Brake Proportioning Valve?

Brake Proportioning Valve?

I've keep hearing people recommending swapping out the brake proportioning valve when doing a drum to disc conversion. I recently spoke to a guy who recently did a rear disc swap on his 95 celica and he claims that toyota told him both the rear disc and drum models had the same parts no. for BMC and proportioning valve. One of the reason I downloaded a Toyota EPC (Electronic Parts Catalogue) were to check that fact and sure enough it checks out. And not only that, the 93-97 corolla also has that same parts no. for the valve as well as the 88-92 models.. I've been told that when using a gauge to check brake pressure on a disc brake ae92 corolla vs. drum brake model the pressure on the drum models were significantly higher... Am I missing something here?

There is no rear disc on the '95 Corolla. I don't know for sure if there is a difference with the AE92 GTS with rear disc though.

You can just use a valve from a mid 90s Celica GT.

-Doc

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I just checked. It appears that the Celica GT and ST brake proportioning valve is the same.

Very interesting.

*edit* It looks like the one from the Corolla, Tercel, Camry, and Paseo might also be the same one.

part no. 47150?

Do you have the whole part number?

Check this out, taken from the '94 Celica BGB:

On the ST (rear drum), if the front brake pressure is 1138 psi, then the rear should be 604 psi.

On the GT (rear disc), if the front brake pressure is 1138 psi, then the rear should be 690 psi.

So, at least on the '94, it's different, but the drums get LESS brake pressure than the discs, so swapping to discs should NOT cause rear wheel lockup.

Okay now on the '98 Corolla: if the front brake pressure is 1138, then the rear should be 605 psi. So it's the same as the Celica ST, and in either case, the rear is getting less pressure than it would with the GT part. Which means that rear disc lockup is NOT an issue.

This is interesting: on the '97 Celica ST, if the front pressure is 1138 psi, then the rear should be 551 psi. The '97 Tercel is the same.

Here are some part numbers:

'97 Celica ST 4715020280
'97 Celica GT 4715020240

'94 Celica ST with no ABS: 4715020280

'91 Corolla Wagon: 4715012250
'98 Corolla 4715012240

'97 Tercel 4715012230

So, they are different, but the pressure is the same.

Well, that's a little confusing. For one thing, your buddy is wrong, the valve for the '95 GT and ST is in fact a different part number, and the pressure is different. But, the bottom line is that the whole "you need to swap your proportioning valve or your rear brakes will lock up" issue is way overrated.

Oh ok, I just figured out how to get the full part number from that EPC program and it does list a couple of different parts numbers. So the brake pressure is actually less on cars with OEM drum setups? Weird indeed. Thanks for the effort.

Milky, get in here!!!
Added: Oct 2, 2013 5:33 PM
after reading this now im really confused.

this. i believe i doing it right the first time so i dont have to come back and redo it later. i had never seen this thread before.

I ran my car with both BPV's and the 8th gen one NEVER locked up actually never really made the pads bite. Swapped to a ae92 gts BPV and the rears came to life, you actually saw on the disk(well the pitted ones i had) it was bitting more.

Make sure you have a good BPV some from junkyards maybe seized and may not deliver optimum performance.

well my bpv works great, i can feel all 4 wheels stopping much better

best mod ever, until i fix the parking brake tho

best Brake mod