Full width hub, sprocket does not fit.

[dennis.t]

I bought a used wheel for my 1956 NH but the chain sprocket does not fit because the stud holes do not line up, they are close but not right. The wheel was described as "Ariel, BSA" and is a full width alloy type. The only part code I can see inside the hub is 'AM2'. Does anyone recognise the part code?
Of course the sprocket may be wrong but I have tried two and both do not fit.
Drags list the parts to 'convert' a BSA rear wheel to Ariel but they do not say if the sprocket hole spacing on part number
4230-56 is different to an Ariel one and I am reluctant to buy their new sprocket if it won't fit my hub.
Dennis

[will_curry]

The BSA and Ariel sprockets are interchangeable - except that the Ariel sprocket
is flat and the BSA sprocket dished so the chains won't line up if the wrong one
is used.

As far as I'm aware all of the alloy rear hubs are the same so some pictures
of both hub and sprocket will be helpful. AM2 was the specification for the brake
lining material If I remember correctly.

I wouldn't buy another sprocket yet.

[dennis.t]

Will, thanks for that information. From what you say I may have an incorrect wheel. I might be better to cut my losses and find an authentic Ariel wheel with full-width hub. Interestingly, the sprocket I have is dished! Both items sold on eBay by different sellers were described as "Ariel" parts. Perhaps I need to buy a genuine Ariel sprocket and take it from there?
Dennis

[will_curry]

Part of the confusion comes from BSA owners referring to these brakes when fitted
to BSAs as Ariel brakes to differentiate them from the later BSA full-width hubs
which are steel.

A full-width Ariel-type wheel from a BSA is near enough the same as an Ariel one from
an Ariel to be quite usable and undetectable. Can you measure the size and position
of the studs on your wheel?

[dennis.t]

Will,

The stud spacing is 2 and 5/8" centre to centre (see yellow line). The studs protrude about 1/2" from the hub. Not sure what the thread is but I bought nuts 42-6095 and they fit.
Regards,
Dennis

[will_curry]

That certainly looks 'Proper'.

I can't get to a wheel to measure for a little while. Hopefully another user may
be able to oblige . . .

If you go onto the Members Only part of the club website and then the Detailed Images
page of the Pictures section you will find over 400 images of an HS 500. The back
wheel is the same as yours should be except for the rim.

[Simon.Gardiner]

There are at least two variations for the Ariel alloy-hub rear sprocket, one with cut-outs and one that's a disc (I've got one of each).
Ariel sprockets have 47 teeth, BSA had 42. If a sprocket doesn't have 47 teeth it's not for an Ariel.
If you've not found it already there's some discussion in this thread but maybe more importantly several photos.
viewtopic.php?t=4874&hilit=sprocket&start=10

HTH

SG

[Roger Gwynn]

The studs are on a 3-3/4 pcd that means as you have measured they should be 2.652" apart, so you were only .027 out. The hub is certainly correct. The thread is 7/16 BSF and Whit into the hub, one of the rare occasions that Ariel used BSF. There are 2 drawings of the sprocket on file, the first shows one with cut outs and was used until replaced by issue 7 that we also have and shows a solid disc. Issue 6 is dated 29/11/55 so the change to solid took place sometime later than this, the later drawing is dated June 1958, which seems a bit late and could just be the date of the drawing. Incidentally there are 2 numbers on the drawings, the 2nd one has an A suffix and indicates that it should be enamelled when used with a chain guard, no enamelling when enclosed in a FERC. It is nice to learn something new about Ariel everyday!

[dennis.t]

Thanks everyone. I am now more confident that the hub is correct and the sprocket I have is wrong. I will find a correct sprocket i.e. 47 teeth, flat and with cut outs. I see that Drags have new ones for sale.
Dennis

[Sean.O'Brien]

Gearbox spares have new ones in stock