Looking for thoughts on converting rear drive, removing doughnuts and changing tp CV drive shafts. Which are the best to go for and and mods that need to be done.
Do a search, the topic has been done to death.
But my vote is CV shafts from Sue Miller. I had a set on my Plus 2 and they were brilliant. Truly a purchase without regret.
I think it depends what you want of your car. if you wish it to drive and behave as Lotus originally intendend then I would say keep it on doughnuts. If on the other you crave the way a modern car behaves and drives then do a CV conversion. The Aussie, Elektricbits CV version, seems the best albeit the most expensive CV conversion from what I read.
Always bear in mind though that you are carrying out a modification. if you do go the CV route you will need to inform your Insurance company that your car is a âmodifiedâ car. Failure to do so could have consequences!
Personally I will be keeping my +2 on doughnuts and I canât see what all the fuss is about. ! like my car as it is and I find it great to drive in this original driveline configuration. I carry out regular checks on the doughnuts and so far in my ownership (6years) I havenât and donât see anything that would persuade me to change my thinking.
Alan.
ââŚIf on the other (sic) you crave the way a modern car behaves and drives then do a CV conversionâŚâ
Given the vast majority of modern cars are either 4WD or front wheel drive, this is nonsense.
âAlways bear in mind though that you are carrying out a modification. if you do go the CV route you will need to inform your Insurance company that your car is a âmodifiedâ carâŚâ
Agreed. No cost option, just add to the list of modifications for the insurance company.
ââŚI carry out regular checks on the doughnutsâŚâ
If you donât want to be jacking and crawling under the car up every two minutes to check the condition of the couplings, fit a CV conversion. I check the CV driveshafts twice a year - pre MOT (mid summer) and as part of winter service check.
All IMHO, of course!
Malcolm
I just installed Elantrikbits CV axles on my S3. No issues fitting, no modifications needed.
The donuts on the car were pretty rough- I chose the âminimal maintenanceâ route and got the CVs. Plus I didnât particularly like the âwind upâ.
I fitted Sue Millerâs kit in 2011 after 30+ years of doughnuts and no matter what the relative costs are, I wouldnât go back to doughnuts. Itâs a personal choice, the only issue I had with doughnuts was the constant maintenance and being sure that any replacements were good enough and not going to shred themselves in 6 months, but driving was fine. But with CVs you know youâre not going to get a catastrophic failure and like all the other millions of cars using the same system, they are very reliable.
Mineâs an S3 and the reccomendation is for shorter travel on the rear dampers which Iâve done during a suspension refresh from Kelvedon. To be honest I did drive the car with the OEM dampers for a while but Iâm not going to be testing the limits of travel and was always careful when jacking up the rear end. I donât think the same problem applies if youâve got a +2.
I also fitted a home made diff brace as on the later cars, donât know if it makes any difference but I did it anyway just in case the CVs were harsher than the rubber joints. .
Yes and this is the problem. Fitting CVâs eliminates any form of âcushionâ in the driveline making it harsher on the various components in our cars.
The diff setup on ours cars is quite fragile compared to other cars with the lightweight aluminium Lotus differential adaptor case just being suspended in mid-air by two rubber mountings and two tie bars to control fore and aft movement. Other cars that have CVâs fitted as original equipment have a lot more secure and less fragile arrrangement.
My thinking is that fitting CVâs to an Elan or +2 canât help but put additional strain and consquential future wear on these components particularly if driven aggressively.
If you do decide to fit CVâs i would definitely check that you have the later heavier duty diff output shafts fitted in your car before fitting the CVâs!
Alan
Alan
Whilst Iâd agree with you regarding the potential for risk to the other transmission components from CV driveshafts, can you bring any evidence of transmission damage/accelerated wear/failure as a direct result of this modification (road going levels of torque and excluding competition or track day use)?
Malcolm
Hi
For me the only downside to the shafts is the additional weight added by the conversion. If you are a clutch dropping tyre smoking type of guy then I might be somewhat concerned about the diff and related components. But there again just price in the additional maintenance that goes along with that style of driving.
