From some earlier posts about rear wishbones/driveshafts/half shafts on my elan sprint I’ve gone from one thing to another - I’ve now decided to fit the rotoflexes and keep the shafts and wishbones as standard.
Rightly or wrongly I’ve made the decision on three points
If one stiffens one part my thinking is that stresses will move on to the next weaker point which could be the diff (in fitting the all metal drive shafts) also they appear quite overwhelming on size.
The car is simply for high days and holidays so do I need to be fitting items that are never going to be put under a heavy load (as in ultra fast road or track use).
The system was designed as a whole and with what I feel will be greater compliance with the rotoflexes the ride ‘should’ be smoother and knowing these to have a propensity for cracking I will inspect regularly for deterioration.
Maybe further down the line experience will tell me otherwise…
“I will inspect… for deterioration” Most of those “rotoflexes” will hide their deterioration and fractures until they fail!
“experience will tell me otherwise” Unfortunately it will! Sooner or later… Lets hope it will be on a light stop (as it happened to me) and not at 60 mph… I converted to CVs joints (elantrikbits.com/)
Richard, I agree wholeheartedly with each of your reasons for keeping the Rotoflexes. I have raced and slalomed (autocrossed) Elans for years. Most had solid u-joints or CV joints of one type or another and I wouldn’t have had it otherwise… for that purpose. I also agree with those who say that they have a more direct feel than the donuts. They do, but donuts in good condition, properly torqued, are not as bad as they were when the cars were new. The Rotoflexes sold these days are a better design (Sprint type, I believe). My current running Elan has Rotoflexes and will through the rest of its life. I have another non-Elan car that is for track use and my Elan is used pretty much as you are using yours.
You’re not going to be stressing the drive train and you intend to check the torque and condition of the Rotoflexes regularly so I believe you’ll be fine.
Hello Richard
I’m with John in the Solid driveshaft camp. Having fitted the Susan Miller type a few weeks ago I can hardly notice any difference. Any difference noticed is in a positive way not a negative way. I don’t thrash the car and it does only go out once maybe twice a week which were my reasons for fitting them!
As with all rubber I surmised that constant usage keeps the flexibility so intermittent usage would create more risk. Furthermore the argument about wear on other components as a result of the solid driveshafts maybe true if you do in excess of 10 to 15,000 miles a year but in my opinion low mileage users would see no difference.
I do side with you on this, but I have to admit to preferring originality! Each to his own, I know.
I have lifted this section from my web site, which I think says a good deal about the issue as of 1970/1. I appreciate that rubber compounds have had to change in the intervening years.
'Tony Rudd was reported on his investigation into Rotoflexes in a 1971 Motor Sport article ?When I visited Lotus some months ago I spent quite a while discussing the relative merits of Rotoflex couplings and sliding spline and universal joints in the rear drive shafts with Tony Rudd, the firm?s Director of Engineering. Rudd had been dubious of the Rotoflex or doughnut coupling before he joined Lotus and agreed that the diabolical surge they caused had to be cured. To this end various experiments were tried when he joined the firm, one of which was the use of the more conventional u/js. However, for some reason, concerned with the elasticity of the doughnuts, the handling undoubtedly deteriorated considerably using the metal joints. So Rudd did quite a lot of research on Rotoflex couplings and after a couple of improvements has now come up with one that almost entirely eliminates the wind up. These are naturally somewhat more rigid and perhaps, because of this, the ride seems to be a little harder than on the earlier and exceptionally smooth riding Elans.? [Copyright Motor Sport]/
Congratulations on your web site lots of useful facts! I learnt the colour of wheels being semi gloss - valuable as the wheels are presently being refurbished!
Heading for 3 years (must be well over 20,00 miles) with my Sue/Mick Miller CV’s!
Fit and forget, trouble free
I did think that there was a clicking when I first fitted them but this DID turn out top be a broken diff-mount. Broken for a good while before the CV went in by the looks of it.
The cost of these at ?690 are steep against TTR at ?450 but do look beautifully made and the design is complementary I feel to the lotus delicacy - I have earmarked these for the future but also interested to see the ones that Sue Miller supplies…
One last hurrah for the rotoflexes being that in Brian (Bucklands) book he suggests that when the rotoflexes need changing the time is anyway about right to fit new bearings to the hubs - but I guess if the bearings start rumbling you will know that anyway!
I also notice from his book that he reverted to rotoflexes - his points being:
“Make sure they operate at full droop which can be a problem and not all do”
“I am told, if you give the Elan the boot from a stand still you can shear off the differntial drive shaft if not cushioned”
“tried them for a 3 month period on my car without a problem although I did think it was a harsher ride and I have changed back”
I would stress that he did not state any particular make.