Speedo adjustment for larger tires

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Fanman69

Member
Joined
Apr 3, 2017
Posts
33
Reaction score
27
Location
Ct.
Ram Year
2016
Engine
6.4
I'm wondering what folks here use for speedo adjustment when upsizing
their tires. I heard one can use a hypertech model 752503 for a 2016 2500 with 6.4. Any advice?
 

rgregg08

Junior Member
Joined
Mar 6, 2017
Posts
14
Reaction score
1
Ram Year
2017
Engine
6.4 hemi
AEV's pro cal is not available to purchase unless you buy their lift. Superchip's Flash Cal isn't compatible with 2017's and the 6.4 (i called), not sure about 2016's my guess is negative. Hypertech is on my to do list to call and ask.

Im in the same boat, waiting to put on a set of 35's on my 17 Power Wagon till a calibrator comes out.
 
OP
OP
Fanman69

Fanman69

Member
Joined
Apr 3, 2017
Posts
33
Reaction score
27
Location
Ct.
Ram Year
2016
Engine
6.4
I already emailed Hypertech last week. They said it was not compatible.
I'm thinking they are saying that because they don't have the full 6.4 upgrade yet.
A guy on another forum said he used the hypertech on his 2016 w/ 6.4 without any issues. It was however the diesel unit, but worked for the tire size.
 

reloaderguy

Senior Member
Joined
Apr 26, 2015
Posts
570
Reaction score
313
Location
Oregon
Ram Year
2016 Power Wagon
Engine
6.4 Hemi
I have a ProCal, it works well for the price.
 

mohemipar

Senior Member
Joined
Nov 9, 2015
Posts
1,494
Reaction score
1,096
Location
Michigan
Ram Year
2017 Laramie
Engine
6.4 Hemi, 4.10's
AEV was supposed to be releasing their ProCal for the HD Rams for stand alone purchase last month or so, but they went silent on it. Hopefully they will get around to it soon. I would like to pick one of those up.
 

reloaderguy

Senior Member
Joined
Apr 26, 2015
Posts
570
Reaction score
313
Location
Oregon
Ram Year
2016 Power Wagon
Engine
6.4 Hemi
Some of the AEV dealers sell the ProCal on the DL.
 

rgregg08

Junior Member
Joined
Mar 6, 2017
Posts
14
Reaction score
1
Ram Year
2017
Engine
6.4 hemi
Some of the AEV dealers sell the ProCal on the DL.

I emailed the one shop that I believe everyone was gettting them from. They said no dice unless I was getting the truck serviced there. I'm in Texas they are in the northeast........................rattttttsssss. If you know somewhere else please shoot me a PM.
 

rgregg08

Junior Member
Joined
Mar 6, 2017
Posts
14
Reaction score
1
Ram Year
2017
Engine
6.4 hemi
I already emailed Hypertech last week. They said it was not compatible.
I'm thinking they are saying that because they don't have the full 6.4 upgrade yet.
A guy on another forum said he used the hypertech on his 2016 w/ 6.4 without any issues. It was however the diesel unit, but worked for the tire size.

I emailed Hypertech today as well, same response "nothing offered for that vehicle at this time".
 
OP
OP
Fanman69

Fanman69

Member
Joined
Apr 3, 2017
Posts
33
Reaction score
27
Location
Ct.
Ram Year
2016
Engine
6.4
Update on the Hypertech:

Picked up the Hypertech 752503 model yesterday. It is for the diesel, but worked without issue on my 6.4
I updated the unit via internet before using it on my truck, worked great.
One note, my tires are 37" on paper, but Nitto specs say 36.77". Unit increments are .25", so I used 36.75. Speedo was off +2MPH. Speedo was off -5MPH before programming. I adjusted the programmer to 36" even, and speedo is dead nuts with GPS.
So it does work, just a little tweaking to dial it in.
BTW.. In order to use the unit on another vehicle, you have to reset back to stock on the original vehicle. So basically, one unit for each truck.
Cheers.
 

rgregg08

Junior Member
Joined
Mar 6, 2017
Posts
14
Reaction score
1
Ram Year
2017
Engine
6.4 hemi
Update on the Hypertech:

Picked up the Hypertech 752503 model yesterday. It is for the diesel, but worked without issue on my 6.4
I updated the unit via internet before using it on my truck, worked great.
One note, my tires are 37" on paper, but Nitto specs say 36.77". Unit increments are .25", so I used 36.75. Speedo was off +2MPH. Speedo was off -5MPH before programming. I adjusted the programmer to 36" even, and speedo is dead nuts with GPS.
So it does work, just a little tweaking to dial it in.
BTW.. In order to use the unit on another vehicle, you have to reset back to stock on the original vehicle. So basically, one unit for each truck.
Cheers.

