Just Installed Firestone Destination XT in LT255/75 R17 C Load. PSI and Speedometer/MPH Conversions.

[lazynorse]

Truck: XLT Crew Cab FX4. Stock suspension.

Picked these tires after much research. Went with them because they're rated well in all conditions, specifically wet handling (needed in WA State), weigh less than same size C load BFGoodrich , Coopers, Falkens and other ATs and are cheaper ($288/tire) than some of the most popular ATs. They just might be the tallest tires you can fit on a stock suspension. No rubs and still some clearance from the crash bars.

A couple members here gave them high marks too. I only have 5 driving miles on them so far, but the drive home was fine, didn't notice much difference over the stock Hankook ATMs.

Stock Hankooks were 30.5" while these new Firestone Destination XTs are 32." That is on paper. Once I got home, on the truck they measured just over 31." This must be due to the deformation of the tire carrying the load of the truck. It must be 32" fully inflated off the truck.

Wanted to figure out what PSI adjustments - if any - I might need. Same goes for Speedometer. This is purely theoretical, as its all internet research based, using established calculators against Ford Ranger specs and my exact new and old tire specs.

At some point, I'll either take the plunge to figure out ForSCAN (is this even still an option? thought I read problems on new licenses?) or buy a terribly overpriced device that just does speedometer calibration from tire size. I'd rather my speedometer, odometer and MPG estimator be more accurate. Once I get some paved and unpaved miles under them, I'll report back on these Destination XTs.

Here's the source material, and my MPH increase cheat sheet. Hope this is helpful, let me know if you notice any errors. Love to hear your attempts to adjust to different tire sizes.

Tire Pressure Calculator
https://overlandracksontario.com/tire-pressure-calculator/

Ford Ranger Specs
https://www.thecarconnection.com/specifications/ford_ranger_2022

Firestone Destination XT Specs
https://tirepressure.com/firestone-destination-x-t-tire-pressure

Firestone Destination XT LT255/75/17 C Load Pressures
34 Front, 37 Rear OR 33 Front and Back (using max GVWR divided by 2, more conservative than gross axle weights )

Speedometer Calibration Calculator
https://tiresize.com/speedometer-calibration/

Old MPH = New MPH (265/65/17 to 255/75/17)
40 = 42
60 = 63
70 = 73.5
80 = 84
90 = 94.5

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[Frenchy]

Assuming you might have something like the Livernois My Touch there is a way to calibrate the Spedometer. Just need to find the revolution per mile. How to get that? Call Firestone Directly. Do not call the different Firestone Auto Cares as they dont seem to have that info.

As for pressure i will ask this, what does the door placard say? Mine said 30 and I stuck with that. Never had an issue. Your placard might say 38 so if you have it low it may cause problems. Also a low tire pressure usually results in better ride quality. Too low can result in low traction(30 to 38 you wont have that issue)

 

[Cabose-1]

This might help with forscan. This is on a thread somewhere here in the forum. And i would do a chalk test to get psi. J have those same tires but have not put them on yet.

I have taken a many screen shot here to save info

 

[Cabose-1]

My notss for future reference with forscan.

 

[Cabose-1]

So value from cactory is what is on the truck bcm now. From factory. It nneds to be changed to the value on wiki for forscan. It has been tested to be true here on the forum.

The numbers that say app, is the numbers from a tire comparison app. So strange that the real numbers and app numbers are so off. Guess the app isnt so great. Just a reference guide

 

[jadatis]

Made you a pressure/axleload list, after I googled your tire for the loadindex.
Was 111/108
Only for singleload axle so 2 tires on the axle

Maxload single 2403 lbs a tire so 4806 lbs AT 50 psi, per axle.
In front of psi using 90% of the loadcapacity calculated for the pressure, and behind no reserve, as is given in official pressure/loadcapacity-lists.

I determined 90% using for 99mph maxload, to give maximum reserve with still acceptable comfort and gripp for onroad use And I use a even safer calculation then the official european, comes close to lineair calculation, as is used in the calculator of your link. 90% using has same effect as first adding 11.1% to the axleload before calculating, the linked calculator uses 5%.

