beating an old horse
 

i have a 2000 silverado 4.3 i need a programmer for larger tires what one is recomended

i have no mods to engine yet i plan better flowing heads and a intake w/electric fans

but right now i can't pass on intersate maybe its just the truck??

please help

Re: beating an old horse
 

You can always have any GM dealer reprogram the tire size with their Tech 2 scan tool. All they need to do is change the rolling diameter of the tires in the ECM. It is a couple minute job that that dealers usually only charge $20 to do. It helps them if you look up the rolling diameter of your tires a head of time before walking into the service department so they don’t have to look it up for you (and charge more for doing so).

A 4.3L in a full-size with larger than stock tires are not a ball of fire. Not much you can do but regear or swap in a V8.

Re: beating an old horse
 

what do you mean by rolling diameter as in 285 or 32" tall

Re: beating an old horse
 

Rev’s per mile at 45 MPH is what I mean by rolling diameter. For example, a 285/75R16 has an overall diameter of around 33” but the Rev’s per mile (and what the ECM needs to know) is 630. There is a mathematical method of converting a tire size to rolling diameter but I cannot remember how it goes, so.....let's take BFG’s word for it…. Check this out and it will make more sense.

http://www.bfgoodrichtires.com/specs...t-a-ko/44.html

Re: beating an old horse
 

i can get to a tech 2 so i'll play and let ya'll know

Re: beating an old horse
 

I found this in a search. It is from http://www.tirereview.com/?type=cc&id=179&53L3c73d=179

Speedometer Change Calculator

Whenever you change tire diameters, you also impact the accuracy of the vehicle’s speedometer. A tire with a larger diameter revolves fewer times per mile than a tire with a smaller diameter. Change tire diameter and you effectively change the revolution speed of the vehicle's drivetrain, to which the speedometer is connected.

To determine a tire’s revolutions per mile, divide 20,800 by the tire's overall diameter. Example: 20,800/28.9 = 719.72 revs per mile.

With that information, you can now measure the impact a tire change will have on speedometer accuracy:

Determine the revs per mile for both the current and recommended tires. Use either the tire maker’s databook or the calculation method above.

Divide the figure for the current tire by the figure for the tire you’re recommending. Example: If the current tire measures 842 revs per mile and the recommended tire measures 800 revs per mile, the formula is 842/800 = 1.0525.

Multiply the result by a speedometer reading in miles per hour. Use 60 mph as a baseline number. Example: 1.0525 X 60 = 63.15. So a 42 revs per mile change means that when the driver’s speedometer reads 60 mph, his true speed is 63.15 mph.

Remember that the difference grows exponentially as speed increases. If you calculate against 80 mph, for example, the difference is 4.2 mph. At 100 mph, the difference is 5.25 mph.



Tire Diameter Calculator


The overall diameter of a metric or P-metric sized tire can easily be calculated by using the tire’s stated size. To calculate overall tire diameter, you must first determine section height and section width. The section width already appears in the sizing nomenclature. For example: For size P225/50R16, the section width is 225 millimeters.

Convert the metric measure to inches by dividing by 25.4. (225 ÷ 25.4 = 8.86 inches)
Multiply the section height in inches by the aspect ratio (in this case, 50) to determine the section height. (8.86 x 50% = 4.43 inches)
Multiply the section height by 2, then add the wheel diameter as noted in the tire size. In this example, the wheel diameter is 16 inches. (4.43 x 2 + 16 = 24.86 inches – Overall Tire Diameter)
This formula will work for any metric or P-metric sized tire

Re: beating an old horse
 

I have an Excell spreadsheet that uses these same calculations. It is better to go with your tire manufacture's info if it is available. Look at the 2 charts on the top and plug in your tire size, this is for the P-metric tire sizes only (ex. P225/70R15). PM me if you want it. I can't upload it as it is not compatable with this site.

Re: beating an old horse
 

i went into tech 2 and it asked tire size and i put in 285 75 16 im going for a long ride on highway i'll let you know when i return

any one else have ideas for fuel economy or pep at the pedal

Re: beating an old horse
 

You know that is funny, I did my 2005 HD yesterday for the 255/85R16’s that were just installed but that size wasn’t in there so I had to go with 285’s as well. I was very suprised to see actual tires sizes to select from. Apparently, I was way wrong with my previous post stating you needed rolling diameter. I swear not long ago you had to enter rolling diameter as tire sizes were not in the Tech 2 that I recall. Not sure if the latest techline updates to the Tech 2 changed that or if I confused that with the Allison Transmission DOC software. Sorry….glad it worked out though.

Fuel economy should increase on the highway but I suspect it will be a little more sluggish out of the hole. Getting rid of torque management would probably help with that part.

Re: beating an old horse
 

better mpg but still not there on pep i am thinking programmer any thoughts??