dave91gt

I ran 295 70 18 Trail Grapplers on my 2012 Screw FX4 for a year. That truck had 3.73's and it stayed completely stock. Honestly, I thought it drove great for the heavy, larger rubber. But the 3.73's probably had the most to do with it. It would still spin from a dead stop and the trans shifted completely normal. The only thing of notice was the speedo being off 3-4 mph at 70. I towed with it and it did fine. In your case, likely the 3.55's are what is causing your pain. Your final drive is down now. If you live in a non flat area, it will be more noticeable. You have a couple of options. Tune it, or gear it. Tuning will be the cheapest option.

sodacraft

If your power returns to normal with stock wheel/tires than its the tires and lift.
I recently had to put on LT E loaded tires and the 4 of them weigh 180 lbs. Thats a lot of weight at the worst place, the furthest from the outside of the rim. Rotational mass will make the wheel harder to turn exponentially. Raising you truck also moves your center of gravity higher, and also produces an effect of moving mass more difficult. I noticed you have a topper as well, all of these things are gonna slow you down. I have a G-tech pro and measured all the losses I had when I made some changes. After just the lift to 2 inches I lost an equivalent of 9 hp. After the tires I lost closer to 21hp. So there's 30 right there. Remember too, you have not calibrated for your new tire size so your transmission shift points are off now as it thinks your going a different speed.
To counteract all this I got a tuner from 5 star. Their package deal of an X4 tuner plus 5 tunes. I only used the 87 perf/tow and re-calibrated for my tire size which was like 607 revolutions per mile. This alone brought me back to stock power plus 10hp. This is based on an equivalent that G-tech calculates
using an accelerometer. My next change was a 4.10 rear end. This gear ratio
IMO should have been offered on the 5.0. This brought me to a total of 27hp over stock and there is a torque calculation but I don't have it here. I am very happy with the way the truck now. I think these two things are your only real options to get your power back unless you go back to a stock wheel and tire set up. Or get a supercharger. Hope this helps.

sodacraft

I dont believe the Fuel Mavericks weigh more than stock..maybe even less. That could be why you didn't experience much power loss. Are our tires the same as stock height? This could also be why. The OP said his rims are very heavy, which certainly doesn't help in conjunction with a heavy tire. You can't cheat physics.

Crash89

Just a thought......

What pressure are you running in the Trails?

When I had a set put on, they shop said to run them at 35 psi. The rolling resistance was terrible, it felt like the truck did not want to move from a stop.

I upped the pressure to 45 psi front/40 psi rear.

that made a HUGE difference. My acceleration was back to normal, and the truck would roll again.

Cardinal Fan

That along with AricsFX truck being a lifted 2WD, plays into the factor also.

AricsFX

iTrader: (3)

295/60 trails are almost a 35 inch tire, so no. I went from stock 18s which are like 30 inches tall to these, and nothing happened here. I don't believe the 2wd would make a difference, as I think the ops truck is also. Only difference would be less BHP and heavier curb weight.

What about when you tow on your stockers? Does it still behave the same way? Because a load behind the truck exhibits a lot more strain than bigger tires.

Also to each their own on tuning a N/A engine. There really isn't much to be gained besides a slight change in throttle response and adjustments of shift points. So, suggesting this is normal is not remotely true as I've never heard this happening unless something was wrong.

Can't find stock 20 inch info, but the mavs weigh 32 pounds

Mange

Stock FX4 20's are around 43 pounds per rim.

AricsFX

iTrader: (3)

Stock 18s weigh 29lbs, and the 20s weigh 43? How is that possible?!

Mange

I guess it just depends on how much metal is cast for that particular design. That weight was confirmed by a member of another forum who actually weighed his wheels.

winchested

If you feel no difference going from a 31.5" tire to a 35" tire I think you're just dense. That is a huge difference! I felt a differece going from stock 20" wheels and tires to 18" XD's with 32x11.5" tires (Kelly safari TSR).