I own a 1995 4runner with 31 inch tires. Just a few weeks ago the police were testing a unit in my neighborhood that tells me how fast im going. My speedometer said i was going 18 but it said i was going 21. I would assume this is correct because since the tires are not stock, but larger, they would read my speed incorrectly.

How would i go about getting this corrected to read the speed correctly. Today my speedometer said i was going 90 but if the 18/21 ratio stayes the same.. 90 = 105 MPH :eek:

also.. is there anything i need to change with teh gear ratios?

Thanks in advance!!

-Jason

 

Jason: I also have the same problem as you with the 31" tires on my '91 Runner (which the same color as yours). My truck came with the wimpy skinny tires and I put the 31x10.5 's on it. At the lower speeds, the speedo is not too far off but at the higher end (55 & 65 mph) it is off. I use a 5 mph buffer while driving at those speeds......I know that the speedo will read about 55 mph when the truck is going 60 mph. Time yourself between mile markers on the interstate......you are going 60 mph when you travel from one marker to the next in one minute. Look at what your speedometer reads during the test and the difference between what your speedo reads and 60mph is how much your speedo is off at that speed. You also can calculate the time that it takes to go between the markers at other speeds and that will tell you how much the speedo is off at those speeds. I'm telling you this quick & dirty way for you to determine your true speed because it is pretty costly to replace your gears (gears in your differential.....or differentials if yours is a 4WD). If you want to go the gear replacement route, be prepared to spend about $400-500 per differential.


David

 

I was told it was just a fix in the comptuer or something...

thanks for the info though

 

Not in our years (90-95). We have cables that turn our speedometers. The newer vehicles (96 and up) use a electronic signal generator to feed theirs and these can be adjusted by altering the signal. The nice thing about this is that your odometer is showing less miles than actual..... ......if your speed is measured 10% low by your speedometer, then your mileage on the odometer is lower by the same amount On a different but similar note, when the larger tires were put on your truck that not only changed your speedo but also changed the way that your truck performs/shifts. Some of us with the 2nd gens with larger tires have found that when we run with the ECT PWR button on, the shift points are moved up closer to where they would be if our trucks came with the 31" tires from the factory. Try it and see if you notice an improvement in the way your Runner behaves. Some of the guys have found this makes a difference in fuel economy too.

David

 

Just thought i would bump this thread. Does this also effect my odometer? Because i fill my tank up every 100 miles.. thats right.... 100 miles of city driving and around 130 highway driving. its pretty bad... but im not sure if those milage readings are true.

since my speedometer is off, is my odometer off also?

 

Gotta correct you on this one Dave after 92 I think they did away with the speedo cable. Corey doesn't your 91 have a cable?? Anyways my 94 DOES NOT have a cable it's all electronic. And yes your Odo will be off as well. Drive 10 miles with a GPS and compare it to your odo. That will give you a good ratio to work off of. Mine is off 7 miles for every 100 with 31's.

 

I haven't checked to see if my speedo in my '95 is a cable or electronic, however I am having the reverse problem w/ my speedo. Mine says that I'm going faster than I really am. So when my speedo reads 75 I'm only doing 70 (wich sucks 'cuse my milage is recorded as more than what I'm really doing.)

Just though I would post my problem, any ideas would be apprecieated.

EDIT: I am running 31" and the truck came stock w/31"

Eric

 

When I installed my indiglo gauges, I noticed had a speedo cable. I think automatics get an electronic type, and manuals have a cable.

 

Mine has the cable, and when it's real cold outside it will also act up.

For a few minutes of driving the needle will jump all over, and the noise from it is very loud.
Just a dry cable, but I'm not going to tear the dash apart to fix it.

Since I run 31" tires that did not come form the factory, my speedo is off also.
I use a GPS to test it once in awhile, and when my speedo says I'm doin' the double nickel on the freeway, the GPS says I'm doing about 59.

 

To find the ratio that the speedo and odometer is off: If they were both correct with the stock tires, figure out the ratio between the stock tires, and the tires you have on. I went from 26's(this was a stock 2wd tacoma, 5-lug) to 31's, so when my speedo reads 26, it is actually 31. The true reading on the speedo and the odometer is then 1.20 times more than what it says (31 / 26 = 1.19) So take the speed on the speedo, and multiply it by the ratio of the tire sizes. Lucky for me, toyota has a quick fix for my tacoma. I am running the same size tires as the pre-runner tacomas(265/70/R16) so I have been told I could just install the wheel sensor from a pre-runner and it would give me a true reading.