Tire options - Goodyear/Goodrich? 31/33?

[Gsmblue]

Currently I am running Goodyear Wrangler Duratrac 31x10.5x15 on both my Bronco and my F150.

The Bronco has a ~3inch body lift and the 31" tires are not enough to look balanced. My original plan was to undo the lift.

Now my wife said she doesn't want me to undo the lift and I am thinking of different tires instead.

The Goodyears are ok. no good in slippy conditions, like frost/ice/compacted snow. So I am looking at BFGoodrich - All-Terrain T/A KO2 in 33x12.5x15 but I have no experience with them.

My 2 questions are:

1. Are there any other considerations I need to keep in mind by bumping up to 33inch tires? like clearances?

2. Has anyone here run KO2 tires in winter conditions and have any thoughts on them?

Thanks!

 

[Gsmblue]

And a pic for context.

and the bottom of this pic:

[Gary Lewis]

And a pic for context.

and the bottom of this pic:

What gears are you running? 33's would look better but they'll give you higher effective gearing. 35's would look great but really change the gearing.

Use the calculator (Documentation/Driveline/Calculators) and see what the tires do to overall gearing and RPM. But the really tall OD on the AOD might not like the 35's if you have 3.55 gearing.

[Gsmblue]

What gears are you running? 33's would look better but they'll give you higher effective gearing. 35's would look great but really change the gearing.

Use the calculator (Documentation/Driveline/Calculators) and see what the tires do to overall gearing and RPM. But the really tall OD on the AOD might not like the 35's if you have 3.55 gearing.

Thank Gary,

I never bottomed out what the gearing is. I will tinker with the calculator.

All I can say is, it is too low!

Another reason to move up in tire size...

[Gsmblue]

Thank Gary,

I never bottomed out what the gearing is. I will tinker with the calculator.

All I can say is, it is too low!

Another reason to move up in tire size...

Played with the calculator.

I have previously noted @55mph on the speedo I am seeing 2100rpm on the tach. The speedo has been accurate to the extent the digital speed signs on the side of the highway confirm I am doing 55mph when the speedo says 55mph.

With the rolling diameter (on paper) of my 31inch tires being 30.8 this would suggest my final drive is in the order of 5.3 or so.

I knew it was low but I was not expecting that. So not a factory final drive...

When I get the Bronco back I will try this again and use GPS for the speed and make notes at different speeds to tabulate.

Going to a 33inch class tire could see me get ~100rpm less at 55rpm which would be nice.

[Rusty_S85]

I have a set of KO2`s on my truck 31x10.50-15. I wanted to stick with the KO1`s but when it came time to replace the other two tires to have a full set of KO1s I was informed they were discontinued in favor of the KO2s.

They ride great and provide great traction but only thing I dont like is the aggressive shoulder now scrubs my radius arm where the KO1 and the Discount Tire house brand Pathfiders never scrubbed.

I dont have a lift kit but I will be installing new springs front and rear with coil springs I think its 2 1/2" taller than stock as a leveling kit without using the blocks.

[Gary Lewis]

Played with the calculator.

I have previously noted @55mph on the speedo I am seeing 2100rpm on the tach. The speedo has been accurate to the extent the digital speed signs on the side of the highway confirm I am doing 55mph when the speedo says 55mph.

With the rolling diameter (on paper) of my 31inch tires being 30.8 this would suggest my final drive is in the order of 5.3 or so.

I knew it was low but I was not expecting that. So not a factory final drive...

When I get the Bronco back I will try this again and use GPS for the speed and make notes at different speeds to tabulate.

Going to a 33inch class tire could see me get ~100rpm less at 55rpm which would be nice.

Yes, I get 2131 as the R's at 55 MPH using 5.3 gears. Wow, that is LOW! 33" tires net 1,989 and 35" give 1,875. You could easily turn 35's with that 351.

I'm more familiar with R's at 65 MPH, and with 35's you'd be turning 2,216. And with 33's it'd be 2,350. Those are still a bit higher than I like for relaxed cruising. For comparison, Big Blue turns 1,795 at 65 MPH in 5th gear, and 2,362 in the 1:1 4th gear. So with 33's you'd be turning what I'm turning in 4th, and I went to the ZF5 to get the 5th gear.

Depending on what you are going to do with the truck, you might consider 35's. Any highway use and you'll like the bigger tire.

Another way to look at it, the ZF5's 1st gear is a creeper gear and it gives an overall gear ratio of 20.31:1 with my 3.55 gear. But your AOD's 1st gear isn't nearly that low and gives an overall gear ratio of 12.72:1. That's not bad as my 2nd gear gives a 15.34:1 overall ratio, so you'll still have a reasonably low 1st gear.

[Gsmblue]

Yes, I get 2131 as the R's at 55 MPH using 5.3 gears. Wow, that is LOW! 33" tires net 1,989 and 35" give 1,875. You could easily turn 35's with that 351.

I'm more familiar with R's at 65 MPH, and with 35's you'd be turning 2,216. And with 33's it'd be 2,350. Those are still a bit higher than I like for relaxed cruising. For comparison, Big Blue turns 1,795 at 65 MPH in 5th gear, and 2,362 in the 1:1 4th gear. So with 33's you'd be turning what I'm turning in 4th, and I went to the ZF5 to get the 5th gear.

Depending on what you are going to do with the truck, you might consider 35's. Any highway use and you'll like the bigger tire.

Another way to look at it, the ZF5's 1st gear is a creeper gear and it gives an overall gear ratio of 20.31:1 with my 3.55 gear. But your AOD's 1st gear isn't nearly that low and gives an overall gear ratio of 12.72:1. That's not bad as my 2nd gear gives a 15.34:1 overall ratio, so you'll still have a reasonably low 1st gear.

Thanks Gary, that is all super helpful.

I think 35s will look too big. I can handle the the higher RPM for now, most of the driving will be around town and on roads that are 55mph or less (to get to the lakes).

Previously with the C6 transmission I was at ~3krpm at 55mph!

I can re-gear the rear axle at a later date, it is on my to do list for 2022.. looks like a straight forward process to drop in a new pumpkin.

I am leaning towards the BFG KO2 at this time. The spec is an outer diameter of 32.5inches.

[Gary Lewis]

Thanks Gary, that is all super helpful.

I think 35s will look too big. I can handle the the higher RPM for now, most of the driving will be around town and on roads that are 55mph or less (to get to the lakes).

Previously with the C6 transmission I was at ~3krpm at 55mph!

I can re-gear the rear axle at a later date, it is on my to do list for 2022.. looks like a straight forward process to drop in a new pumpkin.

I am leaning towards the BFG KO2 at this time. The spec is an outer diameter of 32.5inches.

If you are going to re-gear then the smaller tires may be just right.

[Gsmblue]

I have a set of KO2`s on my truck 31x10.50-15. I wanted to stick with the KO1`s but when it came time to replace the other two tires to have a full set of KO1s I was informed they were discontinued in favor of the KO2s.

They ride great and provide great traction but only thing I dont like is the aggressive shoulder now scrubs my radius arm where the KO1 and the Discount Tire house brand Pathfiders never scrubbed.

I dont have a lift kit but I will be installing new springs front and rear with coil springs I think its 2 1/2" taller than stock as a leveling kit without using the blocks.

Thanks for the feedback on the KO2. I think that is the way forward.

My rims are 8.5inch so not sure you can even get 35s on there!