Using a smaller MC in KE70 after removing brake booster

[poissondavril]

Hello guys, just registered for some info on the above.

The current / standard MC has a 13 / 16 bore iirc, while the KE30 MC is 3/4. Has anyone tried using the 3/4 MC in their KE70 after removing brake booster, to help give it a softer pedal? Any potential issues with this?

Also, first time doing these things, what other parts of the assembly will I have to modify for this...

Tried a search function and found a thread that talks about removing brake boosters, but not so much the step by step to then modify the assembly as necessary.

Feedback much appreciated and thanks.

[lexsmaz]

My first thought is why do you want to do this .. I don't know where you live but if its in Australia there is no way it would pass a road worthy as playing with brakes like that is a no no unless you get it engineered & doubtfully they would pass it either ??

If you take off the Brake booster you will have to bolt a metal plate on the firewall to then mount the brake master to as there will be a fair sized hole in the firewall once you remove the booster & then you have to try & work out a suitable linkage rod to the brake master cylinder as you wont be able to use the brake booster one or not without altering / lengthening it, I'm assuming the KE30 doesn't run a booster you could use that link rod maybe ?? ..

Running a smaller master cylinder will help the pedal effort as you have removed the booster but it may still not be enough & the pedal still could be quite hard to push ?? ( apply the brakes hard ) if you go to small in the Master cylinder you will have increased pedal travel though ..

[jondee86]

Yes... driving the car (in some place without other traffic) with the booster vacuum hose disconnected, will demonstrate the kind of pedal pressure that will be required after you delete the booster. Changing from a 13/16 to a 3/4 MC will reduce the piston area by 15% and increase the system pressure by 17% for the same non-boosted pedal effort. The pedal travel will also increase by 17% to move the same volume of fluid.

Here are a couple of booster delete plates for other Toyotas...



And this thread is worth a read...
http://www.dorikaze.net/showthread.p...Booster-Delete

Cheers... jondee86

[SHEPPO3930]

7/8" datsun dual circuit master cylinder, sold by Datsport. You'll need an adapter plate to make it work. This is what i am using on my TA22, check out by build thread.

[Xauterus]

You can also get remote mounted boosters like vh44.

[poissondavril]

Cheers for the responses and recommendation guys, am also reading up on some of the related threads here before I proceed.

I'm in Malaysia at the moment and thinking of doing this mainly for the pedal feel and control lexsmaz, I've driven it without booster assist before. It's just that it was a little too hard for emergency braking, so was thinking of ways to reduce a little the pedal pressure required without having to go back to using the booster.

[oldcorollas]

KE70 and KE30 have same size caliper pistons., and I think KE20 does also, but can't remember if KE20 is boosted?

KE10 has unboosted, and it's dic brake caliper pistons are 10% smaller than the KE70 pistons..

running KE10 MC with KE70 calipers, and KE70 disc (218mm), gives a pretty firm pedal that needs a good push
I believe KE10 MC is single circuit 11/16"

the early Mitsu/Chrysler Galants (GA to GD) had dual circuit unboosted masters with both 11/16 and 3/4"... and they fit pretty easy into KE10/20's..

[Bananaman]

KE20 is not boosted standard

[oldcorollas]

thanks

other way to reduce pedal hardness is.. much larger discs

[allencr]

Softer pads.
Most if not all PB/non-PB cars have a much more different MC then 1/16(Thank You jondee86!) of an inch, but if you're not an average driver or an old lady, It'll be fine.
Also, if your experience I've driven it without booster assist before. It's just that it was a little too hard for emergency braking, is in another car or yours with the booster/servo disabled, or broken/engine not running/no vacuum source kind of experience, then it will not be similar. Gut It.