New tyres

[chrishewett]

Had the new tyres fitted last week. Yokohama A.drive 175/70R13 82H ( ?25+vat). Putting the last wheel back on I discovered a badly torn rotoflex. Managed to get one delivered by Chrisneils today ( only ordered thursday 4.30pm). Having fitted the coupling I took it for a proper blatt this afternoon and I can recommend the tyres. Now the tracking is ok I will see how the tyres wear, if nothing else goes wrong in the meantime!
Chris

[gordonlund]

Chris,

You shouldn't fit rotoflexes in ones. A pair on one side at least. You run the risk of overloading the other now you have one stiff new one and a less stiffer old one. Keep your eye on the others as you may induce premature failure with disasterous results.

Sorry to be a kill joy but you wouldn't replace one worn tyre on the same axle as a semiworn tyre on a high performance vehicle for the same reasons. I posted a fair bit of Dunlop Technical stuff under Things in Common subject Rotoflexes dated 23 Jan 07, which shows the design loading parameters. If you do the sums on these for torque ratings in first gear many Elan owners would cut out 0-60 sprints. Chapman never took washers racing!!!

Gordon

[oldokie]

Spot on!! Well, disasterous result may be a bit of an understatement, I had a failure changing up to 2nd, the center section came up through the bottom of the boot, ate my spare, the plywood, and a car cover that had jumper cables folded inside. At the time I was sure it was coming thru the seat back and was the last sound I would ever hear!!

[thor]

And once again I now want a CV joint conversion NOOOWWW !!!!!

[chrishewett]

Gordon,
The reason I only replaced one was that I have spyder (?) driveshafts which have only one rotoflex per side. The other was replaced a few miles ago and I think had only failed because the universal joint had siezed upon that side.
Although I bought two I only replaced the failed one as I have decided to fit cv driveshafts. I think it is too much of a lottery using these rotoflex couplings these days, I am sure that the original items lasted longer, no one would put up with this rate of failure on a new car surely?
Having said that I have just had a 200mile return trip to Bedford autodrome in the elan and it performed like a dream. When they are going well they really go well!
Chris

[tower of strength]

Have the quality of rotoflexes really deteriorated over the last few years? I ran a 130 over 10000 miles on new ones from CN and had no problems, my mum ran her plus 2 daily for over 25000 on a replacement set in the 80's.

Could the problem be that they are weakened from sitting in one position for prolonged periods on summer cars?

Just a thought.

Mark

[gordonlund]

Mark,
I think you have hit the nail on the head there. My Rotoflexes on average last between 8,000 and 20,000 miles. I do not use the car so often now as I used too, about 4,000 miles a year now with 2,500 of those in France on hols. In the 1980's I used the car regularly and covered about 10,000 miles a year. I change rotoflexes about once every two years. I don't wait until they break!!!! Rubber does deterioate with age especially bonded components as highly stressed as these. My analysis of Dunlop Technical information and torque loads in first gear coupled with the max angular movement, take them far beyound their design capability. Typical Lotus. Even in the 70's, rotoflexes were always high on the replacement list as were rear wheel bearings and dampers. Things hav'n't got any worse, things are still the same. It wouldn't be a Lotus otherwise, would it. Modern car owners are spoilt!!!
Gordon

[chrishewett]

When it comes down to it rotoflexes on elans are a ridiculous idea whether they last for 2000 or 20000 miles. When they go they can cause massive damage. I have not had a big failure because I monitor them constantly. The only sensible way to go is with a cv driveshaft mod if you want any confidence in the car.
Chris