265/70/17 Tires

[sona]

Hey guys, I just got a set of BFG KO All Terrains on my 2006 Explorer. I'm extremely happy with the look and fitment. They do rub at full lock on the fender liners, but I'm going to re-drill the holes and pin them back a little bit to correct that.

The issue I do have with the new tires is the MPG. If I keep it at 60 (65 with normal tires) I can get around 21 MPG on the HWY. But If I do anything above that, I go down to 16-18. Which is damn unacceptable. I called an off road shop to see what I could do about it, and they recommended a tune. They charge $330 for it. It essentially corrects the new tire size in the ECU and changes all of the shift points, corrects the off-kilter speedometer.

I was wondering if anyone on here has done this with any luck? I can see it fixing the speedometer, but I don't know what to expect for gas mileage improvements.

I really want to weight out my options because if this MPG is what I'm stuck with, I will have to sell the tires.

Also, does anyone know if I could benefit from re-gearing? Everything is stock except the tires.

4.0 V6

 

[FLOffroad]

If they want $300 just to fix the speedo, I'd say buy a handheld basic tuner yourself. And, you don't really need to regear for 265/60R17; if you went to 4.10s, you might be able to pull off better city mpg, but your highway will drop. Also, after you reprogram, your mpg will probably increase because currently the computer is calculating as if you had stock tires.

My old local dealership only charged me an extra $50 to reprogram the speedo when I got my tires.

 

[sona]

If they want $300 just to fix the speedo, I'd say buy a handheld basic tuner yourself. And, you don't really need to regear for 265/60R17; if you went to 4.10s, you might be able to pull off better city mpg, but your highway will drop. Also, after you reprogram, your mpg will probably increase because currently the computer is calculating as if you had stock tires.

My old local dealership only charged me an extra $50 to reprogram the speedo when I got my tires.

Are you running the same size as me?

And all they did is make the speedo accurate?

They said it changes shift points as well.

Or maybe by correcting the speedo, you correct the shift points?

 

[FLOffroad]

My dealer just changed the speedo, not shift points; however, doing the recalibration to fix the speedo may actually change the shift points as well (I don't know exactly how the units work in our vehicles).

I don't have the same size tire, I have 255/60R18; however, they shouldn't charge more because your tire is slightly larger. It's just a bit of tapping on a computer.

Also, with the handheld tuner, you can modify your shift points, correct for re-gearing (if you decide to ever), and various other tasks. Without a doubt, a serious tuning shop can do a better job with shift points, etc. than a hand-held tuner, but if fixing your speedo and mpg is your main concern, the handheld tuner will be up to the job (and then you can read your own diagnostic codes too).

 

[RJ]

Hey guys, I just got a set of BFG KO All Terrains on my 2006 Explorer. I'm extremely happy with the look and fitment. They do rub at full lock on the fender liners, but I'm going to re-drill the holes and pin them back a little bit to correct that.

The issue I do have with the new tires is the MPG. If I keep it at 60 (65 with normal tires) I can get around 21 MPG on the HWY. But If I do anything above that, I go down to 16-18. Which is damn unacceptable. I called an off road shop to see what I could do about it, and they recommended a tune. They charge $330 for it. It essentially corrects the new tire size in the ECU and changes all of the shift points, corrects the off-kilter speedometer.

I was wondering if anyone on here has done this with any luck? I can see it fixing the speedometer, but I don't know what to expect for gas mileage improvements.

I really want to weight out my options because if this MPG is what I'm stuck with, I will have to sell the tires.

Also, does anyone know if I could benefit from re-gearing? Everything is stock except the tires.

4.0 V6

To answer your question - what's your rpm at 65 mph when your mpg starts going downhill? More importantly, is your converter locked?

If it is, with 3.55s, you must be around 1700 ish. If you re-gear, it would only hurt your level ground hwy mileage.

If your converter is UNLOCKED, your rpm would fluctuating all over the place from 2000 to 2800ish. In this case, a re-gear to 4.10s would allow you to stay locked longer and improve mpg quite a bit.

 

[CDW6212R]

Look into a flasher like the SCT Excal III, and James Henson here to tune it. A basic dealer reflash computer update will not compete with a real true PCM tune like James does. The flashers run around $350 new(with programming too), but used units can be had for half of that usually.

