Rear Brake S/A pinch bolt info required

[Bee-Za]

Hi Guys'n'Gals

I'm fitting the rear brake leaver on my A10 GF
 
I'm looking for the thread size of the A10 swing arm rear brake pinch bolt. Its dia and if bsw or what.

Also what would you recommend as a fine thread metric equivalent as its only a pinch bolt.

I've tried to use the pinch bolt from the clutch leaver side but can't get it to fit as the brake pinch hole/tread may be damaged.

[idie]

Your pinch bolt is most likely 26tpi cycle thread. The one from you clutch lever if orginal would be 1BA. If a later replacement most likely metric.

[DAVE BRADY]

Hi,

Are you talking about the pinch bolt on the splined part of the brake pedal for gripping on the splined crossover shaft?

Dave.

[V500]

Sounds like it.
I'd go for 1/4 BSCy from memory.

[Bee-Za]

Yes, the pinch bolt on the splined part of the brake pedal for gripping on the splined crossover shaft and 1/4 looks about right.
I was looking at a 'Cycle tap die' sets but a tad too expensive at to justify £70 mminimum as I'm nearing 70 myself.

I've got metric. BSW and BSF tap sets. So I think I'll just metrify (new word for the dictionary) the bolt to 6mm or 1/4 bsw. Maybe a coarser thread but the splines are very coarse. Anyway bolt appears to be used mainly for side drift off the shaft.

Below is info from https://britishfasteners.com/threads-cei
Cycle Engineers' Institute (CEI) or British Standard Cycle (BSC)These are different names commonly used for the same threads. 60 degree thread angle, rather than the 55 degree of BSW and BSF. For sizes from 1/4" through 1/2" by far the most common are 26 tpi, although 24 tpi appear as well.

[DAVE BRADY]

Hi,

Have you tried a BSF thread?  I had 'Allen' type ones in mine so probably BSF.

Dave.

[Bee-Za]

Managed to get an old bolt to fit but having problems with the shaft being too short.
I think its too short because I may have fitted the engine plates incorrectly.
Is there a pic of the correct engine plate arrangement on the A10 s/a.
I've tried to attach a picture but keeps asking for a URL address so I can't add annything

[DAVE BRADY]

Hi,

The shaft goes through the hollow swinging arm spindle so engine plates will have no bearing on it.
The splines protrude just enough to get the brake pedal and the shirt lever on.

Dave.

[Bee-Za]

Thanks Dave the shaft fits ok now. But where does the return spring attach to return the rear brake lever.
Its 50yr since this was on the road and even then I had a Triumph Bonnie front and back wheels on it, so this is my attempt to get it with BSA front and rear wheels.
So I'm trying to identify what I've got.
I've got full width iron hub front and rear with the rear brake cable attached to RHS shaft which is ok. But its a question if its the proper brake lever

[DAVE BRADY]

Hi,

The spring hooks under the lever and behind the frame.

Dave.

[Bee-Za]

Ok that's cleared that up. I've got the wrong spring. Can I assume your brake lever is hard against the  hollow swinging arm , and the spring has the brake arm going through it. (i.e. the spring hooks onto the frame then travels a couple of times around the brake arm, then hooks onto the bottom of the brake arm acting as its return.)

[Bee-Za]

The brake arm I've got looks similar to yours with the extra tab for the brake switch. I noticed a part No of 4347 on the brake arm on the inside of the arm (had to burn off the power coating to read it). I've ordered a new spring which should be here on Wednesday..

[DAVE BRADY]

Hi,


Yes. Spring fits as you say.

Dave.