brillmtb

When putting larger tires on the truck is there and electronic adjustment so that the speedometer can read correctly?

jlbrown

Check out this url. http://www.superlift.com/speedcal.asp

brillmtb

thank you for the post.<br><br><br>Does the dodge have the ability to flash the rom like I have heard the chevy trucks have. Seems like this is all you would need to do?

pinzgauer

I've been tracking this subject since May. There was a bit of discussion a while back about dealing with tire size via the factory computer. Here's what I remember:<br><br>1) You can tell it rev's per mile to deal with different tire sizes, but it will not go up high enough for the 315/70's<br><br>2) It would seem like you could tell the computer the vehicle had 3.73 gears if you started with 4.10's and went to the 315/70's. (The ratio is almost identical). But this would goof up the anti skid brakes. So most thought this approach would not work.<br><br>3) One person indicate approach #2 will work, you just have to change the number of teeth on the &quot;tone ring&quot; setting in the computer to match the new ratio. He apparently had access to a programmer or a very friendly dealer. It makes sense, but there are not enough details on making this work.<br><br>I'm hoping that by the time my factory tires wear out that there will either be aftermarket support for this, or dealers will understand how.<br><br>Have fun!<br><br>Alan

Sawbones

Haven't found a solution yet either. With the 315's there's an almost exactly 10% difference in actual speed (confirmed by gps) vs the speedometer. ie at 30mph, your acually going 33, at 50mph, your actual speed is 55, etc, etc.

bulabula

Heck, I've got a speed discrepancy right now between speedo and gps, and I'm running factory tires/wheels. Speedo reads a little fast.

crabman

OEM speedo's are almost always a little fast thanks to product liability lawyers. Superlift has not rated the Truespeed for the 03 yet but one enterprising individual wired it up anyhow with a few changes and said it worked fine. When I spoke to them some weeks back they said getting it worked up for the 03 was on their list but they hadnt started yet.

Matt400

Depends on how big you want to go. Find the RPM's (Revolutions per mile) spec for the tire you want to run then stop in at your local Dealer and have them check to see if that RPM is listed as a selection in Chrysler's DRBIII scan tool.
If so just have them plug that number into your ABS computer and your good to go.

I changed to 285/70R17 Toyo's that have an RPM of 636 that was simply programmed in.
Now that doesn't mean that all 285's are 636 cuz every manufactures tire molds are different so its best to get that RPM number from the manufacture.

Go much bigger than that and there may not be a selection to choose.

Steve034x4

Does anyone know if that this program adjustment will also reflect in the overhead computer reading for mpg's ?<br><br>While digressing to the overhead computer topic, I'd like to hook up a secondary fuel tank under the bed - any way of re-programming the fuel tank capacity to indicate I've added an extra 20 gals or so ?

Matt400

[quote author=Steve034x4 link=board=17;threadid=16678;start=0#158433 date=1057857237]
Does anyone know if that this program adjustment will also reflect in the overhead computer reading for mpg's ?[/quote]
It should because data for the overhead is gathered from the ABS computer that is looking at the speed sensor.

That would be tough because the overhead is looking at the tank float readings and doing the calcs from there.
Are you talking just the DTE reading? Why not just rig up a transfer pump and dump that extra 20 into the main when there is room for it? The overhead will see it and re-calc the DTE.