New Yokahama Tires=Lower Fuel Mileage?

Three months ago we put new low pro Yokahama drive tires on. Ever since then we have had three issues with the truck.

1) The truck will occasionally squirm on the road. Just like it was hit by a big gust of wind. The tire shop said that it would do this until the tires were broke in, but it has been over 25,000 miles and it is still doing this. This is the second set of Yokahamas that we have bought; the first set squirmed for a few thousand miles then were fine.

2) Our fuel mileage has dropped about 1-1.5 mpg. We were getting high 6's to low 7's; now we are lucky to see 6.2 with 10,000 lbs. in the box. It seems to have more difficulty on take off and going up hill.

3) We are getting this fault code on a regular basis: SAE J1939 MID 136 SID 231 FMI 2 According to the Merritor/Wabco troubleshooting guide---"J1939 speed plausibility error. NOTE: This fault indicates a discrepancy between vehicle speed reported on J1939 and ABS sensed vehicle speed. Recommended action---Check the speedometer calibration. Check for the tire size mismatch. The Vehicle speed reported on the J1939 databus does not agree with the wheel sensor speeds."


I read on another thread about errors with the ABS could cause an engine derate and it would not show up as a fault. Could the fault we are having cause an engine derate? How could we tell if the engine was derated? We bought this truck used and transferred the old Yokahomas onto it. Would the difference in tread height between the old and new tires cause the ABS fault. I know that the new tires seem to have at least an inch more tread

Any suggestions on the squirming? Would that cause a drop in mph? We need to get the squirming under control because I feel like a bobble head and I am getting seasick ;(

This truck is a 2008 D13 485 HP 10 speed manual transmission with 400,000 miles. Should this truck be able to pull 40,000 lbs. with little trouble and still get 6-6.5 mpg at avg speed of 68 mph in normal terrain?.

 

I have never checked. It is assumed that they would be because they were bought at the same time. And they are wearing evenly. I rotate my drives every 30,000. My last Yokahamas, I got almost 300,000 miles on them and still had enough tread to get $75 credit each. I rotate the steers every 15,000 and get over 100,000 miles on them.

 

Yes, the new tires are taller/wider due to having the full amount of tread. The speedometer show 1-2 miles slower than actual speed. On wet roads the squirm more, I am dreading winter. I hope I can resolve this issue before then.

 

I suspect that the sensor fault is due to the new tires and I can live with that. I just want to know if this fault can cause an engine derate resulting in the loss of power and MPG.

Something I forgot to mention, is that when I go around a tight curve or corner it feels like I might tip over.

 

I will check when I get it in the shop this weekend. If either is jammed on wouldn't it have burnt out after running on dry pavement for the last few months?