How to calibrate Speedometer 89-96 Ford Truck Bronco F150 F250 F350
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- čas přidán 10. 11. 2018
- How to calibrate your speedometer in your OBS ford truck or bronco. Whether bigger tires or smaller, I show you the math and the process in what I hope is a very easy manner. Takes minutes.
TOOLS REQUIRED:
-Piece of wire about 2' long with alligator clips on each end or a digital multimeter set to Continuity.
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#OBSfordSpeedometer #CalibrateOBSfordSpeedometer
1991 and older have 5 digit mechanical odo. I've owned 89 and 91 F150
So you can't calibrate it correct?
I loved the "I have no friends all videos are made alone"lmfao🤣
Just switched 14's to 15's on my 96 Ranger that has the same instrument panel as in the video, should be an easy fix now. Thanks for the video.
Thanks for this video! Been trying to track a transmission issue and turns out someone had tried this and had the speedo reading way faster than ground speed.. which had the trans shifting WAY early! Done this and now it shifts perfect!
Sons truck is on 37’s, calculations came to 735 which got me within 6mph.. changed to 765 calibration and got it within 1mph!
37’s on 18’s?
Thanks so much! Just did this on my 93 Bronco. I would suggest going to the manufacturers website. My 33x12.5x15 BFG ATS were 640 revs. Stock 235 were 972. 640x.0135=864. I would use GPS or find a Radar sign to check mph.Again you made my day!
You can only do that on a digital odometer,my 89 is cable driven
So how do I find the number to multiply it If I have 18 inch rims?
Im here from the link you posted on my video! Awesome, I’m gonna try to calibrate my truck, hopefully it works on my 91, although I doubt that since my cluster is mostly mechanical.
Thought supposed to take revolution per mile multiply by tone ring tooth count divided by 8000
"...because I have no friends..." same bro. Same.
Ehh, better off anyhow, friends are overrated, they get so needy lol
Thank you
You can do this ratio metrically. Just drive next to a friend on the highway that has an accurate speedometer. Then blow your horn and both of you look at your speedometers. Doesn't matter how fast, just make sure the speed is steady and you are both gong the same speed. If your speedo read 60 and his read 68, just divide 60/68 and multiply the result by your PSOM setting.
What about for 35x12.5x15??? Still the .0135?
Yes, all 15's use the .0135
I would love to know how this is done on a pre- 1992
Me too I have an 88 with 33x12.50s and the speedo I waaaaay wrong lol
Would this work on a 2006 e-250? I have gone into the settings by holding down the button and can scroll through but mine only has a single single button. Just curious if you had any experience with that type cluster?
Can you tell me where you got the multiplier for the 16 in rim. I have 22 in rims.
Fishing through the forums. I can't remember exactly where so you'd have to look yourself. There appear to be 4 different calculations. Sometime when I have time to experiment I may be updating the information in this video to see which calculation is most accurate. What I have posted here is from Ford themselves for 15 and 16" wheels, I can't find an exact Verified calculation for anything larger.
Anyone know how to do this for a 86?
Has anyone else had a problem of their select button not doing anything?
Most likely a PMOS ground issue, run a new ground wire to the frame.
that's what I was thinking also, but I haven't had a chance to try it yet, thank you though
What’s the calibration number accounting for? I have 35x12.50x17. Why does the number go up just because you have taller rims?
My thought too. If the tire size is exactly the same but wheel size is different, there shouldn’t be a chnage in rpm’s of the wheel/tire
Question the speed sensor is in the rear differential right? I have a rwd f250 put bigger tires on the rear so I have to calibrate my speedometer? Thanks nice video
No on the transmission on driver's side.
@@rednecktech82 ok so change rear tires and it will need recalibration thanks
.0135 is for a 15 rim what would be the number for a 20inch rim?
Ford only gives us numbers for 15" and 16" wheels as back in OBS days that was pretty much the only options. I've searched the Web far and wide and found all kinds of weird formulas but none I can verify will work. I imagine rim size shouldn't matter it should only matter the total diameter of the tire and revolutions per mile. There should be some calculation dealing with those numbers that tell you the code but I can't find anything definitive to give you so my above suggestion is the best I can personally come up with to get you a starting point.
