Lotus Elan and Lotus Elan Plus 2 Forums

After nearly 4 years ownership and a lot of body/engine restoration I decided to give my 1972 +2 130S a short run.

Unfortunately there is a knocking sound from the final drive above 15 mph. The only possible cause I can find is that the metal segments of the rotoflexes are making contact with the safety tube that fits through the inside, although the rubber appears quite sound. Attached photos show rubbing marks on the safety tube. Also shown are the existing rotoflex /safety tube fitting which has plenty of space to move around, compared with a new rotoflex that is a tight fit over the safety tube.
Is there anything special about the rotoflexes used by Spyder? The installation looks similar to photos I have seen on line but I don't have the original instructions from when the conversion was supplied to the PO in 1998. Can anyone PM me a copy?
It would certainly be useful to get some advice before I start the struggle to rebuild the shafts.

Thanks, Richard

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Can't quite see what's wrong here, but all I can tell you is that I have the same shafts on a late S3 Elan and find them perfect. I like the idea of a cv on the outer side, and a doughnut on the inner, virtually zero wind-up, and having the doughnut on the inner is much kinder on the diff.
Hope you work out what the issue is,
Steve

Thanks for your comments Steve.

The more I think about it the less I believe the rotoflex/safety tube could be causing the noise, which is a definite knock at drive shaft/wheel frequency. I'm now part way through changing the rotoflexes, having already bought a new pair.
If the noise persists I plan to remove the new 14" MInilites and try it with the original 13" Lotus wheels. I've already change one UJ and turned the propshaft through 180 Deg, so now running out of ideas. Hopefully there is nothing wrong with the gearbox, diff or hubs!

Richard

Have a look on the inside of the wheel faces and check the outer wishbone bolt heads are not fouling

Thanks for the suggestion Graeme.

The wheels and tyres are quite close to the wishbone bolts and spring bases but no sign of any contact. The fact I am not getting the knocking noise until 15mph is making it difficult to pinpoint the location. Having stripped the rotoflex out of one side; the diff, outer CV joint and hub appear to be turning smoothly. It will take a few days before I rebuild that side and tackle the other one.
If the new rotoflexes don't cure the noise I will put the old 13" wheels back on. With hindsight that would have been a more sensible course to take before changing the rotoflexes. I'm hoping to make that job easier with some motorcycle spring clamps to raise the shafts in line with the diff.

Richard

Are you sure the new wheels are tight?

FWIW, I had a difficult to diagnose rear suspension knock that turned out to be a failed rear wheel bearing. I was running rotoflex couplings, and when I jacked the car up, the suspension droop caused the rotoflex to pre-load the bearings and no play or noise was apparent. It was only when I jacked up under the bottom of the strut so the driveshafts were horizontal that the play and noise became apparent.

In your case with one cv, it may not have the same effect, but may be worth checking out if all else fails.

Have you checked the nut that secures the top of the damper for tightness? That knocks like Black Rod if it is loose.

Leslie

New rotoflexes fitted and I was pleasantly surprised how well that job went. Whilst drive shafts disconnected the diff, CVs and wheel bearings appeared to run smoothly. With 14" wheels and 2.5mm hub spacers there is ample clearance between wheels and wishbone bolts.
However, although the gap between tyres and spring perches looked adequate I remembered the advice from Spyder when I bought the 14" Minilites and fitted their recommended 185/60 tyres. They said the spring perches may need tapping back to give clearance. So I hammered them a little just to flatten the curve where the tyres may be touching.
Road testing showed the previous noise had gone, but now with increased speeds I am getting a clunk when going on or off throttle. Not enough to put me off taking the car up to 60 mph but obviously something moving in the rear suspension that needs sorting.
The engine ran nicely for a couple of miles but then was reluctant to pull cleanly from say 30 to 50 mph. A bit like fuel starvation and dropping down to 3 cylinders before picking up when a lot of throttle applied. Time to get the Dellorto book out and work through the possible causes.
Thanks again everyone for the advice. Impending holidays will slow progress for a few weeks but I hope to put in some decent running-in miles during the better weather.
Richard

I had a similar CLUNK a long time ago, I think it turned out to be the bolts that hold the diff. The nuts were a tiny bit loose. Not detectable by hand.

Needs a mole wrench or person to hold the nuts in the boot, and a second person under the car with a socket set with two extension bars plugged into each other to tighten the bolts from below.

Thanks Donels, Andy, Leslie and Bill for the latest advice. When I get the car up in the air again I'll make the diff mountings and tops of rear dampers a priority. Both jobs need the rear seat out.
I've taken the carbs off to clean them and decided it's a good opportunity to change the heater pipes; looks like a fun job with the engine in!
Richard

I note you changed the wheels for Minilites, have you checked the fit of the studs that locate the wheels. I wonder if they are not a good fit, then the wheel may be moving slightly on the studs

Thank you Tony.

The wheels appear to be a good fit on the studs and I have tightened them whilst off the ground. Not easy to hit the spinners with Minilites as the wheel spokes tend to be very close. I am using a copper hammer with a thick rubber sheet behind.

I can't find anything underneath at the back that could be causing the clunk when on/off throttle and there is very little backlash in the drive from gearbox to wheels. Yet the feeling when it happens is like some slack is being taken up. The engine mounts are new but I will check the gearbox mount as it was covered in oil when I bought the car. The silencer is in contact with the heat shield but it all feels very solid.

Holidays will now limit progress so I will have to go over it all again in a few weeks time.

Richard

Richard,
The issue could be the steel spacer for the Minilite wheels. I found that on the rear the steel rings bottomed out on the webs on the rear hubs giving a tight spinner but not a fully clamped wheel. If this is the issue you should see marks on the hub webs and the hub side of the spacer.
I fixed it by skimming a little off the length of the spacer on the hub side, if you don't have a lathe then measure all 4 spacers and fit the thinnest on the rear.
Hope this helps.
Neil

Richard
I think both Neil and I are suggesting the same possibility, that the wheel may not be fully seating, in which case there will be some witness marks on both the studs and the hole in the ring on the wheel. It does not take much clearance here to cause the type of symptom you describe. If the wheels are a definite good fit then I would check the diff mountings to ensure that as the drive is taken up, that the diff is not moving causing the clunk.
Tony