Tire/Wheel size on a 67 with a ZF and 4:10/4:11

[Adam7118]

Hey guys. Looking for some advise on tire/wheel sizes. Building a 67 with a Coyote Motor, ZF5 trans, 4:10/4:11 gear ratio. Cosmetically I'd like to fill the wheel well, but I'd also like the nicest ratio/ride possible (and maybe take advantage of some Black Friday deals). I was hoping for 33's. but the 2 inch body lift to fit the coyote and 2.5 inch suspension lift might look a little funny with 33's.

 

[Bitch'nBronco]

Is your bronco cut? Stock width axles? I have the same total amount of lift as you. First picture is on 33x12.5r15 and second photo is 35x12.5r15 to give you an idea of how 33 and 35 fits the wheel wells with 4.5" of total lift over stock

 

[nvrstuk]

Tough call for ya.

Looks vrs fun to drive.

For me, I'm 98% practical

 

[DirtDonk]

For me, I'm 98% practical

Meaning, you only change it if it breaks?

 

[nvrstuk]

Meaning I usually change stuff b4 it breaks. Least I used to...

that started changing when Gary helped me with my first doubler...that's when things started twisting... hear that GY? lol

All your fault buddy!

Now I do it because it's a challenge & fun- like the doubler b4 there were ways to do it over the counter.

 

[Broncobowsher]

You are at an odd place.
While you have the lift for larger tires, and the asthetic choice to run them to fill the wheel wells.
But the gearing says to run smaller tires.

 

[Tricky Dick]

Is your bronco cut?

This is the most important piece of info to give good feedback. If it's uncut or just flared quarters you can get by with a much smaller tire. If you have cut out flares: have to go much bigger.

A Coyote F150 will commonly have 32" tires with a 3:55 or so axle, with both the 6 and 10 speed autos having a steeper OD than the manual ZF. Mathematically both a 33 and 35 should work just fine with your gearing.

 

[Hallboss]

Is your bronco cut? Stock width axles? I have the same total amount of lift as you. First picture is on 33x12.5r15 and second photo is 35x12.5r15 to give you an idea of how 33 and 35 fits the wheel wells with 4.5" of total lift over stock

Great comparison… thanks for the 35’s pic on the Falken’s. I’m an inch taller at 5.5 and very satisfied with the look/performance of the 35x12.5r15s

 

[Broncobowsher]

This is the most important piece of info to give good feedback. If it's uncut or just flared quarters you can get by with a much smaller tire. If you have cut out flares: have to go much bigger.

A Coyote F150 will commonly have 32" tires with a 3:55 or so axle, with both the 6 and 10 speed autos having a steeper OD than the manual ZF. Mathematically both a 33 and 35 should work just fine with your gearing.

The trouble with comparing to a modern F150 is the Bronco doesn't have the aero that the new truck has. The modern autos will downshift for the slightest hill and you won't even know it. Rowing a 5-speed and having to drop to 4th on every grade (or lug the engine if not too bad) will get tiring real quick.

 

[Tricky Dick]

The trouble with comparing to a modern F150 is the Bronco doesn't have the aero that the new truck has. The modern autos will downshift for the slightest hill and you won't even know it. Rowing a 5-speed and having to drop to 4th on every grade (or lug the engine if not too bad) will get tiring real quick.

That's true, but it doesn't have the weight or frontal area either. Plus 5th in a ZF5 is similar to 8th in a 10 speed, so you're already "downshifted" twice at all times.

 

[bsquared]

Mine is uncut and I have the same lift and gears and run a 5.0L EFI in front of my ZF with 31's. They are about perfect for the overdrive. You should be able to move up to 33's with the added power of the Coyote but I would think you would be downshifting a lot with the 35's.

 

[AZ73]

You didn't say which ZF5 trans you have as the first gear varies and will make a difference on your choice of tires.

	1st	2nd	3rd	4th	5th	Reverse
ZF S5-42 Close	4.14:1	2.37:1	1.42:1	1.00:1	0.77:1	3.79:1
ZF S5-42 Wide	5.72:1	2.94:1	1.61:1	1.00:1	0.77:1	5.24:1
ZF S5-47 Close	5.08:1	2.60:1	1.53:1	1.00:1	0.77:1	4.66:1
ZF S5-47 Wide	5.72:1	2.94:1	1.61:1	1.00:1	0.77:1	5.24:1

I'm too busy to get into the detailed math (there's calculators on the internet you can plug and play with)

 

[Broncobowsher]

Close ratio was only offered with a diesel engine. You can't use a diesel transmission on a gas engine, the bellhousing and input shaft are both wrong. The gas engine ratios are the same.