Lotus Elan

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

PostPost by: tdskip » Sun Apr 28, 2019 12:27 pm

Good morning, hope everyone is having a good weekend.

Given that my Elan has been off the road since 1992 and the doughnuts will need replacing as a matter of course now would seem to be the time to convert to CV joints.

This will be a road car and driving around town and on touring trips so, based on my research, the kangaroo gentle throttle take off could be a real bummer.

Other than money is there is reason NOT to convert to CV joints? Are there other options I should be aware of?

I?d rather bite the bullet and get it sorted right up front.

Thanks!
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PostPost by: SENC » Sun Apr 28, 2019 12:54 pm

<1k miles since my switch (working on other things), but I haven't found a reason to be unhappy. I rebuilt the suspension front and back and replaced all of the suspension bushings at the same time, so if the cvds added any harshness I couldn't tell as the overall ride quality improved significantly overall. Definitely eliminates the traditional wind-up, which I don't miss, and I find I like the solid feel. The safety upgrade is big, and when you figure cost of donuts over time the money difference is negligible if any.

I also added a pair of adjustable rear wishbones from Spyder as I had a little toe out on one side, probably from someone jacking on the bone in its history - a worthwhile upgrade while you are in there if yours are at all suspect. Pull
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PostPost by: 69S4 » Sun Apr 28, 2019 1:12 pm

I'm quite happy with doughnuts. I don't mind the 'surge' characteristics and their driveline cushioning must be part of the reason my diff has lasted 50yrs with next to zero attention. However ... They're now both expensive and - by reputation - not what they used to be, a combination that gives me some cause for concern. I'm now on my last set of 'old school' doughnuts and as they're starting to look past their best, what to do about them is something I'm pondering.

CV's seem to be the obvious fit and forget route to go but other posts seem to suggest that most of the current crop have articulation issues that need solutions devising. Droop limiting straps seem to be the 'poor man's' fix, with droop limiting spacers inside shock absorbers the next level up. I presume (unless others can expand on the subject) that this means replacing a perfectly good set of rear dampers with a new pair containing the necessary alterations. Those, I also presume, will be a specialist purchase at a price to match. There are CV sets that don't need these alterations but they seem to have price stickers to match.

How much of a shock the rest of the driveline is going to get when a set of CV's take the place of doughnuts is also a concern. Should I change the driveshafts as a precaution? How about diff mounts, bearings etc? It all starts to make buying more doughnuts look like the easy route but not if they only last a few hundred / thousand miles. How many miles are 'modern' doughnuts doing?
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PostPost by: nmauduit » Sun Apr 28, 2019 1:42 pm

One reason may be originality. This has a degree of merit that highly depends on the owner.

An other is weight (I understand you're only considering the CV joint conversion, not the UJ "solid" driveshaft option which has merits and disadvantages of its own).
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PostPost by: Elanintheforest » Sun Apr 28, 2019 2:27 pm

I?ve never quite understood the idea that without the Rotoflex couplings the shock provided by CVs will somehow wreck the transmission of an Elan. The differential is standard Ford, as is the gearbox, and no Ford has Rotoflex couplings. They are bomb-proof assemblies even in the much heavier cars, and are amongst the last components to fail..

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.

The Rotoflex couplings were installed as a cheap option, and surely a CV drive shaft is a better engineering solution? They are also a darned sight easier to fit than the Rotoflex.

All that said, my Elan has Rotoflex couplings, and I do like the feeling of the slight surge given by them in the 2 seat car, but that can get a bit more pronounced in the Plus 2.

Although you ask for comments aside from cost, have you seen the cost of a set of couplings and bolts today? The whole lot is not far off the cost of a pair of CV drive shafts.

A final thought is the durability of the modern ?repro? Rotoflex. There was a time, up until only a couple of years ago, when they started to fail after just a year or two and with very little mileage. Some of this was put down to the glue between the rubber and the metal, and some down to the rubber itself. I?ve heard they are better now and last longer.

