Bolt On Subaru Master Cylinder Upgrade

Crow Horse

Well-known member
Just a couple of items that need clarification before I get into the nitty gritty?

*This upgrade is not my brainchild. This is Yankee Tim & Yankee Bob?s baby. They ?discovered? it and made it work so the credit that is due is theirs. I am merely the beneficiary of their research, testing, and generosity. I?m only documenting what I did for others to see. That said, thank you to Yankee Tim & Yankee Bob??

*The specific year/model Subaru isn?t cast in stone as of yet. From what I?ve found so far on Napa?s site is that a 1998 Legacy with ABS appears to be an exact match to the one I?m using. I?m sure there are other models/years that will work as long as it has a 1 1/16? bore.

*If you have the original brake proportioning valve, you might want to consider replacing it. I've had used a few "good" used ones, but they eventualy leaked. After all, they are nearly 20 or more years old. I once did a "autopsy" on one and discovered that they can leak internally for quite some time with no external sign of the leak. I replaced mine with a new one just to be safe.

A couple of items you?ll need:

Subaru master cylinder (1 1/16? bore for ABS) as compared to Suzuki's 7/8" bore

Subaru master cylinder wire connector Master cylinder to booster gasket (or RTV silicone)

Small tube bender

6mm x 1.0 bolt, app. 50mm long (grade 8.8 or better)

The swap:

Remove original master cylinder. Save gasket if possible (use old gasket as a template for a new one).
Reach into booster and remove the booster push rod.
Remove the ?tip? of the pushrod.
Cut the head off the new 6mm bolt. Clean up threads by ?chasing? with a die.
Round off one end with a grinder to make the new booster push rod tip. As an option, you can use a 6mm acorn nut, grind off the corners of the hex, then loctite it on.
The original push rod length was too short, so the new push rod will have to adjusted to the proper length. There needs to be zero tolerance between the tip and it?s mating surface inside the master cylinder. This will take a couple of minutes to adjust properly.
If the Subaru master cylinder doesn?t have an ?O? ring on it, swap the Suzuki one onto it.
Once the pushrod is adjusted properly, Bolt up the master cylinder after you?ve bench bled it. Use the gasket you cut or RTV.
Using a tube bender, bend the brake lines to mate to the new master cylinder.
Splice in a connector (Subaru) to the Suzuki wires.
Bleed the brake system.
Enjoy the improvement in braking.
 

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More pics of the swap almost finished.

The last pic is of a 2005 Impreza master cylinder.  Looks very familiar...... ;D
 

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The Suby MC increases the volume of fluid being pushed to the brakes.  The stock MC has a bore of 7/8" and the Suby one is 1 1/16".  The bigger bore is really important when you have rear discs or larger calipers on the front.

Kevin
 
Crow Horse said:
*This upgrade is not my brainchild. This is Yankee Tim & Yankee Bob?s baby. They ?discovered? it and made it work so the credit that is due is theirs. I am merely the beneficiary of their research, testing, and generosity. I?m only documenting what I did for others to see. That said, thank you to Yankee Tim & Yankee Bob??


Brain child!?!?  HA, more like brain-fart.  We do that alot.  Glad you like it, and sorry for the loooooonng delay in *finally* getting that M/C to you.
 
Yankee Tim said:
Brain child!?!?  HA, more like brain-fart.  We do that alot. 

Well, if that is true, I'd like to have you and Bob over for dinner.  The menu - beans, beans, and more beans.......

If you can fart like this, be my guest and fart away!

Thanks!
 
Is this more of an offroad upgrade where you need the better braking to stay put on rocks and such? I find that on the road especially wet or slightly wet pavement my brakes lock very easy sending me into a slide. Wouldn't stronger brakes sending me sliding ever easier? I'm sure a better wet pavement tire would increase my stopping...is it possible to be too light!?!?
 
RazorRodent said:
I swapped on the whole booster, mc assembly from my 4dr kick donor. It much larger and has the same bolt pattern.
  Do you have the M/C diameter from the Kicker M/C?  The number is underneath it on the end on the M/C.  I think it's only 1".
 
kick m/c looks to be 1" w/o abs and 15/16" w/ abs according to parts store
but booster might have bigger diameter so more assist  ???
 
zukiowa said:
kick m/c looks to be 1" w/o abs and 15/16" w/ abs according to parts store
but booster might have bigger diameter so more assist ???

It's not really the assist that's the problem as the stocker seems fine at that.  It's the increase in fluid displacement brought on by rear disc conversion and/or larger front Kicker calipers.

But, since bigger tends to be better in many, uh-hem, areas, why not swap a Kick booster and a Subie M/C together for a bigger set-up.

I'm off to the yard.
 
zuku26 said:
Is this more of an offroad upgrade where you need the better braking to stay put on rocks and such? I find that on the road especially wet or slightly wet pavement my brakes lock very easy sending me into a slide. Wouldn't stronger brakes sending me sliding ever easier? I'm sure a better wet pavement tire would increase my stopping...is it possible to be too light!?!?

This probably shouldn't be done on a stock Sami. If you have larger tires, or other break upgrades (4 wheel disk, tracker disk etc) it might be a good idea for you.
 
zukiowa said:
kick m/c looks to be 1" w/o abs and 15/16" w/ abs according to parts store
but booster might have bigger diameter so more assist  ???

I am gathering my parts to do a kick front / disc rear on my Sami.  Maybe I should get the kick m/c & booster as well.  I want to keep it as much Suzuki as possible.
 
zuku26 said:
Is this more of an offroad upgrade where you need the better braking to stay put on rocks and such? I find that on the road especially wet or slightly wet pavement my brakes lock very easy sending me into a slide. Wouldn't stronger brakes sending me sliding ever easier? I'm sure a better wet pavement tire would increase my stopping...is it possible to be too light!?!?

My 87 never had brakes that were as good as my 91.  My 91 was pretty much stock with just slightly larger tires.  My 87 has 30's and it carries an enormous amount of weight compared to stock.  If you're running larger tires and you aren't satisfied with your braking, the Subi M/C is a pretty good place to start.

My 87 doesn't see much off-road and is my daily ride.  It needs to be able to stop on a dime and give $.09 change......

At one time I had a set of Remington tires that I actually ran for 103,000 miles till they got too squirrely on wet roads.  When replaced, the tread was still legal.  I believe the reason I got that kind of life out of the was that they had a hard compound.  Good for longevity, poor for wet roads.....
 
How well will this mod work on my 2-door Tracker?  I'm looking to upgrade to the 4-door calipers and rotors soon and I'm thinking that it would be a good time to do this as well.  What do you guys think.

Also for those that have done this mod, how is it doing so far?

Thanks!!
 

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