37KO3s @ Real World Dimensions

[kmc0929]

The OEM Goodyears are listed as having an actual diameter of 35.1" @ 65LBS - Looking at KO3s in 37x12.50R18, these show a specification of 36.5" in actual diameter @ 66 LBS.


This question gets asked all the time, I understand that 37s will fit, however what are the ramifications of that 1.5" increased diameter on power / drivetrain / steering. That seems like a small amount of increased diameter. Anyone with KO3s using the existing Tremor / Diesel suspension? Seems shocking that the 37" KO3s would be so similar in weight to the OEM Goodyears? Vehicle in question is a 2024 250 Diesel Tremor.

 

[mrmag00]

These trucks have plenty of power and brakes to handle 37” tires. Not sure if you’ll even feel the difference, other than mileage.

 

[ramv]

I had 37”s on my Power Wagon (and my ‘01 Ram 1500) both were fine with OEM 4.10s but went to 5.13s on both and they were better. Honestly withe the diesel and 3.55s it feels a little low geared, I try to start in second empty. I think 37”s would be a minor change.

 

[TX Crawler]

You'll never notice the difference. Other than at the pump....

 

[Blade420Play🔪🏆]

You'll never notice the difference. Other than at the pump....

A little with shifting too. At least at first

 

[Avslash]

I just swapped my OG Duratracs for KO3's in 37.5x12.5x18.

Honestly don't notice much, if any, difference in driving. I did notice the difference in step in/out height until I got used to it.

I'm not a MPG tracker by nature so I don't have any detailed comparison, but I feel like it's about a 1-2mpg hit on MPG. In about 1,500 miles since the change I'm averaging 18.3 in mixed driving per the truck. I drove 600 miles last weekend and played with it a bit on that trip. At 75, I could still hit 21mpg on the dash, but it gets uglier the faster you go, and this is Texas, so we do go...

The above is all based on a stock suspended truck with about 250 pounds in the bed.

 

[kmc0929]

I just swapped my OG Duratracs for KO3's in 37.5x12.5x18.

Honestly don't notice much, if any, difference in driving. I did notice the difference in step in/out height until I got used to it.

I'm not a MPG tracker by nature so I don't have any detailed comparison, but I feel like it's about a 1-2mpg hit on MPG. In about 1,500 miles since the change I'm averaging 18.3 in mixed driving per the truck. I drove 600 miles last weekend and played with it a bit on that trip. At 75, I could still hit 21mpg on the dash, but it gets uglier the faster you go, and this is Texas, so we do go...

The above is all based on a stock suspended truck with about 250 pounds in the bed.

Did you do the KO3s with the factory suspension and wheels? Have a photo?

 

[Avslash]

Did you do the KO3s with the factory suspension and wheels? Have a photo?

Yep.

Give me a minute and I'll upload here.

 

[Apples]

This question gets asked all the time, I understand that 37s will fit, however what are the ramifications of that 1.5" increased diameter on power / drivetrain / steering. That seems like a small amount of increased diameter. Anyone with KO3s using the existing Tremor / Diesel suspension? Seems shocking that the 37" KO3s would be so similar in weight to the OEM Goodyears? Vehicle in question is a 2024 250 Diesel Tremor.

Usually as I get to a near-2" increase in overall tire diameter, I start thinking about spending the money to re-gear my truck, but that was a Coyote-engine F150...

I drive a Godzilla Tremor with less than HALF of the torque output of either 6.7 Powerstroke offering, and I just went from the 35.1" Duratrac to a Nitto Recon Grappler in a 37 X 11.5 X 17 (had to change wheels too).

Of course a Godzilla Tremor Package truck has 4.30 axles. After driving it in stock form, the adding better shocks, a cat-back exhaust the gearing began to feel almost too short!

When a tire diameter leaves the 33" range and goes larger, the greater diameter matters in that when we increase the diameter from our true 35" to a nominal 37" creating only a 1.5" increase in overall diameter... there's far less penalty to our overall effective final drive gearing.

In fact! the 1.5" increase to my truck's effective final drive gearing was/is AS IF I HAD KEPT THE 35" Goodyears and changed the ring-and-pinions to a 4.10. That's it.

