MR2 Brake master and proportioning upgrade

[Joshstix]

This is a copy of my post in the AW11 owners thread but I though it might come in useful for other MR2 owners so I've moved it over here for reference purposes.

Without strut brace:



With strut brace:



Yes I know my strut tops are poked

Details.

It's a Landcruiser 1 inch master cylinder, aftrermarket part number TJB1879.
We also have a B&M Line lock and a Wilwood proportioning valve.

The piston area of my current calipers, ST185 single piston fronts and SW20 Gen3 rears is ~1.29 times as large as the original AW11 parts. A 1 inch master cylinder has a bore area 1.3 times as large as the stock 7/8's master cylinder so it should bring it back to stock pedal feel. It turned out my master was leaking a little so the new one feels even firmer than I expected, it is quite nice though.

You can't see it in these pics but I completely removed the stock proportioning valve a while ago, replacing it with a T piece for the fronts and a straight through connector for the rear. Even then my bias was all messed up due to the extra weight and grippy tyres in the back.

The current hydraulic line layout has the pipe that was going between the proportioning valve and the rear breaks shortened and connected straight to the master cylinder. The pipe for the front brakes comes out of the master then curls down towards the buard and up into the proportioning valve. Then up out of the proporting valve into the line lock. Then down out of the line lock and across under the master cylinder to the T piece to split into the two front lines.

As you can see the Landy master cylinder has the lines connecting on the opposite side to the AW11 one which was ideal for me to mount my line lock and prop valve between the master and strut tower. I used one of the stock captive nuts on the strut tower and a single hole drilled to mount a nutsert to secure the prop valve and line lock.

For those just looking for a bigger master there are some hilux and/surf etc masters in 15/16 and 1 inch that bolt straight up to the stock booster with the hydraulic lines on the same side as the stock AW11 master. This should make it a plug and play fit without even needing to reflare any lines.

[merc-blue]

Mate very intresting. more info on your brake setup would be good, i couldnt quite follow it in the AW11 anon thread.
I have just bought a early model, im thinking instead of going late model brakes i will do a more radical upgrade, as the car will see abit of track work in the near future, saw thinking of using 944 calipers just for equivilent size and pad availablility and how available they are

[allencr]

For reference purposes,

Don't do this if it doesn't have a huge rear weight bias

The pipe for the front brakes comes out of the master then curls down towards the buard and up into the proportioning valve.

Joshstix, you're right, no I haven't seen yours or worked on anything that would need this 'cure' except a kart.

[Joshstix]

For reference purposes, if you drive & want it to stop as well as it can and especially to not lock up the rear brakes & swap ends,

DO NOT

The pipe for the front brakes comes out of the master then curls down towards the buard and up into the proportioning valve.

BULL

It currently locks the fronts extremely easily, with the proportioning valve adjusted to limit front pressure by a very small amount. The AW11 has serious issues with lack of rear brake bias and with my brake configuration it was much worse than stock.

With a completely gutted stock proportioning valve, ie giving full effect of the master cylinder to front and rear brakes the car locked the fronts so easily that it had trouble passing the brake test for a pink slip unless you very gently increased the pedal pressure.

Sure on most cars running a proportioning valve on the front brakes is the opposite of what should be done but don't tell me that it will swap ends because of this in my car. I know, from testing, that with no proportioning the rear does practically no work and the fronts lock up much too easily. Therefore to get the car to stop as well as it can we require less bias to the front which is the purpose of the proportioning valve.

Can I ask how much experience you have with the braking systems of MR2's or mid engine cars in general? I see from your profile that you have an AE86 and a FWD rolla. Sure in those cars there is no need to reduce front brake bias as they have no weight in the back, a mid engine car is the opposite.

[Joshstix]

As to the question of what my brakes actually are:

Fronts
ST185 Single Piston calipers
Redrilled ST185 front brake rotors

Rears
Late model SW20 turbo calipers, part number 22V-R
Front AW11 rotors with a spacer between the hub and rotor

Oh and a big thanks to Rod for helping me out with flaring pipes and things to get this setup installed.

[merc-blue]

Sorry for contuing the OT but do they fit under 15"s i have seen conversions with 205 4spots which need 16s, but i would prefer to be able to run 15s (can get cheap 1/2 worn advans)

[YLD-16L]

Nice write up Josh.

Out of interest though regarding the MR2 rear calipers, did you buy them new or second hand? (your part number quote is making me think you went for new ones).

[Duk]

Great info . So the late model SW20 turbo calipers have the same bolt spacings as the AW11's?
merc-blue, I also have ST185 GT4 brakes (big single piston calipers) and they fit inside the 15's I'm using, but not inside another set that I have, so the answer is a deffinate maybe

[Joshstix]

I pulled the rear calipers off the half cut actually, then rebuilt them to use in my current setup. I only specified the number because it's actually cast into the caliper itself, and I get asked all the time on other forums.

For wheel fitment, that one is really dependant on the wheels themselves. With my 16's if I put metal valve caps on the front they hit on the calipers, as I found out when it raped my valve stems on the way to the drags in Dubbo.

And yes the SW20 calipers bolt straight up to the AW11 rear hub carrier. The caliper mounting tabs on the hub carrier aren't as long as on the SW20 carrier though which is why I ended up running a smaller rotor than the SW20.

[YLD-16L]

Thanks for that info Josh, I was kind of hoping you'd say you had picked them up from Toyota for $20 each

I'd imagine they are not too easy to come across second hand? I'm toying with the idea of using a set mainly because of the integrated handbrake mechanism in the caliper and that they are wide enough for vented discs.

[Joshstix]

The grass is always greener

I've been trying to figure out how to get rid of the integrated hand brake.

[Duk]

The grass is always greener

I've been trying to figure out how to get rid of the integrated hand brake.

Stimple, use AW11 front calipers.

[merc-blue]

ok one more question SW20T fronts or rears?

Sorry had brain fade.
to have a handbrake they must have been rears.
confirmation woudl be handy though

[Joshstix]

Yes they're Gen 3 MR2 turbo rear calipers.

[merc-blue]

Josh just curious what series landcruiser the MC is off?