front and rear wheel cylinder mounting bolt sizes?

[bloodysalmon]

I don't appear to have any bolts that fit the front nor rear brake cylinders to the back plates; what are the sizes and threads please?

[frenchblatter]

They may be UNF, try it.

[Steve Simmons]

1/4" UNF.

[Duncan M]

I seem to recall one size for front, and smaller in back.

[Marv]

Brake component were supplied by Lockheed (Now Delphi) Lockheed was all SAE threads try 1/4" and 5/16" fasteners, I believe they were fine thread 1/4-28 and 5/16-24. I think...

[bloodysalmon]

cheers for this, I didn't think of UNF ... doh! Now ordered 10 of each 1/4" & 5/16", both 1/2" and 5/16" long too

[frenchblatter]

Chris, kindly remember that I'm not far away and have stocks of UNF, UNC, Metric, Whitworth and BSF screws, bolts and nuts as well as washers. If you need anything just pop up and get it.

[Steve Simmons]

Oops, reading too fast and thought it was a question about fronts. I should stop browsing the web on a mobile phone. I agree rear are different and 5/16-24 sounds familiar.

[bloodysalmon]

Having bought 20x 1/4" UNF and 20x 5/16"UNF bolts I can confirm the 1/4" work fine but ... the 5/16" UNF bolts dont ... if fact they are not as good as the BSF 5/16 nor the M8 bolts ... whats going on?
Is it because the 5/16 UNF has the incorrect tpi ! I've looked around and I cant determine if there are any other 5/16" UNF that dont have 24tpi ... do you?

[Marv]

Chris: you say the 5/16 BSF seems better than the UNF 5/16 24. BSF is 22tpi Does it thread in all the way or hang up. The M8 x1.25 has 20.32tpi. The SAE size you may want is 5/16 - 18 UNC. There are other 5/16 SAE tpi's of 28 and 32 but these are highly specialized and fasteners are very expensive.

I'll pull one of mine and check the threads, will get back to you shortly.

[Marv]

OK Chris: I've verified it with mine. They are 5/16-18UNC not UNF Mine are fully threaded 3/4" length under the head with a flat and lock washer in tow. If your source is slow or unavailable, I can pop 8 or 10 in a packet and send them across the puddle for you.

brake cylinder bolt-front.png (292.64 KiB) Viewed 3650 times

[bloodysalmon]

Hi Marv, appreciate your input. I'm assuming 5/16"UNF default tpi is 24. If this is the case I suspect this is what I have bought ... but this was based upon assumption and no other obvious alternative.

[Marv]

Yes Chris, 24tpi is the standard UNF for 5/16" SAE. 18tpi is the standard for UNC SAE.
I am surprised that the fronts are 18tpi as most Lockheed brake components I'm familiar with use the fine thread pitch. They must have had a reason. Another thought is that BSW is almost a direct match in the 5/16"-18 size. Can't imagine that to be the reason but it may be. I did use my Whitworth socket to remove that bolt in the picture. But only because it was handy. If you can source 5/16" BSW, try it, I'll bet it works... otherwise, if I can help source SAE, let me know.

[bloodysalmon]

cheers for the update Marv, I did wonder what they were going to be. Crazy what ... rears 1/4"UNF and the fronts 5/16"UNC !!
I've just ordered a dozen 5/16" UNC bolts at 3/4" long which should be with me Mon/Tuesday, but thank you for the offer Marv