I installed taller tires on my truck(285's). Is there a way to adjust the speedo using the ECM?

 

The dealer is the only place I know of. The price depends on where you go.

 

Dealer job unless you have the DRBII.

Adjustment is made on the PMC, tech needs to know revs/mile of your tire.

http://www.discounttire.com/dtc/broc...tireMathNS.jsp

 

superchips programmer claims to be able too.

 

I have the superchips and it does offer tire sizes to 38" in 1/4" increments, plus you get a code scanner and if you use it with an ez or van aaken the bottom end is unbelievable!!!! BTW 285s' are barely worth worrying about shave 3% off your speed

 

And your odometer.

 

The charts I looked at showed about 10% difference? How do you figure 3%.

 

Depends on what you had to begin with.

245-75/16 to 285-75-16 is 7.8%

265-75/16 to 285-75/16 is 3.7%

I did mine the expensive way, Superlift Truespeed, about $250.

This was before the ECM solution was discovered, as previsously they thought they could only go up to a 265, which is what mine came with from the factory.
(many still think that is as high as they can go)

The procedure is listed step by step in here somewhere, and is quite simple, if you can talk the tech through it.
I did a search and couldn't find it though.

It is in the ABS menu, there is a choice of tire sizes or "other", then you set the revolutions per mile of whatever size you want.


phox

 

You may be correct if you are adjusting just based on using p-metric tire sizing. If you go by revs per mile, your options are much broader.

 

I'd like to know where he came up with the 3% also....

I was running 285's on my 99 and was stopped by CHP for going 14 mph over what I showed on the speedometer - and my dealer even told me that it wasn't more than 3 or 4 mph off.. WRONG! LOL

Luckily the CHP officer was decent, he let me go with a butt chewing - he also had a truck with over sized tires and understood when I told him what the dealer told me - I had just put the tires on the truck a few days before.

I recently switched to 295's and had the rev's per mile with me when I went to the dealer and they FINALLY got my speedo setup right! At least now I can try to get a good check on my MPG...

 

ok ok ok!!! I have a GPS and I know for a fact it's 7% off. AND, I drove 100 miles on the interstate and the ode said 93. My math says 7%.
OK, so we know how much its off, does anyone know of a way to reprogram the ECM without going to the dealer??? I have Superchips and can not use it because it promps you to adjust the speedo for and upgrade in the chip, no can do, because I allready have an Edge fuel module and can not run a chip with it.
OK people, any ideas?
Thanks,

 

Does that thing allow you to adjust the speedo? If not, the only other way would be to go to a speedometer repair shop that I can think of.....

 

I had my truck paced with a stock truck and without going to the ten thousandth mine was off just a fudge over 3% I suppose since my truck was bought used it could have been recaled. Even if it was 7% and you got a 14 over ticket you should do the math...200mph + 7% =214....and he let you off!!!!!! you got the luck!

 

Could it be that your truck came stock with 245's? I think that may be the difference. That would double the finding for my truck. I did the math with mine (265's to 285's) and as stated above my speedo is off 3.5%. Verified with GPS. Abott also makes a box for around $180... Good luck, Phil

 

Thanks Phil.