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onewheat
09-20-2007, 10:21 PM
I have a bone stock Chevy 1500HD (6.0 liter gas) with the 3.73 gears. I tow my X-15 back and forth to Norris (moderately hilly and ~260 miles each way) 6 - 10 times a summer. I was debating going from the stock 245/75-16 tire to a 265/75-16 tire purely for better looks, but I am wondering what that will do to my towing? I currently average 65 -75 mph in the 2200 - 2600 rpm's with a lot of shifting on long or steep hills. Anyone have some good data on what this will do to my pull?

Another consideration is the addition of a cold air intake. Any pros/cons on this for an otherwise stock truck?

TMCNo1
09-20-2007, 10:50 PM
According to a tire book I have,

245-75-R16 = 30.31" diameter, 6.60" tread width
no 265 listed, but
255-70-R16 = 29.94" diameter, 8.00" tread width

So, if you find a 265-70-R16, the diameter should be near the same, yet you will have a wider tire cross section and wider tread on the ground.
Resulting in practically no change in towing performance, just a little more rolling resistance and a small decrease in fuel mileage.

canadianskier
09-20-2007, 11:00 PM
I deal with tires in my line of work, your new tire is going to be wider/bigger foot print and very slightly lower profile. that being said TMCNo1 is right, you won`t notice any differance at all, but will look way cooler.

rspiecha
09-20-2007, 11:54 PM
I had a 2500 with 3.73 and 6.0 liter, I had 285/75 R16 on it and it was always downshifting on the way to the lake. So don't go crazy.

Rob

Thrall
09-21-2007, 10:10 AM
It will downshift more than it does nowbecause you're creating a higher final drive gear ratio, but not much at all only going to 265's. It will lower your highway cruising rpms slightly as well.
IMO, cold air intakes, TB spacers, chips, etc, don't do much for increasing performance. Certainly not to amoutn claimed, 15 hp for this, 20hp for that, etc. If you do the ricer math, you can add "100hp" to your truck just with bolt ons. My experience w/ a Dodge 5.9L gasser, I tried all that stuff and it didn't do a whole lot for performance or fuel mileage.
I wouldn't spend money on bolt on hp adders for a gas motor, unless they were to supplement real changes (cam, headers, blower, etc).

beatle78
09-21-2007, 10:17 AM
It will downshift more than it does nowbecause you're creating a higher final drive gear ratio, but not much at all only going to 265's. It will lower your highway cruising rpms slightly as well.
IMO, cold air intakes, TB spacers, chips, etc, don't do much for increasing performance. Certainly not to amoutn claimed, 15 hp for this, 20hp for that, etc. If you do the ricer math, you can add "100hp" to your truck just with bolt ons. My experience w/ a Dodge 5.9L gasser, I tried all that stuff and it didn't do a whole lot for performance or fuel mileage.
I wouldn't spend money on bolt on hp adders for a gas motor, unless they were to supplement real changes (cam, headers, blower, etc).

:twocents: I disagree with you slightly on this.

My cousin has a '89 2500 HD and he added a K&M intake (~$100) and a larger diameter exhaust from the cat back (Flowmaster I think ~$175).

He said he in his application, he got ~1-2 mpg better fuel economy just by letting the engine breather better on both ends.

OhioProstar
09-21-2007, 11:12 AM
I ran 285/75/16's on my 1500 5.3 and didn't drop off much in terms of towing miles going to the same lake you referred to from SW Ohio. If you would like larger tires to increase ride height, don't go with lower profiles since you will just be exchanging you current height for width, which in the winter is not preferable.

My take on all the aftermarket gear is that if GM/Ford/Dodge could squeeze another 1-2mpg out by simple add-ons they would do it to meet federal CAFE standards on mileage. I know that changing shift points and fuel curves can make it perform better, but you have to believe that the R&D departments of major automakers have spent more time optimizing their product than K&N or Borla doing it across hundreds of platforms.

onewheat
09-21-2007, 03:39 PM
I deal with tires in my line of work, your new tire is going to be wider/bigger foot print and very slightly lower profile. that being said TMCNo1 is right, you won`t notice any differance at all, but will look way cooler.


I did have a typo on my question. I was thinking about going from a 245 to a 265, but still sticking to the 75 series profile. That would make me 20 mm taller and 15 mm wider (not significant in either direction). I wasn't sure how much the extra height would affect the final drive ratio. The stock 245 tire looks way undersized for the truck, especially if you park it next to a Ford or Dodge with their stock tires. It is really noticable if you park it next to one wearing the stock 20" tires. I do realize their gears and profiles are designed for those sizes and I'm not looking for a 'Monster Truck', just a slightly larger appearance for my daily driver where towing and mileage are still important.