After installing 2001 SE wheels (225/50/17) on my 98 GLE, I noticed a roughly 2.0 mph difference on the speedometer vs the GPS speed on my Torque application. OEM size was 205/65/15) This is much larger than originally anticipated. Tire size calculators showed a 1.4% slower speed on the larger tires which translated into a 0.9 MPH difference on the speedo (at 60 mph).

Do I have any options in correcting this difference (ie tuning the ECU)??? My 06 SUV has a PCM that was tuned to do just that).

 

It's been asked many times before & truthfully as far as I know the only way to have your speedometer corrected is to get the gauges itself redone which I believe cost a lot of money + they wouldnt be OEM looking..which is one reason why I dont wanna rush to get rims....I love knowing my correct speed...

 

If you good with disassembling and assembling things then it should be pretty easy-risky lol.take off front cover of speedometer and pull off the MPH needle. Drive on freeway and put it on cruise once you hit 60mph(check ur GPS for speed or course).While doing 60,put the needle back in.All set.

 

Other way to do it is if u lift up one front end tire.Jack it up and do same thing.Only difference is that the cruise won't stay on(since one tire its not rotating),and its kinda hard to keep it constantly on 60.It'll feel like if you're revving it on park..with a little vibration of course from tire rotation

 

retarded and unsafe, and those needles are'nt easy to pop on and off like that they're very fragile. when i did my indiglow gauges it took me awhile to set those back on there straight. and dude, i've had 17 inch wheels for like 3 years and had 15's for years before, the difference is so small it's not worth stressing over it. but you allready know that.

 

Yes Mom it IS retarded.Sorry I wont do it again.I have tried your way and it takes MUCH longer to get it right.[Stop,pull needle out,put back in,drive] x (who knows how many times to get it JUST right]=.
GM vehicles have it simple.I have done at least 20 clusters on GM trucks/cars and its pull and push back.
Anyways to get it safer(if you're doing the freeway thingy),get a friend to put needle back while you steer

 

Please stop typing....

 

OP, use this http://www.miata.net/garage/tirecalc.html

The difference is minimal for most applications and with the wide variety of aspect ratio's available you can put on rims up to 18" and still have an accurate speedo

 

These guys are awesome, This might solve your problem

 

That's the dumbest thing I've ever heard. 60 MPH would be the only speed that was correct. Above and below that would be wrong.

 

Please stop reading.....

 

OP, use this http://www.miata.net/garage/tirecalc.html

The difference is minimal for most applications and with the wide variety of aspect ratio's available you can put on rims up to 18" and still have an accurate speedo[/quote]



Anyways yea..difference is minimal.Don't beat yourself up over it