Best speedo correction approach for larger tires
 

Finally over the "15" hump!...

'99 Gen3 Base model 2WD 4cyl. Auto...

After purchasing this truck my first priority was new tires. Just a city / highway truck, no offroading. What I immediately encountered was similar to my experience with a recently restored '92 Celica Convertible...very limited choice in the original tire size of 225/75/15. Also, the 15" rims on the truck were rather shabby looking, missing two caps. I liked the look of the stock 16" rims and was fortunate to find a set at a local boneyard which I acquired and am in the process of repainting. Got a great deal on some stock size 265/70/16's from Tire Rack. Now I must deal with correcting the speedo...the larger tires as most of you will know throw it off by about 8mph on the plus side.

Yes, I have already researched this, here and elsewhere but many of the references I came across were rather old. So I'm looking for fresh input and first hand experiences...what I hope for is the most practical, most accurate, easiest to install. I have seen and read about the SpeedoHealer and Yellow Box. But if this vehicle had an option of 16" tires wouldn't there be a way to re-gear it? I would really prefer to get this accomplished without yanking the dash / kickpanels apart if possible. Really need to get going on this ASAP due to it being January...I live in Ohio...and the tires on the truck are in no way Winter worthy. Supposed to be 68 degrees tomorrow...but that sure ain't gonna last long. Very much appreciate any and all help and info for this issue...

I don't think you are going to see that great a difference in your speedo/odo. I switched from 265/70-16 to 245/75-16 on my 4runner, and the difference is less than 5%. Best to just do it and see where you end up, using maps on your phone or a gps to verify. With the oe tire size your speedo is already reading high, as per federal regs. It will probably just be closer in accuracy with the larger tires.

Cross that bridge when you get to it.

I agree I switched to 32.8 inch tires from stock and my speedo is only off 2mph.

Guys, he's going from 225/75-15 tires to 265/70-16 tires - it is a fairly large change in rolling diameter (similar to going from stock tires to 35's on the 16" wheel trucks).

Assuming the OP's truck has ABS, the speedo is driven off the ABS system. Re-gearing will have no effect on speedo reading, only tire size has an effect. Re-gearing is a good idea though, and 4.10 rear 3rd members should be easy to find cheap.

I used a Dakota Digital speedometer interface to correct my speedometer. See my thread here: https://www.toyota-4runner.org/2456477-post12.html

There is no plug-in solution for reprogramming the speedo or anything like that (sorry, it isn't a domestic truck...). You will have to wire something in.

-Charlie

It won't be an 8mph difference, I wouldn't even worry about the change or bother with the correction, no need when it won't affect daily driving.
IF you still wanted to somehow correct it, you can change the speedo sensor plastic gear inside your t-case...but im reading now you have a 2wd so I believe your speedo sensors are part of your ABS system.
Best to let a sleeping dogs lie.

It is a 5.7 mph difference at 70mph (8.1% change in rolling diameter). I'd say that's worth correcting... And if he wanted to go up to "32's" for his next set of tires, it would be an 11.7% difference, which is even more of an issue - and also why I suggested gearing would be a good idea too.

All ABS equipped 3rd gens use the ABS system for the speedo whether 2WD or 4WD. Only non-ABS 4Runners use the sensor on the trans. 1st gen Tacomas generally use the gear on the transmission though...

-Charlie

phattyduck, you are correct...I may have plugged in an incorrect number. I use a cool site I was turned on to...tiresize.com...it's great for these changes. Gives you an excellent numeric and side-by-side visual comparison of two different sizes, as well as how much it will throw off the speedo. It is an 8.1% increase in diameter, but will still bump the actual speed up by nearly 6mph when I'm looking at 70 on the speedo. I'd really like to correct that.

And to be totally honest, I haven't had the truck long enough to know for sure if it does have ABS or not. Not driving it much with the crappy tires it's now riding on. I'll have to check on the ABS...if it is non-ABS, with the sensor on the tranny, I'm hoping that might be the simplest way to go. In the meantime I will check out that Dakota Digital unit.

