I have an error message. I tried to post it in the HPTuners board, but it won't let me, tells me I am banned even though I have never posted there before..... WTF? So I beg for help here, and hope the HPT guys read that it banned me on their board so they can fix it. Username: shimp

So, I have not attempted to calibrate my speedo, but I think I need to because my truck came with 235/75/16 tires and I now have 235/70/16. They are a little shorter than originals. Also, my GPS used to read dead-on with my dash speedo, but now it varies from 1mph off at about 35mph to 2mph off at 70mph to 3-5mph off at 100mph. So I want to fix it to make it accurate. No need me going 48 or 49 in a 50mph zone. Or 67-68 in a 70mph. So my 130mph post earlier was probably more like 124-125mph.

I found using some tire diameter calculator online that they are 29.0 inches. My HPT Speedo window says Error on the current tire size and the commit button is greyed out, will not let me click it. And says calculated tire size is 29.08. I don't have this problem looking at the file from my girlfriends truck (2002 Sierra), the commit button is there and tire size says 29.21 for current and 29.62 for calculated.

So what is up with that?

What diameter are my new tires really? 29.0 don't sound right. More like 28.something I would think by looking at them.

Here's a screenshot of my Error:

 

Whats your screenname over there...I'll see if i can get you unbanned if thats the case.

 

Hey shimp try now...

 

That was fast. It works now. BTW: Can I use the numbers that are generated from tire size and gear ratio change in my girlfriends 2002 Sierra file and just paste them into my file and write the flash? Her file lets me change gear ratio and tire size, and gives me new numbers to work with. Then I just undo the changes in her file and do not save it so it won't mess with her speedo setting.

 

Im not sure, but I'll make sure they see the thread & hopefully get you a fix if possible.

 

Thanks. BTW if anyone has a good tire size calculator that takes into consideration the squishing of the tire by the trucks weight please post link.


Thanks!

 

I don't think you will find one that can account for weight "squish". There are too many variables on that like exact weight per tire, air temp and the brand of tire. I know my Michelin's seem to have a softer sidewall than other tires and the front ones tend to look a little low on air at times even when they are not. But I have had good luck getting over 85,000 mile on a previous set of Michelin's.

 

I gather the best way is to just keep trying different tire sizes in tenths of an inch at a time or so until I get my speedo back to being matched with the GPS. It literally used to be dead-on at any mile per hour with the GPS. Will I need to recalculate the Transmission tables to stop it from getting off with higher speeds or will it all fall back into place if I leave the tables alone because they were perfect before?

 

I dont have any idea about that since I don't yet have HPT, although I plan on buying it soon, but I would think the tire size calculator should compensate for all of that.

 

I have a thread over at HPTuners Board and I am sure they will help me get it worked out. Their support is very quick to react. I am very impressed so far, definately worth the money I paid. There will always be a few hitches with anything high-tech.

I am happy with my purchase, I just wish I knew more about tuning with it. I have read some guides and it's starting to make sense, slowly but surely. Just takes time, anyone with a good grasp on how a combustion engine works, and a little experience with older non-computer engines can learn the HPTuners. Don't have to be a scientist, it just looks that way at first. It's those darn tables. There are so many of them.... When you get it, take it slowly and read as many of the guides on tuning with it as you can. That's what I am doing.