The slow process of fixing & upgrading my FC has come to the point where I have a 5 lug swap sitting on the back of my Subaru waiting for installation.

I'm getting stainless steel brake lines to go with it, because the factory lines are just old, and while they feel fine, I'd rather have something a bit more solid for track days.

One thing I've heard from several places, though, is that the 4-piston calipers are a pain to bleed properly. I've heard mention of having to take them off the mounts to be able to fully remove the air bubbles.

The ones I have are basically dry. They're in good shape, but they definitely have a good deal of air in them. Any suggestions on bleeding? Would speed bleeders help at all?

-=Russ=-

 

I didn't think it was that big of a deal...

 

I take a spare master cylinder cap although it's not hard to find something that works if you don't have an extra one, and drill a small hole in the top of it. I have someone go to each bleeder valve one by one and open it. I use an air compressor to blow into the hole in the cap of the master cylinder. This pressurizes the system and sends fluid out the caliper bleeds. Make sure to use low pressure. You don't need much. 10 psi is easily more than enough and possibly less. Pressurize it and have the other person open the line. Start at the farthest brake first an work your way closer. When they see no more air coming out of the line, they close it and move on to the next one. Make sure to watch you fluid level. It drops pretty quickly. This technique makes bleeding your brakes a few minute job. Very easy and you always get it right. You do not have to remove the calipers to bleed the brakes.

If you are doing a 5 lug conversion, you absolutely need to use the master cylinder, booster, and proportioning valve from the 5 lug setup as well or it will never stop good. The hard lines are th same.

 

i already have 5-lugs on my car got a mc/booster from an s4 automatic single pot and they stop just fine. The prop. valve would be good though.

 

I have never heard of anything about taking these calipers off the mounts. I just got done bleeding the two front ones I put on my car from my 4-piston caliper rebuild tutorial. Just the traditional 2 man method, although it took a while. That pressurizing the system method sounds like a nice way to speed things up though...

 

rotarygod is right i have a machine similar to that in my shop its called a automatic brake bleeder. The 2 man method is just as good...

 

What's the difference between them? I ask this honestly - I believe the 5-lug setup has a larger diameter master cylinder, but aftermarket suppliers use the same diameter for both. I can't imagine the brake booster operates any differently either. The proportioning valve is something I should look into, though.

-=Russ=-

 

The 5 lug brake booster is physically larger than the 4 lug booster.