Very much appreciate the input, what a great site...

I use my ScanGauge. You can plug in correction factors, have a digital accurate speedo, and room for 3 other gauges.

Same with the Ultra-Gauge. There's a little formula you figure out using a GPS speed and the UG speed. When I upgraded my wheels that came with taller tires; my speedometer started reading right on the money so didn't need to use the digital readout.

Ultra-Gauge formula: Not mine. I copied it from another member here.

How to calibrate distance using a GPS and a calculator:

NOTE
This distance calibration method is based on using GPS speed.
GPS speed is most accurate when driving in a straight line at a constant speed.

Step 1: Add a speed gauge (e.g. on page 1 zone 1 of the Ultragauge)
MENU Gauge/Page Menu .. Select Gauge/Page .. Select Gauges Select Page 1 Gauges
Use UP & DOWN keys to Navigate to MPH or KPH
Press MENU. This will cause the cursor to blink.
Pressing UP or DOWN change the number to 1
Press MENU to assign the Gauge to that Page 1 Zone 1.
Leave the menu by selecting Back, etc
The Ultragauge should now show the MPH or KPH on page 1
Step 2: Grab your calculator and your GPS navigation device, get in your car and head for the motorway.
Step 3: While driving at a constant high speed for at least a few seconds note down the speed readings of the Ultragauge and the GPS.
The readings are probably different.
Step 4: Find a convenient place to stop, switch on your calculator and do the following calculation: GPS speed reading divided by Ultragauge speed reading.
Step 5: Adjust the "Distance cal." factor in the Ultragauge
Menu - Vehicle Setup - Calibration - Calibrate Distance
Note the distance value shown by Ultragauge and on the calculator multiply this by the factor found in step 4
Press MENU and press UP or DOWN to adjust the distance value to the calculated value.
Press MENU to store the updated distance value. The Ultragauge now shows the new Distance cal. value
Leave the menu by selecting Back, etc
Switch off your calculator
Step 6: Take another drive on the motorway and check if the GPS speed reading and the Ultragauge speed reading at constant speed are now the same.
Step 7: If necessary make fine adjustments to the distance calibration value until GPS speed and Ultragauge speed are identical.

Does anyone know if there is an identifier within the VIN which designates what size tires the vehicle was originally equipped with?

You can register your VIN on the Toyota Owners site and access original vehicle build specs, which at least in my case, indicated original tire size as well as additional useful info:

Logged Out My Vehicle Page | Toyota Owners

Or just have a look at the driver's side door jamb sticker, which shows original tire size and pressure info.

Hey thanks bdNY...laughing here, just found that this morning and reading my build sheet. I've been calling my truck a "base" model, they refer to it as the "standard" model. I knew what the original tire size is...I'm trying to figure out the best way to correct the speedo after I install the 265/70/16 tires (also stock)...without a big hullabaloo. Build sheet says my truck does NOT have ABS...so it would seem to me that there might be a chance that all I will need would be the correct speed sensor for the transmission / tire size combination. Keeping my fingers crossed...

Checked my build sheet on the Toyota Owners Spec. site...my truck is non-ABS. As per your earlier reply, do you think it possible that there might simply be a correct speed sensor for the 2WD auto trans. / 16" tire combination?

Base model - you don't have ABS and you have a manual speedometer cable. They make mechanical speedometer calibration boxes.

rknToy...correct, it is a base model...no ABS...but my odometer IS digital, does this not mean that the entire speedo is digital (electric)? Are we talkin' apples-to-apples here? This is the simple, straightforward fix I'm hoping for if you are right...BTW, the truck does have cruise control if that might also be a factor.

I called a Toyo dealer / shop I've had good vibes with in the past, explained the whole deal to him. He said if I could come up with a VIN from a nearly identical truck (2WD-4cyl-Auto) that came originally with the 16" stock wheels he likely could help...long shot I know but I might see if anyone on here has a truck with that original setup...Thanks for your input...