Brake Issues With TBU

[DrewZ28]

So I've done a good amount of research and can't find a lot of information on the issue that I'm having. I'm wondering if anyone else has ran into this. The brakes work and will stop the truck, but not very efficiently. I cannot get the pedal to be firm. It is soft for about the first half a travel then semi-firm. The brakes will stop and the truck will not start rolling with the brakes applied. The pedal does seem to slightly sink though. It feels like I am not getting enough hydraulic pressure to the front in all honesty. The master cylinder has been replaced and has less than 1000 miles on it. I used a new Aisin master. Both front and the rear rubber lines have been replaced with braided Steel. The rear brakes are all 100% brand new including the wheel cylinders. The front brakes have less than 1000 miles on it. I have the Tundra 13WL calipers and Power Stop drilled/slotted rotors with the Z34 heavy duty pads. I have bled the system multiple times and I am positive that there is no air in it. I have been told that with the Tundra calipers the stock master cylinder cannot push enough fluid to push the caliper Pistons enough which would cause my issue. But I also have read multiple threads of people running this brake setup and having no issues at all. In fact I read that a lot of people notice their truck stops a lot better than stock. Just wondering if anybody has had this similar issue with the Tundra brakes? Or maybe should I switch out the master cylinder with an OEM one? I have been recommended to remove the Tundra set up and go back to stock brakes. I would like to keep this setup if I can get a firm brake pedal. Truck is a 97 Limited 4x4. Any input it is appreciated!

 

[brillo_76]

I Use the other Tundra brake calipers 13WE not the 13WL as those are a much larger calipers and seem to be spongy because the volume of fluid is different.

My build thread has the comparison between the stock 13WE as they are the closest to the OEM stocks. The larger calipers[13WL] will not fit alot of stock 16 inch rims. Startin around post #335.

I am very happy with my 13WE tundra calipers. Work just the same or better then. The stock oem and my pedal seems the same.

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[RandyBobandy]

You probably don’t have all the air out of your system, try activating the abs on a gravel road several times and bleeding the brakes again. I know the larger tundra calipers are known for a softer pedal but you shouldn’t have reduced braking performance. Since the master cylinder was replaced there is almost certainly air in the abs pump if you haven’t activated it before bleeding the brakes

 

[DrewZ28]

I Use the other Tundra brake calipers 13WE not the 13WL as those are a much larger calipers and seem to be spongy because the volume of fluid is different.

My build thread has the comparison between the stock 13WE as they are the closest to the OEM stocks. The larger calipers[13WL] will not fit alot of stock 16 inch rims. Startin around post #335.

I am very happy with my 13WE tundra calipers. Work just the same or better then. The stock oem and my pedal seems the same.

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How much bigger are the 13WE calipers over the stock Limited calipers? If I swapped to those from the 13WL, I'm guessing I'll need new pads, but will the rotors still work? Also, I saw on RockAuto a 13WG caliper. Is this a different one, or did they miss-print 13WE?

 

[DrewZ28]

You probably don’t have all the air out of your system, try activating the abs on a gravel road several times and bleeding the brakes again. I know the larger tundra calipers are known for a softer pedal but you shouldn’t have reduced braking performance. Since the master cylinder was replaced there is almost certainly air in the abs pump if you haven’t activated it before bleeding the brakes

I have before will no difference, but maybe I'll try it again. Not sure why that needs done on these trucks, but not other vehicles?

 

[brillo_76]

How much bigger are the 13WE calipers over the stock Limited calipers? If I swapped to those from the 13WL, I'm guessing I'll need new pads, but will the rotors still work? Also, I saw on RockAuto a 13WG caliper. Is this a different one, or did they miss-print 13WE?

They use thicker rotors then OEM. Same diameter as the stock 199mm as your rotors are probably 231mm.

They are I believe the same size as stock just accept a lot wider then stock rotor. Look at my build thread for comparison as I have photos showing the rotors and calipers from stock and my replacement 13WE.





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[jaher]

You may find this thread helpful. I personally choose the 13WE because there were less reported ABS issues. It doesn't exactly discuss soft pedal issues, but I assume there is a correlation.

