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2bbs 2021 bronco build

tiresize.com

37X12.50R16 Tires

37X12.50R16 tire conversion. Convert 37X12.50R16 tire size to inches and compare prices on available tires from the top brands online.
tiresize.com tiresize.com

37x12.5R16 is 545 revolutions per mile. 116.2" circumference. [5.72:1 gear ratio]

33x10.5R16 is 611 rev per mile. 103.6" circumf. [ 4.70 :1 gear ratio]

Stock, each turn of the pinion/driveshaft in whatever gear is 1:1 transmission, would get you 22.04" [103.6/4.7] of forward progress

Currently, each turn of pinion gets you 20.31" [116.2/5.72]

Your max available gear is 5.38 in the computer, so what tire size gets you 20.31" of forward progress with 5.38 gear? 20.31*5.38=109.26" circumference divided by Pi = 35" tire [34.8]

35" tire is 109.9" circum divided by 5.38 = 20.42" forward progress.

you could also try out a 24" tire [185/55r16] with a 3.7 gear ratio, that'd get you 20.37" of forward progress per pinion input. That'd be pretty close to the 20.31" you are currently making in the real world with a 37 and 5.72


and now i'll go and read the linked thread to see how close I am with other people :homer:
 
2big bronco said:
Thought about that also. Leave gear ratio alone at 4.70 where the computer likes it and see how small of tires it will allow.

But at this point the calculation of what size is beyond my 🧠 capacity
Click to expand...
20.3" x 4.7 = 95.47 / 3.14 = 30.40"

20.3" is our target travel distance for what really happens

4.7 is the ring/pinion reduction

95.47 is the circumference required to make that distance

3.14 is close enough to the ratio between circumference and diameter

30.40" is the result for 4.7 ring/pinion

If it will let you put in partial sizes, that'd work. Otherwise, 30" tire would be closer than 31"


edit: looks like I went about it in the same way as everybody else
 
Provience said:
20.3" x 4.7 = 95.47 / 3.14 = 30.40"

20.3" is our target travel distance for what really happens

4.7 is the ring/pinion reduction

95.47 is the circumference required to make that distance

3.14 is close enough to the ratio between circumference and diameter

30.40" is the result for 4.7 ring/pinion

If it will let you put in partial sizes, that'd work. Otherwise, 30" tire would be closer than 31"


edit: looks like I went about it in the same way as everybody else
Click to expand...

It will let you input partial sizes as it actually wants the circumference in mm
 
Provience said:
well....that's miserable [though it does save on math] :laughing: Gotta get the rolling circumference for you particular tire then. What brand/size are you using, other than just 37"
Click to expand...

If he didn't have the portals throwing a wrench in the mix, the common practice is center of hub to the ground to get your radius, since that's what is actually happening.

Gearing is 22% lower than stock, and tires are 12%? Larger, so basically my dumb short cut math says 30" tire should be very close to stock.
 
alright, had to go back to page 3 :rasta:

tiresize.com

Cooper Discoverer STT PRO 37X12.50R17

tiresize.com tiresize.com

Cooper STT Pro 37" tire is listed 565 revolutions per mile

5,280' (1 mile) divided by 565 equals 9.345 feet per revolution, equals 112.14 inches per revolution times 25.4 to get to MM is 2,848.39 mm per revolution....divided by 5.72 gear ratio gives us a TARGET of 497.97 MM distance for each driveshaft revolution

497.97 times 4.7 gear ratio gives 2,340.459 MM circumference target.
 
YotaAtieToo said:
If he didn't have the portals throwing a wrench in the mix, the common practice is center of hub to the ground to get your radius, since that's what is actually happening.

Gearing is 22% lower than stock, and tires are 12%? Larger, so basically my dumb short cut math says 30" tire should be very close to stock.
Click to expand...
sure, but who has a metric tape measure :confused: the MM requirement is what I was calling miserable :rasta:
 
Provience said:
alright, had to go back to page 3 :rasta:

tiresize.com

Cooper Discoverer STT PRO 37X12.50R17

tiresize.com tiresize.com

Cooper STT Pro 37" tire is listed 565 revolutions per mile

5,280' (1 mile) divided by 565 equals 9.345 feet per revolution, equals 112.14 inches per revolution times 25.4 to get to MM is 2,848.39 mm per revolution....divided by 5.72 gear ratio gives us a TARGET of 497.97 MM distance for each driveshaft revolution

497.97 times 4.7 gear ratio gives 2,340.459 MM circumference target.
Click to expand...

