If you do the tundra brake upgrade, just remember there are two separate sizes. There’s a 199mm caliper (casting S12WE) and a 231mm caliper (casting S12WL). The 199s will fit under factory Toyota 16” rims. The 231s will need some rim grinding on the back side, spacers, or an upgrade to a bigger rim or different offset. That said, both tundra calipers both use the same rotors, which as Timmy’s video points out, are considerably thicker and much less prone to warping.
I chose the 199s (just pulled them last week off a tundra being parted out) because I can’t afford new rims and tires right now with so many other things still needing addressing. Plus the idea of grinding the rims makes me think they would be harder to balance (it will be a semi-daily driver, seeing I’m retired).
So I just ordered the R1 rotors and pads combo (20% for Mother’s Day!). I hope to get the swap done this week. I also went to my Toyota dealer and ordered new hard brake lines from the flex line to the rotors, since the 199s go in at a different angle/position from the factory 4Runner. Picked those up Thursday. I’m thinking hard about a complete brake fluid flush and fill, but bleeding those will be a lot more work once air gets in the lines. It was supposed done 4 years ago or so, but probably wouldn’t hurt. I just hate lying in the ground that long with my bad back.