Lotus Elan

Other than money, any reason NOT to convert to CVs?

PostPost by: jimj » Tue Apr 30, 2019 9:15 am

Back to back comparison? I have the Miller CVs on our S3 solely because the rotoflexes were needing replacing just about every year, about 6,000 miles, though we do give the car plenty of beans on competitive classic rallies. They`ve been fine for about 40,000 miles. It makes financial sense.
On our Sprint, which is near perfect, the whole car is to factory spec so I`m keeping that on rotoflexes. We use it more sparingly, only about 4,000 miles in 5 years and the rotoflexes look (and work) fine.
The CVs are a touch harsher but only a bit, and I can`t tell any difference in handling. If I was converting to CVs now, from what I`ve read, I`d pay the extra for the elantrikbits.
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PostPost by: trw99 » Tue Apr 30, 2019 10:07 am

At the risk of being a contrarian and as an originalist, I'd like to make a case for the retention of the doughnut, prompted by what Jim wrote above.

After all, we could all make a case for a number of improvements to the original car, given the passage of time, newly discovered materials and increased knowledge. For example, why stop at CVs; why not replace the water pump with a cassette, why not replace the wiring loom with a modern, fully relayed job, why not use electric headlamp lifters? You get my point. My view is that as original an Elan as possible replicates more truly the driving experience of the time it was made.

Having said that and in recognition of the problem with current rubber compounds, there could be a close alternative. Modern chemistry has provided newer alternative materials to rubber. David, lotustastic on here, has been experimenting with prototype couplings made of tough polyurethane. This has improved reinforcement and superior material properties, such as better elongation, peel strength and weathering. This material is very resilient, tenacious and tough enough to withstand constant flexing and stresses. David aims to maintain the dampening effects in the Elan driveline, reducing vibration, harshness and wind up and to improve service life. In addition he hopes to increase the bonding strength between the metal inserts and polymer. His prototype flexes at full droop deflection without issue, but needs a bit more flexibility, which is where he is with his experiments currently. If he is successful with this Elan owners will have the best of both worlds, the ability to retain the original design as well as benefit from new technologies.

I have asked David for an update on the original thread he started, back in 2014.

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PostPost by: jono » Tue Apr 30, 2019 12:22 pm

How real is this modern rubber 'problem', though?

I replaced the bottom arm bushes on my 'modern' Subaru Legacy last year - these are a bonded rubber/metal doughnut and aside from being a bit soft they were in remarkably good condition after some 65,000 miles and 9 years of use in a much heavier car - in fact they would have done another 10k miles quite easily

Is it not just a case of the repro Elan bits being made with an inferior rubber compound?
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PostPost by: rgh0 » Tue Apr 30, 2019 1:32 pm

jono wrote:How real is this modern rubber 'problem', though?

I replaced the bottom arm bushes on my 'modern' Subaru Legacy last year - these are a bonded rubber/metal doughnut and aside from being a bit soft they were in remarkably good condition after some 65,000 miles and 9 years of use in a much heavier car - in fact they would have done another 10k miles quite easily

Is it not just a case of the repro Elan bits being made with an inferior rubber compound?


Modern rubber is not the problem its the cheap rubber used in cheap inferior quality repro bits unfortunately
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PostPost by: denicholls2 » Tue Apr 30, 2019 1:34 pm

Elanintheforest wrote:You’re also not obliged to drop the clutch at the lights or snatch the gear change at every opportunity, so providing no shock to the transmission in the first place.


For any car driven like this, I would expect the input shaft bearing on the transmission to be the initial point of failure. While it's true that putting rubber bands in the whole system creates a safety valve for the whole system, that is only after the initial torque load has been applied, in this case to the whole system because the rubber bands are last in line.

As a conventional system without the rubber bands, there is considerable damping in the basic mechanics, particularly the metal mass and high-viscosity goop in the transmission and the ring and pinion in the diff. At each new junction, thrust loads are being parceled out to the bearings. Differential failure would point to that part as being the weakest link in all of this, which I don't believe it is.

Either driveline approach underscores the importance of not anchoring the car to the ground with gigantic tires it wasn't engineered to cope with. And this form of restraint, in addition to giving you a better handling Elan with a lighter feel, also saves you from having to apply butt-ugly arches to cover the tires, plus allows your Elan to chirp like a bird as you leave the drive-in. :)
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PostPost by: tjb0274 » Wed May 01, 2019 11:48 pm

Either driveline approach underscores the importance of not anchoring the car to the ground with gigantic tires it wasn't engineered to cope with. And this form of restraint, in addition to giving you a better handling Elan with a lighter feel, also saves you from having to apply butt-ugly arches to cover the tires, plus allows your Elan to chirp like a bird as you leave the drive-in.


Good point. It's perfectly valid to use bigger modern rubber and stiffer springs if performance is the goal, but it does make cars like ours handle very differently. My Europa had 185 section Toyo Proxes on it when I bought it. The road holding was unbelievable, but the lightness of steering and the handling were gone - and the ride was awful. I've now got it on narrower period style rubber and the handling and ride are sooo much better. Doesn't have the ultimate grip level, but much more fun on the road.
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PostPost by: tdskip » Thu May 02, 2019 12:02 am


Good point. It's perfectly valid to use bigger modern rubber and stiffer springs if performance is the goal, but it does make cars like ours handle very differently. My Europa had 185 section Toyo Proxes on it when I bought it. The road holding was unbelievable, but the lightness of steering and the handling were gone - and the ride was awful. I've now got it on narrower period style rubber and the handling and ride are sooo much better. Doesn't have the ultimate grip level, but much more fun on the road.


Excellent point - I ruined my Bugeye by putting wider modern tires on it.
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