Lotus Elan

Rotoflex condition

PostPost by: Concrete-crusher » Mon Jul 22, 2013 6:18 am

Hi I fitted new rotoflex doughnuts about 20 years ago but have hardly used the car, maybe only 200 miles.

I now notice they have small cracks in the rubber, is this likely to fail an mot

Thanks steve
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PostPost by: vernon.taylor » Mon Jul 22, 2013 6:42 am

Salut Steve

I think most Elan owners would consider them very fortunate if their rotoflexes lasted 20 years!

Rubber ages poorly especially if not used. IMHO you should change them immediately if you have cracks - a flailing driveshaft could cause all sorts of expensive damage.

You could consider the CV alternatives available if you don't want any worries in the future. There are lots of opinions on the forum debating their merits.

@+

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PostPost by: AHM » Mon Jul 22, 2013 7:32 am

Small cracks will probably get you an advisory - these are now recorded on the MOT.

Pay particular attention where the rubber is bonded to the metal.
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PostPost by: rgh0 » Mon Jul 22, 2013 10:55 am

In my experience most donuts will show very shallow "cracks" of 1 to 2 mm deep after a short distance of use of a few hundred km's between the metal components and the rubber. These "cracks" are rounded and look more like "grooves". These appear stable and don't grow. If they become sharp edged and grow beyond a couple of mm deep then they are true cracks and they will grow quickly and you need to replace the donuts as they are on the way rapidly to failure.

cheers
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PostPost by: rcraven » Mon Jul 22, 2013 11:23 am

I doubt if they'll be safe to use after 20 years. I once bought a spare (I'm not sure why) and after 15 - 20 years or so of storage it looked far too cracked to be safe.
Try jacking the car up to let the wheels droop and see what happens to the cracks when you rotate the wheels.
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PostPost by: ftsoft » Tue Jul 23, 2013 12:03 pm

I finally replaced mine at around 85000 miles and 47 years. There was at least one pretty decent crack.

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PostPost by: billwill » Tue Jul 23, 2013 12:57 pm

ftsoft wrote:I finally replaced mine at around 85000 miles and 47 years. There was at least one pretty decent crack.

Frank



That's amazing. I've lost count of how many sets of doughnuts I have fitted over the years. Did you perhaps have your car professionally reworked at some stage(s) and they changed the doughnouts as a matter of course (preventive maintenance).

My technique for replacement:
lotus-gearbox-f37/replacing-the-doughnuts-t16456.html?hilit=doughnuts#p186272
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PostPost by: ftsoft » Tue Jul 23, 2013 1:55 pm

billwill

I can't remember having them done (of course I can't remember lots of things these days). I use to do most of my own work, so you would think I could remember having that done. The bolts were so seized that I finally gave up and took the car to D&D Classics who previously rebuilt my engine. They couldn't get them out either and wound up cutting them out. It was a pretty messy job. I agree that they lasted longer than they should have. I did monitor them since the engine rebuild 5 or 6 years ago and finally the crack appeared. What's weird is that I raced SCCA regionals and solo 1 events from 67-70, so the car was stressed pretty well during that time. I only do 500-1000 mpy now so I'm hoping that the new ones last for a while.

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