another tire question

i tried searching but couldn't really find anything.

is 305/50x20 the same as 33x12.50x20?

 

32x12x20

google "metric tire conversion"

 

Using the revs-per-mile numbers for the General Grabber AT2, the 305/50-20 is about 4% larger than stock and the 33x12.50-20 is about 14% larger than stock.

245/75-16 = 679 revs/mile
305/50-20 = 652
33x12.50-20 = 597

On my truck, the 305/50-20 would just about correct the speedometer error, but throw the odometer off by a bit.

Mike

 

I thought the odometer and speedometer used the same sensor? How would they be different?

 

The speedometer needle mechanism just isn't as accurate as the odometer on my Tacoma or any other vehicle that I have owned. Legally (by DOT regulation) the speedometer cannot read lower than the actual speed. It hasn't always been this way. There used to be a DOT specified margin of error. Now there is only no higher than indicated. I think that the manufacturers err on the side of caution, so some speedos read only only slightly high, while others can read wildly (like 15 MPH) high on older cars like my Volkswagens.

Mike

 

I've unplugged the speed sensor on a couple cars when doing my exhaust or other things and everytime the speedo and odo wouldn't work. I think they pull the same signal off the tranny speed sensor. And yes I agree the speedo is slightly high to avoid lawsuits.

 

Under the Mods & Tutorials drop down at the top of the site there is a tire size calculator

http://www.tacomaworld.com/forum/tirecalc.php

 

This tire calculator does not produce accurate numbers, even for the stock Tacoma tire sizes. Tire dimensions change as you drive, and the rim width affects the dimensions, too. Revs/mile is the most accurate way of comparing speedometer offset and torque/gearing differences. I most often use Tire Rack for the specs, but have occasionally found that their numbers are significantly different from the manufacturer's data.

Mike

 

Say it ain't so