All the best
Berni
With all due respect to Alanâs view, the choice of Rotoflex by Lotus was driven by cost. They werenât much good in period, and I am afraid they are probably worse now. Tony Rudd in his book âIt was funâ mentions that Rotoflex failures were the biggest cause of warranty claims during the Elanâs production run.
26Rs had UJs and sliding splines from the factory, nobody I know (and I checked the entire grid a few years back) in historic racing uses Rotoflex. They donât fail safe, and can flail around doing significant damage or jam up and lock a rear wheel.
I am convinced that if plunging CVs had been available at reasonable cost at the time, the Elan would have had them fitted, along with inboard disc brakes (idea was ditched because of the wind-up of the Rotoflex).
If you like the feel of bouncing along on Rotoflex, then thatâs fine, but I really donât like them.
Picture shows frame damage caused by Rotoflex failure.
The âRotoflexâ couplings available today are nowhere near as tough or long-lasting as the ones available when the cars were new, so it just isnât possible to âdrive as Lotus intendedâ. They were not brilliant back then anyway; in conversation with Ron Hickman some years ago he said he wouldnât have anything but CVâs these days and, as he designed the Elan, thatâs good enough for me.
I fitted Mick (Sue) Miller CVs years ago and found that the rubbish differential rubber mounts available these days didnât last very long, as the drive-line is subject to increased loads under accelleration/braking (all ârubberâ components seem to be inferior now) I fitted Tony Thompsonâs racing diff mounts top and bottom and have had no issues since then.
Iâll stick up for Allan! - of course if you hit something with a steel hammer the object you hit is going to be in a worse shape than if you had hit it with a rubber mallet. Do the standard Lotus components have enough in reserve to cope with the loads of being hit with a hammer instead of a rubber mallet? Who knows - but it certainly is a valid question to ask.
I think it would be useful for this thread to hear from Breezehill ( Sorry donât know your name) how long he has owned his car and driven it in itâs present doughnut format?
Also how many miles does he drive in the car per year?
His he not happy with way the car drives presently?
This may then help towards answering the question why he personally feels that he wants to change to CVâs at this time?
Alan.
[quote=âalanrâ]
I think it depends what you want of your car. if you wish it to drive and behave as Lotus originally intendend then I would say keep it on doughnuts. /quote]
So, as Lotus originally intended
On a Federal emissions car
Crack the throttle, mixture changes from traveling 3 feet through a tiny tube to straight through the intake.
Timing changes from full retard to standard advance
delay of almost a second
meanwhile, your brain senses the lack of motion and tells your foot to keep pressing
engine starts motivating, but wait, that motivation is winding up the donuts
finally the car rockets forward, everyone in surrounding cars shakes their heads and thinks âa88hole!â
You let off the throttle a little too harshly and the car bucks, rocking at the resonant frequency of the rubber donuts.
Took me a week to wire open the secondary throttle plate.
Yes, the majority of this is not the donuts fault, but âas Lotus intendedâ always makes me laugh
They also intended that the wipers virtually stop at stop lights and the windows come to a grinding halt at idle, no, generators were cheap.
It really is necessary to filter out the engineering genius of Colin Chapman from the brutal cheap-ass of Colin Chapman
The halfshafts on the Elan are too short for U joints, and CVs were too expensive.
Not about design, its about money.
If the donuts gave you lots of warning of their eminent demise, or they did not wreak havoc when they failed I would say keep them. If new donuts were high quality and reliable, perhaps. IF they were not a screaming pain in the sack to deal with when doing other things on the rear suspension, again, perhaps.
But all of these things add up toâŚbuh bye donuts.
gus,
Your car is obviously in need of some attention! My +2 doesnât do any of those things!
Alan.
Certainly seems to be quite a few nuts with lots of dough on this forum
Very good!. Made me laugh! :lol
Alan
I am an originality nut, keeping everything as original as possible. This included keeping rotoflexes (they were replaced just before I collected the car). But you do not want a rotoflex failure, and I wish I had replaced them earlier.