Nice video, cool they have that feature but I don't think this will work for early 80s trucks like your title suggests. My 85 is all mechanical with a speedo cable.
Thank you for the feedback, after doing some searching online it appears this procedure may only apply to F-series going back to 89 at earliest so I will get this updated. Thanks again!
My guess that the rim size is needed because same tire diameter on a 16 inch rim there is less tire squish?
Your phone went out of the screen as you brought that info up, I'm on their website now and cannot find the conversion number for a 20inch rim
Dont have an answer for that but heres what id try...we know .0135= 15" and .015=16" ...divided out comes to .0009 and .0009375 so you see it increases exponentially as tire gets larger. So try .000938 x 20 = .01875 gives you a starting point and should at least be close. Follow a friend at 35mph and 70mph and see where you're at.
@@rednecktech82 so what do I do for a 18 inch rim?
I like to do the speed limit + 10%
Qustions: I have the same truck. For your truck what Engine? Differental ratios? and how much lift? You truck looks perfect. Any rubbing.
3" or 4" lift w/ 33's (metric tires so around 10.8" wide NOT 12.5"), 4.9 L, no idea on diff but she gets 15 mpg still :)
All the f-150's that i have seen that have never been changed starts out 972! If you do the math on the factory 235/75/15 the number should be 943! I wonder why it is defaulted at 972?
I did the calculation for my BFG 35x12.50 on 17 inch rims. I estimated the multiplier to be .0165 and came up with 602 Rev x .0165. This gives me 993. If it starts at 972 how do I increase the calibration number? Thank you!!! Great video! 93 Ford Bronco
Schedule some time in your day and do a lot of clicking lol, it counts down from 972 when it gets down to 400 or so it goes back around to 1100 and down again.
My 95 f250 doesn't have a digital odometer or digital anything in the instrument cluster.
It most definitely should.
i’ll be your friend bro
If your Speedo is fast, should you increase the number?
just have to do the math and see what it says your speedo should be set to based on tire size etc.
When I get to the CAL screen my select button won’t change the number even tho my select button usually works
I'm having the same problem with one of my trucks...think it's a bad connection from the PSOM to the cluster, I haven't had time to investigate and find out for sure yet.
@@rednecktech82 I thought that too but the select button works normally and I have a new wiring harness underneath the dash so that’s why im at a loss
@@tymcdonald8473 I have 5 of these trucks...and have worked on many others. This is the first time I have encountered this problem. My select button works for everything but changing the PSOM value to get my speedo matched up to my larger tires. If not the physical wiring then has to be an issue with the cluster itself...in it's circuitry I mean. I'd take a good look and see if you have any bad solder connections or burned traces anywhere. I know a weak solder point causes odometers on the 97+ F150's to go out....odometer keeps adding up but the display goes out. I've had to take a few of those apart and resolder them.
@@rednecktech82 well if ya could let me know if ya find the problem
@@rednecktech82 hey I changed my ground I grounded it to the Frame and it worked I suggest trying that
I did this process and recalculated my 31x10.5x15 tires at 879 and made this change from the 972 factory setting. Then I drove the truck and checked the speed. At 65\70\75MPH I noticed that the speedo was reading 4mph slow consistently. I discovered that another CZcamsr had done this process and had a 'factor of 30 which makes sense when you calculate the stock tires and the 972 that was entered by default. By adding this 'factor' to the number, I believe this will fix my incorrect speedo situation. Hopefully this helps others tinkering with their trucks as well. CZcams link here: czcams.com/video/aG6-g-GaFNw/video.html
Also, there is a calculation change for OBS Fords that are 3/4 ton and up and have a bigger differential.
You'll definitely want to verify with a lead vehicle at different speeds to fine tune your calibration. I've found 3 different formulas for this, this was the most widely accepted but doesn't always work for larger wheel/tire combos.
@@briansardou6008 what might that be my man ? I have a 96 f250 7.3 and have 235/85R16 tires
611 x .0135 doesnt equal to 82.485. Do the math again.
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