2nd Gen Non-Engine/Transmission Oversized tires & Factory electronics

[4xquadrod]

Does anyone know the relationship or effects, over sized tires have on the computer as far as shifting points etc,?



I noticed a large top end power loss on the grades, it seemed to be where it shifts in relation to hp or torque curve.



4 speed auto with 4. 10s and 35" tires.



I figured with the torque of the Cummins 35's wouldn't hurt much.

My stock tires were 3" shorter in diameter the odometer is at 93% accurate. At 70 mph actual is 73 mph.



Im considering removing the 3" lift and going back to my stock tires.



Thank you in advance for any thoughts



Steve

 

[illflem]

Even though you have a 3rd gen truck I'm moving this to 2nd gen for more exposure.

 

[RADdodge]

I noticed a difference in power and shift points when I went with larger wheels and tires. My difference was just over 10%. The transmission didn’t shift soon enough. The dealer couldn’t (DC wouldn’t) change the computer to adjust for the difference, though technically it would be a simple matter. I ended up getting a Superlift TruSpeed Sensor Calibrator and solved the problem. After that the transmission shifted more like it did before I changed the wheel/tire size. I think you might be closer to going 75 mph when your speedometer is showing 70 if your change was 7%. Did you measure it with a GPS?

 

[4xquadrod]

I took the truck to a speedometer shop and they put it on a rack and ran the truck.



A buddy of mine is a diesel truck mech. and might have something that plugs in and reconfigures for the tire size. However I am skeptical of having him touch my truck. They work on the large Peterbilt trucks.



Still doing some checking, I might replace the stock tires for now.

Waiting for the wheels anyways.

 

[Blakers]

I think many of the speedometers are way low with stock tires. My truck has 265's and it's still indicating about 5 mph slow at 70.



Unless you're pulling a trailer all the time and need all the power, I would suggest leaving your 35" tires on and you'll just get used to them. A lot of it is psychological. It works that way for me.



Blake

 

[Udaloy]

I just put 35'' tires this weekend on my '02 automatic with 3. 55's and I didn't notice any power loss. I have however noticed a big difference in speedo readings. At 40 mph on the speedo, I was doing 46. 5 and at 60 on the speedo, I was actually doing 68. 5 according to my GPS. So with that, it appears that the issue gets worse the faster I go.



Has anyone used anything besides the Superlift TruSpeed Sensor Calibrator? I'm going to look into this product as I haven't heard of any other options. Thanks.

 

[Silver]

www.atrol.com also makes a calibration device. Click on "ERA" on the left side. (I've never used one. Not affiliated)

 

[DEZLPWR]

I have the ERA....

Works great! I have 35's, and the speedo is dead accurate... .

 

[Udaloy]

Re: I have the ERA....

Originally posted by DEZLPWR

Works great! I have 35's, and the speedo is dead accurate... .

DEZLPWR, Thanks for saying so because it's cheaper than the Superlift piece and it made me wonder if it was as good. I think I'm going to order it ASAP!

 

[CSloat]

Steve,



I just sent you a PM



~Craig

 

[Chipstien]

Re: I have the ERA....

Originally posted by DEZLPWR

Works great! I have 35's, and the speedo is dead accurate... .

DP, did you get it locally? If so, where? Thanks

 

[DEZLPWR]

Re: Re: I have the ERA....

Originally posted by Chipstien

DP, did you get it locally? If so, where? Thanks

No, I actually ordered it from Jannetty Racing 2 years ago. They still sell it as far as I know... It should be on their web site.

 

[Chipstien]

Nothin better than a quick reply. Thanks DP.

 

[Udaloy]

I took delivery of the ERA over the weekend but I'm not going to install it. There has to be at least a hundred posts on people having trouble with the install. I called Abbott and the nice lady tried to direct me to someone else's website for the correct instructions. She didn't know where the directions were but that I should just "scroll down to it somewhere". The site sold a lot of different products and I'm not about to use instructions for a washing machine for cutting into my wiring.



I've never been so disenchanted with a product that I didn't even install before. Like I said, the lady was real nice, just not helpful enough. That's no fault of hers as it's the company's duty to supply the correct instructions for their products. JMTCW.



Udaloy