Acceptable speedometer error?

Does anyone know what Toyota would consider to be acceptable error on a speedo? Mine if off by a full 5 mph at highway speeds as compared to my GPS. When my speedo says 80, my GPS says 75. It's off a little less the slower I go, obviously.

I stopped down and made an appointment to have the techs verify it next week but the service writer said he THINKS that Toyota considers anything within 10% to be acceptable. I think that is ridiculous.

What I THINK might be the problem is that my truck came with 16" tires, whereas most other Tacoma models come with 17's. I'm wondering if all of the Tacoma ECM's are programmed the same?

The service writer also said that he didn't think there was any way to adjust the calibration, which I found odd. I can't believe it can't be adjusted.

 

I don't have a GPS or anything, but every time I pass one of the speed detectors that the police put by the side of the road here in NC my 05 with 17" factory wheels is off about 3 MPH at 50 MPH. If my speedo says 50, I'm going about 47.

 

5MPH at 80 doesnt seem too bad to me, i know my truck read about 2-3 mph slow at 60-65 so yours seems to fall in line to me. with my larger tires now mine reads a tad slow if anything. to my knowledge there is no way to calibrate them at the moment. the 16" vs. 17" really wont make a difference, the overall tire diameter is what will make the difference not the wheel.

 

Well, atleast it's showing to high instead of too low. Not knowing you're going 5 mph faster than your speedo shows could get expensive.

 

Isn't there a way to reprogram it with one of those gismos that allow you to change computer settings. A friend of mine has a Mustang and when he said that when he put on larger wheels and tires, he entered the new tire size into the unit. Maybe he was blowing smoke up my a**...

 

yeah,(but anyone correct me if im wrong) i think there is a program out there that you can install onto your laptop, and you can ajust the settings on your car computer.

 

Mine came with 265/70/16's. They say if you switch to 265/75/16's it corrects your speedo or at least gets it much closer. Mine is about 2-4 MPH slow compared to the GPS or the Garmin. In about another 20K I will find out because I plan to go with the 75 profile with new tires.

 

When I left the service desk I went out to the salesman who sold me the truck. I bitched about it to him about it and he claimed they'd "make it right" no matter what Toyota says (we'll see). He mentioned swapping out tires for a larger size so maybe I could talk him into a more aggressive tread pattern at the same time.

 

Unless the odometer is also off, which means your warranty expires early.

 

My speedometer is off by 5 km/h slower that's about 3mph, i have 265/65R17 wheels

 

Ya know...I never thought about that. Does the speedo error mean that the odometer is racking up miles faster than I actually am? I would think so.

 

Yep, it's a conspiracy...

http://www.tacomaworld.com/forum/technical-chat/17034-possible-conspiracy.html

 

yep, its a conspiracy.......yay! over size tires = more warranty 5% larger tire= 37888 miles out of my 36000 mile warranty!

 

I just found the tire size calculator thing and, according to that, I would need to go from a 265 up to a 305 tire to correct that much error. I assume that this is not an option without a lift kit.

 

True, true.

 

Toyota states an acceptable indication error could be as much as 3-6 miles per hour check this link it is for a 05-06 Tacoma but it gives you and idea what Toyota says is acceptable.

 

Thanks Beeftaco, that chart would seem to indicate that mine is outside Toyota's own acceptable limits. We'll see what they say.

 

Mine was also off until I installed my Lift and new wheels and tires!
Now GPS is RIGHT ON!!!

(Maybe Toyota will pay for my lift wheels and tires? The amount i paid to correct the issue... just kidding)

 

Yeah, mine was about 3 mph fast at 65 before the new tires (according to the Scangauge). Now, my speedo is about 2 mph slow at 65.

 

This doesn't matter because they're the same outside diameter regardless of rim size.

Everyone who's tested theirs has found the same or similar, approx. 3 MPH off. I tested mine with both GPS and radar and that's exactly what it was. On my Tacoma now, with larger tires (from 30.5" to 31.6"), it's dead on.