Rotoflex Couplings

[Hamish Coutts]

"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!"

David,

When I fitted my TT driveshafts they had flat faces where they mated up to the diff and hub. The only tricky bit is getting off the old units. I removed the bolts at the bottom of the chapman strut and swung it out to release the bolts on the old rortflexs and allow the driveshafts to drop out.

The only really awkward part is cutting off the 'anti flail' pin from the outer driveshaft and diff output shaft. On mine the metal was soft so it wasn't too difficult, only awkward. Otherwise it's a breeze! The new units should bolt straight on.
By the look of the Susan Miller units they seem to have similar flat faces so I wouldn't think you would have to disturb the build of the rear hubs to fit them on.

Best of luck you'll feel an amazing difference. No more surge! (chant, chant!!)

Hamish.

[Matt7c]

David, is that just the CV joints themselves or the full package - diff to hub? I'd be interested in knowing the costs of the 'full monty' if anyone has an idea.
Matt

[Hamish Coutts]

Matt,

If you are interested for comparison, the 'full monty' from TT was about ?425 - ?450 for the pair. He claims they are approved for competition.
They certainly are 'robust' and well made and dead easy to fit. Think the postie had a hernia delivering them.

Hamish.

[david.g.chapman]

The SM CV joint kit comes up as a complete solution, with captive male studs to connect to the diff and rear brake disc ends. The nuts are included- all for ?385 + VAT etc.

When fitting to the discs, you have to remove all of the existing bolts to get the new studs in. At that moment the rear disc will come free. If you can keep the foot brake on while doing this the disc should stay put (I think - though it may move slightly as the pads centralise).

I will find out later this afternoon.

Dave Chapman.

[Matt7c]

Thanks fellas, you have made my mind up. Although I like the idea of spending only ?250 and getting the Rotoflexes, I don't like the idea of them lasting only 3000 miles. So for ?450 to fit and forget, I'll also go for the new shafts with CV joints.
Matt

[david.g.chapman]

I have now fitted the CV driveshafts, and am pleased with the result.

I did find that I had to reduce the diameter of the studs with a file, as they would not go through the holes in either the diff or the wheel bearing "tripod" coupling shafts.
My theory is that my tripod arms have suffered some distortion in the past, and the clearance between the stud and the hole is meant to be small to avoid backlash in the assembled shaft - hence the jamming.

I am only talking about a fraction of a millimeter - keep filing down (if you need to!) until the coupling slides in with no play.

Dave Chapman.

[Matt7c]

Dave, glad you have yours now fitted. I will be ordering a set tomorrow. Mind if I ask how long it took you to fit them and can you discern any difference in feel when driving?
Matt

[nebogipfel]

Hi All,

I bought my Mick Miller driveshafts from Susan today. If they fit and perform as good as they look they will be A1.

Susan is also a friendly helpful person which is a bonus

John

[david.g.chapman]

I have now had a chance to try the car out with the new CV couplings. The surging has vanished of course, and it feels solid and responsive.

There seems to be less vibration at high speed - I have had what I thought was wheel balancing issues before with my steel wheels.

If the engine misfires for any reason (If I put the choke in too early!) then you feel the jolt through the car much more. This is of no concern to me though.

All in all, it's thumbs up.

The work took a few hours, as I had to ease the stud diameters to fit on the new shafts with a file - no big deal though.

Dave Chapman.

[nebogipfel]

Hi All,

Just a quick update, I fitted the Mick Miller driveshafts yesterday and they were simple to fit.

I am working on a seperate chassis so I actually dropped the strut by removing it complete with lotocone to give me more room to fit them. I'm not sure how easy they would be to fit to a complete car?

The only thing I don't like the look of is the very sharp angle they will be running at because even with the car fully loaded the shafts will not be anywhere near horizontal.

I wonder how long the CV's/Boots will last?



The stud diameters were slightly out and using a new brake disk as a guide I suspect it is more likely to be due to manufacturing tolerences. Just a few thou' out and they would be tight. Mine fitted however with slight persuasion and no filing

[type26owner]

Hey John,
Here's a tip. Pull the convolutions apart by stretching out in the boot and tying it with a strap such as a tie-wrap. If they touch when the suspension is drooped, they rub on each other and will quickly wear right through. Bummer!

[rgh0]

John

The shafts are close to straight at normal ride height. The rubber boots and joints should have a near infinite life. I have over 50,000 miles on 2 sets of cv joints on my Elan and Plus 2 with second hand VW joints and rubber boots and have never had to replace a rubber boot and just replaced my first CV due to wear. The joints and boots probably had over 100,000 miles on VW's before I bought them.

The manufacutring tolerance on the disks and hub shaft spider joints bolt pattern is in typical lotus fashion fairly loose. This is not a problem with the rubber donuts as each bolt can take its own path though the outer assembly of disk and hub shaft spider. With the CV joint system each bolt is held rigidly parrallel with the CV and cannot move to adapt to misalignments of the other assemblies. I found with both my cars the need to match drill the disk and hub shaft spider to get the bolts to fit properly. No problems at the inner end as the bolts only fit though one shaft spider.

Rohan

[nebogipfel]

Hi Rohan,

On my S4 (all standard except for the CV shafts) I would probably have to fully compress the rear springs to get the drive shafts anywhere near horizontal! It looks like it is because the shaft itself is so short on the baby Elan. I imagine +2's run at a better angle because the shaft itself is longer? Perhaps your driveshafts are longer on your design?

I take your point about Lotus tolerances but mine were slightly different even end to end using a new brake disk as a guide. As I say it wasn't a problem, I didn't need to relieve any holes at all.

[rgh0]

John

The drive shaft angle is certainly less in the plus 2 with its wider track. On my Elan with my CV adapters which are a little thinner than the Miller ones ( that come from the Elan Factory I believe) you have a slightly longer shaft and thus a slightly lower angle. But all this is very marginal differences. If you look in the manual drawing of the rear suspension you will see that at normal ride height only a small angle in the drive shaft should exist. If at normal ride height you have an angle such that your worried about CV joint and rubber boot wear I would suspect your ride height is too high.

regards
Rohan

[berni29]

Hi There

I am considering some sort of CV setup for my plus 2, but was worried about possible lock-up if the car takes off completely as a result of a hump in the road or whatever. Also, are they as efficient as the rotoflexes in terms of power transmission? I am wondering if you loose efficiency if they are not running parallel.

Many thanks

Berni