Lotus Elan and Lotus Elan Plus 2 Forums

I just checked my rotoflex couplings, and have found one (the oldest one) with slight cracking along a couple of the bolt holes, at the interface between rubber and metal.

A poke with a screwdriver reveals they are 1 to 5 mm deep.

Is this a case of change the coupling immediately, or have I got more time? Is the rubber now less stressed so will the rate of cracking slow down?

Any thoughts from your collective experience?

Dave Chapman.

Dave

In the good old days they would hang on for ages and often quickly developed slight cracking which posed no problem.

Nowadays I'm reliably informed that they are not as good and for what it's worth I would not be happy driving a car around when the bond twixt metal and rubber is failing.

You've got to ask yourself "do you feel lucky", "well do you ****" because if the coupling fails at best it's a pain and at worst it will flail around and cause havok!

<_< Are you sure? I think you missed the * off the end!!

I didn't know that **** was now considered a swear word. Johnny Rotten will be pleased...

Dave, sorry to hijack your question, but I too have heard mixed things about the quality of today's Rotoflex couplings. Indeed, I note that Mick Miller's now refuse to stock them. However, I find myself in need of a set for my restoration, and wondered whether there was any reliable evidence out there about the quality issue, and whether any one brand is better than another. Anyone know?

It's not really I was just being polite In case Dave doesn't know Dirty Harry

I started a thread on this question some time ago and there are very mixed views. I had decided to stick with Rotoflex's on my own resto' but have now decided to go for CV joint shafts, mainly because donuts are quite expensive and I have seen one set where the rubber parted from the metal interleaf at around 3,000 miles! So ?250 pounds every 3,000 miles (or at best the worry of flailing driveshafts) or a bit more expense to fit and forget. I decided it is no contest.

I'd replace it, unless you're the only driver of the car and can resist driving it like a Lotus. The depth you mentioned on the cracks seem very close to what I"d call a tear. I've got old, older rotos on my +2, they've got a lot of stress/age cracks but nothing near 5 mm. On the other hand, if you don't drive hard, it can last 1000's of miles. Avoid high speed acceleration. HA! If you feel a new high speed vibration or sudden extra springingness under load, it's goiinnngggg...

David,

I replaced my rotoflex couplings a few years ago (via Chris Neil) and when I removed the old ones, I discovered that one of them had torn completely through in one place and another had torn completely through in two different places! And yet, they were still holding the drive shafts on. I know many will think I was just plain lucky but the fact of the matter is, the couplings will still hold the shafts on even when torn completely through. I'm not advocating that you wait until they are torn completely through, but I'd say if all you have right now is a couple of surface cracks, it's too early to worry. However, I would at least inspect them on a regular basis.

The Sprint models came equipped with stronger and less flexible couplings. It is my understanding that these are the only replacement couplings available. Beware of Sunbeam Imp couplings though. They will fit, but are of inferior quality.

Good luck! And I mean it!

Frank Howard
'71 S4 SE
Minnesota

Replace them Dave,

When they go they are frightening!

I had one let go (with only 3500 and 18 months wear on it) at slow speed turning right off a main road. The back locked up and left me stranded sideways across a main road. Even though I was doing about ten mph the resultant carnage to wishbone, body, chassis and brake rods was drastic. At higher speed I just dare not think..... When I complained to the (reputable) supplier of the Rotoflexes, their response was "3500 miles isn't too bad". I checked with other suppliers who said much the same things (including that the 'modern' ones with spot welded metal plates forming the bolt holes are not a patch on the original design) I run Mick Miller CV joints now and they make ethe car so much more drivable they are worth it just for that, let alone the strength and peace of mind. My CV shafts now have 10000 miles and two classic Rallies on them, so they even make sense financially if the expected life of donuts is 3000 - 4000 miles

Its a grotty job getting the Rotoflexes off though!

Bite the bullet

Roy

Doe this meam that the anti-flail driveshafts don't work? I thought that the extension pin on the end of the shafts was supposed to stop it flying around when a rotoflex shears. Or are you all refering to to the earlier type shafts without this feature?

<!--QuoteBegin-Robbie693+Feb 2 2005, 10:23 AM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Robbie693 @ Feb 2 2005, 10:23 AM)</td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> Doe this meam that the anti-flail driveshafts don't work? I thought that the extension pin on the end of the shafts was supposed to stop it flying around when a rotoflex shears. Or are you all refering to to the earlier type shafts without this feature? [/quote]
Sod's Law always applies. On a 1972 car I had one anti flail spiked drive shaft and one which was not. Guess which side let go!

Roy

Aren't the rotoflexes designed to absorb some of the stress from the driveline? I would have thought that removing them would transfer the strain to the next weakest point - maybe the diff output shafts. I might be wrong and there's no problem in normal use - any other views / experiences?

Simon

My experience is the antiflail pins on the later shafts are not strong enough. When the donut lets go the pin just shears off, been there done that, now use CV joints.

The only good thing about donuts is they normally fail at low speeds when torque is at a maximum. Never heard of any failing at high speed and hate to think of the carnage if one did. They do enough damage at less than 10 kmh as observed.

Drive line protection from the shock absorbing protection properties of the donuts is a old Lotus tale to justify why they used them ( rather than cheapness which was the real reason). The gear box and diff were used by Ford in much heavier cars with more torque and less drive line shock protection without problems.

regards
Rohan

Simon,

The first (and I think best) piece of advice from the guys in Club Lotus Scotland, when I bought my +2 was to get rid of the rotoflex couplings as they were more trouble than they were worth. Did I hate the surge!
I bought a pair of driveshafts from Tony Thomson. Big and heavy but they have transformed the car. The Club guys also said that all this nonsense about drive train shock is just that - nonsense. Seems they were right.
I was ordering stuff from Mick Miller Lotus yesterday and they said they do a CV version of a driveshaft. They also won't stock the new rotoflexs because they're not sure about their longevity.
Our chums at Spyder also do a half way house with one CV joint and a rotoflex - don't see the point of this one really as it only halves the problem.
There's lots of options out there - go on take your pick.

Hamish.

Thanks everybody,

I have taken the plunge and ordered a set of Sierra CV joints from Susan Miller.

The only tricky bit iI can see in fitting them is to avoid disturbing the rear brake discs - They have both been carefully shimmed to get the run-out into spec!

Dave Chapman.