How do you calibrate speedometer after bigger tire size?

Went from stock 275/65r/18 to 275/80r/18 tire size.....what is that computer software we can download....Tech Stream.....what do I do after I down load it....and I think it’s just a dummied down software for us novice users.....so where do I download it from?..... now I been using Forscan for my Ford vehicles.....that works great....but I’ve never used Tech stream.....Am I going in the right direction with tech stream to correct my speedometer....Thought I’d ask our members...and I’ll google the how to use tech stream to correct my speedometer.....I hope that’s the proper way for us do it yourself amateur back yard mechanics.....ha....lol...Sunny and warm in Puget Sound.....

 

Mine reads 70 and I’m actually at 73mph. Thought about it but 3mph at 70 is easy to live with..I have no clue if tech stream can correct the Speedo?
http://www.hypertech.com/SpeedometerCalibrator.aspx

 

I'm pretty sure you can't adjust for tire size with Techstream. Hypertech or something similar. After I changed my tires I found that with my speedometer reading 65 I was going 68 by GPS, not enough for me to worry about.

 

For those who have done this, how bad is the install? Took a look at the instructions, and that looks like a LOT of dismantling.

Also, does the module somehow detect what it needs to make the correction, or do you have to pre-program it with your tire/gear info?

 

Thank you...yes you are correct about us using tech stream not being able to correct the speedometer....looks like I’ll have invest in recommended equipment.....when I’m doing 20...I’m driving 22 ...30....33....40...44....50...55...60...66....70...77...80....88....dang....I better get this corrected....most my driving is on the interstate....so I think it’s pretty important to get it corrected...

 

http://www.hypertech-inc.com/ProductManuals/InLineSpeedo/730103_VSS_Instlltn_Prcdr.pdf

 

Check with GPS before you spend the money. That's about what the calculator said for mine, but it was actually much less. Your call obviously, for me 3 mph at 65 wasn't worth $200 to fix.

 

Techstream cannot calibrate your Speedo/Odo. The Hypertech can, because it is actually scaling the signal that goes to your instrument cluster before it ever makes it to the speedo/odo (and cruise). Follow the install instructions - it’s very easy to do and while it might look like a lot of tear down it’s actually not bad and can be done pretty quick.
The calibration of the Hypertech has to be done using a computer app and connecting the unit to the computer using a USB cable. It also isn’t an exact thing - you’ll have to fiddle with it a bit and check against radar and GPS to get it dialed just right. SO, the best thing to do is to keep the USB cable attached to the unit and just tuck it up behind the knee panel so you can pull it out to plug in a laptop and run new settings until you get it where you’re happy.

there’s a couple reasons for why you have to fiddle with the settings:

1. Tire sizes are nominal, and the actual OD (which is what matters to the speedo/odo calculator, because it is converting hub rotations to distance travelled) varies by individual tire make/model and someday even by the pressure you run them.
2. Toyota uses a standard calibration across all different factory options in the truck, which includes many different make/model/size tires. And they also need to be sure they’re not setting a truck up from the factory to read too slow. So my experience was that they actually have the speedo/odo calibrated for something a little bigger than stock, because when I took my actual numbers (actual OD on original and new tires), the calculated difference did not match what I ultimately used to get the Hypertech to match with GPS and radar across a full range of readings.

Again - install isn’t tough, but leave yourself an easy way to plug in the USB cable to fiddle a little without having to tear it all apart to program it again

 

MTRock —

Yeah, that’s what I was referring to having looked at. Seems straightforward, but I get squeamish about ripping out the whole dash. Just get nervous I won’t be able to get it back together. Was hoping someone could say how easy or difficult the actual process was. I’ve been fooled by directions before.

Edited to add: Rain Man posted while I was typing. That’s what I was looking for. Thanks!

 

Once you get the courage..tearing the dash apart isn’t difficult..Pretty simple..I’ve torn a few late model Toyota’s apart lately to install stereos haven’t broke anything yet!

