Question for those with front disc and rear drum.

[Lugnutz65]

If you have disc front and drum rear, what hard line are you running to the rear wheel cylinders? 1/4" or 3/16"?

I'm about to plumb new hard line. I'm keeping my original 1965 rear drums. I'm nearly 100% sure my rear drums have the stock setup with 3/16" hard line running back from the common 1/4" front drum line.

Has anyone switched their rear drums to 1/4" line? My new front disc brakes will be 3/16" line. The MC uses a 1/4" line for the rear brakes and I was thinking of switching the rear drums to 1/4".

[scoot_mcgrute]

I did factory replacement lines down the frame and on the axle and they are 1/4" on the frame and 3/16" from the tee fitting to the wheel cylinders. I'm running a 1" Wilwood master, 1/4" to the front calipers as well and seems to have good pedal thus far. I'll find out for real when I get it on the road soon

[canadian_diesel1964]

I have the 96 blazer set up and I'm 1/4 to 3/16 in the rear...3/16 to 3/16 split to front...worked great

[canadian_diesel1964]

By the way Lugnutz I'm dropping my T 5 in next week...the clutch is in..thank you your blog helped me a ton!

[jayoldschool]

My 65 was 3/16 from the front to all the way to the back. Don't think it will make a difference once you start swapping components. Just make sure you have your lines connected correctly.

[vetnat]

1961 GMC - I'm in the process of doing disc conversion on the front, keeping the drums in the rear. I have figured: 3/16 to the front discs, 1/4 from proportioning valve to rear brake hose, then 3/16 to wheel cylinders. Strange thing is, I ordered replacement rear axle brake lines from Classic Industries, and they sent 1/4", which does not fit. Waiting to hear from customer service.

[Lugnutz65]

Originally Posted by scoot_mcgrute

I did factory replacement lines down the frame and on the axle and they are 1/4" on the frame and 3/16" from the tee fitting to the wheel cylinders. I'm running a 1" Wilwood master, 1/4" to the front calipers as well and seems to have good pedal thus far. I'll find out for real when I get it on the road soon

The 1/4" to your front calipers may be unique to your calipers and booster. My CPP kit uses the very common early Chevy calipers. The CPP supplied brake hoses will only accept 3/16" line. Can't make 1/4" fit the front brake hoses.

Originally Posted by canadian_diesel1964

I have the 96 blazer set up and I'm 1/4 to 3/16 in the rear...3/16 to 3/16 split to front...worked great

I will likely end up with the same setup. Thanks.

Originally Posted by canadian_diesel1964

By the way Lugnutz I'm dropping my T 5 in next week...the clutch is in..thank you your blog helped me a ton!

I'm always happy to help. Glad my BLOG pages were useful.

Originally Posted by jayoldschool

My 65 was 3/16 from the front to all the way to the back. Don't think it will make a difference once you start swapping components. Just make sure you have your lines connected correctly.

I intend to examine a 1995 Chevy blazer rear brake line at the backing plate to see if it's 1/4" line or 3/16". Under the Blazer hood, everything runs through the PV and then into a block which I assume is for antilock brakes. Anyway, if the Blazer uses 1/4" to connect to the rear wheel cylinders then I might try to go that way too. I'd need to use wheel cylinders designed for 1/4" since I know mine are designed fro 3/16".

Originally Posted by vetnat

1961 GMC - I'm in the process of doing disc conversion on the front, keeping the drums in the rear. I have figured: 3/16 to the front discs, 1/4 from proportioning valve to rear brake hose, then 3/16 to wheel cylinders. Strange thing is, I ordered replacement rear axle brake lines from Classic Industries, and they sent 1/4", which does not fit. Waiting to hear from customer service.

This should work fine, especially with a PV in the system. However, if the PV was only designed for 1/4" line to the rear drums, then having 3/16" line mixed in will change the pressure that the PV sees. As I think about it, if there is 3/16" line anywhere in the rear brake line, then it's just like the whole line is 3/16". A 3/16" line has higher pressure than a 1/4" line which means that the PV will open earlier in the pedal stroke.

So I'm really only concerned about the rear brake line circuit. I'm concerned that if I use 3/16" line in the circuit with a PV that was intended to only have 1/4" line, then the PV will not likely function as well as it should.

[vetnat]

Interesting point, I agree 3/16 line anywhere in the circuit makes it like all 3/16 line. I'm not sure why the line going to the rear is 1/4, and then the rear axle line in 3/16. I'm using the proportioning valve out of a 1979 K-10, anyone know what diameter the rear axle line is in those trucks?

[scoot_mcgrute]

Originally Posted by Lugnutz65

The 1/4" to your front calipers may be unique to your calipers and booster. My CPP kit uses the very common early Chevy calipers. The CPP supplied brake hoses will only accept 3/16" line. Can't make 1/4" fit the front brake hoses.

For a frame of reference, I found that 65 used 3/16" lines while 66 was upped to 1/4". I bought the full brake line kit for the truck and set it up to work with the manual Wilwood master. I don't remember any adapters into the front hoses for the CPP disc brake setup but I did buy adapters, 3/8-24 male to 7/16-20 female, for a few other places in the system.

[racecougar]

I'm running 1/4" down the frame to the rear brake hose, then 3/16" from the tee on the axle to the wheel cylinders.

[vetnat]

Found this post over on the square body forums. It appears that those trucks had 1/4 line splitting into 3/16 for the rear. So, if using a proportioning valve made for a square body truck, should be golden.

Originally Posted by 1984Silverado4x4

These trucks use 1/4 in steel line along the frame rail. When it splits at the rear axle to go to the two wheels its 3/16 steel line.

Dont know what length you need. I just bought a couple of pre flared lines and if I needed any more just went back to the parts store and got what length I thought I needed.

A little warning with the pre flared lines though.
I replaced all the brake lines front to back on a teachers truck and every single one of the connections leaked because the second flare was bad so I had to reflare the lines myself.

The other trucks that Ive done I just bought a roll of brake line and cut and flared it myself.

[Lugnutz65]

Just an update for those who are following this thread.

I went to the salvage yard today and confirmed a few things about the 1995 Blazer brakes. The Blazer uses a 1/4" line from the MC to the PV and then to the antilock mechanism box. Then more 1/4" line along the frame rail to the rear brake hose. Then it changes to 3/16" from the brake hose to the rear drums. The Blazer front brake circuit is all 3/16".

Why all the fuss? Well I just wanted to make sure the Blazer PV would function properly since I plan to keep my 3/16" brake lines that are currently on my 1965 C10.