my truck came with 205/75/14....I just swapped on those larger tires. how do I figure out my speed? TIA

 

you can do a couple of things. I did the same with my 94, the speedo remains pretty close, the odometer is off by 4 miles per 100. you can either get out on a highway and run at 60 mph over a measured distance like 10 of the mile markers. Start the clock when you go by the 1st and then not time when you cross the last. Then do a search for a milage conversion site. I used to have one but cant find now. it will ask for your time for the distance and tell ya the speed. Its important to maintain the chosen speed. also you will have noted the odometer and then you can calculate the difference. found a link for ya:

http://www.machinehead-software.co.u...time_calc.html

An easier way is with one of the new navigators they have a speed readout that is accurate as sit is GPS based.

Ford also sells a converter gear for the trans. Tell them the tire sizes and the trans rear end info and they will sell it to ya less than $10. I got one but it made things worse so I left my original in.

 

A quick and dirty way is to maintain a steady speed on the speedo between two mile markers and time yourself. Then divide 3600 by that number. Like 60 seconds = 60 MPH, 50 sec = 72 MPH. Another way is to go to a Ford dealer and have him flash your computer with the new tire size.

 

Most GPS units show your speed too.

 

Thanks for all the feedback....I used the GPS idea and that was reporting 65 from the when the speedo said 60...........I also found this calculator and that came out to be just about the same.......the speedo says 60 and you are actually going 66

Tire size calculator

 

With over size tires, the faster you go, the worse your speed-o-meter gets. I can read only a couple of miles per hour faster than you are actually going at 25 and be 8 or 10 mph off at 65.

 

If you google "tire size calculator" you will find lots of little apps to calculate the difference in tire size and effect on your speedo reading, including:

Tire Size Calculator - Compare Tire Sizes


Later: Oops - sorry. Missed the OP's response where he had figured/found this out already!

 

I'm about to do the same, got any pics? I wondered how much room I would have in the front.

 

no pics. I bought them off of CL. the tires are almost new..probably about 5k on them....goodyear wrangler rts?.......they came off an explorer...........the aluminum rims are pretty beat up.......I paid $200........truck riudes much better.....the old tires made it feel like driving a go-kart compared to these.

 

Yeah me too except the rims were pretty good, the tires are shot and I only paid $100. I have a pic of them in my photo gallery propped in front of the existing wheels.

 

check your speed between mile markers.then get different teeth speedo gears like the one that goes in to your tranny.then pick the one that is as close as possible.i used to run 30-950-15s.untill i wore them out.but when i figured out which gear worked.my speedo was accurate within one tenth .
thanks for the 96 2.3 timing picture.
yes im working on a 72 sedan deville that i got for 500.00.the guy i bought it from put a new timing chain.it runs good .now im detailing it .
thank everybody
lrd56

 

Here is a link to a program that may do what you want:

GearCalc

Give it a try.

 

Question, if my ranger has smaller than stock tires, will it make a difference in the speedometer? If so, what kind and I plan to bring it back to stock....

 

"Question, if my ranger has smaller than stock tires, will it make a difference in the speedometer? If so, what kind and I plan to bring it back to stock.... "

Yes. Use the previously posted GearCalc program to determine the difference. To bring your truck back to stock, you need to get the proper sized tires. Using undersized tires may result in exceeding the load capacity of your present tires.

 

I ran undersized tires once (to save money on the tires). I noticed that I had a slight increase in power on the hills and an equally slight decrease in gas mileage. The speed-o-meter registered about 6 or 8 MPH faster than I was actually going at 60. After i wore those tires out, I returned to using stock tires. (98 Ranger 3.0 5 speed)