Thanks for the update. Wondering why they say it won't work but does??? Yep on the tweaking. I would chalk measure my jeep tires to get it dialed in. I assume your truck drives different now, shifts points in line, etc now?
 

RainDesert

Senior Member
Joined
Mar 13, 2017
Posts
223
Reaction score
122
Location
ID
Ram Year
2022
Engine
2.7
Update on the Hypertech:

Picked up the Hypertech 752503 model yesterday. It is for the diesel, but worked without issue on my 6.4
I updated the unit via internet before using it on my truck, worked great.
One note, my tires are 37" on paper, but Nitto specs say 36.77". Unit increments are .25", so I used 36.75. Speedo was off +2MPH. Speedo was off -5MPH before programming. I adjusted the programmer to 36" even, and speedo is dead nuts with GPS.
So it does work, just a little tweaking to dial it in.
BTW.. In order to use the unit on another vehicle, you have to reset back to stock on the original vehicle. So basically, one unit for each truck.
Cheers.

Thanks for the info and report.
 

SwollenMonkey16

Senior Member
Joined
Apr 15, 2016
Posts
622
Reaction score
167
Location
Texas
Ram Year
2017
Engine
6.4
if you run the same size tire as stock but just wider adding about 11-13 pounds per tire will it have the same affect as running a larger size tire diameter wise?
 

R.L.K.

Senior Member
Supporting Member
Joined
Dec 1, 2013
Posts
12,803
Reaction score
12,500
Location
Bristol , Tn.
Ram Year
2014 4X4 QC Express 6 speed auto 355 differentials
Engine
5.7 Hemi
if you run the same size tire as stock but just wider adding about 11-13 pounds per tire will it have the same affect as running a larger size tire diameter wise?
The Simple answer is No.

Speedometer being off is all diameter of the tire not width or weight .

A larger diameter tire travels further per revolution , hence the difference in speed .
 
Last edited:
OP
OP
Fanman69

Fanman69

Member
Joined
Apr 3, 2017
Posts
33
Reaction score
27
Location
Ct.
Ram Year
2016
Engine
6.4
The Simple answer is No.

Speedometer being off is all diameter of the tire not width or weight .

A larger diameter tire travels further per revolution , hence the difference in speed .

I agree, however tire manufacturer's sizes are never equal to what the actual size is. My 37's are actually 36.77" in diameter per manufacturer's website. Doesn't sound like much, but .75" change on my truck computer equaled 2MPH difference. I also think their size is based on tire with full pressure, but no weight of vehicle. I'm guess that could change the final OD as well.
 

ocwill1

Senior Member
Joined
Feb 23, 2016
Posts
295
Reaction score
128
Location
Severn, MD
Ram Year
2023
Engine
5.7 eTorque
Here are my .02.. I went from stock 20's, 2016 2500 to 305/70/18's and did a little test. set cruise to 70, and had waze running on phone and it bounced between 70 and 71... I am assuming because the computer has the stock pressure at 65 and 80, and I am running at 50/45, that may have something to do with it.. But, moral of story, save myself $230 by not having to buy the hypertech...
 

Ratket

Senior Member
Joined
Jul 14, 2014
Posts
3,571
Reaction score
1,300
Location
Arizona-
Ram Year
2018 1500
Engine
Hemi 5.7
Skip the hypertech and get a diablo with a. Custom tune??
 
OP
OP
Fanman69

Fanman69

Member
Joined
Apr 3, 2017
Posts
33
Reaction score
27
Location
Ct.
Ram Year
2016
Engine
6.4
Skip the hypertech and get a diablo with a. Custom tune??

I doubt one can find a diablo for $200.
I think the 6.4 has plenty of ponies as is anyway.
Was looking for a speedo calibration tool for a reasonable price.
If I get the need for speed, I have other toys for that.
 
OP
OP
Fanman69

Fanman69

Member
Joined
Apr 3, 2017
Posts
33
Reaction score
27
Location
Ct.
Ram Year
2016
Engine
6.4
Speed is accurate, which is always nice. Odometer is keeping correct miles traveled. I'd like to say the tranny shift points improved, but can't be certain as the tires when on the same day as the adjustments were made.
 

Members online

Forum statistics

Threads
194,902
Posts
2,863,861
Members
155,252
Latest member
radikio
Top