I just realized yesterday that vehicles that came with 15" wheels from the factory have different calipers than vehicles that came with 16" wheels. When I bought mine it had OEM 16" wheels but searching the VIN reveals it had 15s from he factory.

Is there a performance difference between the 2 setups or is it just the physical size of the calipers? Have I been rolling around on underpowered brakes?

I'm looking at doing the 199mm TBU since the brakes need some work anyway. Besides needing to trim the dust shield, are there any additional considerations when going from a stock 15" setup to the TBU?

First, be VERY careful in assuming you had 15" wheels from the factory. A VIN check will show 15" wheels for most if no all 3rd gens, then the optional 16" wheels are listed elsewhere on the build sheet. The only way to know for sure now is to measure your rotor dimensions. 11.5" = 15" wheels, 12.5" = 16" wheels. Along with the smaller rotors, the calipers are smaller and the rear wheel cylinders are smaller (same drums/shoes, smaller wheel cylinder piston).

I ended up having 16" wheel knuckles with 15" wheel brakes for a while around the time of my 4WD swap. Here's a reference for what 16" wheel brake dust shields look like with 15" wheel brakes:





231 Tundra vs. 15" 4Runner brakes:





Installed:



Hope that helps.

-Charlie

Well, the spare that came with it, which seemed original, was on a 15" wheel and when I did the rear axle seals and brakes the wheel cylinders seemed smaller than the ones I installed which were for the 16" wheels. I'll see if I can get a look at the front dust shields and compare them to your pictures though. Anyone happen to know the casting number for the 15" calipers?

S12WE=15 inch wheels
S13WM=16 inch wheels

Yep, mine are S12WE

So since they use the same pads I'm assuming the only difference between the 15" and 16" calipers is that the 16" calipers extend out an extra half inch radially to accommodate the bigger rotors and give slightly better mechanical advantage. So I'm basically running the wimpiest version of brakes available.

So will the bigger diameter rotors fit within the smaller splash shields?

Time for a bit of cut and bend... maybe you can get away with just bending, but you'll be cutting for the calipers anyway.

-Charlie

How well do you think they brake? Are those 4 piston rotors?

I have the next size up, w/12.5" rotors and have never felt they were underpowered or I had a need for more, even when towing a 1000lb trailer with 2 SxSs on it. Maybe something to consider if they fit your wheels.

They are 4 piston calipers. I've had one instance where I noticed a red light at the last minute and had to panic stop. It felt like the car should have stopped a good bit sooner than it did. But that's just one experience.

That said, I am considering just moving up to the 16" stock setup. It's just really going to bother me if I have to mangle the splash shields to get anything to fit.

Hmm.. I don't think I saw any with the 15 inch wheels. All mine came with 16 inches on and most of my spares were swapped out for aluminum before I got them. Interesting. I will have to check the stamping on the calipers.

I couldn't keep the rotors from not warping, so that's why I went to the 199mm tundra calipers. The wider beefer rotor keeps them from warping.

I found out through research and asking around that the warping is most likely being caused by brake pad material on the rotors or the hubs themselves go out of round. Thus causing the rotors to warp.

Mine you could always see the rotors round out with your eyes so mine was most likely do to the hub being out of round. ;-)

Since i did it a few years ago. I never warped any rotors again...

I've seen a couple around with 15s. Usually they're running steelies. They also typically don't have any fender flares or fender trim, which mine doesn't have so it makes sense that it came with 15s originally.

I'm thinking about getting the 16" splash/dust shields and cutting them in half to mount them without having to take the spindle apart and doing the 199mm TBU.

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My dust shields rotted away years ago...:/

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Considered just removing them but my inner engineer whispers in my ear and says, "If an engineer at Toyota decided they're important, don't you think you should have them there?" But in practical application, it sounds like plenty of guys run their rigs without them with no issues.

That said, I spoke with @JZiggy and he has the 199 TBU with the 15" splash shields and said they work fine with some minor bending. Mine are completely rust free so doesn't seem worth cutting them off.

They have to be pretty lightly optioned. My '99 SR5 2WD was a 16" wheel truck - it also had no sunroof. Luckily it did have side steps, roof rack, dust deflector and hitch....

15" wheel trucks have no flares or chrome strips - but the non-wide strips/flares are easy to remove so it isn't a 100% giveaway.

-Charlie

If your driving style isn't warping the rotors, I wouldn't worry too much about the bigger brakes. I don't think I drive mine too hard, but I got a pulsing brake pedal not too long after I bought it. And after watching my wife fight with the same issues on her '96 for a while, only finding a solution with the big TBU, I just went ahead and did the same, and never had issues with the brakes again.

You just need to trim a little off the dust shield. A minute or two with the tin snips. When I had my hubs rebuilt recently (manual hub swap, rebuilt them with new bearings to put the ABS sensor rings on) I just got some new Tundra dust shields and installed those while the hubs were off.