I checked them regularly, every couple of months, and there was no sign of deterioration. But in September 2021 I took the car out for one of my usual (reasonably spirited) drives. Turning off from one road to another, there was a fairly steep hill. Putting my foot down, there was an almighty bang and then lots of banging and thudding. After a couple of seconds I realised what must have happened, but stopping on a single lane country road halfway up a steep hill was not ideal! When I went to put the handbrake on, it didnât work (it was wrapped around the driveshaft). Even with the car in gear it was rolling backwards (cue lots of frantic emptying of the boot of spare wheel, jack and anything else to jam under the wheels).
In the end, I think I was fairly lucky damage-wise. The handbrake rods/tree had to be completely replaced (and calipers stripped down to bend the operating levers back). The chassis took a lot of pounding, which had to be straightened out and welded. The wishbone was also completely destroyed. Fibre-glass damage was limited to a couple of impact areas where the brake caliper hit (the wheel was pushed backwards).
Iâd overhauled the front suspension during 2019/2020, so the back was next inline, anyway. So it no longer looks like the grotty photos. But it was off the road for another 8 months, just when I wanted to drive it after lockdown 
I still donât know why the rotoflex failed. The rubber had split along one of the strengthening metal inserts, but Iâm not sure if that was the failure or it happened as a result. You may be able to see from the photo that all the bolts holding the rotoflex to the differential output shaft are missing. I went along the road trying to find them (I had plenty of time in the 8 hours it took to be recovered).
I found one bolt shaft and one nut-end, which were obviously from different bolts. Perhaps the bolts had come loose, and the stress had caused them to break? This is not something that can be checked from visual inspection. So another reason to replace the rotoflexes. Theyâre simply not worth the fuss of a failure.
The drive shaft bolts will fatigue and break if not tightened adequately(or come loose) or not a good quality grade 5 bolt. This is more likely in a Donut set up compared to Cvs where the bolt is subject to more complex and higher bending loads by the donut and the resulting failure of just 1 bolt leaves a lot of damage. In a Cv has one loose bolt is less likely to cause catastrophic damage.
cheers
Rohan
All, thanks so far for all the honest opinions.
For all and Allan, the car a late 1970 +2S appeared in Club Lotus magazine about three years ago after weâd just bought it back and known as The Prodical Lotus. Correct bought back having first bought the car as a project back in the late 70âs when it was in a state, unloved, badly maintaind along with damaged chassis where some numpty had jacked the car on the front cross member which was badly punctured allowing the section and drivers side upright to rot.
So new Spyder chassis a full nut and bolt rebuild, all bolts assembled using copper grease. And most of the running gear where necessary replaced. The whole scenario took five years, two house moves before returning to the road in the early 80âs. However and Iâm sure there are some out here who experienced the same when children arrived somewhat to go sadly the Lotus. Once sold did keep in touch with the new owner who shared the various car events where heâd won best in class, really did cheer me up.
Moving on 2019, just scanning the pages of the usual online car magazines and always checking the Lotus for sale spotted one that looked very similar then zoomed in on the picture and bingo it was our old Lotus. Contacted the dealer just for a chat and sent some photos of the rebuild Iâd done. Basically suggested that the new owner could contact me and Iâd run them through all the work that had been done. On a whim decided to go and see the car, guess what bought it.
Sadly the car had been standing outside unloved for a couple of years, mice had taken up residence in the boot and behind the panels where the seat belts are fitted along with damp in the carpets which needed ripping out.
So car back with us, all trim taken out and mice nests removed we put it back together to get it back on the road for summer. Oh yes, the mice had eaten through the loom in the boot and behind the seat belt panels so new harness throughout.
Weâve now used the car and trips around our area to local car meets and the pub. However our last trip out last autumn there was a grinding noise from the rear which showed as failed bearings in the drivers side rear. Since then the car has been up in the air in our workshop, where the rear running gear, diff and suspension has been removed hence why I now have the question on CV drive shafts. Thank goodness for the initial rebuilding using copper grease on all bolts meant they all came apart.
We donât do great distance with the car and mainly only during the best days of summer etc. mileage wise probably most 5000 per annum.
So does it warrant CV or retain doughnuts ?
