Bigger tires - Spedometer Correction

[zon]

Now that I have my 4Runner lifted I am thinking of putting on slightly bigger tires. The stock tires are P265 70 r16 and I am considering P265 75 R16.
The Michellin LTX AT/2 tires are 31.65" in diameter for the 75's and 30.63" in diameter for the 70's.
Is there a way to adjust or calibrate the spedometer/odometer on the '08 4runner to compensate for the 1 in diameter difference?

 

[chaz]

speedo

theres the super-lift truespeed for up to 06, $ 285 at autoanything. maybe it can be used on the 08, call em. but since your not changing the gears, your speedo wont be off by that much, - probably alittle over 1 mph at 30, around 2-3 at 60-70. if i were you, get the tires on , then drive past those roadside speed moniters, & see just how far off it reads, then decide if its worth the 285. i just drive 2-3 mph lower than what the guage says, just to play it safe. in fact, i only went up 1 tire size, 265/65 to 265/70 , & am pretty much reading correctly at speeds 30-45. i had this brand of recalibrator in my last vec., had much larger tires & lower gears installed, & this unit worked great. it does need to be hard wired in tho. hope this helps

 

[chaz]

just found 2 other brands that may make one for the 08 t4r, for you, theyre much cheaper,(100-200 something) search for SPEEDO HEALER & YELLOWBOX.

 

[CJ3Flyr]

Now that I have my 4Runner lifted I am thinking of putting on slightly bigger tires. The stock tires are P265 70 r16 and I am considering P265 75 R16.
The Michellin LTX AT/2 tires are 31.65" in diameter for the 75's and 30.63" in diameter for the 70's.
Is there a way to adjust or calibrate the spedometer/odometer on the '08 4runner to compensate for the 1 in diameter difference?

It's only a few percent... Can you just live with it? I'd cruise with a GPS and learn the percentile.

If I was making a huge change like 33" tires I might go for the recalibration but at 5% I wouldn't worry about it.
:cheers:

 

[DaBoostCreep]

Well I wonder if Toyota has a way to use the service computer to log into the ABS computer in the vehicle.

On my F350 a Ford dealer can log into the ABS computer and change the amount of revolutions per mile, and such to correct speedometer, transmission shift strategy, and ABS calculations.

In my opinion, there is much more to a TRUELY CORRECT speedometer than just the indicated speed. Anyone a Toyota tech that can find out???

 

[jonz]

I put the P265 75 R16 Michelin LTX AT/2 tires on my 04 4 runner and found that I have about a 7% error on the speedometer and odometer. I ran 400 miles with GPS on and showed 400 miles on the odometer but 428 miles on the GPS unit. GPS speed and speedometer reflect a 7% variation, too. I haven't done anything to correct it....I just pay more attention to the speedometer now. 75 MPH true has my speedometer needle in the middle of the

 

[chaz]

ok, theres a web site called THE MIATA.NET TIRE SIZE CALCULATER, you put put in the stock , then new tire sizes, it gives an automatic readout of how far the speedo is off in %. i ran your #s & it states that your exactly 3.4 % off, so when your speed reads 60 , your really going 62. in my opinion, thats nothing to worry about. if you cant find the site, www.miata.net/garage/tirecalc.html, pm me your email address & ill send the link. i have trouble inserting on this forum. if you cant pm me, go to forum home page, go to 3rd gen. & check the speedo fix with bigger tires post, theres a link to the cal. there.

 

[zon]

Well I wonder if Toyota has a way to use the service computer to log into the ABS computer in the vehicle.

On my F350 a Ford dealer can log into the ABS computer and change the amount of revolutions per mile, and such to correct speedometer, transmission shift strategy, and ABS calculations.

In my opinion, there is much more to a TRUELY CORRECT speedometer than just the indicated speed. Anyone a Toyota tech that can find out???

Thats what I'm talking about. If Ford can do it maybe Toyota has the capability too. I'll call my service rep and see what is possible and post back.



.

 

[Fuzion]

I have 32" tires and every speed measurer I pass indicates my spedo is right on.

 

[chaz]

yep, thats my point. around town, my 1 size up tires read the correct speed on the police road side radar meters, if anybody is worried about it, in my opinion, those are the ones that matter the most.

 

[zon]

yep, thats my point. around town, my 1 size up tires read the correct speed on the police road side radar meters, if anybody is worried about it, in my opinion, those are the ones that matter the most.

I'm not so much worried about accurate speed as I am about accurate milage for things like maintenance schedules, accurate odo readings, etc.



.

 

[chaz]

i believe your odo will read less than what you have really driven, guess thats good if you sell it. but it shouldnt be that far off with just 1tire size difference. if you went to 33 or more, thats different. , im sure you know,even if tire companies state a certain size, they might not be the same. some 32s may be a little more or less than that depending on the brand. this also will cause different readouts with two seperate brands, but same size tires. there can even be quite a large, visual difference. as for maint..., for example, if you have your oil changed at 3000, are they going to give you a hassel if you bring it in at 2990 or 3025? dont take this the wrong way, im just trying to give some input, but the answer still comes up the same,- if your really that worried about this, either spend the $ , & get something like the tru-speed, or stay with the same stock size . then again, you may be able to pay a tech to set it up for the larger tires, but when you trade it in or sell it, you should let who ever know thats been done in case they want to go back to stock size. in case you cant find anything for the 08, take a look at what the scangauge 2 does, that might be usefull to you. good luck