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Discussion Starter · #1 ·
I have a friend who is getting rid of his 31x10.5 tires and rims and I would like to put them on my '99 Taco V6 with 235/75 R15s, but I want the speedo to be accurate. So my question is, how does Toyota set the speedo calibration? Are there different sending units in the tranny? Is it the ECU? Or are there different speedo guages? He has said that if it is just the sending unit on the tranny and it can be removed easily I can take the sending unit off his truck and put it on mine. If it is the ECU or the guage I am a little hesitant to start swapping parts. So if I change tire sizes what is the easiest way to keep the speedo accurate?

Also, he has the stock fender flares and has offered them to me as well if they aren't installed with holes in the fender. How are stock fender flares installed? And can they be removed without leaving holes or weird marks?

Thanks for the help.
Todd Blanset
Bishop, CA
 

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on my tacoma the speedo read about 5mph faster than i was going with the stock 31's. when i went to 32's, it reads about 1-2mph faster than i'm going. find one of those big radar things and see if the speed on it matches your speedo. chances are if your truck says faster than the radar, the bigger tires will bring you closer to actual speed. the only way i know of to calibrate them perfect is w/ the dakota digital calibrator or whatever it is
 

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Apparently there are plastic (I think) gears in trans that can be replaced to correct or the Dakota Unit Yo T spoke about
 

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I think the speedo reads 3mph slower for each inch bigger in tire size. Keep in mind it is actual tire size because alot of 33's or any size for that matter dont really measure out to their rated size.
 

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You can swap the speedo gear, but I don't think 31's are going to cause that much of a difference.
 

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I just reread you're question. Are you putting his 31's on your truck or just his rims or what? Where does the metric tire size come into play here?
 

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Discussion Starter · #8 ·
I'm putting his tires and rims on my truck. His tires are 31's and I currently have 235/75 R15's. But based on that website it looks like the difference in speed is only 3.5MPH. And someone earlier said the stock speedo read 3MPH fast anyways so I guess I'll be right on. No worries and thanks for all the good info everyone.

Todd
 
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