If they were half the price or less of the CV drive shafts then I would probably take a punt and put new ones in. But given the price, the ease of fitting of the CV shafts and their longevity, I will probably fit the CV shafts when the time comes.

That is unless someone comes up with some evidence that installing a solid driveshaft, like just about every other car made, harms the transmission!
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PostPost by: h20hamelan » Sun Apr 28, 2019 2:37 pm

How many vehicles use rubber/poly these days, and if so. Is the new rubber/poly used similar to what can be purchased for the elan. Do the new ones have low to no fail rate, and wont do damage if they let go?
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PostPost by: Slowtus » Sun Apr 28, 2019 3:05 pm

Elanintheforest wrote:I?ve never quite understood the idea that without the Rotoflex couplings the shock provided by CVs will somehow wreck the transmission of an Elan. The differential is standard Ford, as is the gearbox, and no Ford has Rotoflex couplings. They are bomb-proof assemblies even in the much heavier cars, and are amongst the last components to fail..

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.

The Rotoflex couplings were installed as a cheap option, and surely a CV drive shaft is a better engineering solution? They are also a darned sight easier to fit than the Rotoflex.

All that said, my Elan has Rotoflex couplings, and I do like the feeling of the slight surge given by them in the 2 seat car, but that can get a bit more pronounced in the Plus 2.

Although you ask for comments aside from cost, have you seen the cost of a set of couplings and bolts today? The whole lot is not far off the cost of a pair of CV drive shafts.

A final thought is the durability of the modern ?repro? Rotoflex. There was a time, up until only a couple of years ago, when they started to fail after just a year or two and with very little mileage. Some of this was put down to the glue between the rubber and the metal, and some down to the rubber itself. I?ve heard they are better now and last longer.

If they were half the price or less of the CV drive shafts then I would probably take a punt and put new ones in. But given the price, the ease of fitting of the CV shafts and their longevity, I will probably fit the CV shafts when the time comes.

That is unless someone comes up with some evidence that installing a solid driveshaft, like just about every other car made, harms the transmission!



My understanding was that those were concerned about such things were concerned about damage - should any actually occur - to the diff.

Never heard anyone mention concern about damaging the transmission by swapping out the 'flexes and for what it is worth I was putting 240hp/153tq at 9000 rpm through a stock diff for a while - in a heavier car.
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PostPost by: Grizzly » Sun Apr 28, 2019 3:16 pm

Elanintheforest wrote:I?ve never quite understood the idea that without the Rotoflex couplings the shock provided by CVs will somehow wreck the transmission of an Elan. The differential is standard Ford, as is the gearbox, and no Ford has Rotoflex couplings. They are bomb-proof assemblies even in the much heavier cars, and are amongst the last components to fail..

I agree with everything you said but at the same time have seen two cars with the diff ears snapped off....... i guess fitting a diff brace would have possibly prevented this but still it was damage caused as a direct result of CV joints (can't say if the owner dropped the clutch at the lights to do this but both owners think way too much of their cars to do that in my opinion) that said i have had a Rotoflex fail and snap off the rear caliper so i guess swings and roundabouts.......


Personally i think modern Rotoflex joints are just junk, i would have stayed with Rotoflex couplings if i could find some i felt confidence in but that was a non starter so i went with CV joints.
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PostPost by: prezoom » Sun Apr 28, 2019 3:45 pm

I can remember driving an Elan back in the 60's when I had my Super 7. First thing I noticed was the "wrap up" when taking off. I decided back then I didn't like it. The Elan owner eventually converted to a U joint, sliding spline arrangement. Both my S2 and my Plus2 are CV equipped. Would not have it any other way.
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PostPost by: tdskip » Sun Apr 28, 2019 3:59 pm

I will make sure to ask about the best motor oil/tire/color/year just to keep things interesting? Grin.

