Lotus Elan

Time to decide between donuts and CV joints

PostPost by: tdskip » Sun Sep 01, 2019 9:32 pm

Hello gentlemen, I know this has been a topic of much discussion but wanted to poke at it before placing an order.

I’m not personally focused on originality to the point of installing donuts but default, and the cars I’ve seen wind up on itital acceleration has be concerned. Not sure if that is just to be expected or it is indicative of other contributing factors.

Thoughts?

(I will duck for cover now)
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PostPost by: tedtaylor » Sun Sep 01, 2019 10:44 pm

irrespective of the pros and cons of each (and they are many) the bottom line is it comes down to what YOU intend to do with, and how you intend to drive your car, plain and simple.
harder, competitive, long term use, less inspections = CV joints
road driving, occasional spirited, originality, more frequent inspections = donuts.
that's the short of it.

Have fun!
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PostPost by: Grizzly » Sun Sep 01, 2019 11:13 pm

As a purist who has been through exactly this scenario recently i'd advise you skip straight to the CV shafts.

The problem isn't the donuts as such (in fact i think they add character to the car) but modern rubber isn't what it once was, having tried two sets of rotoflex couplings both were showing signs of cracking/separation within weeks they just didn't inspire confidence.

I have Kelvodon CV joints on my 2 seater and apart from a ripped boot (think i may have punctured it with a handbrake rod) they have been flawless and i have given them some abuse.
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PostPost by: billmoore42 » Mon Sep 02, 2019 4:05 am

I put UK made donuts from R Dent in my 67 Elan S3 Coupe last year. They are still fine after 1200 miles, and if you read Brian Buckland's book, he thinks the modern donuts might be good for 20,000 -30,000 miles or so.

I am hoping and praying that this is true, as it was a bear of a job to replace the donuts for this first time Lotus owner, with a couple of floor jacks and a rachet tie down to hold the outer hub up as high as possible to try to get the rear drive shafts level (if the shafts are level, the donuts are much easier to install).

I also bought a spare driveshaft on Ebay and used this with 3 hose clamps (jubliee clips for those in the UK) to try to get the holes to line up with the drive shaft holes before getting under the car. I believe this made it much easier.
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PostPost by: 69S4 » Mon Sep 02, 2019 6:44 am

I'm still using donuts on my car as I bought a number of them years back, but I'm now on my last set and they've been in there for a while. So I've been finding myself driving more carefully, no harsh acceleration, limiting top speed etc for fear of something letting go. I've not seen any rips or tears on inspection but when one does break I'll also have to decide which way to go.

The problem seems to be that the scales are finely balanced. CVs are a little more expensive than a complete set of donuts but not enough to rule them out. Donuts individually are much cheaper and, if made from decent rubber, long enough lived for road use that replacing them is an infrequent task. But they do seem to have become both relatively more expensive and of poorer quality in recent times making changing a complete set an expensive gamble. There's plenty of reports of low mileage failures but not much quality assurance from the usual suspect vendors. If they fail it's down to us fitting them badly / thrashing the car / it's all we can get, take them or leave them. Decent quality donuts are cheaper + original + perfectly satisfactory for the job but what you get handed to you over the counter is unknown until it's too late to take them back. CV's are a one time fix but some come with problems of their own like articulation lockup on the 2 seaters that requires changes to the shock absorbers at extra cost.

Quite what I'll do if (when) one donut fails I'm not certain. I quite like the feel of donuts so would prefer to keep them but not at the expense of having to change my driving habits to compensate for their poor quality. Anyone immersed in the donut world enough to know what current production quality is really like?
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PostPost by: ericbushby » Mon Sep 02, 2019 8:00 am

Fitting Kelvedon/Sue Miller CV shafts made a great improvement to the feel of my car.
Before then I had to be cautious engaging the clutch to pull away as the engine would rock a little and sometimes the carbs would tap on the footwell. This along with the slightly jerky acceleration was disconcerting.
With the new shafts, it was completely different and the car would accelerate from rest smartly and confidently like a sports car should.
Two of the Rotoflex couplings were just beginning to peel away from the metal, but the other two appeared sound and I gave them to someone on this forum to solve a short term problem.
Yes the maximum suspension droop has to be reduced by 25mm, but if the shocks are in good condition this can be done by fitting a spacer inside, or in my case as I could not find how to open them, I shortened the shafts.
Kelvedon also sell shorter shocks for this purpose if yours need renewing anyway.
From my experience I would recommend fitting new CV driveshafts if the time has come.
Hope this helps
Eric in Burnley
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Last edited by ericbushby on Mon Sep 02, 2019 11:17 am, edited 1 time in total.
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PostPost by: 69S4 » Mon Sep 02, 2019 10:15 am