Axle 90%/ psi/ per axle
=11.1% res/cold/no reserve
1901 lbs/ 20 psi / 2113 lbs
1984 lbs/ 21 psi / 2205 lbs
2067 lbs/ 22 psi / 2296 lbs/ min onroad EUR
2149 lbs/ 23 psi / 2388 lbs
2231 lbs/ 24 psi / 2479 lbs
2314 lbs/ 25 psi / 2571 lbs
2396 lbs/ 26 psi / 2662 lbs/min onroad US
2477 lbs/ 27 psi / 2753 lbs
2559 lbs/ 28 psi / 2843 lbs
2640 lbs/ 29 psi / 2934 lbs
2722 lbs/ 30 psi / 3024 lbs
2803 lbs/ 31 psi / 3114 lbs
2884 lbs/ 32 psi / 3205 lbs
2965 lbs/ 33 psi / 3294 lbs
3046 lbs/ 34 psi / 3384 lbs
3127 lbs/ 35 psi / 3474 lbs
3207 lbs/ 36 psi / 3564 lbs
3288 lbs/ 37 psi / 3653 lbs
3368 lbs/ 38 psi / 3742 lbs
3448 lbs/ 39 psi / 3831 lbs
3528 lbs/ 40 psi / 3920 lbs
3608 lbs/ 41 psi / 4009 lbs
3688 lbs/ 42 psi / 4098 lbs
3768 lbs/ 43 psi / 4187 lbs
3848 lbs/ 44 psi / 4276 lbs
3928 lbs/ 45 psi / 4364 lbs
4007 lbs/ 46 psi / 4453 lbs
4087 lbs/ 47 psi / 4541 lbs
4166 lbs/ 48 psi / 4629 lbs
4246 lbs/ 49 psi / 4717 lbs
4325 lbs/ 50 psi / 4806 lbs/ referencepress
4404 lbs/ 51 psi / 4893 lbs
4483 lbs/ 52 psi / 4981 lbs
4562 lbs/ 53 psi / 5069 lbs
4641 lbs/ 54 psi / 5157 lbs
4720 lbs/ 55 psi / 5245 lbs
4799 lbs/ 56 psi / 5332 lbs
4878 lbs/ 57 psi / 5420 lbs
4956 lbs/ 58 psi / 5507 lbs
5035 lbs/ 59 psi / 5594 lbs
5113 lbs/ 60 psi / 5682 lbs/ sometimes given maxcold

 

[Frenchy]

Made you a pressure/axleload list, after I googled your tire for the loadindex.
Was 111/108
Only for singleload axle so 2 tires on the axle

Maxload single 2403 lbs a tire so 4806 lbs AT 50 psi, per axle.
In front of psi using 90% of the loadcapacity calculated for the pressure, and behind no reserve, as is given in official pressure/loadcapacity-lists.

I determined 90% using for 99mph maxload, to give maximum reserve with still acceptable comfort and gripp for onroad use And I use a even safer calculation then the official european, comes close to lineair calculation, as is used in the calculator of your link. 90% using has same effect as first adding 11.1% to the axleload before calculating, the linked calculator uses 5%.

