Rotoflex hub bearing seizure

[trigolf]

Hi all,

Just finished reading the latest Practical Classics mag and saw that Nigel Clark has had a hub bearing seize on his GT6 Mk3,after three months use, following a conversion to the Rimmer CV driveshaft kit. I'm following the story closely as I plan to fit the same CV conversion kit. I recall that when he dismantled the hubs prior to the conversion he found no shims or spacer fitted to either side, which I thought was strange. He then got an engineering shop to build up the hubs fitting brand new OEM bearings, but also without measuring end float and selecting the correct size spacer and shim(s) etc. I'm awaiting the next issue of the mag to see what he discovered - I suspect that lack of, or too,much bearing end float will be likely cause...

Has anyone else fitted the Rimmer/Jigsaw/Classic Driving Developments CV  (not the Canley type) conversion and had any problems at low mileage ?

Gav

[Pete Lewis]

Gully had a bearing fail but untill hes on here dont know whos' shafts were used

took a good bit of trail to get the float right , its still running so thats  good .  

most failures are due to pre load , not excess float 

Pete

[Nick Jones]

As Pete says, the bearings fail faster due to too much pre-load rather than too much end float.  Shimming these (whether for the OE shaft or a CV conversion) is a fairly fiddly procedure and easy to cock up if you've not done one before.  So could well be just down to incorrect shimming.

Having said this, I am also very curious about the longevity of the standard bearing setup when used with the Rimmers/Jigsaw/CDD shafts.  The reason for this is that whereas the Canleys shafts use 1500 FWD CVs at the wheel end with exactly the same spline and support-land profile as the OE shafts, the others use a modern CV that has been modified to have a much shorter support land. Basically the generous radius between CV face and spline has been machined square.  While this does provide enough room to park the spacer and shims it will hardly protrude into the hub at all.  The original shaft support-land did protrude well into the hub and was in fact a light interference fit as well, thus providing considerable re-enforcement to the rather thin spigot that the inner bearing sits on, even expanding it slightly to fit the grip the bearing.  My concern is without this the bearing may spin on the spigot or the unsupported spigot may fail.

I have some evidence for this risk as my very first CV conversion used Ford outer CVs that happened to fit the Triumph hub.  It lacked any support land at all and had a large radius at the end of the spline meaning nowhere for the shims.  My solution for this was to get a spacer made and put it and shims as needed between the bearings.  This is actually stronger than the OE setup because the whole lot is clamped up solid when the hub nut is tightened - and it worked fine for the 20k miles I put on it.  However, others who semi-copied the idea, but with shimming arrangements similar to OE, had persistent problems with the inner bearing and spigot failures.  It is a simple mod to put a spacer and shims between the bearings but doesn't make the shimming process any easier.

There are quite a few of these shafts out there now and I've not heard of any failures...…...

Nick

[Gully]

On 30 January 2019 at 12:37, Pete Lewis said:

Gully had a bearing fail but untill hes on here dont know whos' shafts were used

took a good bit of trail to get the float right , its still running so thats  good .  

most failures are due to pre load , not excess float 

Pete

Robsport fitted my CV conversion, including new bearings. From recollection, the CV shafts / joints were supplied via TR-GB. I suspect the bearing that failed was pre-loaded as even in its rough running state there was no sign of end float before disassembly.

Gully

[trigolf]

Thanks Gully.

Hopefully a few other people will let us know how their CV conversions are holding up.

Gav