ccannon222

I recently swapped my 4.10 diffs with 4.30s and upgraded to 199mm Tundra brakes. I used new rotors, pads, reman calipers, and wheelers SS brake lines. Durning the swap I had my rear axles out for a few days and my brakes bleed down (I capped the lines but it leaked). After putting everything together I filled the MC and used my power bleeder to flush all of the air and old fluid out of the lines. I took the truck for a test drive and the brakes were very soft. I bleed them again using the brake peddle pump method that I’ve been using for years. No air bubbles. I driven the truck twice and I made the ABS kick in on my gravel road hoping to break up any air pockets. Still no air coming out of the lines, all new clean fluid.
Any ideas? The truck stops good, but it requires most of the peddle travel to do so. For 11 years, my Taco’s brakes have been hard as a rock.

Thanks

Chris

4byrunner

This is a very tempermental upgrade. Seems like a lot of people don't have the soft peddle after this swap and some do and never find a reason why. Don't know if it comes down to just the luck of the draw but if it's not error in bleeding your brakes then most people just think it's a fluid volume difference between what the smaller stock brakes need and the bigger tundra brakes require to stop the truck. The bigger rotors/calipers require a larger volume of fluid in the lines/mc over the stock brakes therefore the brake peddle will travel further down before stopping.

My $.02 is try again to bleed them and get someone to help you out so you can make sure no air is getting into the MC from the fluid getting too low while bleeding the brakes.

I've read about too many problems like this happening and i scratch my head at why people mess around with their stock brakes. Braking is too important to mess around with just to do a mod on your rig. Good luck this!

sebastianholmes

get a larger bore master cylinder

ccannon222

My gut is telling me that I air in the system, either in the MC or the ABS actuator. I will try to bleed the MC again. I have been doing the bleeding with someone’s help making sure the MC does not get too low and I always use a tub off of the bleeder valve into a cup of brake fluid just to make sure air does not get pulled back into the system. However the MC did drain empty the couple days the rear axle shafts were out.

I’ve driven older 80’s Toyotas where people have put larger V6 calipers but left the stock 13/16 bore MC. Normal peddle feel, but much longer travel needed. My truck doesn’t have the normal feel, it’s very soft.

As for a larger MC, I checked 4wd tundra’s with these brake calipers they are calling for a 13/16 bore MC while the Tacoma has a 1” bore. I do not see how this is possible. I know the T100s with ABS had a 1 1/16 more MC. I could change to that to shorten the peddle travel. However, since my brakes feel very soft, and many others have done this upgrade without much change in the peddle travel, I do not feel this is the problem.

I checked my MC and there are not leaks, and I also stopped on a steep hill and held the brakes to see the peddle pressure would bleed down which it did not.

Current plan of attack:
1. Bleed again.
2. Make ABS kick in and bleed again to see if any air has been released from the ABS. As a side note, the ABS works normally.
3. Bleed MC again.
4. Ask my neighbor who’s a Toyota tech to bleed my brakes at work using their vacum bleeder.
Any other ideas?

Thanks

Chris

J2F42C

How did the calipers/pistons look before you put them on? I rebuilt both of my Tundra 231s before putting them on. You may want to try and remove the front pads, crack open the bleeder, and see how easy the piston can be pushed back in while noticing how easily the fluid flows out.

I would agree though that it seems as if you still have air in the system. Does the Tacoma have a LPSV? If air is trapped in the ABS actuator (at least in my experiences), usually bubbles are present in the fluid.

scuba

yes

doubletaco

I too had a very soft pedal after doing the tundra brake upgrade but it firmed up back to normal on its own after a couple of days.

ccannon222

The calipers I used were new remans and all 8 pistons moved freely. Thanks for the idea tho. Keep them coming.

The reason why I did the upgrade was because the stock brakes do not work well in the mtn's when I have a load of firewood on the truck.

Chris

warpigg

mine seem realy soft when you first press them then it firms right up but i dont have ABS ethier. my brakes were also soft when i first did it then i bled them more and its like it is now. i think mine are like they are because im using the regular MC.

ccannon222

Bleed them again and got a little bit of air out. Then I took it for a drive, kicked the ABS in, and bleed. No air. I'm gonna drive it a couple days and see what happens.

Chris

ccannon222

Update:

I've driven the truck a couple days and bleed it twice getting air out once. Then I noticed that the DS brake line banjo bolt was wet with brake fluid. Not enought for it to drip, just damp. I cleaned it off, tighted the bold down some more and bleed again. Now my brakes feel correct. The peddle is softer then stock and takes a little more travel, but it's no longer mushy.

I am planning on trying a 1 1/6 bore MC to see if it will stiffen the peddle and shorten the travel back to stock. If it stiffens too much, I'll just change it back. Overall I am happy with these brakes. I hauled a load of firewood yesterday and the truck stopped better than it ever has loaded.

Chris

BajaRunner

Sounds to me like you still have air in the system. I once broke my axle shaft down in Mexico and it tore off the entire drum brake. I had to leave it down there for a week with it "capped" the best I could (silicone).

When I got back and replaced all the parts, I had to bleed the entire system. Took like 2-3 hours until I got it back to normal. :/