Tire size v. speedometer

Greetings! I've just gotten a really nice 2001 Tacoma that has S-Runner wheels and tires on it. It's not a S-Runner (a previous owner added the wheels/tires) so I'm wondering if anyone knows how much speedometer error I can plan for with the 16" wheels in place of the standard 15"? Or is the speedo controlled by an onboard computer that senses and corrects for the wheel/tire size?
Thanks in advance for your help and advice!

 

Rim size wont matter....tire diameter is where it counts.

It might already be off. Best thing to do is go for a drive and see what the speedo says in relation to GPS speed.

Larger tires will make the truck say its going slower than it actually is.

Undersized tires will make the truck say its going much faster than it actually is.

Nothing self-corrects, but most OEM wheel/tires are undersized, so the speedo usually tells you you are going faster than you actually are. Getting oversized tires on there often "corrects" it closer to actual.

Example I have seen - If you put giant 35" tall tires on, your speedometer will read maybe about 6MPH SLOWER than you are actually driving....on the plus side, that would be less miles on the truck odometer than were actually driven! Itll make you MPG look horrendous too lol.

 

https://www.tacomaworld.com/forum/tirecalc.php