13/16 or 3/4 on early 68 520 wheel cyls

[Ofeargall]

I have an old Chilton's and it says my wheel cylinder brake bore needs to be 3/4 but my front wheel cylinder has 13/16 stamped right on it. Which is it supposed to be? Does it matter?

Ed the Datsun Photo Gallery

[datsunaholic]

While the master should be matched to the wheel cyls, the only thing that REALLY needs to be matched (particularly on single-circuit brakes) is all wheel cyls should be the same size. You absolutely don't want mismatched ones on the same axle.

 

I've only been able to find 13/16ths in SAE recently, but I have found them.

[banzai510(hainz)]

I have mismatched sets on my truck. I didnt notice a reall difference.

Its up to you and how long you want to wait.

Japan made ones are the best if you can get them

the others I have seen are Italy and taiwan made ones. last about 5 years on daily driver

 

If I use the commone denominator method 3/4 = 12/16 so is 1/16 going to be a big deal from 13/16s?

[Ofeargall]

Funny story is I sat there at the parts store counter when they asked "13/16 or 3/4?" and did the mental math too. Now, mind you, I'm a photographer and I only know how to calc shutter speeds and f-stops so, I was stumped until I whipped out the iPhone and did the math. 1/16 didn't seem like a whole lot to me either. My biggest concern was that one would have SAE threads and the other would be metric where the flex line threaded in.

 

I did make a purchase, I hope they're not super bad... I should have researched the Japanese part. I went with NAPA because I didn't know if Rock Auto would have anything substantially better and I wanted to be able to take the parts back to a 'human' in the event they were the wrong size. The folks at my local NAPA are pretty good to me and I prefer to support a local business when I can.

 

I purchased a new MC, and clutch MC at the same time. I just ordered the clutch slave from Rock as well as 3 of the flex line (1 for each front brake, 1 for the clutch and NAPA couldn't get me the parts...).

 

Thanks for your help, guys. If you're ever in the Salem, Oregon area look me up.

[banzai510(hainz)]

yeah be carefull but I think the trucks are mostly SAE .

Mine worked fine.

[DanielC]

I know more about 521 truck, but not 520 trucks.

On a 521, there are both 13/16 and 3/4 rear wheel cylinders available. both sides of the truck should be the same. Rear wheel cylinders have two pistons the front wheel cylinders have only one piston. I have not seen a 3/4 front wheel cylinder for a 521, but they may be out there.

There is also a rubber hose in the brake system between the rear axle, and the frame of the truck. This hose is just as old as your other brake line hoses were, and may also need replacing.