I have a 99 4x4 F150 4.6 with 3.55 LS rear end. The stock tire size was 235/70/16. I am currently running 265/75/16 and would like to go up to 33's. The problem is towing my ski boat which is about 4500 lbs with the trailer and gear. The engine already lugs a bit when not towing but seems to rev to high when towing w/o overdrive. Would the 33's be in the sweetspot for towing at highway speeds (overdrive off) or will the engine lug even worse? Also would the skinny 255/85/16 help compensate by losing some of the rolling resitance of the 285/75/16?

Regearing to a 4.10 is out of the question at this time.

Thanks for your feedback.

 

Actually, the 4.6 "sweet spot" (which should be where it gets it peak torque) is around 3500 rpms....... Running in third going 60 mph, you should be pulling right around 2300 rpms.... Hardly revving too high..... Even going 70, you should be right around 2700 rpms....

I've got the same gears and tire size, but I've got the 5.4 which does develop a bit more torque at a lower rpm then the 4.6.

I find the truck drives real nice in third. I usually stay between 60-65 mph (2300-2500 rpms) and it does fine. Oh, I've got 140,000 miles on the odo too!

IMO, I don't think the skinnier tires will make up all that much difference in rolling resistance. Going to the 285's will just kill whatever low end you already have....

Might try for a nice free flowing muffler and keep the air filter clean (or get a K&N, but some don't like 'em....) That's the only 'mods' I've done to my truck and it does make a difference.....

Good luck!

Mitch

 

I've got the K&N for what its worth. Exhaust is next and I am considering a tuner to correct for tire size and towing performance. I hate being practical but that's probalbly what I will do and stay with the 265's on the next set. I also have 135,000 on the odo. Why in the world did they put such little tires on a stock 4x4? The 265's look and perform decent but the 285's seem be the perfect size for an unlifted truck. I just can't justify spending money on a lift, regear, rims, tires for my truck. I guess I'll save all that for the Jeep I plan to build with my son in a few years.

 

I hear ya on the 'practical' side...... I was real tempted to go with some 285's on my latest set of tires...... but, I knew better, as I don't want to regear either.

The 265's are better then the stock size, that's for sure... I think the only reason they put those little 235's on is $$$.. A lot cheaper to buy millions of those tires then the 265's....

I think you will see a difference in how the truck shifts once you recalibrate the speedo to the taller tires. That might be why you feel the truck is revving too high?? With the taller tires, your speedo (and odo too) will read slower then your actual speed. If you show 60 mph on the speedo, you are really going around 64 mph.

I'm lucky in the fact that all I had to do was swap out the VSS gear. 1999 and above, you have to do it in the computer.... I know that once swapped out the gear, it shifted and seemed to run better.