So since you seem like a math god to me right now...

Stock tires were input into the bronco computer as having a circumference of 2525mm wich is a bit smaller then the advertised 33s



So 2525 mm circumference with 4.70 gears is what the computer sees as stock

And according to your math above the cooper 37s have a circumference of 2848mm with my new 5.734 gears.

I think these numbers are as close as we can get^^^
 
2big bronco said:
So since you seem like a math god to me right now...

Stock tires were input into the bronco computer as having a circumference of 2525mm wich is a bit smaller then the advertised 33s

So 2525 mm circumference with 4.70 gears is what the computer sees as stock
Click to expand...

That'd put the stock setup showing 2525/4.7 = 537.23 mm for each driveshaft rotation [edit: this number doesn't really mean much though, since we can change it. it's more important to get it to read the speedometer accurate, as then the engine RPM will be matching the ABS Tone Rings. Iffin you've got the portal reduction matched between front and rear due to where they read before/after reduction]

you are currently making 497.97 mm for each driveshaft rotation

Iffin' your speedometer was real good and your GPS was real good, you should be traveling 8% slower on GPS than the speedometer shows.

in 7th (1:1) at 50 mph on the speedometer, GPS should show 46 mph. That's the only thing it should be doing. Since ford is super cool and wants to use a calculated speed, that must be outside the threshold of acceptable difference between engine RPM
 
bdkw1 said:
Man you people like to over complicate a simple math problem.
Click to expand...

I thought so also :laughing:

All I did was 1.22 ratio in the portals (what I recall)

37 ÷ 33 = 1.12

My dumb math says he's 10% lower than stock and a 30" tire is about 10% smaller :laughing:

So put in about 2275 and see what happens.
 
YotaAtieToo said:
I thought so also :laughing:

All I did was 1.22 ratio in the portals (what I recall)

37 ÷ 33 = 1.12

My dumb math says he's 10% lower than stock and a 30" tire is about 10% smaller :laughing:

So put in about 2275 and see what happens.
Click to expand...
only thing that misses is taking account of the max input gear ratio being different than the actual installed gear ratio. but otherwise, yeah if you are just taking it all on the tire, add in tire and portal and have at it


edit: because all the math I did was assuming the sensors are not reading the portal reduction :rasta:
 
Provience said:
only thing that misses is taking account of the max input gear ratio being different than the actual installed gear ratio. but otherwise, yeah if you are just taking it all on the tire, add in tire and portal and have at it


edit: because all the math I did was assuming the sensors are not reading the portal reduction :rasta:
Click to expand...

Obviously there is a very complex system on this rig that maybe none of us fully understand.

I agree, the sensors aren't seeing the portals. Which is why I think I'd leave the r&p ratio, and just mess with tire size.
 
Without research I’m thinking front and rear revolutions are off compared to each other?

Isn’t that the only thing that changed besides the rack?
 
bdkw1 said:
Man you people like to over complicate a simple math problem.
Click to expand...
Make it really simple, put a piece of tape on the side of the tire front and back and mark where it is on the ground, have somebody watch it and drive it till it makes a full revolution. Mark that spot, measure the number of inches of tape measure and multiply by 25.4.
That gives you the loaded tire circumference (which will vary based on tire pressure) in MM, then use the difference in differential ratios to give you the gearing differences.

Aaron Z
 
Sounds like the ECU compares front axle sensors vs rear axle sensors. Did they say how many teeth are on the factory tone ring vs the new modified one? Sounds like no matter what gear ratio you pick it won’t be happy if the new tone ring doesn’t have the right amount of teeth. The ECU will think the clutch is slipping all the time because the signals won’t be within an acceptable range.
 
So no luck changing tire sizes and leaving gearing alone. Tried 30.4 and 30" tire sizes with 4.70 gears.


Other person with the manual bronco has 200 miles on his problem free. Only difference is he used a procal tuner, 40" tires, also has a new centerforce clutch.

I still really dont want to believe my clutch is slipping.... at all. Spins the tires, and bogs when it gets traction. Freeway driving rpms stay consistant with speed.

