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yes, you can do this, and yes it will work.

i am getting ready to do it on an 04 DC for exactly the same reason. i drive a lot through the ozarks hills/mountains and tow different sized trailers.

i think you are right about the diff ratio on the 05-06s. the 04 had the 4:10 rear axle, so i am lucky in that respect, but your truck has about 40 more HP with vvti so you got the lower rear axle ratio (higher gearing) that came in the regular and access cabs before the DC's came out.

anyway, point is, changing tire diameter significantly will effectively change your gearing. i don't think the change you are considering, though, is going to do much for you. it works as a straight percentage. change diameter 5% smaller, rpms at same speed go up 10%. i think you are safe going plus or minus about 10% from stock. otherwise, i would suggest regearing. my understanding is you are only going down in diameter by 1 inches, so that is only about 3% change. think of it this way. during the life of the tire, the tread wear changes about that much. so, worn out tires are 1.5-2% smaller than when new. not really much significance.

i'm planning to go from stock size 265/65r17 in my case which is also about 30.5 inch outside diameter, down to about a 28 inch diameter. that is about a 245/60r17 or something in that range. that's 2.5 inches smaller diameter or about 8% smaller. read as 8% more torque, 8% better braking, 8% higher rpm at same speed, etc. hopefully, not 8% worse fuel economy! i'm actually hoping to do better around town due to lighter unspring mass, narrower contact patch, etc. i'll let you know.

the main problem with going smaller is load carrying capacity is proportional to volume of air in tire and inflation pressure. so, as you go lower and lower, you find less and less load carrying capacity. eventually, you get into tires that are strictly sized only for passenger cars, not light trucks.

the stock oem tires are rated for about 2250 lbs each. if you routinely tow heavy loads, you don't want to go much below that. it's tough to find LT rated or decent load carrying capacities in a tire much smaller than stock. another good reason to stick with the +or- 10% rule.

just sharing what i know about this, since i've been researching the same thing myself. you won't find much on tirerack to help you out with this, either. i suggest taking the problem to a GOOD tire shop that can get a wide variety of odd size tires. tirerack only carries sizes and brands that sell well and are popular, and what we are contemplating is not nearly as popular as UPsizing and regearing the other direction. mastercraft makes a courser tire in a good size for this, and one of the goodyear wranglers is lt rated and also sized right. problem is, there are no reviews to help guide in the selection, so you'll basically be striking out on your own and trying a largely un-reviewed tire model.

good luck! i would be interested in your results if you go through with the plan.
 

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i did it. put continental crosscontact lx tires on in the 235/65r17 size. these are good tires. i have driven them in a driving, heavy rain with much water on the road and did not have squirrely feeling or hydroplaning. they are 108 rated tires so they can carry almost all the weight of the stock tires. the smaller diameter helps significantly with torque and braking and still drives very nicely. i do tow alot and carry something in the bed almost always, so having a little extra in the torque dept is very nice. i noticed about a 1 mpg drop in the summer. i believe this is due to the increased traction over the stock duellers. it would be hard to beat the stock tires in the mpg department, but in all other aspects, the continentals are superior. i have about 4-5000 miles on them and at this point, i would buy again. they are quiet on the highway, have very good around town manners and corner much better in this size. the truck is a real pleasure to drive with these tires and the hellwig sway bar.

cupidstoy
 
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