1st Gen Brake master cylinder upgrade?

Hey all
I recently did the Tundra 231mm caliper mod in my 03 3rz. Now my brake pedal feels very mushy and I didn’t notice any difference in stopping distance. I have bled the system at least a half dozen times.

I have heard a rumors of an upgrade from the oem master cylinder to a larger master cylinder. When I googled around on the topic I got very conflicting info so I thought I would ask here. Any info would help. Thanx.

 

I haven’t heard many people doing a new master cylinder, but I’ve also never hears of someone doing the tundra brakes and not noticing a significant improvement in power. The softer feel is common from what I’ve seen, though.

I wonder if a tundra master cylinder could fit...

 

I head something like some tacomad have a 3/4” master cylinder and they swap it to a 1”

But idk where i read that

 

I have heard various ideas that the oem master cylinder has a 7/8” or 13/16” barrel (seems odd it isn’t metric but 25.4 is your friend ). Others say the tacos with the 5vz had a bigger one than the 3rz. This doesn’t seem to be the normal google search and a thousand other people have already done the mod type deal like normal

This is a hot topic to me because I am going to put the LC engineering supercharger on my 3rz and use my truck to pull a small trailer for my business. Thanks to everyone.

 

So after a little digging around it appers tacomas already have the 1” bore.
The size should be stamped on it I believe.

The upgrade is for older model pickups and 4runners.

But i guess you can use the one from a Fj80 (also a 1”) if you wanted to convert to disc breaks in the rear of the tacoma. Idk if that will do anything if you stay drums.

Your only hope is for tundra breaks up front , and a break controler for the trailer (with a trailer that has breaks of course)

 

Thanx for the info. I may go the FJ80 MC route and look into rear disc brakes.

Does anyone know if there is a kit offered that will keep the ABS functional and work with the emergency brake. I had heard this was an issue with some kits.

 

Idk about abs, but I believe the rear disc break conversion requires you also running a 2nd small caliper for the emergency break or a line lock. Or just swap to a fj80 axel.

 

Ok after some more digging i found you can use a gm 1.25” master
http://www.lowrangeoffroad.com/toyota-booster-to-gm-master-cylinder.html
This is normally only used for sas swaps that have large calipers. so idk how it will do on ifs with stock calipers and stock drums

 

I appreciate all the response. If anyone has any other lines on a disc brake conversion don’t be shy. Less than a year ago I just dropped over a grand into a TRD elocker swap so if possible I would like to upgrade the brakes but keep the axle I have.
Thanx for all the help.

 

"The bigger the master cylinder is, the more fluid you get but less pressure at the caliper. The smaller the master cylinder is, the less fluid you get but you’ll have more pressure at the caliper. Think of it like putting your thumb over the end of a water hose. As your thumb decreases the amount coming out of the hose, the more the pressure increases."
https://www.daymotorsports.com/info/technical-info/article/difference-in-master-cylinder-bore-sizes

https://www.joesracing.com/rt-4172-master-cylinder-math.html

Putting a larger master cylinder on your truck will make your brakes feel even softer. If you want them to feel the same, you actually need a smaller bore cylinder. There have been a few people on here that actually swapped to a larger cylinder with poor results.

 

Chasing this possible MC upgrade. Anyone confirm this? ^^^?

it’s the volume that is not sufficient, not the pressure - so it tracks that a slightly higher volume unit could help.

 

I have a ‘swapped Subaru’
1998 2dr Impreza body
2005 STi everything else

in 2007 when swap completed
Way mushy brakes
With
Larger Brembo calipers/STI mc/STi abs pump/PCM but 1998 booster

I swapped the STi booster in 2008
Perfect since

IMO
If you start swapping brake components from another compatible vehicle, change everything major component