I also have verified that my computer is in fact holding whatever input I am giving it.... so not sure what procal would do differently
 
I wonder if a tuner with a four wheel dyno is what you need to troubleshoot this.
 
cj3a said:
I wonder if a tuner with a four wheel dyno is what you need to troubleshoot this.
Click to expand...

Hmm... that makes me wonder if there's a PID available... and if something like an Edge CTS3 could see it real time??
 
rockota said:
Hmm... that makes me wonder if there's a PID available... and if something like an Edge CTS3 could see it real time??
Click to expand...

So reading the wheel speed sensors in real time showed very close to true mph... all 4 of them... so either the tone rings are correct in thier 22% different tooth count, or the computer is compensating somewhere.


So I played around some more... the further I tried to move things to where the computer would like my intputs, the quicler everything would tweek out..... so I started going the opposite way.
Now im at 540 gears and 36" tires and ive gotten 25 miles on no light or reduced power. The seconed farthest ive gone without problems. The computer down inside it is throwing a code for "out of spec" but its not causing an actual issue... yet and not throwing any check engine problems.

Also its a hard code that cant be deleated without changing specs back to range and doing a relearn to the awd modual and pcm. I could live with the hard code if everthing else stays good
 
Hi folks! Had to register to post here...new to this forum! Some of you guys know me from the Bronco 6g forum. I'm the other guy who installed 74Weld portals on a 7mt Bronco. I was in the process of unpacking my pallet when Snacktime hipped me to this thread. I think I have wrapped my head around what it going on for 2BB, but (knock on wood) I have not had this problem. I already had a procal device married to my Bronco, so instead of Forscan I used that to set tire size and gear ratio. I'm still a smidge off on the tire size, but the maximum 5.40 gear ratio it will allow me to set, appears to be working for me! Don't know if that is a procal limit, or a Ford software limit...have not tried ratio change in Forscan, and not sure where to do it. Either way tire size and gear ratio are 2 different internal calculations and the computer won't accept you trying to spoof one w/the other. AT doesn't have this problem because of OBD requirements, So AT guys don't worry about it! I have run about a tank and a half of fuel through it, and I'm happy w/it right now!
 
Bmadda said:
Hi folks! Had to register to post here...new to this forum! Some of you guys know me from the Bronco 6g forum. I'm the other guy who installed 74Weld portals on a 7mt Bronco. I was in the process of unpacking my pallet when Snacktime hipped me to this thread. I think I have wrapped my head around what it going on for 2BB, but (knock on wood) I have not had this problem. I already had a procal device married to my Bronco, so instead of Forscan I used that to set tire size and gear ratio. I'm still a smidge off on the tire size, but the maximum 5.40 gear ratio it will allow me to set, appears to be working for me! Don't know if that is a procal limit, or a Ford software limit...have not tried ratio change in Forscan, and not sure where to do it. Either way tire size and gear ratio are 2 different internal calculations and the computer won't accept you trying to spoof one w/the other. AT doesn't have this problem because of OBD requirements, So AT guys don't worry about it! I have run about a tank and a half of fuel through it, and I'm happy w/it right now!
Click to expand...
Nice to see you over here... I used your inputs converted from revolutions per mile over to circumference in mm for forescan and have about 20 miles problem free.... but ai donr have my hopes up yet. I am running 37s to your 40s and it looks like your input gets you to 36.1" tire. My speedometer is off by about 2.5 mph at 60 reading low.
Anyhow, im hoping to put some more miles on it this week.
 
2big bronco said:
Nice to see you over here... I used your inputs converted from revolutions per mile over to circumference in mm for forescan and have about 20 miles problem free.... but ai donr have my hopes up yet. I am running 37s to your 40s and it looks like your input gets you to 36.1" tire. My speedometer is off by about 2.5 mph at 60 reading low.
Anyhow, im hoping to put some more miles on it this week.
Click to expand...
I have found that the math doesn't work out. What I do is pick a random number based loosely on how far it's off, then I put a gps on the dash (or my phone w/a gps speedo) and set the cruise at say 70-75 on the interstate, and lower the number till I find the sweet spot. Tedious process cause you can't do it while the vehicle is on the road. You gotta make a mental note of how far off it is, then stop somewhere to make the adjustment Haven't quite dialed the 40s perfect yet, when I get some time I will, but I went through this whole process w/the 37s and even put a stagger tape on them, but the math doesn't work!
 
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