Any way to correct cruise control speed?

Hey all, have had my 33s on for around a year now. Speed was off as expected, and I got a rough country speedometer calibrator to fix that. I think it got better but still 2-3 miles an hour off. I read that there’s gonna be some error but that you can manually correct it if you want. Obviously it accounts for tire wear, but still reads few miles an hour faster. Does anyone have a good correction factor for 255/80/17 tires, out of curiosity?

anyway, I’ve been noticing that when using cruse control, I’ll have the crusie speed set to like 74 and the truck will be doing 79 or so, and if the truck is set at like 69, the truck will be doing like 74-75. Is there any way to fix this? I’m asking you guys who have bigger tires who have used calibrators and such to correct the speedometer difference in wheel speed. Is there any way to fix the speed disparity, or is this just something I need to deal with when using cruise control? Thanks.

 

I use a scan gauge 3 to monitor my speed when i went up in tire size and set the speedometer to an 11% difference than stock

I’m on skinny 35s well 34.6s but whatever

 

I didn't know you could do that, which scan tool did you use to do this?

What tire size and rim are you running?
I'm on 255/85/16 and the oem OR rims, from what I can tell the speedo is off by about 3mph at 65mph.
Ideally I'd like to get new rims but want to minimize rubbing and not cut anything.....getting the backspacing/offset right.

 

it’s the new touch screen scan gauge 3. You can adjust all sorts of stuff in the settings. It’s fuckin sweet and super easy to use, worth every cent.

Im on 255/85/17s method 701s with 0 offset and 4.75 backspacing.

At 70mph I’m really doing 77ish

 

Did you update the module before you installed it? There was a firmware update that addressed some cruise issues.
Did you use a ratio or input tire sizes? On a hypertech or rough country video (same device rebranded), they said to use sidewall size for original size and to actually measure the diameter of your new tire (my “33s” came out to 31.75” average) for the new size.
Using this method I was within 1/2-1mph first try.
It sounds like you’ll have to pull it out and program it either way. You can leave the cable dangling behind the dash and fish it out of the trim after you reinstall the calibrator so you can mess with it without uninstalling, or so I’ve heard

 

Thanks a lot! I’ve had it installed a year, but did update it before I installed it. Maybe they came out with an update between then and now. It hasn’t been removed since, I’m pretty sure. I’ll definitely try try measuring my actual tire diameter and inputting that. However, should I maybe subtract a little bit from that measurement to compensate for tire wear?

 

Hope this helps if you haven't checked it out before!

 

Eh, stock speedo doesn’t compensate for wear. The difference between new and worn will be nominal imo

 

Not sure what is meant here, but my sr5 is bone stock except for 265/70 16 a/t tires. The cruise control always works fine just like in my tundra. You set it for 75 mph, and its always dead on.

 

Correct me if I’m wrong, but I think the SR5 and lower trims come with the smaller 16 inch rims, making their size 265/70/R16, which is equivalent to the 265/65/R17 of the trd sport trim and up. The smaller wheels use a taller sidewalk to compensate for the inch lost being a smaller rim than a 17”. So perhaps that explains your dead on speed?

 

Your correct. I've passed these road side speed signs that use radar, or laser to measure your vehicles speed in these posted areas. Those sign's always read exactly what the digital speedo in my truck reads, if anything at times my truck is 1 mph reading slower.

 

Install the Waze Map app on your phone. It shows the GPS calculated MPH as you are driving as well as the speed limit. It has become my speedometer when I'm on a highway.

 

Yup. That’s what I’m using to compare the speed. I find myself using that a lot. Just wanted to try and get my Speedo within 1mph all the time instead of 2-3, since I figure it’ll add up on the odo after a while, having accrued more miles than I actually have…