Black Shadow rear brake drums?

Len Matthews

Well Known and Active Forum User
VOC Member
Yes John, there is a bewildering variety of hub bolts. I think those with a taper and two flats are very early ones. An ex-Argentine "B" I worked on had those and because it had pressed steel brake drums they were slightly shorter. Whatever, they've got to be better than metric Allen screws!
 

A_HRD

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VOC Member
Metric Hub Bolts

Actually, I just measured some stainless 'M8 A4-80' allen bolts with plain shanks on which I got a while ago for my Ducati. They are just the right length for hub-bolts with the overall length cut down a bit. The shanks are consistently 0.311 - 0.312 diameter which is a perfect fit for hub-bolts, I'm sure Len would agree. (The collection of standard/original 5/16 BSF hub-bolts I have collected over the years have shanks varying from 0.302 to 0.313 inches - deplorable!!). The M8 heads need a flat to be milled or filed on; so locking as std is guaranteed.

Just as good, the stainless M8 Nylocs I have for them have a nice black nylon insert (not the gaudy blue inserts which are the mark of cheap imported nuts). The 13mm across flats is only about 10 thou down from that of the nominal 0.525 of 5/16 BSF Nyloc nuts; so no-one would know. :p

For those who remain totally allergic to metric threads, you can buy longer M8 allen bolts with a plain shank at least 1-1/8 long, cut to length, thread 'em 5/16 BSF on a lathe and file the flat on the head.

Either way, the cost-saving is huge and the all important fit is probably better. Use A2-80 or A4-80 in preference to A2-70; they're a little stronger.

I promise I'll get out more.....

Peter Barker
Bristol, UK
 

john998

Well Known and Active Forum User
VOC Member
Brake drum bolts.

Hello Peter,
I like the sound of those bolts, as they will as you say be a better fit.
The heads on metric cap screws must be larger than the nearest imperial,
as they fit without any machining or filing. A clean out with an 8mm reamer, if necessary will probably be an improvement .
The main reason for using cap screws is ease of assembly, most of the tightening can be done using an allen key. With lock nuts and a final pull up with a spanner I have never known one to back off.
If I used 8mm cap screws I would probably turn down the head so it would turn in the drum.
Regards John.
 
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