kalimba

I've seen some other threads on how to change the wheel coefficient in the navigation system so that the vehicle's travel is tracked more accurately, but is there a way to change this coefficient on vehicles that do not have a nav. system? It sure would be nice to be able to change wheel/tire sizes to something smaller/larger than factory and still have accurate speedo readings, no?

Manaray

honestly, the speedo difference is not even something to worry about...

As for the Nav, dunno, my 2003 Lexus Navigation works fine on 20's...

kalimba

Depending on the final wheel & tire diameter/circumference after upgrading, the difference may be significant. Sure, the speedo isn't going to read 80 when you're driving 60, or something else as absurd as that. I guess it's just the principle of the thing: You've got this expensive luxury car and you've spent even more $ customizing it. Yet the simplest thing, like the speedometer, doesn't work correcty.

It's disheartening to think that after upgrading my wheels & tires that a $15 Timex watch would be more accurate than my speedo...

Anyway, back to the original question: Does anyone know if there is a wheel coefficient setting for non-Nav vehicles?

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Manaray: Perhaps your new wheel/tire combination has a coefficient that is very close to the original wheels/tires. Tell me the factory wheel/tire size and what you have now, and I can determine what the new coefficient is.

GSXOTIC

iTrader: (6)

can you kindly refer me the thread about the navi set up. I have navi and don't even know we can do that.

kalimba

This may only apply to GS's -- and even then only to specific models/years -- but it would appear that you have a GS (at least according to your screenname). Here's the thread:

https://www.clublexus.com/forums/sho...threadid=79095

legendary

Just a question....

wouldn't it just be easier to get the wheel/tire combo that is exactly the same OVERALL diameter as stock? That way, unless you are going to 21, you won't change a thing.

Let us know what your plans are

kalimba

Yes, that is the best solution, but wheels and tires are only available in certain dimensions, which sometimes makes obtaining "exactly the same OVERALL diameter" impossible. If you are able to get within 0.1% of the original diameter, I'm sure the difference is degligible, but anything greater than 1% is significant, IMO. Even at a 1% difference, your odometer will be clicking 1 mile more (or less) for every 100 miles you drive.

Tranman

iTrader: (1)

I remember a friend with a 240SX kept getting speeding tickets all of a sudden....found out why. He had just gotten a "deal" on a set of tires...but they were way oversized compared to stock. So when we did the calculations, he was 17% off of stock!!!! So when he thought he was going 65mph, he was actually going 76mph.

Tranman

iTrader: (1)

From my understanding, I believe that the Nav coefficent is only used by the Nav computer to check the position of the car more often (especially if the wheel diameter is change significantly). Otherwise, I believe it has nothing to do with the speedometer itself. In order to change the calibration, I would imagine you'd have to reprogram the ECU itself.

kalimba

That was my understanding from the start -- it makes the most sense. The point about the ECU makes sense, also. Thanks for pointing me in the right direction. Of course, I don't really know how easy or difficult it is to just "reprogram the ECU". Just doesn't sound like something one does on their own...