Big Tires on '06 Dually??

[fullthrottle]

I have a '06 F-350 dually with 4:10 gears and 40,000 miles. I do a bunch of towing ( 42' Toy-Hauler at 16,000 lbs ) however I'm off road a bunch too. There has been more than once where I've had to lock it in 4x4 to get where I need to go. I even got stuck once. I have had two sets of tires so far, Nitto Terra Grapplers 295/70/17's and a set of Toyo Open Country A/T 285/70/17's. I have the Nittos on there now. I have been very dissatisfied with both. They lasted less than 20,000 miles. I guess because I tow a bunch, according to the tire shops. My allignment is dead nuts and the tire wear is straight with no chopping or uneven wear.

Anyway, with this all said, I want to put a more aggressive tires on it. I'm looking at the Mickey Thompson ATZ or MTZ line. I have heard pretty good things about these tires except they cost a lot. I'm thinking on putting 315/70/17's on it which is a 35" tire. Right now the Nitto's are a 33" tire. I know the 35's will fit because I have a 2" lift on the front and Air-Bags in the rear. My other option is to stick with the Mickey Thompsons but put the 305/65/17's which is equivilent to a 33" tire. A 33" is what is on there now.

Right now at 70 mph I'm at 2150 RPM. I think with the 35" tires I'll probably be down around 2000 RPM. Could that potentially cause damage to the motor since it is working harder? Anybody running this size on yours and do you tow with it? Again, this question is all about towing. I know there wouldn't be a problem with these tires if I didn't tow.

PS... All my towing is in Florida so it's all flat.

 

[fordtrucker4life!]

I would say the lower the rpm's when towing the better fuel economy and the motor would be working less hard.

 

[bushpilot]

I would say the lower the rpm's when towing the better fuel economy and the motor would be working less hard.

'zactly my thought...the BEST mileage for me seems
to be in the 1850 range...and im STILL w/in the power range
(not lugging the motor)

 

[fullthrottle]

Well, that is not exactly accurate when towing. The lower the RPM's the more boost is required to maintain the speed of, lets say 70 mph. The more boost, the harder the engine works and the more fuel it consumes. When you are not towing, there is very little resistance and yes, the lower the RPM's the better. Now add in a trailer that is 16,000 lbs, 8.5 feet wide and 13.5 feet tall. Here is where RPM and Torque are needed. When towing something this big, the higher the RPM the better fuel economy. This is why some of the 350's and most of the 450/550's have really low gears like 4:30's or lower. They are meant to do one thing, tow and keep the RPM's up. The bigger the tires, the worse the fuel economy. I know that by putting bigger tires on the truck will result in more fuel consumption especially when towing but I'm concerned with the stress on the motor, more boost, hotter EGT's.

 

[fordtrucker4life!]

I still wouldn't believe that much of a difference. You said you tow mostly on flat ground so there is not a concern for hills. Just my 2 cents.

 

[Kleetus]

You are correct in the bigger tires will hurt you power wise, but I really don't think it will make any appreciable difference in your area, here in western PA, yeah, maybe, but down in FL, doubt it. You'd probably see a bigger difference from driving into or with the wind.

 

[Maxtor]

2000 rpm should put you into the peak torque, but like Bush said, 1850 seems to be the best for mpg. On flat ground, anything between 1850 and 2100 rpm should be fine. Going up a grade, you would want to keep the rpm at 2000 rpm and higher. Just my

 

[solrpwrd]

for what its worth i love the dick cepek fc-ii's on my jeep tho i would stick with an e rated tire if i were you. not sure whats avail. i would look on a tire sellers site for rpm/tire size table to figure what your rpm will be. i'm w/ you on your analysis of mpg, etc. i'd have appropriate gauges if not already installed and watch the egt's. have fun from there!

 

[JRJ04]

what about bfg a/t's? i dont do a lot of towing, but i know they make a load range e. they have been great tires and do alright off road. they are certainly not the best mud tire at all, but will get the job done in light to moderate mud. just my 2cents.

 

[fullthrottle]

Yep, I use BFG A/T's on my work truck and they are great tires. I usually get around 50,000 miles out of them but I do not do any towing. Truthfully, I was kinda looking for something a little better looking on my personal truck. Those BFG's are great tires though...

Thanks!!