BTW, if you cannot keep those 265/70/17s, my sister could use them for her Jeep Wrangler Unlimited, here in Knoxville.

 

[sona]

To answer your question - what's your rpm at 65 mph when your mpg starts going downhill? More importantly, is your converter locked?

If it is, with 3.55s, you must be around 1700 ish. If you re-gear, it would only hurt your level ground hwy mileage.

If your converter is UNLOCKED, your rpm would fluctuating all over the place from 2000 to 2800ish. In this case, a re-gear to 4.10s would allow you to stay locked longer and improve mpg quite a bit.

I currently have no tach or speedo because of an unrelated issue. Ill get back to you on that.

What do you mean by my converter being locked?

 

[sona]

Look into a flasher like the SCT Excal III, and James Henson here to tune it. A basic dealer reflash computer update will not compete with a real true PCM tune like James does. The flashers run around $350 new(with programming too), but used units can be had for half of that usually.

BTW, if you cannot keep those 265/70/17s, my sister could use them for her Jeep Wrangler Unlimited, here in Knoxville.

That is the advice a local off road shop gave me here.

How much would a tune from James run?

I may consider it if I can't find a viable solution.

 

[RJ]

I currently have no tach or speedo because of an unrelated issue. Ill get back to you on that.

What do you mean by my converter being locked?

Your torque converter.

When it's locked your RPMs are steady like a manual. When it's unlocked, it jumps all over the place, even within a gear. That's good for acceleration and throttle response, but had for heat and fuel economy.

If your gear is too tall, then it'll stay unlocked longer, more often.

 

[CDW6212R]

Look into a flasher like the SCT Excal III, and James Henson here to tune it. A basic dealer reflash computer update will not compete with a real true PCM tune like James does. The flashers run around $350 new(with programming too), but used units can be had for half of that usually.

BTW, if you cannot keep those 265/70/17s, my sister could use them for her Jeep Wrangler Unlimited, here in Knoxville.

That is the advice a local off road shop gave me here.

How much would a tune from James run?

I may consider it if I can't find a viable solution.

Contact James here about costs and possibly a used flasher. Buying a new one includes the tune(or two to three), from a tuner like James a used one he will price it to you with the tune needed(or without if you wanted to have someone else do it).

http://www.hensonperformance.com/

 

[sona]

Your torque converter.

When it's locked your RPMs are steady like a manual. When it's unlocked, it jumps all over the place, even within a gear. That's good for acceleration and throttle response, but had for heat and fuel economy.

If your gear is too tall, then it'll stay unlocked longer, more often.

Oh wow, How do you lock it?

 

[sona]

Contact James here about costs and possibly a used flasher. Buying a new one includes the tune(or two to three), from a tuner like James a used one he will price it to you with the tune needed(or without if you wanted to have someone else do it).

http://www.hensonperformance.com/

I will likely have him tune it once I get this issue figured out and I actually have a working instrument cluster again.

http://www.explorerforum.com/forums/showthread.php?t=411024

Conveniently enough I actually live in Birmingham, where Jame's shop is.

 

[RJ]

Oh wow, How do you lock it?

The computer does it for you, if conditions are right.

Say at 65 mph, if your throttle is light enough (10%, rough guess), then it locks it and stays locked unless you punch it (then it unlocks first, and downshifts if needed).

If your tires/gears are too tall, and you need say, 15% of throttle to keep a constant 65 mph cruise. The computer NEVER locks it.

You'll feel it and see it by watching your tach.

 

[CDW6212R]

The computer does it for you, if conditions are right.

Say at 65 mph, if your throttle is light enough (10%, rough guess), then it locks it and stays locked unless you punch it (then it unlocks first, and downshifts if needed).

If your tires/gears are too tall, and you need say, 15% of throttle to keep a constant 65 mph cruise. The computer NEVER locks it.

You'll feel it and see it by watching your tach.

Also to see it unlock, to make it unlock, drive a steady speed and watch the rpm level. While driving steady with the right foot steady on the gas, gently touch the brake pedal with the left foot. With no real brake effect(just touch it), watch the rpm's jump up a few hundred. That is the computer sensing the brakes being applied, and it unlocks the converter(which raises the rpm).