 

Once you’ve done it once, it becomes old hat. I’ve had mine apart so many times now it’s ridiculous (just look at my build thread!).

 

Thank you to all who posted advice.....grateful in Puget Sound.....

 

If you can do math in your head it's pretty easy, especially if the numbers you listed are what you've actually recorded, then it's just a 10% increase. On 35s I have right at a 5% speed difference which is easy to calculate on the fly, just divide the first number on the speedo by 2 and add it, so 60 is 63, 80 is 84, etc. Not worth the money personally, but to each their own.

 

Use an inch measurement instead of binned tire size when you go to inputting the change in the hypertech unit. It helps avoid some of the guess and check.

 

I also did it so that my odometer reading would be accurate, and so my mileage would be accurate as well. More so for the ODO - over the course of the 10+ years I plan to own the truck. A 5-10% difference adds up (my 2008 was realistically around 310k actual miles when I traded it because I didn’t use a calibrator on it).

 

This was a little bit of a concern and reason why I did the calibrator on mine (also because if the wife drives it, didn't want her lead foot to get her in even more trouble). I didn't know if leaving the stock ratio in place could be construed as odometer fraud or anything like that, but I'm guessing there's probably some gray area there.

 

What is one of the better devices to use for tire size calibration. My speedo is off by only 3 or 4 mph, however it has greatly impacted my true odometer reading as well as my trip meter.
I had installed a tow/ haul module from hypertec for other towing, only to find out it was killing my mileage and I had better results when using manual mode or the tow/haul button. Removed it, waste of money.
Any advice or personal experiences would be appreciated, thank you.

 

Hypertech, rough country, same thing different box basically. The other hypertech stuff has a reputation for being junk

 

I just say "sorry officer...math isn't my strong suit"

 

One thing not mentioned here is while it may only be a few mph, the computer shifts the transmission on all the parameters it knows to be true. Start changing those parameters in tire size wothout correcting and you will get funky shift point along with that few mph off and incorrect odometer readout. Food for thought, some dont care.

 

The first hypertechs only corrected the speed signal going into the instrument cluster. The engine ECU was still receiving the old un corrected signal and it controls transmission ect.

I think Hypertech has since updated the product to send a corrected signal to the Engine ECU also. The 2018s have a “Set Crusie” speed that is displayed on the cluster. This value comes from the engine ecu.

Either the engine ECU sees the new signal or they are also correcting the “Set Cruise” value as it’s coming into the cluster.

One guy with a 2018 showed 70Mph on his gauge (corrected) but the Cruise Set was 64Mph coming from the engine ecu not corrected.

 

Luckily I haven't had any issues. My speedometer and GPS read the exact same thing. Here is my comparison from when I swapped out my OEM Sport setup...

 

4 years ago I installed a hypertech module behind my cluster with the USB dangling behind the driver kickpanel. Easy install with supplied PnP harness. Works fine.

 

Is it bad that I’ve done this for the heck of it multiple times in one day

 

So I was thinking about trying to recalibrate my speedo as well but damn the equipment needed to buy isn't cheap. Deciding on whether to purchase is whether it is worth it and which one will work the best. If I don't buy one is it bad for the vehicle to not do it? I just don't want to have any issues down the road if I do not make the change and buy what is needed.

 

Should be fine it you don’t care about a 2-3 mph difference in speed. Also the odometer being a little off(which I wouldn’t care about)

 

Hi,
Police and mileage is my concern.
Anyone in Ontario Canada that would like to share their Hypertech? Ill buy lunch and dinner!
Running 35's on stock everything.

 

You can’t exactly share a hypertech. It’s is a physical unit that must be installed in the truck to correct the signal. It reads in and modifies the speed signal that drives the speedometer and odometer. Remove the device and speedometer will no longer be corrected.

It is not a flash programmer that can fix the problem and then be removed.

 

Ohhh. Sry. Thx.

 

Instead of going through all the hassle and expense, you could just drive the speed limit. If you know you are actually going 65mph when the speedo says 60, then just drive with your speedo at 60.

It's not difficult.