This might be in the wrong sub-forum, but I thought I'd try here first.

I have a 2005 4x4. I have the Bilstein adjustable shocks and plan on installing a 1.5" aal. I want to run 305 BFG ATs.

My question -- whats the easiest and cheapist way to correct the odometer. I really don't want a tune as that is the only mod I want to accomplish.

Thoughts? If it is a tuner, care to recommend one?

 

What size BFG's? 305 is the width in mm, the overall tire diameter is what you are concerned with.

If you are going from a stock 32" tire to a 33" tire you probably will not need any correction as the factory gauge usually reads a bit over actual speed (my truck does anyway, verified with my GPS).

Give us you stock tire size and what you plan to go with and we can help you a bit more.

 

You can find the rev's/mile for the 305's at Tirerack.com's website. Go to the sizes and specs section and all of the tire info is listed. If a tuner is what you want I have a Superchips 1815 I'll see you and it will correct for the new tire size too.

 

The BFG 305x65x18 tire is close to 34 inches tall and probably will throw your speedometer off about 3 to 4 mph. I have an Edge programmer to correct for my 315x70 BFG's. I was off about 5 mph.

 

Most dealerships charge around $80 to recalibrate the speedo/odometer.

 

I have a Lariat with the factory 18" wheels. I still have the oem Goodyears, which iirc are 275/75/18?

I want the BFG 305/65/18 size.

I hope that helps a little.

Wandell, can all dealerships do it? My local dealer said the computer could not be calibrated to a different tire size.

 

Your stockers are 275-65-18 which are ~32.1. The BFG's in 305/65/18 which is ~33.7.

That is only a ~5% difference which I would be willing to bet is within the current margin of error of the factory speedometer.

I would suggest trying to find someone with a gps to test your actual speed at 60-70 mph. Your difference at 70mph will only be ~3.7mph so it is really not that big of a deal.

Yes your computer can be re-calibrated if you are really concerned about it. Try a different dealer.

 

In my neck of the woods, that 3.7 mph could cost about $300 bucks a ticket. The CHP will give you 5-8 over the limit, but that's about it. If you think you're doing 5 over and are actually closer to 10, it could cost you. I have to get mine corrected (315-70-17's).

 

Hence:



Bottom line:
Get tires
verify actual speed with GPS
Find dealer willing to calibrate computer if necessary (or buy inexpensive tuner and DIY).