speedo issue

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.

bigtigga84

Senior Member
Joined
Dec 19, 2010
Posts
3,459
Reaction score
35
Location
dela....where?
Ram Year
2006
Engine
Hemi 5.7
Damn thing keeps riding up my ass..... oops sorry wrong speedo. So on the highway yesterday there was a radar sign that tells you how fast your going. Needle was at 65 with cruise on, but the sign said 60. Had a friend do a test a little later and im 4-5 mph off. Have stocker 33's and recalibrate with the supechips. Not really understanding what the issue is. Which way do I need to go to get the speedo dialed in closer to actual speed?
 

TheSatinPumpkin

Senior Member
Joined
Mar 7, 2011
Posts
3,280
Reaction score
272
Location
Robles Junction/Three Points AZ
Ram Year
2004 Dodge Ram
Engine
5.7L
Do you just enter the tire size that's on the sidewall or did you manually measure the rear tire(s) height? Also the tire OD will go lower as the tread gets increased wear.
 
Last edited:
OP
OP
bigtigga84

bigtigga84

Senior Member
Joined
Dec 19, 2010
Posts
3,459
Reaction score
35
Location
dela....where?
Ram Year
2006
Engine
Hemi 5.7
Its just has inches not the crap 275 yadda yadda yadda. So actually measuring the tires is what I need to do?
 

BlackedOutHemi

Senior Member
Joined
Feb 27, 2011
Posts
5,454
Reaction score
196
Location
DFW, Texas
Ram Year
2012 & 2012
Engine
5.7L HEMI & 6.7L Cummins
When I put mine on the dyno with 31" tires I was about 8 mph off on the speedo. Since I was driving around on them, I used the diablo to adjust the speedo, and put in the size of the tire on the sidewall. When I finished, we ran it again, and it was about 4-5 MPH off the speedo. So I'd measure them yourself.
 

quietpeen

Senior Member
Supporting Member
Joined
Jul 14, 2010
Posts
25,442
Reaction score
3,905
Ram Year
2021 TRX
Engine
Hellcat
yea with superchips i think the actual number you need to put in for the stock crapyears is 31.5
 

03MopaRamman

RAM SPORT / 18 SRT
Joined
Jul 3, 2010
Posts
3,580
Reaction score
185
Location
Southern Alberta
Ram Year
2019 (2003 Forgottens SOLD and 2014 SOLD)
Engine
Hemi 5.7 (392 Hemi) 86 Ford .308 HO Roller
That should be pretty close (what Butch says) . Measuring Tape of tire on the Truck is usually bang on. A good way to confirm is with your GPS and from there make the tire bigger or smaller (can't remember which way. I beleive smaller actual size will lower your speedo). I had to tweak mine by .25 " to get it bang on. My next Data log will be even more acurate and hopefully break into the High 5's.
 

nussdawg395

Senior Member
Joined
May 27, 2011
Posts
625
Reaction score
3
Location
PA
Ram Year
2002
Engine
5.9 Magnum
Ya know I got 35s on my ram and I changed tire size with my superchips and it threw my speedo way off. So I put it back to stock and checked with gps and one of those signs and I was dead on. Weird but true.
 
OP
OP
bigtigga84

bigtigga84

Senior Member
Joined
Dec 19, 2010
Posts
3,459
Reaction score
35
Location
dela....where?
Ram Year
2006
Engine
Hemi 5.7
Changed to 31.5 and its dead on now according to the gps app for my phone. Gonna check a little later today with a friends gps to make sure. Thanks for the help guys.
 
Top