So it looks like I have three options if I assume the current donuts are parished;

1) replacement rubber one and just swap them out on a regular basis in deal with the drivetrain lash

2) replacement design based on CVs

3) replacement design based on u-joints?

I know number 1 will be way cheaper than number two or number three. Is there a big cost difference between number two and number three? That won?t drive the decision but I?m curious.

Thanks!
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PostPost by: ericbushby » Sun Apr 28, 2019 4:02 pm

Hi, Stuart,69S4
My shock absorbers were in good condition and looked almost like new, so I did not want to buy new shorter ones.
I shortened the shafts on the existing ones to suit the limited droop on the new CV shafts.
I turned back the shoulder at the top of the shaft and hand ground the flat area with an angle grinder, finishing with a diamond wheel. The shaft was hardened, but with a tipped tool and a 10 thou. cut we got there.
Then a tubular spacer was made up to go under the nut, to make up the difference.
IT may be simpler to fit a spacer in the top of the shock absorber, but I could not get into mine.
If they are in good order there should be no need to buy new ones.
Hope this helps
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PostPost by: gherlt » Sun Apr 28, 2019 5:01 pm

Elanintheforest wrote:I?ve never quite understood the idea that without the Rotoflex couplings the shock provided by CVs will somehow wreck the transmission of an Elan. The differential is standard Ford, as is the gearbox, and no Ford has Rotoflex couplings. They are bomb-proof assemblies even in the much heavier cars, and are amongst the last components to fail..

None of the Ford's had 105hp, I think 61hp at most in the Ford Anglia.
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PostPost by: 74Twincam » Sun Apr 28, 2019 5:10 pm

I'm in the same position as you, so great timing on the topical question - trying to decide between CV upgrade and replacing donuts and sorting through all the information here on the subject.

My car's very original, but the fear of putting in questionable roto flex couplings makes me uncomfortable to spend the money on the donuts. The originality seems great, but at the same time, all the parts may include the inherent weaknesses and aging.

I am leaning toward the CV conversion from ElanTrikbits, thinking that this is a good start since they seem to be able to accommodate the droop angle without a strap or other limit needed, price seems not extreme for what you get, and it seems that I could put the CV kit in without the snow-ball effect of "now I need to change x, y and z"... I could always put the original parts back in and donuts if I wanted to put it back to stock. Some of the other kits also change the diff. Output shaft and bearings as well, so there's some value if you decide to go that route (such as with Dave Bean or RD Enterprises here Stateside).

Maybe, though, that's where I'm going off- with a new CV conversion, is it foolish to not to change the differential output shafts (and bearings and seals) and the final drive / tapered axles at the same time? The slippery slope seems eminent...!
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PostPost by: tdskip » Sun Apr 28, 2019 5:20 pm

Good to hear the question benefits others, trying to give something back by asking thoughtful questions that will benefit other new owners.

No slippery slope talk!

Any idea on what those cost delivered from AUS? RD has a $1,600 option which is more than I?ve spent on some of the cars I drive. Gulp.
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PostPost by: 69S4 » Sun Apr 28, 2019 5:42 pm

ericbushby wrote:Hi, Stuart,69S4

I turned back the shoulder at the top of the shaft and hand ground the flat area with an angle grinder, finishing with a diamond wheel. The shaft was hardened, but with a tipped tool and a 10 thou. cut we got there.
Then a tubular spacer was made up to go under the nut, to make up the difference.
IT may be simpler to fit a spacer in the top of the shock absorber, but I could not get into mine.
If they are in good order there should be no need to buy new ones.
Hope this helps
Eric in Burnley
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So how much are we talking here? 1"?, 2", more? The rotoflex droop when you raise the rear is quite substantial (and I presume it's the shock absorber topping out that prevents it going even further). How far down can the CV's go before they bind? How did you calculate how far down to grind?

I'm trying to get as much info as I can on this area (so this is a very timely discussion) as I suspect it'll be next winter's major strip down (along with the gearbox which is starting to sound noisy in 3rd). All ideas and experience taken on board.
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