231mm / 199mm Tundra Brake Upgrade ABS Function Survey

 

[DrewZ28]

Let me make sure I got this straight. Being a Limited I had the larger 4Runner brakes to start. Upgrading to the 13WE Tundra brakes keeps the same size pads and same diameter rotor, but takes a thicker rotor which helps resist warping. The brake pedal and ABS still feel and act as stock. Upgrading to the 13WL Tundra brakes use the same rotor as the 13WE calipers, but adds larger (longer) pads. But being a larger caliper, they hold more fluid, which makes the pedal feel soft and can mess with the ABS operation. Is this all correct?

 

[Bad Luck]

Let me make sure I got this straight. Being a Limited I had the larger 4Runner brakes to start. Upgrading to the 13WE Tundra brakes keeps the same size pads and same diameter rotor, but takes a thicker rotor which helps resist warping. The brake pedal and ABS still feel and act as stock. Upgrading to the 13WL Tundra brakes use the same rotor as the 13WE calipers, but adds larger (longer) pads. But being a larger caliper, they hold more fluid, which makes the pedal feel soft and can mess with the ABS operation. Is this all correct?

13WE and 13 WL calipers have the same piston size so there will be no change as long as nothing else changes in the brake system. Both calipers use the same rebuild kit. The brake pad backing plates for the two are different sizes, but the brake pad material is roughly the same foot print between the two. TBU 231mm vs. 199mm Pad Size

EDIT: To further elaborate why your pedal feels the way it does, your master cylinder is putting out the same volume but the brake caliper pistons are larger so they require more fluid to move the same distance as a smaller brake piston would. This results in a further brake pedal travel and less foot pedal effort. The textbook correct way to do this upgrade would be to get a larger master cylinder as well which some people have done, but it requires a lot of work to either find a compatible/bolt on master cylinder or make an entirely different one work by either changing the booster and/or deleting ABS.

 

[brillo_76]

13WE and 13 WL calipers have the same piston size so there will be no change as long as nothing else changes in the brake system. Both calipers use the same rebuild kit. The brake pad backing plates for the two are different sizes, but the brake pad material is roughly the same foot print between the two. TBU 231mm vs. 199mm Pad Size

EDIT: To further elaborate why your pedal feels the way it does, your master cylinder is putting out the same volume but the brake caliper pistons are larger so they require more fluid to move the same distance as a smaller brake piston would. This results in a further brake pedal travel and less foot pedal effort. The textbook correct way to do this upgrade would be to get a larger master cylinder as well which some people have done, but it requires a lot of work to either find a compatible/bolt on master cylinder or make an entirely different one work by either changing the booster and/or deleting ABS.

From what I have read and researched if you don't want to upgrade your master cylinder keep your abs and same pedal feel. You use the stock or the 13WE calipers only. The main reason everyone upgrades to to eliminate the rotor warping on stock. :becky:

 

[Bad Luck]

From what I have read and researched if you don't want to upgrade your master cylinder keep your abs and same pedal feel. You use the stock or the 13WE calipers only. The main reason everyone upgrades to to eliminate the rotor warping on stock. :becky:

13WE pistons are larger than stock and the same size as 13WL pistons so the pedal will feel the same between the two.

 

[DrewZ28]

13WE pistons are larger than stock and the same size as 13WL pistons so the pedal will feel the same between the two.

With the overall size of the caliper being different, won't the 13WL caliper take more fluid than the 13WE? At least this is the conclusion I've come to with my research.

 

[Bad Luck]

With the overall size of the caliper being different, won't the 13WL caliper take more fluid than the 13WE? At least this is the conclusion I've come to with my research.

The volume to fill the caliper will be different, but once you've bled the system and removed all air it doesn't matter. When you press the brake pedal the only moving parts in the hydraulic system are the master cylinder (volume input) and the brake caliper pistons/wheel cylinders (volume output). As long as the caliper pistons are the same size between the two calipers it doesn't matter how much volume it takes to fill the calipers.

 

[brillo_76]

13WE pistons are larger than stock and the same size as 13WL pistons so the pedal will feel the same between the two.

