Drum to RS rear disc conversion

[Stew]

Well shoot, maybe I'll see if I can swing into a dealer tomorrow and see if they can provide any additional info. Thank you again and I'll let you know what I find.

I was skimming through a bunch of rear disc pics I'd saved, mostly from cruzetalk, and I think you're right. It looks like the cars that come with rear discs have a one-piece parking brake cable but the drum cars have a two piece cable.

In that case I may have to figure out some kind of adapter, I've already got something in mind but I won't be able to test it out until I do the conversion. Good times.

-------------------------

Edit: Wasteoffilm beat me to it. I'll crawl under my car to see how much of a pain swapping the whole cable would be, I guess it's either that or some kind of adapter.

 

[wasteoffilm]

The caliper to pin bolts are 8mm x 1.0 x 23.5mm, #13300856

 

[Stew]

Thank you for the help wasteoffilm!

I went ahead and ordered the parking brake cables and then placed another order for those bolts since I didn't see the bolt post until I had already ordered the cables, doh!

In for a penny, in for a pound... With these two part orders I doubt they'll get here in time for this weekend, will probably have to push it back until the following weekend.

 

[wasteoffilm]

You're welcome, and thanks for blazing the trail! I hope to do this soon, front and back.

What are your plans for the hard line between the upper and lower hose? If we're lucky, a little creative bending of the drum line will make it happen.

 

[Sneakerfix]

I just got everything but rotors hopefully this weekend I'll have it done.

 

[Stew]

You're welcome, and thanks for blazing the trail! I hope to do this soon, front and back.

What are your plans for the hard line between the upper and lower hose? If we're lucky, a little creative bending of the drum line will make it happen.

I need to look at that and see.

I just got everything but rotors hopefully this weekend I'll have it done.

Cool, take some pics and report back how it goes!

 

[Stew]

What are your plans for the hard line between the upper and lower hose? If we're lucky, a little creative bending of the drum line will make it happen.

Alright, pulled a back wheel off again to look closer and crawl under the back end to look at the layout of things. I honestly hadn't considered this being an issue up until your post.

First, regarding the parking brake cable, as long as the parking brake cables I ordered are the correct RS ones, I don't expect too much of an issue swapping those out. It will be a little bit of a hassle because of how they're routed and pass from the outside to the inside, but shouldn't be a problem.

Second, the brake line.

The hard line coming from the front connects to the flexible hose at the red circle, the flexible hose is of course to accommodate the suspension movement, it then connects back to a hard line in the rectangle where it then screws into the back of the wheel cylinder.

The RS flexible brake line is not long enough to connect at the red circle and still reach the caliper, and you can't connect it to the flexible line in the red rectangle because the threads are the wrong gender. Thus the creative bending that wasteoffilm was talking about.

This gives us two options. Either get a longer custom made brake hose, or...

Connect the RS flexible brake line to the end of the hard brake line that would screw into the wheel cylinder. I was able to fit my measurement caliper on the exposed threads and it looks compatible with the RS flexible brake hose. This may not be the most aesthetically pleasing solution but will give us the length we'll need and if we secure everything nice and neat should be 100% safe.

Thoughts?

 

[Stew]

Went back out and was looking at lengths, etc and if we cut the last length of hard line where I marked the red line just before the bend and re-flared the end to be in that location everything would fit perfect and look factory.

I've never worked with brake lines before, I might be up for giving it a go, I'm not even sure where I would go to have that done around here.

 

[Stew]

I think I have the ideal solution. Sorry for spamming the thread with posts, just wanting to make sure this is all figured out before I have my car taken apart!

Unscrew the hard brake line from the back of the wheel cylinder, bend/rotate that last 90* bend so it's pointing up. Everything will fit, no need to cut and flare brake lines, will still look reasonably factory to the unknowing eye.

Unless someone knows why this would not work, this will be what I do.

 

[Sneakerfix]

Is the disc brake line shorter then the drum line?

 

[Stew]

Is the disc brake line shorter then the drum line?

I'm not sure what all the rear disc brake lines look like on the Sonic so I can't say. On the drum cars there are a couple short sections of hard and flexible brake lines and I don't know if the rear disc cars have a similar setup.

On the Cruze the rear disc brake lines seem to be completely different than the Sonic, the Cruze flexible brake line looks like it's twice as long as the RS flexible brake line so that makes me think it's not even the same Cruze to Sonic.