I've got Spax adjustable inserts (can't remember their code no) as my rear shockers. I didn't think those were user rebuildable? It's been a while since I've seen them so I might have it wrong but are the tops not crimped over rather than screwed together? If that's the case then fitting a spacer isn't going to be possible and they'll have to be replaced - at some cost. What shocks are DIY rebuildable so you can put a droop restrictor inside or is this a case of having to buy pre restricted new ones? I'm not terribly enthusiastic about the restraining strap approach for a road car.
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PostPost by: tdskip » Mon Sep 02, 2019 2:50 pm

Is the restrictor to prevent the CV from overextending or the shock from overextending?

Is that an issue on a road car in every day use or only if you lift it in the air?

Thanks!
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PostPost by: 69S4 » Mon Sep 02, 2019 3:53 pm

As I understand it all CV joints have angular articulation limits but on whatever vehicle they were specified for originally those limits would not be, well, limiting - usually because the driveshafts are long enough to keep the deflection angle low. The 2 seat Elan rear suspension in particular has short driveshafts + soft suspension and, under droop, can exceed the articulation limits of the joints. Short of re-engineering the joints the easiest way out is to limit the amount of droop - either by limiting the travel of the shock absorber or by preventing the A frame moving down too far with a wire (or similar) strap.

Are you ever likely to approach those limits on the road? Difficult to say but if you've ever misjudged a humpback bridge and had the wheels unload you're in enough trouble already without having to cope with the driveshafts locking up as well. I suppose if you just drive the car gently on the road it might never be an issue.
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PostPost by: tdskip » Mon Sep 02, 2019 4:03 pm

Thanks for the response, sounds like the limiting is needed then as I do like to press on.

Is a strap an effective / low brain damage option then?
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PostPost by: tvr78 » Mon Sep 02, 2019 9:06 pm

I have the sue millers on my sprint and on my S130/5 without the limiter straps.i have done 20 k miles driving like a maniac in the sprint and 5 k in the s130/5 without any trouble at all.They are still like new,i’m very satisfied with them.
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PostPost by: Famous Frank » Mon Sep 02, 2019 11:35 pm

If you drive like my father use to or my friend Greg, Donuts are probably fine. But decades ago, 1972 if I remember correctly, I was at a SOLO II event, (sometimes called a gymkana or an autocrosss). There was a driver there with a gorgeous looking Elan. He was driving it very, very hard. It looked so cool to someone my age to see a car oversteering out of a corner and then accelerating as hard as possible down a short straight. It was wonderful to watch! Then something broke, made some horrible noises, sparks coming out of the bottom of the car under the trunk area, just before he pulled off the course. We all ran up to see if the driver was okay and what went wrong. The driver was fine. There was fuel dripping like crazy from under the car. Amazing it didn't catch fire! I crawled under to see what broke. It was my first glance at a donut as my VW had CV joints. The Donut broke allowing the axle shaft to flail around. It bent the lower A-Arm, dented up the frame, and broke the fiberglass floor and punctured the fuel tank. I said to myself, "Hell! I'm never buying one of these cars!!!" (now I own 7)

When I purchased my first Elan not long after that incident, no one manufactured a CV conversion kit so along with a couple of Lotus friends we made our own from shortened VW axles.

That's how I drive and that's why I'll always have CV joints or sliding splines.

It's up to you! Good luck and stay safe!
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PostPost by: tdskip » Mon Sep 02, 2019 11:41 pm

Thanks all - I’m going to budget for CVs.

On to the next piece of the build planning!

Very much appreciate all of the input gentlemen.
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PostPost by: SENC » Tue Sep 03, 2019 1:37 am

Check out elantrikbits - no limiter needed, and the owner an elan owner who participates here regularly.
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PostPost by: mbell » Tue Sep 03, 2019 2:22 am

Or rdent.com which come with new integrated out shafts. Not cheap thou.
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