Find Me a Brake Caliper?

Scheming future brakes for another rally BRZ- the brakes on the current rally BRZ work, BUT I go through 3 sets of rear pads to a single set of fronts thanks to the absurdly small pad area. 

Requirements:
-Fixed caliper (no slide pins)
-Cast iron (no aluminum because the gravel eats it)
-Tough (no external crossovers to damage)
-Availability (of both the caliper, and good pads)

The upgrade path for the fronts on a BRZ that needs to fit 15" gravel wheels and tires is simple, 4 piston WRX calipers fit up there just fine.  My current concept, if I don't come up with a better idea, is to ditch the stock parking brake drum and adapt front rotors to the rear hubs (for the much larger pad area) and just run the 4-pots on all four corners, but it would definitely be comically overbraked on the rear and require some goofy proportioning built into the system.

fixed mount *and* cast iron *and* small enough to make sense on the rear = unicorn.  IDK if that exists.  I've never seen one.

in theory, if the front caliper will bolt up to the rear knuckle, and center up on the rear rotor, you could machine some plates to weld onto the back of the front (now rear) pads to make up the gaps.  these plates would have to include the ears that engage in the abutment rails, so it doesn't just shuck the pads the first time you apply them.

*in theory*

Look at old ATE front calipers from 70s/early 80s BMWs (and probably other German cars). Two-piston fixed calipers, mostly cast iron, and fit under 13" wheels, so should be plenty small enough. The trick is going to be finding good rebuilt ones, or getting cores and rebuilding them yourself.

In reply to AngryCorvair (Forum Supporter) :

I'd just put the entire front setup on the rear and size the master cylinders appropriately- whole front 4 piston caliper, rotor, pads, in the appropriate relative positions.  I'll need wheel scraper brackets back there anyway so I can build a bunch into the adapter, it'll just be way bigger than strictly needed.

Early Vanagons have a cast fixed caliper with 2" pistons that go over non-vented rotors. Not a huge pad, though, and pad choices are mundane. 

What if you put some ducting on your rear brakes to keep the temps lower?

01-05 Lexus IS300 Rear Calipers might be an option

Or 98-05 Lexus GS / 2001-2010 SC430 Rears

Keith Tanner said:

What if you put some ducting on your rear brakes to keep the temps lower?

Possible but difficult, especially to keep it from turning into a dirt funnel.  I'm also not sure they're actually getting too hot, I think it's just wee little pads doing their thing appropriately but running out of material a lot faster than the 3x larger front pads.

HotNotch said:

01-05 Lexus IS300 Rear Calipers might be an option

Or 98-05 Lexus GS / 2001-2010 SC430 Rears

 

Ooooh, these look the closest so far.  Non-vented rotors back there though so they're narrow, but these cover many bases and come from a parts bin that I like.

¯\_(ツ)_/¯ said:

HotNotch said:

01-05 Lexus IS300 Rear Calipers might be an option

Or 98-05 Lexus GS / 2001-2010 SC430 Rears

 

Ooooh, these look the closest so far.  Non-vented rotors back there though so they're narrow, but these cover many bases and come from a parts bin that I like.

/runs to rock auto

yes.... these look niiiiice

[i

In reply to AngryCorvair (Forum Supporter) :

I guess I will also ask you, as our resident brake expert, if there's really anything wrong with oversizing the rear calipers and running a 5/8" MC up front and a 1" MC to the rear to get the bias around where it should be again?

As 02 said, BMW e21 front calipers meet those requirements.  1977 models were made for a vented rotor but are harder to find.  Biggest concern to me would be pad choice.  

Is it possible to add rim scrapers?

They should take care of most of the debris and possibly open up the choice of calipers to include Al?

Alternative scraper layout.

¯\_(ツ)_/¯ said:

Keith Tanner said:

What if you put some ducting on your rear brakes to keep the temps lower?

Possible but difficult, especially to keep it from turning into a dirt funnel.  I'm also not sure they're actually getting too hot, I think it's just wee little pads doing their thing appropriately but running out of material a lot faster than the 3x larger front pads.

Maybe pull from an upper surface? Keeping that material cooler will help them last a lot longer. 

In reply to Lump :

I have wheel scrapers and will definitely have them again- as far as I know the aluminum calipers still expire eventually, though.  Ultimately it's a safety issue, I'd rather not lose rear brakes in the middle of a rally just because my scraper didn't hold up.

Lump said:

Is it possible to add rim scrapers?

They should take care of most of the debris and possibly open up the choice of calipers to include Al?

yes but I think he doesnt want to. Mine worked great for LSPR but it was less muddy than I was anticipating too though. 

In reply to fidelity101 :

I'm fine with them, but if I'm changing the rear brakes anyway it doesn't hurt to consider all the options.

I *almost* hate to say this, but 

Jaguar.

When I recently redid the front brakes on my xj6 (1987, old style) I noticed the calipers were legit. 4 piston, fixed, super easy to replace pads with slide pins, internal fluid passages, I believe they are made of cast iron, and the stock jag wheels are 15s. Because I think this part is the same jag caliper as comes on xjs and maybe even xke, there are plenty of racing pads available. 

I also think it may be the same part for both sides, just with the bleeder in the other port. 

I almost think some wilwood circle track brakes are basically jaguar calipers. 

¯\_(ツ)_/¯ said:

In reply to AngryCorvair (Forum Supporter) :

I guess I will also ask you, as our resident brake expert, if there's really anything wrong with oversizing the rear calipers and running a 5/8" MC up front and a 1" MC to the rear to get the bias around where it should be again?

does the 5/8" bore MC have enough stroke to feed a pair of 4-pots?  and do you have enough pedal travel available to accommodate it?  i assume the car is plumbed front/rear?

In reply to AngryCorvair (Forum Supporter) :

Unsure, I know the standard for these is a .7" front MC when using a dual master/bias bar setup.  Front/rear plumbing, fully manual.

In reply to Robbie (Forum Supporter) :

Those are even huge-er than the WRX 4-pot fronts!  Interesting option for sure for something.

doh, rereading a little more carefully and maybe you dont want the big jag fronts. The rears would probably work for you too, and they are shared across more platforms

Also, you can tell people you are running "ferrari", "lamborghini" or "cobra" brakes. 

86-95 Toyota 4x4 (and maybe 2wd?) front calipers look awful similar to the Jag Stuff.  I know the late T100 Pickups had the largest pistons.  Might be too big, size wise, though.