[funfinder4]

Does anyone know what size tire is on the non-TRD/non-limited/non-Texas badged regular base DC's?

I have a TRD that came with the 265/70/R16 BFG. I tow a (smaller sized) travel trailer and during spring break we traveled over 1,500 miles with it. Towed great in overdrive (5th gear) for the most part and the highest tranny temp I saw was 145 degrees in the Ozark Mountains in Mo. & Ar. Of course I had to kick it out of overdrive when we hit 20-25 mph head winds and for the constant hills we went over. Best mileage was 15 mpg (following my grandparents Class A @ only 55 mph and possibly had a tail wind) worst tank was 9 mpg with an over all average of 11 mpg for the trip.

I feel if I had just a little extra torque/rpm's while in 5th gear it would give me better acceleration/power for holding hwy speeds up slopes and in head winds. So this is were my idea of betting a smaller sized tire for at least the rear wheels while towing comes to play. I've done the calculators on 4lo.com and if I went to a 245/70/16 tire it would give me an effective rear end ratio of almost 4.10 (my stock is 3.92 right?). This would on average increase my rpm's by a little over 100 at hwy speeds (65-70 mph). What does everyone think?

 

[XS Speed]

I thought I read somewhere that our rearends contained 3.73s

 

[integraGSR]

i didn't think that by just changing the width of the tire would affect the ratio? i know that if you change the aspect ratio of the tire up to a 75, i know it'll change, but didn't know that the width did.

 

[Marazzito]

It looks good with the tires you have on it now. I would add exhaust and maybe intake if you haven't already. The combo would probably give you more power than tires with a half inch smaller diameter.

 

[funfinder4]

i didn't think that by just changing the width of the tire would affect the ratio? i know that if you change the aspect ratio of the tire up to a 75, i know it'll change, but didn't know that the width did.

per 4Lo.com :: Metric Tire Size to Diameter in Inches Calculator

265/70/R16 = 30.6" Diameter
245/70/R16 = 29.5" Diameter

Here's the formula:

Also, it looks like I was wrong on the rear end gear ratio... I think I found some documents that say it's 3.91:1. Does that sound right? Do all DC have the same rear end ratio? Even those without the LSD and the smaller tires?

 

[funfinder4]

It looks good with the tires you have on it now. I would add exhaust and maybe intake if you haven't already. The combo would probably give you more power than tires with a half inch smaller diameter.

I don't believe in exhaust and intake mods/changes. I'm not looking to "hot rod" a truck or make it look and sound different by adding a so called "performance exhaust and intake". It's been proven time and time again that exhaust and intake mods (performance or those just for looks) result in a net loss in low-end torque (for gas engines). :td: That very same low-end torque is what you need for towing.

These performance mods have a place if your wanting to improve the top-end.

 

[Hugemoose]

I don't believe in exhaust and intake mods/changes. I'm not looking to "hot rod" a truck or make it look and sound different by adding a so called "performance exhaust and intake". It's been proven time and time again that exhaust and intake mods (performance or those just for looks) result in a net loss in low-end torque (for gas engines). :td: That very same low-end torque is what you need for towing.

These performance mods have a place if your wanting to improve the top-end.

Not saying you should, but probably the only mod regarding exhaust and intake that might actually help you would be some JBA headers. They do ligimitally give you a gain in power without any loss.

Or you could just get a supercharger :devil:

 

[cupidstoy]

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.

 

[cupidstoy]

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

 

[csfisher]

1% drop? are you adusting your odometer when checking this?

 

[funfinder4]

i did it. put continental crosscontact lx tires on in the 235/65r17 size. these are good tires.

Wow, great... I'm going to look these up. Of course my truck has 16" tires instead of the 17's.
The camper I pull now has doubled in length since my last post a year ago.:devil: I now tow a 30' Jayco bunk house @~5,500 lbs... So, maintaining overdrive (5th) isn't really an issue anymore, because I CAN'T! All my towing is now with overdrive off, which keeps my rpms ~3K. So, I'm not sure if I'm still going to go with smaller tires when the time comes for new tires.

 

[ItsBetterNow]

funfinder4 said... "So, maintaining overdrive (5th) isn't really an issue anymore, because I CAN'T! "..ound:'06 DC 4X4 TRD here, mine does downshift even empty more than I expected, I still like it though