35's are the generally accepted limit with an IFS. Does it mean you'll never snap a CV or other front end component with 35" orsmallertires, No. Does it mean you'll definately have problems running 37's, No. But the wear and tear on the front end and chances of failure increase as the tire size and weight (and CV angle) goes up.
I have a buddy who works in a 4x4 shop in north Ga. and their policy is your sign a waiver if you have them put a lift over 4" and/or get tires mounted over 33" there if you have an IFS truck. They also make you sign if you combine a suspension lift and a body lift even on solid axle trucks, and I know a lot of guys who have done so and ride them hard with no issues. So take it for what it's worth.
My personal experience in many yearsoff-roading with a lot of guys whoown lifted trucksis that a a very high percentage of guys who break down off road have IFS front ends and larger tires, much higher than solid axle owners...

 

Yeah I have heard problems with the 37's and am still kind of considering them. I am looking more realistically into going with a leveling kit on my 05 Ram and am hoping that Top Guns Customz will make a 2.5in kit for the 05 QCSB 4x4 1500's. If i did this I would probably do the 315x70x17 Mick Thomp MTZ's onprobably a 17x9 EA rim with 4.5in backspacing. That would probably suit me alot better, but that doesn't mean that 37's are still an option. But with the 4.7 I don't think that 37's would be too smart in terms of power and mileage. However I already have 50series dual FM exhaust right now and Iwill be putting in a Brute Force CAI, Headers, Magnaflow Cat's, 212x cams, and 72mm TB within the next 2 years. But running 35's on 2in leveling kit means I wouldn't need to regear cuz I should have 3.93's since I have a towing package.

 

A larger tire means more load on the suspension components no matter what the geometry. Just like a longer wrench allows you to put more force on a bolt, a larger tire allows the ground to put more force into your balljoints, bushings, and tie rods. A 37 inch tire will put 12% more force into the suspension components for a given side load than a 33 inch tire. Even if you removed the fenders and left the suspension alone, you would still have this extra load on your suspension.

 

Just out of curiosity... where did you get that info from? And a 37 with 17in rims would be about the same weight as a 35 on 20's. I am going to be running the 17's so how would that compare to other IFS Ram's running the 35's on 20's?

 

I would think that running a 37 in a 17 would be the best way to go if you are going to run a 37" tire. It would keep the weight down as much as possible for a 37 and unsprung weight is a killer on brakes and suspension. Plus 17's are always cheaper and you usually have more choices in sizes and brands. I think for me 35's are a better way to go and I am going to try 18's, with 37's and the 3" body lift I am pretty sure my truck won't fit into my garage because of the heigth!

 

Just add it up. The 37" tire has 12% more radius than the 33" tire. Just like a 2 ft long wrench will put twice as much twist on a bolt as a 1 ft wrench for the same push. And I'm talking side load, like turning or running along a slope. Just driving forward, it shouldn't make any difference to the suspension if you're running 33" tires or 37" tires or even 73" tires.

 

Thanks for the info on that... When you don't understand something ask.

And I would be running the 17in rims because I love the look of a big beefy mud tire with alittle chrome rim. If I had my choice I would run 37's on a 15in rim. But I think that having bigger breaks with the 37's would really benefit me. But I parked next to a hummer the other day with 37x12.5x17's and that made me want them on my Ram. My stock 05 QCSB 4x4 with 32.5's still towered over it though. I was just thinking how much bigger mine would be with 4.5in bigger diameter tires along with the 4in suspension lift with 3in body lift. I am still really looking into going with a leveling kit and putting 315x70x17 Mick Thomp MTZ's under it. It would be ALOT cheaper. What does everyone think I should go?

 

What do you guys think of this lift? http://www.rockymountainsusp.com/dodge4_02-03gas.htm It claims that you can run 37x12.5x17 tires on that 5in lift with basically stock wheels. Do you guys think this will fit or is it possibly just false advertising, because their 4in fits 35x12.5's on 17's. What are you thoughts on this? 5in would be close to stock angles on the suspension and this kit comes with a skid plate + 4 shocks for about $1000 which would be a steal.