Rear drum to disc conversion question, Do I need to do anything with the master cylinder? Options

[alltracman78]

I've done the drum to disk swap on 2 cars and neither needed a different valve.
The GT and ST master cylinder are the same.
All of your ST stuff will work fine except you need (GT) the backing plate w/e brake assembly, rear disks/pads/calipers, the rubber lines, and the cables to the e brake handle (all GT stuff).

The GT and ST master cylinders are NOT necessarily the same.
With ABS is the same, and without ABS is the same.
If you have a GT w/out ABS and an ST w ABS the master cylinders are different.
Most likely the difference is the size of the piston, just like in the 5th gens.

Also, rear drum and disc brakes DO require different pressures to work correctly.
This is why there are different part #s for the different P valves.
It doesn't mean your brakes aren't going to work if you don't use the correct valve, but most likely they will work better if you do. Toyota didn't design them different just to spend extra money....

^I have all of that stuff you listed. It was the proportioning valve that came into question; it's my understanding that it is not something that is required for the conversion, but if swapped, will increase braking efficiency.

Exactly

[hurley97]

I believe the only difference in the master cylinders is the amount of lines that come out of it. There still could be internal differences though.

Either way, the master cylinder and proportioning valves for the ST work just fine with GT brakes. I did not change either, which could possibly be why I really didn't feel a huge difference in braking power from the ST front/drums to the GT front/rear disc setup.

The complete GT setup does look much better though, especially with bigger wheels. With the ST fronts and GT rear discs I felt like the rotors appeared to be the same size between front and rear which looked very strange to me.

This post has been edited by hurley97: Jun 16, 2008 - 8:34 PM

[GriffGirl]

Saturday's the day! (bagging the P-valve for now, just wanna get it done)

Any last minute tips/advice from anyone?

[GriffGirl]

DONE!

[BloodyStupidDave...]

DONE!

Prove it. No pictures, no step-by-step how to = didn't happen

[GriffGirl]

I'd love to, but currently my car is with the self-professed Window Tint King of Portland, having its windows tinted!

Pix likely tomorrow, Wednesday at the outside. I could take pix of the nasty bruises on my forearms that prove I've spent a quality weekend with my car, wrestling with the bumper (high beam replacement) and installing said brakes, rebuilding seized calipers (mmm, good times)... I need more iron in my diet, I think, these are some nasty bruises!

[DEATH]

You've risen another rung on the tuner ladder Griffy - congradulations. Now about that tiny motor...

[GriffGirl]

Yeah, that's what she said.

[DEATH]

I believe "pathetic" was the term used

[CelicaST_CALI]

so deaths hows that 20 mpg going

[GriffGirl]

[xs94st]

good job with the conversion griff

can't wait to see pix, as this is the summer of celica lovin

my rear drums are shot to hell, so i've been savin up that $$ n orderin stuff slowly but surely.

also, i don't mean to hijack the thread, but seein as there are a few people online, in reference to the conversion from drum to disc with abs, is it any harder than without? also, my ABS isn't functional at the moment..

[GriffGirl]

I don't actually have ABS, although I don't think it would be any harder than without ABS. I imagine you would use the sensors that are on your car already. They actually detect wheel speed, so it stands to reason that they control the application of the brake regardless of being drum or disc. However, I don't know this for a fact. It could also be that ABS on an ST only has wheel speed sensors on the front wheels, since that's where the majority of your braking load is anyway. Do GTs have wheel speed sensors on all 4 wheels? It seems like I read on here they do. . . IDK.

[Batman722]

glad you did the conversion

GTs with ABS have sensors at all 4 corners.

[GriffGirl]

DONE!

Prove it. No pictures, no step-by-step how to = didn't happen

[BloodyStupidDave...]

Awesome work, Michelle. And I know you are still in pain about that electric windows conversion but it is great to see new things being tried and such mods do put you in a different league.

I guess a little pain is the price of innovation. Hopefully with time you'll enjoy the mod and decide it was worth the effort and hopefully others will follow where you lead and find it easier with guidance than you did working blind.

Still looking for that how-to .

[alltracman78]

Awesome, glad to see you got it sorted out.

also, i don't mean to hijack the thread, but seein as there are a few people online, in reference to the conversion from drum to disc with abs, is it any harder than without? also, my ABS isn't functional at the moment..

Lines in the rear are the same either way, the difference is in the stuff up front.
The only potential problem I can see is if you need different knuckles, you'll need to make sure they're for ABS so they will hold the sensors. I'm assuming you can use your old wheel bearing assy, if not you will need ABS ones for those too.

I don't actually have ABS, although I don't think it would be any harder than without ABS. I imagine you would use the sensors that are on your car already. They actually detect wheel speed, so it stands to reason that they control the application of the brake regardless of being drum or disc. However, I don't know this for a fact. It could also be that ABS on an ST only has wheel speed sensors on the front wheels, since that's where the majority of your braking load is anyway. Do GTs have wheel speed sensors on all 4 wheels? It seems like I read on here they do. . . IDK.

All Toyota cars have 4 wheel ABS, only some early 90s trucks have 2 wheel ABS.

This post has been edited by alltracman78: Jul 13, 2008 - 5:29 PM

[GriffGirl]

Awesome, glad to see you got it sorted out.

All Toyota cars have 4 wheel ABS, only some early 90s trucks have 2 wheel ABS.

Thanks, me too! I'm totally happy with my new brakes. They did AWESOME on my road trip down to Vegas and up through California. We drove up Hwy 101 home (the coastal highway - LOTS of steep curves, mountains, etc!) and the brakes just did great. They felt totally solid. Gotta love that kind of security!

As for the ABS - makes total sense. My last car was a '92 4Runner, which is what I was basing my ABS question on originally.