I tried to find the answer but didn't find anything. I installed bigger tires on my truck. Stock was 275/70/18 and I installed 295/70/18. I am tuned with SCT X4 with GH and had a revision done to reflect the larger size. I went into the settings on the X4 and changed the tire to 34 which is the largest listed. When I convert the size to inches I come up with 34.3. Now I have a CEL with code 1635. My mechanic said he can't change the tire size. Would like the speedo to operate accurate. What is everyone doing to correct this?
Bigger tires
- Thread starter Kenz
- Start date
lincolnlocker
Well-known member
what year truck? I have 35-12.5r18 on my 12 and did the same thing with my sct sf3 and I haven't had a code yet..
live life full throttle
god bless america and the farmer who feeds your fat ass
I read somewhere that the 3:31 geared trucks can't be changed. Some guys have used the X4 to change the gear ratio to 3:55. I am going to give that a try. I also am using my X4 for gauges and when I set up to read vehicle speed it is about 3mph off from the speedo. Does anyone know where that speed and the one for the speedometer come from?
Sleepersilverado
Member
On my 11 with 3:31 I had 35's and bumped the tire size up with my mini max. Never had a issue for 3 years.
PDT1081
Well-known member
I wonder if it's reading one of the wheel sensors. My wheel sensors read different than my speedometer. You can change tire size with 3:31s. At least my 13XLT can. You're limited to what sizes were available as options from the factory.
Edit: I was able to change mine using Forscan and a laptop.
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PDT1081
Well-known member
Did you reset the sensors?
TrickTruck
Member
There's a sensor that reads the ring gear (direct connection to axle/wheel), so nothing will happen by fooling with the gear ratio.
Max tire size is the 34" with any of the tuners I'm aware of. You'll need something like speedo-healer to correct after that.
Max tire size is the 34" with any of the tuners I'm aware of. You'll need something like speedo-healer to correct after that.
Sorry, been out of town hunting. Do you mean clear the codes? I did do that.
PDT1081
Well-known member
Did you go through the process of re-paring the sensors to the truck? I believe it's so many turns of the key, followed by letting some air out of each tire. I believe the process is in your owner's manual.
I can look into that, but wouldn't that be for tire pressure? My issue is with a P1635 which is wheel to axle ratio.
PDT1081
Well-known member
Sorry. At some point I got confused about which sensors we were taking about.
I took my truck to the dealership yesterday to see if they could figure out how to change the tire size. When the tech hooked up his computer he said that there was no tire size selected. He selected the correct tire size, cleared DCT, and when he turned on the key light was back on. He went back into the computer and again no tire size was selected. If the tuner is over riding the tire size it should still show up right? The only thing we thought about trying is to return to stock, let the tech change the tire size, then reload tune and skip over tire size selection. I am thinking maybe I have an issue with the tuner. Anyone have any advice?
