OK...so I'm going with a 3" lift and 31" (or 32") BFGs or Mickey Thompsons...all next week. The problem I have is trying to figure out how I can reset the speedometer settings to accept the new tire sizes without affecting my speedo readings. Is there any possible way to do this? I'm beating my head against a wall and still not coming up with anything. HELP!! (I'm looking to you "Nissan Gurus" on this one...) Thanks!

Mine read wrong until I put on 31's...then it read perfectly.

I have 33's now, so it reads really wrong.



I use the GPS to see my real speed/distance.

BTW - Go with 32's, or 33's, not 31's....ESPECIALLY with the 3" lift...the 31's look really puny under the lift, and the larger tires make it all work better.



So - A GPS will replace the speedometer, or you just time a few mileage markers, figure your % error, and pick a new mental cruise speed for your speedo (Like 55 on the speedo is 65 real speed, so to go 65 on the free way, drive the speedo on 55..., etc.)

After a few miles, you will know anyway.

There is no way to adjust the spedometer. I am running 33s and I keep in mind it is about 5mph off.

The GPS I have also helps out.

Alright...figured something out. The Dakota Digital Universal Speedometer calibration chip has been used by many Toyota owners for a while, with good results (average fix to w/in 1-2 mph). Since the Xterra also uses an electronic signal to the speedo, this chip should work on the Xterra as well. Although Dakota Digital states that this should not be used on ABS-equipped vehicles (the ABS system uses an electronic speed signal and the factory-programmed tire diameter to calculate proper tire clamping power and deceleration speed), Toyota owners who have used this chip on their ABS-equipped Tacos and LandCruisers say they haven't had problems. You will, however, have to understand that this will change their braking characteristics (I am looking into whether or not the dealers can re-program the ECM and ABS control computers to account for different tire sizes, but I doubt it). This mod can be found at Dakota Digital SGI-5 Keep in mind that this will take some time to configure to accurately portray your actual speed.

Maybe this is a dumb question, but isn't changing tires a fairly common practice?

Why isn't there a simple way to accomplish this?

Noobie001

GOOOOOOD question...personally I think it's a dealership conspiracy If any of my wrenching experience has taught me anything, its that modern, computer-controlled vehicles have fairly flexible ECMs in them that can be programmed to fix signal problems by dealership computers. Meaning, that I should be able to take my X to a Nissan dealer and have them re-program the ECM to accept a different standard tire size (the 2.4L POS and the 3.3L VG33E use pretty much the same computer, yet they have different tire sizes...hmmm....). I have also been told that if I were to bolt on a factory supercharger to a non-S/C X engine, I could take the ECM to the dealer to be programmed to accept the changes. So why can't they re-program my ECM to accept that I am now using different-sized tires? Or a different gear ratio? Maybe a Nissan tech can respond to this one for me. Or maybe not. I can't be too bitter towards dealers...one of these days they'll have an important recall for the X like every other 4x4 vehicle out there has all the time. My kudos to Nissan for building the coolest 4x4 ever. Thankfully they're fixing some of its weak points in the '05. Time to go back to sleeping on my desk at work!

OK...I talked to the Dakota Digital people, and the Universal Signal Calibrator (SGI-5) WILL WORK on ABS-equipped Xterras. They clairifed what was posted on their web site, and the SGI-5 chip just can't be used to correct signals actually being sent to the ABS computer. :rolleyes:

I'm gonna go ahead and order one of these and see how well it works out on the Xterra. I'll post results and how they compare to my GPS reading.

Let me know if anyone is interested in results!!

I got one, it works great.
Richard

I've never understood why everyone gets so worked up over speedo "error". AFAIK, just about every vehicle made rolls off the assembly line with a speedo that is anywhere from 5 to 10% optimistic anyway.

By going to 33-inchers, you're probably making your speedo more accurate, not less.

Seems like a waste of money just to adjust your speedo by 2-5%