i tried looking it up, but couldnt find it, and i dont remember how to calculate howw off the speedo is. its an 88 4runner with 36" tires. i think the stock size was like a 235/75-15. i remeber you come up with a percentage or somethin of the sort. i need to know how fast im going when the speedo says 50mph?

 

Maybe this isn't the method you're looking for, but the best way is to get a GPS. Drive around with it for a while and you can note how far off your speedo is.

 

http://www.csgnetwork.com/speedocalibcalc.html

 

If ya need it calibrated then I go to school with a guy and he has speedo calibration equipment in his garage...i gotta get mine done when i get the 4runner back up.

 

It's very simple to find out, nothing special required.
Use a stopwatch (most of us have this feature on our wristwatches these days...) or at least a second hand, and go drive somewhere there are mile posts. Drive at a constant speed. Time some mileposts. Be precise. Be sure and time multiple mileposts as they are not particularly accurately placed.

At 65 seconds per mile, you are going 55 mph. Couldn't be simpler.
At 60 seconds per mile, you are going 60 mph.
At 55 seconds per mile, you are going 65 mph.
At 50 seconds per mile, you are going 70 mph.
etc

Remember that your speedo will be off as a percentage - so if (by way of example) you are reading 50 but are going 55, then when it reads 30 you will be going 33, when it reads 100 you will be going 110. 10% - get it?

(By the way - you would have to tell us what gears you have before we could have calculated it for you.)

 

I just used the calculator that Justin provided above and my odometer is off approximately 11.8% so I think Flamed's explanation of 10% is pretty reasonable.

 

um, the 10% was just used for an example. I have no idea what gears are in runnerboys rig so I couldn't calculate the error.

IF he came stock with 225s (235s were not standard) and 4.10s (manual trans) for example, and now has 36s and 4.10s, then his speedo would be off roughly 30%!!

 

Pop quiz

Factory 225s with 4.10s. How far off with 33x1250s and 5.29s?

 

I can understand that the 10% was based on stock gears. The calculator I used didn't even have an input for gearing...

 

225/75-16's are 29" tires.


(33-29)/29 = 0.13793 (calculates how much your tire difference throws it off)

(5.29-4.10)/4.10 = 0.29024 (calculates how much you corrected with gears)

0.29024 - 0.13793 = 0.15231 or about 15.2% OVERCORRECTED (calculates how much overcorrection you have)

 

Yeah, so you'll get GREAT gas mileage!

 

Hah! Now I can really fool the wife.

"See dear. This DOES get good gas milage".

 

i have still have the stock 4.10 gears. from what was said also i guess the stock tires were 225's. wow 30%. so that means when the speedo says about 50 im realy doing around 65. truck drives better than i thought it would on the highway.

 

Better yet, have a friend help you out and call of time and watch for mile markers as you drive.

 

John, how's that new runner workin out for you? Sounds like you got a pretty good set-up with the SAS and 36s. You ever gonna be comin back to tech for school? I'll be back next semester and we should get out for some trail runs. The taco's come a long way

 

hey man, actually i came back to tech this semester. the 4runner is a whole different ball game than my 97 to drive and wheel. its gonna take me a while to get used to it. lookin foreward to you gettin back to school.

 

please leave your speedo on. thank you

 

It is about this far off [ ]

Don't drive faster than the person in front of you.

How much is mine off:
33" MT/R's from stock 225/75/15
5.29 gears from stock 4.56
A340F tranny from A340H
3.4 from stock 3.0

 

Mine were stock 225 b/c I have a 4X2. Since you have the 4x4, you may have started bigger. Also, most 4x4's if I'm correct came with the 16" wheels while mine came with 15" wheels.

 

I am pretty sure all 80's and early 90s Toys came with 15" wheels