Hmm. Mine feels the same as stock. No soft pedal. Aren't the 13WL longer calipers using the 231mm rotors?



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[Bad Luck]

Hmm. Mine feels the same as stock. No soft pedal. Aren't the 13WL longer calipers using the 231mm rotors?



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The 13WL calipers are larger than the 13WE, but they both use the same tundra/sequoia rotors. 13WL calipers require more fluid to fill the caliper when bleeding all the air out after installation, but once you bleed all the air out the hydraulic side of the brake system only cares about the caliper piston size because the caliper piston is the only moving hydraulic part in the caliper causing a change in fluid volume.

 

[brillo_76]

The 13WL calipers are larger than the 13WE, but they both use the same tundra/sequoia rotors. 13WL calipers require more fluid to fill the caliper when bleeding all the air out after installation, but once you bleed all the air out the hydraulic side of the brake system only cares about the caliper piston size because the caliper piston is the only moving hydraulic part in the caliper causing a change in fluid volume.

Ok.. Makes since. Which caliper uses the 231mm?? As I thought it was the 13WL?


So the OP should be fine with the calipers being 13WL provided everything else is in good working order and no air in the system. Since the movement of fluid is the same and all the pistons are the same size using the surface area of fluid to push. So all these spongy pedals are just air in the system? Interesting learn something new everyday.

 

[19963.4lsr5]

When I did the upgrade on the 97 Limited Puppy Hauler I left the old calipers hang and connected until I had the upgrade connected.

When it was time to connect the new calipers I made sure the MC was full and the bleeder was open before hooking up the new brake hose to give the air a place to go.


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[Bad Luck]

Ok.. Makes since. Which caliper uses the 231mm?? As I thought it was the 13WL?


So the OP should be fine with the calipers being 13WL provided everything else is in good working order and no air in the system. Since the movement of fluid is the same and all the pistons are the same size using the surface area of fluid to push. So all these spongy pedals are just air in the system? Interesting learn something new everyday.

The 13WL caliper is the 231mm. BigFishAllDay explained the difference between the two really good in his write-up:
"The mechanical difference boils down to the updated caliper being much larger to hold a larger pad....The early style pad (in the 13WE caliper) will be less than 5” (4-11/16” or 199.5 mm) in width; the (pads in the) later update (13WL caliper) is more than 5” (5-5/16” or 231 mm)."
This is referencing the brake pad backing plate, but the brake pad material is very close between the two as seen in this post: https://www.toyota-4runner.org/3378920-post1.html

I think what people are saying is a "spongy feeling brake pedal" is really just the nature of the brake system due to an increased piston size in the front calipers. Some cases could be air still in the system or old fluid that has absorbed too much moisture. When the caliper piston size increases then the master cylinder has to move further in order to make up for the added piston volume. This means the brake pedal is easier to push and must be pushed further. Some people will notice it and some people won't. It definitely depends on the driver. I borrowed my dad's car the other day and it shakes horribly, but my dad didn't notice it at all.

 

[brillo_76]

I know my 1998 with the 13WE calipers work great for me. My rims fit without grinding things and the only reason i changed them was to get rid of the warping rotor. :-D

 

[AJPuleo23]

OP out of curiosity, do you find that when you press the pedal when moving - take your foot off the pedal and then quickly press it again that it firms up?

If so, I have a nearly identical scenario going on with mine post TBU.

Just for documentation purposes, I went with the PowerStop KC2324 Z23 daily driver set up with Rotors, pads and calipers and StopTech 95044007 lines.

FWIW With this set up, the rotors were thicker (but same diameter as OE), the calipers larger (had to trim dust shield) and in turn the pads were larger as well. (I am not sure if this set up was 13WE or WL if I am being honest)

It stops. It will stop short. The shudder from the original warped rotors is now gone. But the OCD in me knows the pedal was firmer on the OG set up then it currently is, aside from quickly pressing the pedal the 2nd time when braking. That seems to have a more original feel for me.

That said, I am going to anxiously follow this.

I chalked it up to mine being an 01 with ABS and some people just seemed to have a different pedal after the TBU and dealt with it. I'd love to get to the bottom of it myself.