It's perfect, now.

Of course there may be a small penalty to any 1st gear/Low Range 4WD crawl gearing, but the wheelbase is too long for bashing the boulders on the Rubicon Trail, and I just two weekends ago ran some semi-gnarly trails in Moab with a group from this great forum and the truck performed flawlessly!

Very happy with the 1.5" tire diameter increase and it's effect on my truck's effective final drive gearing. Your Powerstroke will never notice it.

DO IT.

 

[Blade420Play🔪🏆]

I just swapped my OG Duratracs for KO3's in 37.5x12.5x18.

Honestly don't notice much, if any, difference in driving. I did notice the difference in step in/out height until I got used to it.

I'm not a MPG tracker by nature so I don't have any detailed comparison, but I feel like it's about a 1-2mpg hit on MPG. In about 1,500 miles since the change I'm averaging 18.3 in mixed driving per the truck. I drove 600 miles last weekend and played with it a bit on that trip. At 75, I could still hit 21mpg on the dash, but it gets uglier the faster you go, and this is Texas, so we do go...

The above is all based on a stock suspended truck with about 250 pounds in the bed.

I am running only 1-2 mpg less without changing the tire diameter in forscan. Sometimes I get 11.5, sometimes I get 9.5

 

[Apples]

When a tire diameter leaves the 33" range and goes larger, the greater diameter matters in that when we increase the diameter from our true 35" to a nominal 37" creating only a 1.5" increase in overall diameter... there's far less penalty to our overall effective final drive gearing.

To simplify the above gibberish, I mean to say that when a tire diameter gets bigger, any further increase from that diameter has less effect on final drive gearing. The percentage of the increase is less.

Good luck on your install. The only thing you may have to watch out for is the front swaybar at full steering lock. If it's a problem, don't worry. Just spend more money to rid yourself of that issue and go buy a Carli [front] torsion swaybar!

Simple, see!

 

[Apples]

without changing the tire diameter in forscan.

you must change

2799, baby!

Works a treat! and gives the 36.5" tire a near-perfect calibration for the truck.

 

[Blade420Play🔪🏆]

you must change

2799, baby!

Works a treat! and gives the 36.5" tire a near-perfect calibration for the truck.

Mine are 36.9
They say 36.8 on the site, but I am on 8 inch rims so when inflated I get a little extra bulge

 

[DFS]

I put KO3 in 37x12.5R17 on my Raptor, inflated to 34 rear and 36 front, they measured 35.25" diameter. Ended up returning them because they wouldn't balance. Back to OEM KO2 37x12.5R17 that measure 35.75" diameter inflated.

 

[Apples]

^ ^ ^ more than likely a measurement from the ground to the top of the tire, with the truck's usual weight compressing the tire contact patch.

Others can refer to this as the tires' loaded radius. Either way, it is a more-accurate measurement to use when wanting to recalibrate one's speed-O-meter.

 

[kmc0929]

I put KO3 in 37x12.5R17 on my Raptor, inflated to 34 rear and 36 front, they measured 35.25" diameter. Ended up returning them because they wouldn't balance. Back to OEM KO2 37x12.5R17 that measure 35.75" diameter inflated.

Was hoping for an undersize situation. 36" seems like the sweet spot for the Tremor suspension / tire fit.

 

[kmc0929]

To simplify the above gibberish, I mean to say that when a tire diameter gets bigger, any further increase from that diameter has less effect on final drive gearing. The percentage of the increase is less.

Good luck on your install. The only thing you may have to watch out for is the front swaybar at full steering lock. If it's a problem, don't worry. Just spend more money to rid yourself of that issue and go buy a Carli [front] torsion swaybar!

Simple, see!

The conflict here is the "Tremor" suspension. Something feels off about getting the Tremor package and then changing out all the Tremor components

I'd like to add a literal "1 inch" to the front suspension of this truck, however it doesn't seem there is a method to do this without changing out several components or detracting from the upgraded OEM suspension.

 

[jred225]

I love the K03's. I've put 15k miles on them in 7 months.
Towing 18k lbs, long road trips, snow, daily driving. Great tires.