De-Dion Driveshaft Nuts (Strange Approach to Engineering?)

[Baggiebird]

I have a 1996 De-Dion S3.  I am just finishing fitting new discs, calipers (reconditioned) and pads to the rear of the car.

The driveshaft nuts that I removed are, I am almost certain the originals.  The car has only done        14 000 miles.

As the nuts have nyloc type inserts my standard approach, after 40 years working with various vehicles would be to replace with new.  I know there are those who re-use with Loctite but I would rather not, my choice.

Anyway, as well as new braided rear hoses (upgrade to the rather dubious rigid copper design), I ordered some new driveshaft nuts from Caterham.  These are part numbers 6133688 (L/H and L/H thread) and 6133689 (R/H and R/H thread)  The cost of the nuts is £12.90 plus vat each, I am fine with that since it is an important safety critical part.  I put the new nuts in place on the driveshafts and tried to tighten with my 3/4" ratchet drive torque wrench and 41mm A/F socket.  Interesting, socket does not fit the new nuts?  Odd, since my previous De-Dion car used the same 6 sided Draper socket.

So I gave Caterham's parts department a ring.  It turns out that about 3 years ago the design was changed and they were made to order, but not 41mm.  They turned out to be around 41.3mm and so need, apparently a 42mm socket.

My question is, why not make the new ones to fit a 41mm A/F socket?  It just seems a very strange approach.  Everyone with a De-Dion car older than 3 years and who has a 41mm socket needs to be aware of this if they need to carry out work involving the rear drive shafts.

[Jonathan Kay]

I don't know why the change happened, but there's been a lot of discussion of this:

https://www.caterhamlotus7.club/forum/techtalk/rear-hub-nut-0
https://www.caterhamlotus7.club/forum/techtalk/hub-nut-size

And we've already got one offer of a loan socket in the Equipment Register:

https://www.caterhamlotus7.club/comment/2381755#comment-2381755

Jonathan

PS: Thanks for including the part numbers and the date of change: that's about what we'd concluded.

[aerobod - near CYYC]

At 42mm AF size, the tolerance for fitting a 42mm socket should be from 41.00 to 42.00mm, so 41.30 is within the expected range. Just looking at a couple of more standard nut sizes either side, M24 nuts have a nominal AF size of 36mm, but a tolerance range from 35.00 to 36.00mm and M30 nuts have a nominal size of 46mm but a tolerance range from 45.00 to 46.00mm.

I expect they manufactured the nuts from 1-5/8" hex bar stock which is nominally 41.28mm AF.

[John Vine]

...and they were made to order...

I thought CC bought these in from Ford?  (I stand to be corrected!)

JV

[OldAndrewE]

The part numbers certainly seem to be Ford numbers

[Wrightpayne]

Lots of parts on the Caterham website adopt the OEM part number. 

[Baggiebird]

Interesting about whether these hub nuts were 'made to order'.  I was quoting Caterham's parts department but the part numbers are certainly Ford.