tire roll out measurement for pcm programmer

[REC06]

Any body have a tire roll out measurement for 285/75/16? I had to go back to stock for the winter, my son now has the 285's and I need a measurement for the order I placed for the pcm programer. Thanks

[bryantch]

you can find the information at tirerack.com for your specific tire. rolling diameters vary from manuf to manuf. look up the tire you have and go to the specs where you will find the revolutions per mile listed. divide by 5280 feet and you are there.

example: BFG AT KO in you size is 632 rev/mile or 100.25 inches per revolution (pretty sure the math is correct here smile.gif

hope this helps

[Kennedy]

If you want accurate mumbers, measure yourself. Tire specs vary from mfr to mfr. Pressure as well as rim width also play into this. If you want a ballpark, then the specs would be sufficient.

On edit: I should add that this suggestion is made by Steve Cole the actual programmer for the current reflash units/programmers.

[ 12-18-2002: Message edited by: kennedy ]</p>

[REC06]

Placed an order need to give the guys some numbers. I want acurate numbers, but as I said I am back to stock tire for now and the 285's arn't available to measure. So i will spech the tire I plan to put on. I went to tire rack and found the spec's. not sure I did the math right.

(revs per mile) divided by (5280 ft per mile)equals (feet per rev) multiply (by twelve) equals (inches per rev) Multiply (by 2) Equals ( two revs in inches for programmer.????????????????????

Thanks I'll give it a try

[TraceF]

Here is how to measure-

Place a small spot of grease on the center of the tire tread. You can also press a piece of shop crayon between the tread. On a flat surface roll the truck forward slowly until the grease or crayon makes two marks after one full revolution of the tire. Measure the distance between the center of each of the two marks. Divide by 3.1416 for accurate height. If the tire is properly inflated it won't expand much at high speed (centrifigual force) but will at low pressures. This is the best way I know to measure. Good luck.

[REC06]

tracef,

Problem is I dont have the tires yet and was looking for somebody's measurement or math to do it from spec's.

[pinehill]

REC06,

The following will give you what you want:

Divide rev/mile by 5,280 = rev/ft

Divide rev/ft by 12 = rev/in

Invert rev/in (ie, divide 1 by rev/in) to get in/rev

Multiple in/rev by whatever the programmer requires.

Happy Holidays!

[mtomac]

I have bfg all terrain 285's on the stock rims. If this is the tire/rim you will be using I can do a roll out measurement for you.

[REC06]

Michael Tomac,
That would be great.

Pine hill,
Thanks for the math, can't seem to make it come out right. 652(revs per mile) :confused:

thanks for the help

[pinehill]

Using the computation shown above applied to your revs/mile, I get 97.2 inches for one revolution. Seems about right.

[mtomac]

285x75R16 BFG All Terrain T/A KO on factory rims - 99.5" @ rear tire 40psi cold

I run 50psi in front and 40psi in the rear when running empty for more even wear. Loaded I put the rears @ 65psi (max inflation).

Does anyone have the rollout measurement for the stock 245 Firestone steeltex tires @ 40psi cold. I'm curious what they measure out at. With the stock tires I thought my speedo was 1mph low according to a mobile radar booth.

On edit:
I will try to get a rollout measurement at 65psi cold.

[ 12-23-2002: Message edited by: Micheal Tomac ]</p>

[REC06]

Michael Tomac,
stock 245/75/16 tire with 75 lbs air on stock rim gave a roll out of 93.5 inches

[mtomac]

If it wouldn't be too much trouble could you check it with 40psi in the rear. That's what I ran the stockers at empty. With the snow finally gone I'll get a rollout with the BFG 285's w/65psi cold on stock rims

[REC06]

M.T.
sure it will be a few days as the snow is dumping and I have a pallet of salt in the rear. Ill let you know.....

[mtomac]

BFG 285's w/65psi on stock rims - 100" rollout @ rear tire