers so far. 

Yes, I did make an effort of assembling the nuts only fingertight and then driving the car onto a ramp lift to fully tighten and torque them while at ride height.

Joji, 3/8" sounds like quite a lot (I read it like a small gap at the trunnion results in 3/8" at the rubber bushings). Like you, I would believe this to be too much for the rubber, but I didn't see any noticeable gap (or the opposite).

[Grumblebuns]

Peter, you rubber section protruding appears to have just slid out, still looks shiny. Maybe the possibility of a defective adhesion of the rubber to the outer sleeve? My rubber section on the other hands had been torn from the outer sleeve over time.

My rear Spax on the JPS had it's lower rubber bush become detached from the outer sleeve/mount. I had to press it back in and suspect that it will eventually slide off again.

Joji

[HealeyBN7]

I have cycled through a couple sets of replacement rubber bushing failures before settling on the poly bushings.

There are quality and vulcanization issue with the modern rubber replacements.  Paying more and receiving the second set in Lotus packaging didn't improve the issues.   The center tube on one set was so poorly machined that I had to drill it out to remove an internal seam just to get the bolt to go through the eye. 

Even after very carefully tightening the suspension when fully loaded, they would tear out in short order and cause the a-arms to relocate. 

After buying and installing two crappy sets, with no warranty return or acknowledgement,  I felt it was a safety issues and easily justified the cost of the poly replacements.

I haven't noticed any difference in harshness.

Dean

[3929R]

If poly is the answer, the Autobush poly bushes are not so costly - http://www.autobush.com/Lotus/Elan%20Twin%20Cam.htm

[BDA]

Mark,

I assume the Elan front wishbone set (AUB5101) is compatible with the Europa, right?

[EuropaTC]

Yes, I used the same bushes on both cars, but that posting of Mark's is a good find. (thanks Mark)

I didn't realise they were so cheap, the last time I looked they were more than twice the cost of Lotus bushes.  I might try a set at that price. Not so much for the performance aspect but getting away from the "torque up at ride height" thing, it would just make maintenance one step simpler.

Brian

[jbcollier]

The bushes, yes.  Arms, no.

[pboedker]

My first thought was, like Dean writes, that the bushings were of a bad quality. New china rubber, and all that. But I'm not so sure that it isn't instead my suspension arm(s) that is bent. I will return with the result, following a dismantling of the parts later this week.

The autobush bushes look really interesting, I think I'll order a set already now.

[pboedker]

OK, so it's definitely the suspension arms that are bent.

I've dismantled the two lower arms on the right side, which is where the bushing popped out. And then I have measured them, as described in the workshop manual, section C.3, figure 17. The dimension '4' should be 58.7mm (I can't for the moment measure that more precise than 59mm)

As can be seen from the attached photo IMG_Right_Side_Lower_Front_5a.jpg, the arm with the ruined bushing is measuring 48mm, that is 11mm too little! The rearmost arm is measuring 57mm, 2mm too little. Of course these measurements are again not very precise, the arms can wobble a little since they are a little rounded on the flat part, and also the flat area for the trunnion is a little indented so the true measurement point is hard to get to. But it's good enough for government work, as they say.

I lined up the 2 arms (photos IMG_Right_Side_Lower_1a.jpg' & IMG_Right_Side_Lower_1a.jpg) and got to the total of 105mm (48mm+57mm). This is 13mm shorter than the 118mm it should have been, and the 13mm corresponds almost to the 15mm that the bushing has moved.

I take this as a very clear indication, and will take a look at the lower left side also at a later time. The top arms are harder to get to with the rod going into the cabin and all, so I think I will just loosen up the nuts and see if the bushings are jammed in any direction, i.e. if there is a similar problem.

Where did I do wrong?
I think that it was a mistake to assemble the outer ends to the uprights by hand and then believe that the dimensions were correct. It was probably first when I torqued it all up, including the outer ends where the shock bushings has a lot of rubber to compress, that the wrong (bent) dimensions came into play.

So, what to do now?
Since the front arm is definitely bent, measuring it by adding a washer (1.5mm) will bring the measurement to 57mm also, see photo IMG_Right_Side_Lower_Front_6a.jpg. The washer will sit between the shock bushing and the suspension arm,so that when the trunnion and shock bushings are both torqued, the a-arms will keep their proper locations.
Does anyone see a problem in doing this?

Oh, and BTW if any of you who has experienced similar bushing problems have the possibility to measure the dimension '4', it could be interesting to hear what you find.

[EuropaTC]

Oh that must be annoying Peter,  those arms look pristine and I'd have done exactly the same in just putting in bushes and assembling on the car.

Now you know there's a problem I think I'd assemble with new bushes and firmly mount the arms on the car without the upright or damper assembly in place. I'd imagine that would put the arm/bush in it's neutral position as far as twist goes, so you could measure exactly the dimensions where the damper, lower trunnion and upper ball joint should fit. I'd probably have loose components and feeler gauges to determine what, if any, shims were needed.

With any luck the gaps will be too large and washers or shims as you describe will sort the problem. I'd have no problem in packing the gaps but I'd probably aim for stainless washers/shims so it's a fit and forget solution.

If it's too tight....    hmmm.   that would be "swear box" time in my workshop !

Brian