Tuner

[Slayer7391]

Need help as to what settings I should have when you replace stock 18's with 20's so the speedometer reads correctly.

 

[onebadgsx]

Here we go....

 

[Chino]

It should be listed on the tire manufacturers website. If its for a staggered setup, go with whatever is listed for the rears. What size and brand tire?

 

[stkjock]

Wheel diameter is meaningless


Rear tire DIAMETER is what matters and revs per mile.

Of course this info could have been found in a few mins with the search feature.

 

[Slayer7391]

They are Razor 20's with 255/35/20 front - 285/30/20 rear/ tried search but coulnt find anything

 

[RazorbackMustang]

You have to get the revs per mile from the tire manufacturer. A Goodyear 285/35/18 won't have the same number of revs per mile as a Pirelli 285/35/18.

 

[stang1971]

you need to find what the revs per mile are.... once you do.. you change that in the tuner and load it to the car.

 

[stkjock]

They are Razor 20's with 255/35/20 front - 285/30/20 rear/ tried search but coulnt find anything

20 seconds, 1 search query:


http://www.s197forum.com/forum/showthread.php?t=30048&highlight=Speedo+correction

Some times it takes a few combinations to get the right terms.

 

[frank s]

WRT tire manufacturers' wheel revolutions per mile: I've found that they'll get you in the ballpark, and are useful in comparison of the behavior of different-size tires, but over-the-road accuracy is not something you should expect.

I mean that if you change diameters, the best way to make a speedometer adjustment is to do a test of speedo readout versus GPS readout. Most handheld tuners - or at least the ones I know about - allow adjustments in five-rpmile increments/decrements. The FRPP ProCal lets you do it in one-rpmiles.

Underlying all that "precision" is the reality that speedometer needles are designed such that it's difficult to establish a veridical reading: they are wide enough that you have to rely on your mind-eye to come up with an accurate number. Not impossible, but not all that reliable, either, what with all the perspective and other variables.

 

[BruceH]

WRT tire manufacturers' wheel revolutions per mile: I've found that they'll get you in the ballpark, and are useful in comparison of the behavior of different-size tires, but over-the-road accuracy is not something you should expect.

I mean that if you change diameters, the best way to make a speedometer adjustment is to do a test of speedo readout versus GPS readout. Most handheld tuners - or at least the ones I know about - allow adjustments in five-rpmile increments/decrements. The FRPP ProCal lets you do it in one-rpmiles.

Underlying all that "precision" is the reality that speedometer needles are designed such that it's difficult to establish a veridical reading: they are wide enough that you have to rely on your mind-eye to come up with an accurate number. Not impossible, but not all that reliable, either, what with all the perspective and other variables.

I use math. Tire diameter x 3.142 = circumference. 63360 inches in a mile so divide 63360 by the tire circumference and you have revs per mile for your car.

 

[Skunk]

http://1010tires.com/

Tire calculators are amazing tools aren't they...guess google doesn't work on the op's computer.

 

[RazorbackMustang]

Personally, I wouldn't trust an online calculator for this particular thing. I used one when I switched to Hankook V12 Evos in 275/40/19. It was way off. It came up with 721 or something like that. Went to Hankook's website and they say use 751. Speedo is spot on now. So, go to the tires manufacturer's site and get the proper value for revs per mile for your exact tires.

 

[BadHabit2Break]

Personally, I wouldn't trust an online calculator for this particular thing. I used one when I switched to Hankook V12 Evos in 275/40/19. It was way off. It came up with 721 or something like that. Went to Hankook's website and they say use 751. Speedo is spot on now. So, go to the tires manufacturer's site and get the proper value for revs per mile for your exact tires.

Unfortunately for me, Nitto does not put that on their website.

 

[stkjock]

Unfortunately for me, Nitto does not put that on their website.

call them or email them, MT doesn't either, but a call to their tech desk got me an answer when I needed.

 

[BadHabit2Break]

call them or email them, MT doesn't either, but a call to their tech desk got me an answer when I needed.

will do..thanks

 

[jaymoo7]

20" wheels is 705 tire revs per mile on the SCT X3 tuner.

 

[BadHabit2Break]

20" wheels is 705 tire revs per mile on the SCT X3 tuner.

where did you get that number?

I was under the impression that not all 20" tires have the same Revs Per Mile.

 

[Wnt2gofst]

where did you get that number?

I was under the impression that not all 20" tires have the same Revs Per Mile.

They don't. Different tire sizes, manufactures will be slightly different

Just Another 700whp DD 5.0

 

[RazorbackMustang]

where did you get that number?

I was under the impression that not all 20" tires have the same Revs Per Mile.

Correct. Every tire manufacturer has the info and the only way to get it is through actual testing like they do. Don't use one of the online calculators. Unless you're lucky it won't be the right number.

 

[Sky Render]

Unless you're putting some ludicrously-wrong-sized tires on, your speedo won't be off by that much.