Wanted some feedback on the idea of downsizing my stock 265/75/16 if reasonably safe, seeking to increase the stock 3.73 ratio some (and replace worn tires)for cheaper than swapping to 4.10's or 4.30's (x2 for 4x4).
I never realized how much bigger is better for load capacity until I started this track a couple weeks ago.

I have stock lariot package wheels 16x7 AL with 265/75/16E (123/120) and 31.5in circumference. Seeking the smallest load rane E tire that fits my wheel and find two choices: 245/75/16E (120/116)@ 1in smaller (I think was a stock option), and 225/75/16E (115/112) rating w/ 2in smaller diameter.

Also consider stock 265's are 8.1in wide, 225's are 7.1in...so this drops an inch from the overall axle width. I've heard strong feedback this is a very bad idea (the firestone / explorer thing all over again), but can find any science behind these warnings. I see huge box trucks and E350 vans running 225/75/16 (115/112) load range E tires.
?

Neil

 

a lot of dually chebbies run 215/85r16's
Tire Search Results
or
http://www.discounttiredirect.com/di...15&ar=85&rd=16

couldnt find the diameter off hand, but there are as small as i have seen for a LRE.

good luck.
(gonna look different, that's for sure)

 

This is an interesting question.

The reason smaller tires are bad for load capacity is because the weight is carried by the tire through your pressure acting on the surface area of the tire. To carry more weight at the same pressure requires more surface area touching the ground, and that happens through sidewall flex as more of the tread is touching the asphalt supporting the load. So when you make the tire narrower, you have to have a longer cross section of tread touching the road to support the same load, which causes more sidewall flex. That's why smaller tires aren't rated for as much weight.

Most LRE tires are rated for 80 PSI, and therefore the maximum load is calculated by figuring the maximum permitted deflection and how much weight will put the tire at that limit at the maximum pressure. For the BFG Commercial T/A 215/85R16 that's only 2,721 lbs per tire. If your truck is a diesel you would be close to that on your front axle running empty, because a crew cab diesel weighs about 5,000 lbs on the front axle. There would be a few hundred pounds of capacity left so I think it would be safe. The rear would be just over 2,000 lbs under max tire load, so you'd have to watch how much you loaded your truck down with.

BF Goodrich lists that tire as being compatible with rims between 5.5-7" wide, so you should be fine. It would be safe but would compromise the load capacity of the truck. If you're not snowplowing or hauling heavy things you should be fine with this size as long as they are properly inflated.

ON edit: The same BFG Commerical T/A in the stock size of 265/75R16 is rated for 3,415 lbs as a comparison. So you'd be losing ~1,400 lbs tire capacity on each axle.

 

my chevy work van has 245/75/16 tires...I would`nt go any smaller on a super duty

 

thats kinda where I'm settling at...but still seeking the key reasoning

the 245/75/16E drops a 3.73 ratio to 31.5/30.5*3.73 = 3.85

a 225/75/16E drops my 3.73 gearing to 31.5/29.5*3.73 = 3.98

3.98 is closer to what i want, why i'm still holding out some hopes here.

NC

 

What load ratings are you finding on the 225s ? I just don`t think it`s wise to be right at max loaded weight or even within a few hundred pounds at all times.Otherwise if the load ratings are cool I`d do the 225s but I`d be damn certain to maintain the air pressure.

 

all three sizes are load range E...however the bigger tire can take more load (rated for more weight). all take 80psi max pressure.
weight rating:
265 = 3400lbs
245 = 3000lbs
225 = 2700lbs

I should note I'm a 5.4 gasser, no plow, just tow a 6Klb boat / trailer occasionally short distances.

Also have 2in oversized spring in the front, f350 blocks in the rear.

NC

 

My Dually has 235/85R16E transforce currently. They look great on the truck.

When examining my payload and options sticker it said the truck came with 215/85r16's...

I went to pepboys and tirerack.com and they say that SuperDuties never came with 215/85r16's... Well, I have a sticker that proves otherwise. LOL

Seriously, I don't think I would go smaller than 235/85's on a superduty.

 

Hi if you only hauling that much should be fine with the 225's half tons come with p rated tires and are rated to tow more then 6k. the total weight rating of tires is more then the truck is rated for so should be fine.

 

So I lucked out and found a cheap local set of commercial truck tires (steel belted sidewalls) off a box truck to test this out, slightly used LT225/75/16E commercial truck tires, Goodyear G949 RSA Armor MAX. Sidewalls are twice as thick as stock 265's, and weigh in about the same at 49lbs each.

Its not pretty, and handling is not as good as stock tires...but ride is as smooth as glass (highway tread), and the new gear ratio is AWESOME! Wow, biggest power increase I've had yet; over CAMs, Y-pipe, 90mm CAI, e-fan, tuning, etc.

I know its going to help fuel mileage (will calculate over the coming weeks) as I can now hold 45mpg in overdrive on inclines, while maintaining over 10+lbs of intake vacuum.

Man I screwed up by not getting 4.30 gears from the factory!! And of-coarse we are getting a snowstorm now. lol.