Lotus Elan

Rear spindles/hub shafts-replace?

PostPost by: Davidb » Wed Jan 10, 2018 4:04 am

After reading various posts made over the years about the strength of the rear spindles/hub shafts I am still unsure about whether I need to replace them! TT says absolutely yes, others say maybe, what say others? I run 6 inch wheels on 26R style hubs with about 150 bhp but road use only.
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PostPost by: JonB » Wed Jan 10, 2018 7:55 am

I would keep a close eye on your rear hubs, check them regularly for free play (with the wheel on but jacked up) and replace bearings or shaft (as appropriate) if you find any. I have just discovered huge amounts of wear on my left hand outer shaft which I thought was bearing failure, but when I got it out (not easy!) I discovered an enormous groove that is the size of the bearing inner race. See lotus-suspension-f42/rear-wheel-bearing-knocking-from-suspension-over-bumps-t40997-45.html#p287622 (second picture).

If your shafts / bearings are in good condition (meaning by that, no discernible play), I doubt if an additional 25 BHP will over stress them unless you are seriously ragging the car. I think I would be more worried about Rotoflex disintegration (assuming you still use them).
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PostPost by: rgh0 » Wed Jan 10, 2018 9:30 am

It is not the HP but the higher cornering stresses achievable with modern tyres that can break the outer (wheel) drive shafts. In a competition car its a must thus the TTR comment. In a road car it really depends on how hard you drive it :D

On my Elan I have lost a rear wheel many years ago when the shaft broke at the start of the taper just outboard of the outer bearing. The car was remarkably stable when I lost the wheel as I was just exiting the corner corner at the top of Lukey Heights on the track at Phillip Island at about 100 kmh and i was able to drive off the track and park on the grass without drama :lol: The wheel carried on down the track for another hundred metres before running off at the next corner

My Plus 2 has used track day sticky tyres on the road for many kms of enthusiastic road driving with the standard outer shafts without issue. I have not heard of the shafts failing in road cars but I would crack test them whenever I have the rear suspension apart for bearing replacement.

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PostPost by: JonB » Wed Jan 10, 2018 9:51 am

rgh0 wrote:It is not the HP but the higher cornering stresses achievable with modern tyres that can break the outer (wheel) drive shafts. In a competition car its a must thus the TTR comment. In a road car it really depends on how hard you drive it :D



Good point Rohan, I should have thought of that.
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PostPost by: ecamiel » Wed Jan 10, 2018 2:36 pm

Like Rohan, I have had a rear shaft fail. Not fun and a bigger issue on the street than on the track.
The early ones were a disaster and must be replaced if you are using modern rubber.
Maybe Rohan knows how to identify the old shafts?
The hubs and shafts have "reversing" loads which makes the particularly vulnerable and results in a limited service life.
Also, many hubs and shafts have been overstressed during faulty installation and disassembly. They have been torqued too tight, too loose bent and battered about.
For peace of mind, check first if the shafts or hubs are out of true, which is easy. Then disassemble, check again, update the shafts if you have the old ones, Magnaflux and reassemble properly including checking the taper with some bluing or lapping compound.

Then drive as hard as you like without worry - At least no worry about the rears !!!

While you are at it, have a look at the inner shafts as well. Mine were all twisted at the splines even before I added more HP and bubble gum tires

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PostPost by: Davidb » Wed Jan 10, 2018 4:48 pm

Thanks for the responses. When I did my mechanical restoration/upgrade a year or so ago I replaced all of the bearings of course. I seem to remember doing the "Dave Bean mod" to the locating pin groove and I spent considerable effort lapping the new hubs to the shafts. However, I do drive quite hard and long distances and my engine is 1720cc which means more torque.

The cost of the shafts vs the cost of not finishing an event/crashing into a mountainside...

Edit: I replaced the inner shafts with later "Sprint" style last summer.
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PostPost by: USA64 » Thu Jan 11, 2018 4:20 am

I will just chime in because I have read the whole thread and not seen it mentioned. There are two size bearing carriers and two size axles. I just had mine professionally done after I could not get the axles out myself. It turned out that one of the axles was the earlier type which was too small for the larger bearings that fit my S4 bearing carriers and I had to get a new axle on one side. The new axle has no key-groove and came with instructions for lapping in the hub.
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PostPost by: Davidb » Thu Jan 11, 2018 5:34 am

Thanks for that USA64. My car is a 1965 S2 so does that mean it has the early shafts-I would think so. Certainly both bearings are the same size and are 6206RS I seem to recall.
Does that matter?
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PostPost by: rgh0 » Thu Jan 11, 2018 8:48 am

The only difference between the earlier outer shafts with two 6206 bearings and the later shaft with the wider inner bearing was the position of the circlip groove for the inner bearing. As far as i am aware the later shafts used the same steel and were no stronger. Its possible by cutting another circlip groove to make the later shaft fit the older carrier and bearing combination. The reverse is not good practice as the bearing seating area is wider on the later shaft to accommodate the wider bearing and circlip groove location

The shafts without the semi-circular cut out for the rounded pin on the taper were TTR shafts but others may resell them now. TTR also offers them with the pin cutout. These shafts are stronger than the original Lotus shafts due to better quality steel.

You need to lap in the hub and shaft whether it has the pin or not.

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PostPost by: Craven » Thu Jan 11, 2018 11:55 am

Later drive shaft, can be used in the early hub ( issue 16 ) with narrow bearing by simply fitting an available spacer between the bearing and circlip groove.
If you want to use the later shaft and wide bearing you need to change the upright/hub to issue 18 which takes the wide inner bearing but it keeps the same outer bearing.
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PostPost by: JonB » Thu Jan 11, 2018 1:10 pm

rgh0 wrote:
You need to lap in the hub and shaft whether it has the pin or not.

Rohan


What does this mean? I have yet to fit my hub to the shaft. How do I "lap it in"? I thought that is what you do to new valves... with grinding paste.
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PostPost by: rgh0 » Thu Jan 11, 2018 1:20 pm

exactly the same process

use grinding paste and then engineers blue to ensure a good even and continuous contact over the surface of the taper with the hub

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PostPost by: USA64 » Thu Jan 11, 2018 3:33 pm

I still have the early shaft which appears good. I am using it as a paperweight because it cost me so much but if someone needs it they're welcome.
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PostPost by: JonB » Thu Jan 11, 2018 4:20 pm

rgh0 wrote:exactly the same process

use grinding paste and then engineers blue to ensure a good even and continuous contact over the surface of the taper with the hub

cheers
Rohan


OK, have ordered a double ended tub of coarse / fine paste. Will take the key out and discard (have a new one on order), then remove burrs from the keyway (that I accidentally introduced while drifting the inner bearing on), then smear coarse paste on, fit hub and rub back & forth while applying a bit of pressure. Then hub off, clean up, apply permanent marker, refit hub, take off hub, see how much contact there is. Rinse, repeat. Final lap with fine paste before reassembly with new key and torque to 110lb/ft.

Sounds good?
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PostPost by: rgh0 » Thu Jan 11, 2018 7:57 pm

Check and retorque a couple of times after driving until the nut stops moving. I find the nut moves a little for 2 or 3 times then stops.

When reassembling make sure the nut and washer do not bottom out on the shoulder on the shaft or the hub bottom out on the bearing on the inside of it.

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