The Cruze flexible brake line in this pic looks like it would easily reach from the Sonic caliper to the hard line in the red circle in my earlier post, but I don't know if the fitting on the end is the same.

Not sure if this helps or not, we need someone with an RS to take a bunch of pics of the rear discs and post them up!

 

[Sneakerfix]

I have the cruze lines if you need to test. Since I have a cruze not a sonic.

 

[wasteoffilm]

The diagrams show a shorter hard line on the disc brake setups. The hoses are the same from body to axle, regardless of brake system type. The disc brake cars have another hose from axle to caliper, considered a "lower" hose.

GM doesn't appear to sell the hard lines pre-made, they just list straight tubing kits. Depending on what type of ends the line has, you could likely buy a shorter line from a parts store that has the nuts and flares done already. I know every store I have worked at sells 8"/12"/20"/30" etc lengths. You need to know the thread diameter, thread pitch, length, tubing diameter and if it's a bubble flare or inverted flare. It is also common to have different fittings on each end, so check both.

Another thing I noticed last night, is that aftermarket lower hoses, at least from Dorman, are the same left/right, but don't include the mounting brackets. The GM hoses are different, because they do include the hose brackets.

 

[Sneakerfix]

So the easy fix would be to just extend the rubber brake hose a few inches

 

[Stew]

I have the cruze lines if you need to test. Since I have a cruze not a sonic.

Thank you for that, it looks like everything should fit pretty good using what I already have so it looks like I'm good. We'll see when I go to put everything on

The diagrams show a shorter hard line on the disc brake setups. The hoses are the same from body to axle, regardless of brake system type. The disc brake cars have another hose from axle to caliper, considered a "lower" hose.

GM doesn't appear to sell the hard lines pre-made, they just list straight tubing kits. Depending on what type of ends the line has, you could likely buy a shorter line from a parts store that has the nuts and flares done already. I know every store I have worked at sells 8"/12"/20"/30" etc lengths. You need to know the thread diameter, thread pitch, length, tubing diameter and if it's a bubble flare or inverted flare. It is also common to have different fittings on each end, so check both.

Another thing I noticed last night, is that aftermarket lower hoses, at least from Dorman, are the same left/right, but don't include the mounting brackets. The GM hoses are different, because they do include the hose brackets.

That is good to know, the lines are the same up until the very last hard line. If the existing drum lines will work by simply rotating that last 90* up, which it looks like it will, then I'll go ahead and do that instead of getting a different piece.

So the easy fix would be to just extend the rubber brake hose a few inches

Since you're doing this on a Cruze I'm not sure, can you post up a couple pictures of your existing drum brake lines? In your case, looking at that pic of the Cruze rear disc, you might be good just getting the Cruze disc flexible brake line, it looks like its got to be close to 24" long. Is that what you were asking?

 

[Sneakerfix]

The fix I was talking about would be for the sonic..

 

[Stew]

Still haven't received the parking brake cables but I really want to wrap up with this conversion. If the weather isn't totally awful this weekend I think I'm going to give it a go with the parking brake adapter I had in mind.

As long as the length of the drum parking brake cable cooperates, the stars and planets are in alignment and with a little luck this will hopefully work. It's actually really simple, dimensions are approximate for now, it will be a 3/4" H x 2" L x 1/8" thick rectangular piece of steel, which you can get at any hardware store. Cut/file it into a hook shape with a hole at one end like in the drawing below.

It should work like this: The drum parking brake cable will snap into the cable holder on the caliper, hook the drum cable end onto the hook, put an appropriate sized bolt through the hole in the hook adapter which will engage the parking brake lever on the caliper. Spring tension will keep everything nice and secure, just like in the OEM disc setup, there is no way the hook adapter will fail, there simply won't be that much tension on it, if everything actually fits together it will be 100% safe.

Any thoughts or ideas? Anyone actually tried this before?

 

[buickz]

I dont suppose the front brackets could be used on the back for this conversion? I hate to throw the front to the scrapper if they might have a chance.

 

[Sneakerfix]

I dont suppose the front brackets could be used on the back for this conversion? I hate to throw the front to the scrapper if they might have a chance.

No

 

[Stew]

Update: Hey guys sorry this is dragging on so long! My idea of that simple adapter just wasn't going to work but the good news is the special order RS parking brake cables arrived at the company I ordered them from so I should have them in around five days or so. I am REALLY hoping to do the swap on the weekend of Apr 25/26.

Almost there!