Steering head bearings

Paul,

Firstly - there is difference in the front frame assembly ("downtube") between the Navigator - which had the roadholder forks installed and the Jubilee - which had the AMC forks, Nav downtube was part no 23350 and Jub was part no 21147. I think the Jubilee was more vertically raked than the Nav....

Given that the head stocks on these tubes differthen different cups/cones were fitted to accom the differing type of forks. As your Jubilee has been "uprated" to roadholders - the question is - has the downtube been replaced/modified?

For the Jubilee - then the cups required are part no 21709 (2 off) the lower cone is 21710 and the upper cone is 21708.

For the Navigator - the cups are part no 23381 (2 off) and the cones are 23380 (2 off),

Both Jub and Nav take standard 1/4" ball bearings - 18 top & 18 bottom (36 in all) which are quite easily obtainedor Part No 21711.

Rather than try to fit tapered rollers - which would entail modifying the headstock on the downtube - why not just replace the relevant cups/cones from the Spares Shop when you've sorted out which are fitted? I've typed these nos. in and they are now available at £10-00 per cup or cone (unlike some years ago when I had to have a set made up for me!).

Hope this helps

Brian

Previously paul_guttridge wrote:

Hi all, I'm hoping someone can help me as I'm a little stuck.... I have a 1961 jubilee with a roadholder front end. What are my options regarding steering head bearings? It has cup and cone at present but the cup is snapped in half and I am really struggling to find a replacement. Can I fit tapered bearings like most seem to do on featherbed and wideline frames? I can't find any info on anyone having done this to a jubilee?

To Brian Ascoughâs excellent response, I can add just a little that may be helpful:-

1. Working out what is fitted ...

The Jubilee front member features two welded-on U-shaped pieces: one in front, below the headstock, to serve as a steering lock stop; and one behind, at half-height, for the cylinder head steady. The Navigator version uses a separate lock stop plate (it bolts to the headstock) whilst the head steady attachment is provided by a pair of parallel projections, spaced just over an inch apart. [These receive a small forging which attaches in turn to the heads.] The two are thus easily distinguished.

I believe that the headstock casting per se is the identical on the two but, as Brian says, it is set at a different angle within the fabricated assembly. The external dimensions of the cups are thus also the same, such that either type CAN be fitted to either type ...

NOTE however that the steering head offset is less (c. 2.25â {57mm} on the Roadholder fork assembly as opposed to 3â {76mm} on the AMC version) ... which is why the rake is less (closer to the vertical) on the Navigator, in order to maintain a sensible amount of trail or caster. Fitting Roadholders to the Jubilee member will thus result in excessive trail, to the likely detriment of handling.

It is thus best to use the Navigator front member if upgrading to Roadholders although you will then need to re-jig the head-steady arrangement to suit the slightly shorter engine. A simple spacer would allow you to use the standard Navigator head-steady piece, so no big deal.

1. Which cup to fit?

Easy! The races themselves are the same, as Brian says, viz. 2 x 18 x ?â balls ... and the external dimensions are also the same. What differs is the size of the hole in the middle, which had to be made larger (30mm as against 22mm) to suit the Roadholder stem and associated parts. So even if using the âwrongâ front member, you would HAVE to use Navigator cups, or have Jubilee items re-machined to suit.

Best is clearly to buy new; but if you have any difficulty, I can supply a usable second-hand Navi steering cup at no cost ...

1. One last thing:

I have never known a cup to crack, as yours has, but it is not uncommon for them to move within the headstock after years of use and abuse. If they are not a snug fit, the space needs to be taken up with steel-loaded epoxy as a minimum.

>> Roger Kingsbury (Solent Branch)

Previously paul_guttridge wrote:

Hi all, I'm hoping someone can help me as I'm a little stuck.... I have a 1961 jubilee with a roadholder front end. What are my options regarding steering head bearings? It has cup and cone at present but the cup is snapped in half and I am really struggling to find a replacement. Can I fit tapered bearings like most seem to do on featherbed and wideline frames? I can't find any info on anyone having done this to a jubilee?

Hi Paul,

All the parts cups, cones and balls are available from the Club Spares Scheme.

Neil Shoosmith,

Spares Scheme Administrator

If you find 2, I'll have the other one!

Dan