PRV Nut Sizes

[Colsbeeza]

I took out my PRV today from my 1961 A10 GF to check the seats etc. Having forgotten what spanner sizes I needed, I consulted the oracles on this Forum to discover that there doesn't seem to be any firm size for the Large Inner nut.
As mine is an unmolested original with nuts in great condition, I measured them.
Large Nut

I measured mine at 27.83mm across the flats, or 1.096"
A 28mm socket would be good, but as clearance for a socket is poor, I used a 5/8"W open ended spanner. In theory - 5/8”W = 11/16” BSF = 27.94mm or 1.1”
I measured my 5/8”W open ender at 28.25mm or 1.112” and it fitted well with some acceptable slack. Good enough.! This seems to be the best option for this nut.

Small Nut
7/16”W = ½” BSF
I didn't bother measuring the nut, as the spanner fitted well with minimal slack..
Col

[Greybeard]

Yes, I found there is not enough clearance for a socket on the larger part so had to use an open ender. It just asks to be rounded off. I guess that nut doesn't need to be super tight.

What is the designed solution guys?

[chaterlea25]

Hi All,
A ground down 5/8W socket is what I have, but it's difficult to get any ratchet onto it when in the bike, I might modify a ring spanner if I find one cheap?

The replacement units are 1in. AF so a lot easier to access

John

[Swarfcut]

 Standard sockets have a slight chamfer  lead on the internal flats. In effect this reduces the surface to surface contact area between  the  thin nut flats and socket. Grinding the face of the socket to remove this chamfer will give less chance of slippage, as will a 6 sided socket. Sizewise I've got one somewhere..........

 As with any steel /alloy junction a good dose of the hot air gun makes getting one of these devils undone that bit easier.

 Swarfy.

[Greybeard]

Standard sockets have a slight chamfer  lead on the internal flats. In effect this reduces the surface to surface contact area between  the  thin nut flats and socket. Grinding the face of the socket to remove this chamfer will give less chance of slippage....

That's a great tip.

There is hardly any room behind the large nut, (on my bike anyway)  for a socket or ring spanniard.

[Colsbeeza]

Given that most are butchered by now, I admit it was a bit academic. Great Tips Swarfy & JOR. I'd like to get a better setup.
Col

[trevinoz]

I made a tube spanner for this.

[orabanda]

The hex size for the body of the SRM valve is 1" AF.
I turned down the OD of a 1/2" drive socket so that it fits.
Richard

[Greybeard]

From an SRM advert