Axle 90%/ psi/ per axle
=11.1% res/cold/no reserve
1901 lbs/ 20 psi / 2113 lbs
1984 lbs/ 21 psi / 2205 lbs
2067 lbs/ 22 psi / 2296 lbs/ min onroad EUR
2149 lbs/ 23 psi / 2388 lbs
2231 lbs/ 24 psi / 2479 lbs
2314 lbs/ 25 psi / 2571 lbs
2396 lbs/ 26 psi / 2662 lbs/min onroad US
2477 lbs/ 27 psi / 2753 lbs
2559 lbs/ 28 psi / 2843 lbs
2640 lbs/ 29 psi / 2934 lbs
2722 lbs/ 30 psi / 3024 lbs
2803 lbs/ 31 psi / 3114 lbs
2884 lbs/ 32 psi / 3205 lbs
2965 lbs/ 33 psi / 3294 lbs
3046 lbs/ 34 psi / 3384 lbs
3127 lbs/ 35 psi / 3474 lbs
3207 lbs/ 36 psi / 3564 lbs
3288 lbs/ 37 psi / 3653 lbs
3368 lbs/ 38 psi / 3742 lbs
3448 lbs/ 39 psi / 3831 lbs
3528 lbs/ 40 psi / 3920 lbs
3608 lbs/ 41 psi / 4009 lbs
3688 lbs/ 42 psi / 4098 lbs
3768 lbs/ 43 psi / 4187 lbs
3848 lbs/ 44 psi / 4276 lbs
3928 lbs/ 45 psi / 4364 lbs
4007 lbs/ 46 psi / 4453 lbs
4087 lbs/ 47 psi / 4541 lbs
4166 lbs/ 48 psi / 4629 lbs
4246 lbs/ 49 psi / 4717 lbs
4325 lbs/ 50 psi / 4806 lbs/ referencepress
4404 lbs/ 51 psi / 4893 lbs
4483 lbs/ 52 psi / 4981 lbs
4562 lbs/ 53 psi / 5069 lbs
4641 lbs/ 54 psi / 5157 lbs
4720 lbs/ 55 psi / 5245 lbs
4799 lbs/ 56 psi / 5332 lbs
4878 lbs/ 57 psi / 5420 lbs
4956 lbs/ 58 psi / 5507 lbs
5035 lbs/ 59 psi / 5594 lbs
5113 lbs/ 60 psi / 5682 lbs/ sometimes given maxcold

Wouldn't bother with that load chart as I'm still trying to figure out running 50 PSI. Remember that each tire works together to hold the vehicle up. Going that high will make your head rattle.

 

[jadatis]

The average axleweights in this forum will give in the list a lower then 50 psi pressure.

So in fact, I dont see what point you are trying to make

 

[lazynorse]

Btw, here’s how they look on a Cactus Gray FX4. Stock suspension.

Here’s the old Hankook ATMs, below.

I wish the Firestones offered white lettering in LT255/75/17 but they don’t. Height difference - 1.5” - isn’t super obvious from the bottom two photo’s perspective but by eye they fill out the wheel well much better.

 

[Langwilliams]

Those look cool. Looks like they are light for an LT tire at 40 pounds. I went with Nitto 265/70/17 an they weight about 41. I really watch tire weight when tire shopping to avoid the mpg hit an the extra mass spinning while braking.

 

[JasonTremor]

For the general atx 265/70/17 load range C on the Tremor, Ford specs 39psi all around. Might be a good starting point for the new Firestones.

 

[Frenchy]

For the general atx 265/70/17 load range C on the Tremor, Ford specs 39psi all around. Might be a good starting point for the new Firestones.

And the best part is the Firestone Destination XT's are way better than the General Grabbers in many aspects!! The wet traction is great, snow traction is very good for an All-Terrain(ATX and KO2 dont even compare) and are quite thoughout it's life span unlike the ATX and KO2.

 

[Frenchy]

Btw, here’s how they look on a Cactus Gray FX4. Stock suspension.

Here’s the old Hankook ATMs, below.

I wish the Firestones offered white lettering in LT255/75/17 but they don’t. Height difference - 1.5” - isn’t super obvious from the bottom two photo’s perspective but by eye they fill out the wheel well much better.

Yeah I definitely prefer the white letter out myself. My 2019 with 285/70-17's was Blackwall only. My 1993 Pathfinder on the otherhand with 31x10.50x15's has White Letter out!!

 

[Frenchy]

Those look cool. Looks like they are light for an LT tire at 40 pounds. I went with Nitto 265/70/17 an they weight about 41. I really watch tire weight when tire shopping to avoid the mpg hit an the extra mass spinning while braking.

Not just the weight but also the price too!! Compared to other tires in its class it has usually been a lower price and yet it holds up very well OffRoad!! I have experience with that in my 93 Pathfinder and my old 2019 Ranger!! Even with a service van i ran i never got a single puncture!!

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