Why are dealers so afraid to...

recalibrate the speedometer when tire sizes are changed? I called my local dealer today to ask what they charge to do that and was told by the service advisor that there is no way to do that anymore. I know that's total BS. Ford did it on my old f250 years ago just by changing the tire revolution in the computer.

 

not sure if it’s the same, but on my 2010 F150 they did it no problem. On my ‘15 F150 Ford actually locked out this section to technicians. Only way to do it was buy an aftermarket programmer. This was confirmed by a friend of mine, former co-worker who now works as a service advisor at ford dealership. I didn’t want to drop $300 so I got a GPS app and just figured out what my typical speeds were and adjusted

 

Thank you.

 

how are some doing it with the tundra, my miscalibration just bit me in the ass and got me a speeding ticket, lol

 

GPS app, then just remember - if it reads XX, I am really going YY. Plus it might buy you out of a ticket if you have to get it verified.

There are online tire calculators that will show you speed for a given tire size, and compare current to new tire sizes and speeds if you are looking to change diameters.

 

Been wondering about this as well, maybe has to do with the computer program they use versus what Ford uses? When I was working in the industry of making tractors drive themselves, we only had limited options for changing programming characteristics ourselves. The main way guys on here have been recalibrating for bigger tires is the HyperTech speedo calibrator.

 

I switched from 255/70-18 to 285/60-18


Speedo Reading ~ Actual Speed

20 mph ~ 19.63 mph
25 mph ~ 24.54 mph
30 mph ~ 29.45 mph
35 mph ~ 34.36 mph
40 mph ~ 39.26 mph
45 mph ~ 44.17 mph
50 mph ~ 49.08 mph
55 mph ~ 53.99 mph
60 mph ~ 58.89 mph
65 mph ~ 63.80 mph

https://www.tacomaworld.com/tirecalc

 

This is one of the better online calculators I have found.
https://www.discounttire.com/learn/...ina)&msclkid=0234f5ad44c11b088867a9f0fb33c42e

 

Same thing, different source.

 

i've been using a GPS app, my problem is it fluctuates from anywhere from 3-7 mph off

 

My main concern isn't so much the difference in the speed but odometer, mph calculation, and anything else running off the speedometer via the number of revolutions the tires make per mile. The hypertech looks like it still has to be hooked up to a computer to reset which makes no sense that the dealer can't do the same.

 

Hypertech

 

The part number for my 2014 doesn't come with the unit like the one you show. The 2014 has to be re-flashed with a PC or laptop.

 

While an online calculator is nice all you have to do is the simple math. Take the tire circumference for your calibrated tire size. Take the circumference of your new larger tires. Subtract the difference. Divide that by the circumference of your original calibrated tire. Get the percentage. You'll be terribly close. Adjust your head accordingly.

But YES I'm in total agreement that having the Tundra's electronics adjusted is the catz pajamaz.

 

This is not recalibrating the speedo. It’s adding a module that is inline before the cluster and it is spoofing the input info.

I have this on my truck. I’ve used a lot of different brand versions of these things on various vehicles and thus is problem the most archaic one. It’s a pita to get to again if you don’t get the measurements right

Currently, my truck is running about 3mph slower than the speedo reads. Need to pull it out and adjust numbers. I’m going to wait until I regear it.

The weird part is, even though the speedo reads right, the cruise setting still reads factory settings. So setting cruise at actual speed of 65mph, the cruise set number will say like 58 mph.

I don’t think the Toyota dealers have access to a bunch of these things. The Toyota mothership is so conservative and they don’t want their vehicles messed with. They are afraid of the liability.