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I don;t know if this is common knowledge, but my 2007 TRD (stock w/265's) was about 4 mph fast in the speedometer when I got it.

I just installed 285's and it is only 1 mph slow.

This is all GPS verified.

Usually going up in size will get you up to 10% slow on the speedometer due to the larger rotation, but I am assuming Toyota regeared the speedo on trucks that some with 265's over 245's.

Anyway, it is nice for once, to have a larger tire on a vehicle and the speedometer is almost accurate.

Just an FYI...this will effect your gas mileage readings big time....

If you don't have a GPS, use the mile markers on the interstate to check and see if your odometer is accurate. Then you will be able to add or subtract a percentage in order to get accurate fule mileage numbers.

I have to add .05 (negligible, yes) to mine to get an accurate reading now, but before I was subtracting .10.
 

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Yeah, thanks for the info. We all beat this to death in another post a few months ago. Info is good.
 

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I allways wondered if Toyota calibrated each truck to the stock tires used in each model, I supose that they do.

Last week I was at a local ARMY base and in one of the speed limit radars posted around the base (tells you in a display your current speed), I noticed that my speedo was exactly at 23 MPH and the display was exactly at 23MPH so I guess that mine was calibrated at factory.

Stock tires are 265/70-16 :rolleyes: :rolleyes:
 

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with my stockers i was going too slow. now with my 265/75's i am dead on as far as speed goes using my gps. confirmed today when i was passing by one of those trailers that has a laser attached to it showing your speed. i like f**king with those things :)
 

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I don;t know if this is common knowledge, but my 2007 TRD (stock w/265's) was about 4 mph fast in the speedometer when I got it.

I just installed 285's and it is only 1 mph slow.

This is all GPS verified.

Usually going up in size will get you up to 10% slow on the speedometer due to the larger rotation, but I am assuming Toyota regeared the speedo on trucks that some with 265's over 245's.

Anyway, it is nice for once, to have a larger tire on a vehicle and the speedometer is almost accurate.

Just an FYI...this will effect your gas mileage readings big time....

If you don't have a GPS, use the mile markers on the interstate to check and see if your odometer is accurate. Then you will be able to add or subtract a percentage in order to get accurate fule mileage numbers.

I have to add .05 (negligible, yes) to mine to get an accurate reading now, but before I was subtracting .10.
going from 265/70's to 285/75's is only a 6% increase.

On my taco I noticed that it was 2 mph off, not a percentage... but using my SGII and GPS I realized it was only the dash that was off, and the ECU is dead accurate. At first I thought my speedo was 2mph off at all speeds, but the more I look at it about 2mph slow thry 25mph, accurate from 25-45, and from 45 up its 2mph off, must have to do with how the dash reads the ECU signal as its dead on throughout the range.. I was annoyed at first with it reading fast at hwy speeds, but with the ECU accurate the ODO is accurate and thats all the really matters :D

One thing I am curious of, for those tacos without the DAC/VAS/TRAC package where does your speedo get its signal. My output on the xcase is plugged, so it must get it from the wheel speed sensors.... meaning that changing gear ratios wont change your speedo, without a tire size change... There is a guy on CT that has 35's and 5.29's and says his speed is 13% slow, where it really should be about 21% fast with that combo, so it must not get info from the xcase.....
 

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with my stockers i was going too slow. now with my 265/75's i am dead on as far as speed goes using my gps. confirmed today when i was passing by one of those trailers that has a laser attached to it showing your speed. i like f**king with those things :)
is that possible? LOL
 

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My speedometer was dead on when stock. No change in my speedo readings, going from stock 265/70s to 265/75s at 35 mph. It now reads approx. 1 mph less at 60 mph actual. Comparisons made at road hazard radar stations.

But who knows how accurate DOT roadside radar stations are?
 

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i know what you mean, my gps is about 7 mph faster than my speedo
 

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I also really question the reliability of the factory cal on the speedo. There is not a lot of consistency b/t trucks.

My 05 sport was a little slow with the factory tires. Then I went to 265/75's and my speedometer showed 94 miles when I drove 100 using the interstate mile markers. Checked 3 times. So do the math it is 6.3% slow now. I am putting 285's on it next week, so we will see how bad that messes it up.

My wife's has the 245's and it is a little fast. But I will be putting the sport rims and 265/75's on hers next week, so the game continues.
 

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I also really question the reliability of the factory cal on the speedo. There is not a lot of consistency b/t trucks.

My 05 sport was a little slow with the factory tires. Then I went to 265/75's and my speedometer showed 94 miles when I drove 100 using the interstate mile markers. Checked 3 times. So do the math it is 6.3% slow now. I am putting 285's on it next week, so we will see how bad that messes it up.

My wife's has the 245's and it is a little fast. But I will be putting the sport rims and 265/75's on hers next week, so the game continues.
265/75 on 17" rims? Thats not a normal tire....


My odo is pretty darn close, thou I havent checked it against highway miles, but it matches the SGII to w/in a .10 ish, and they do their own calculations, and the speed the SGII shows is very accurate. I also know that the highway mile signs arent perfect, which is why only certain ones are used for calibration checks.
 

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265/75 on 17" rims? Thats not a normal tire....
Yea good call... Still haven't gotten used to these 17's haha, 265/70's. I still think of everything as 265/75's and 285/75's of the good ol days of 16's. But I will have 16's back on there next week hopefully and be happy. Its killing me, damn 1100 dollars worth of tires and rims sitting in the garage and I have been offshore for a little over 3 weeks dying to get home to slap them on. Thanks for the heads up John. I love it when I type something retarded. :banghead:
 

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Yea good call... Still haven't gotten used to these 17's haha, 265/70's. I still think of everything as 265/75's and 285/75's of the good ol days of 16's. But I will have 16's back on there next week hopefully and be happy. Its killing me, damn 1100 dollars worth of tires and rims sitting in the garage and I have been offshore for a little over 3 weeks dying to get home to slap them on. Thanks for the heads up John. I love it when I type something retarded. :banghead:
I figured thats what you meant, but a 265/75/17 could be a sweet tire....
 

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Mile markers are the most accurate option anyways; they're surveyed in, to strict tolerances, your garden variety gps relies on calculating the speed, and like the altimeter function available on some gps's, the speed function isn't always that accuate.
 

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fwiw.... yeah the tacoma speedometer is a bit optomistic.... with stock tires. but the odometer is accurate. be aware of using the odometer to measure mpg's etc after changing tire diameter sizes...
 

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fwiw.... yeah the tacoma speedometer is a bit optomistic.... with stock tires. but the odometer is accurate. be aware of using the odometer to measure mpg's etc after changing tire diameter sizes...
Thats what really annoys me, with stock tires the truck knows exactly how fast it going, but it cant get it on the friggin dash. Each taco i have looked at the speedo has a different resting place for 0mph.
 
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