Bigger tires? Where do they make a difference

[Tundra2084]

I have a 2012 Ford F-350. According to the sticker on my frame the tires (LT 245 75 R17E) have certain weight ratings......I have LT 275 70 R18E tires on my truck. Due to the bigger tires, does this change any of the weight rating and if so which ones and by how much?

[timmac]

Huntindog wrote:

timmac wrote:

azdryheat wrote:
You don't have the authority to change the GVWR or GAWR.

I do

That's great! Ihad no idea it would be so easy. Can you print me a new sticker for my truck?:R

This internet stuff just keeps getting better. More things that were previously hard or impossible to get are becoming easy every day.:B

Its called chassis modifications, G rated tires and air bags oh and a Banks Power Pack system to give it more grunt..

My 08 Bounder was rated by Fleetwood to tow 5000lbs and 500lb tonged weight but Ford rated the chassis for 5300lbs towing so with the said modifications above I can tow 6000lbs safely but can handle up to 7500lbs with 750lb tonged weight.

[Grit_dog]

Tundra2084 wrote:
Ok reading from the Ford site at the following address the difference between 17 in tires and 18 in tires is a 100 lb rise in the GVWR and a 400+ rise in the RAWR

https://www.fleet.ford.com/truckbbas/topics/2012/12_SD_Pickups_SB.pdf

You can easily get higher rated 17" tires. The steelie rims are also up to the task.

[Tundra2084]

Ok reading from the Ford site at the following address the difference between 17 in tires and 18 in tires is a 100 lb rise in the GVWR and a 400+ rise in the RAWR

https://www.fleet.ford.com/truckbbas/topics/2012/12_SD_Pickups_SB.pdf

[Tundra2084]

Ahhhh. Ok sorry have been using the rear axle GAWR
My brain is starting to hurt

[S_Davis]

Rear axle weight rating

[Bedlam]

RAWR = rear axle weight rating
FAWR = front axle weight rating

BTW: Your front axle is a Dana 60 steer axle rated at 7250 lbs

[Tundra2084]

Bedlam.... Now you have just thrown another weight rating at me. What is a RAWR?

[Tundra2084]

IdaD. I am surprised too that the truck is rated on 245/75 R17E tires 5600 lbs front and 6290 lbs rear these tires I believe are rate in the 3400 lb range. But I have 275/70 R18 E tires with a 3640 lbs tire rating.

[Bedlam]

It's not just the tire rating. You need to look at the frame, rim and suspension ratings too. Your weakest link is the maximum rating. In your case, the rims are rated lower than the tires resulting in the lower RAWR (can be verified on the Ford body build website specifications). The frame is the same as the DRW, the bare axle has a 9750 lb rating and the springs are matched to the published RAWR.

[IdaD]

What's your axle rating? I'm surprised an F350 would have 17" tires on it if they're rated down around 3200 lbs or whatever.

[Tundra2084]

The reason I asked the question in the first place was cause I weight my truck and new trailer yesterday. If I figures right I was over by 30 lbs on the GAWR of the rear axle and 350 lbs on the GVWR .
Ok throw out the wife, one dog, extra water hose, extra sewer hose......might leave me room for an extra beer!!!!!! Hmmmmmmm?

[Tundra2084]

So.....what I am getting from some of the posts is.....my axle is actually rated a lot heavier that the GAWR and my tires dictate what I can carry on my rear axle. I my case the 18 in tires are each rated for 3640, thus I could carry up to 7280 lbs on my rear axle.
Hmmmmmm. If that's right now if I could just get the GVW up on the truck. Lol

[MitchF150]

Tundra2084 wrote:
I know I can't change the GVWR or GAWR, only in this case Ford can!!!! But does it give me more GVW or GAW???

Only in your mind... 😉

You will get a nice warm and fuzzy feeling that you know your tires are not the limiting factor if you do decide to go over the sticker ratings on the other components... 😉

That has been and will always be the limiting factor to YOU, the owner and driver of said vehicle.

You could put on some 19.5" G rated tires and claim the same thing..

Up to you in the end.

Good luck!

Mitch

[blt2ski]

Huntindog wrote:

timmac wrote:

azdryheat wrote:
You don't have the authority to change the GVWR or GAWR.

I do

That's great! Ihad no idea it would be so easy. Can you print me a new sticker for my truck?:R

This internet stuff just keeps getting better. More things that were previously hard or impossible to get are becoming easy every day.:B

Depending upon the state you live in, they may not recognize the door sticker as being the law per say. Only what you pay in fees to drive down the road. So in a sense, yes it is easy to change out the gvwr of a given rig by paying money to your local licensing agent. I've had 8600 gvwr rigs licensed to 12K, an 18200 licensed at 26K, been pulled over at 27k, no overweight ticket mind you. Just told to up license to 28K with in 10 days. As I was under the road bed design limit. Ie 20K per axel, or 500 lbs per inch width of tire, which ever is less. Also assuming your axel are spread apart enough to "BRIDGE" the load over the road bed enough. Hence "Federal Bridge Laws" from a weigh load issue.
With this in mind.....AN LEO CAN and WILL get you off the road if you have an unsafe rig. For the OP, this will not be enough to worry about.
Taller tires as noted WILL lower you initial take off ability. Going from a 31" diam tire and say 4.10's to a 32" diam tire, will now net you an approx 3.95 axel ratio. Go up 2" you are now a 3.73 effictive ratio.
GCWR is a performance standard, look at the new SAE ratings, it is not a law that you can not go over this ratings. Nor is the gvwr that the manufacture lists a law. I have yet to see this stated in ANY states I have looked up. Including here in Washington state where I am. All that matters is the paid for slip of paper in my truck. If I am over this amount....techniquely I am over weight. Even if at say 8200 lbs on my 2000 C2500 which has a door sticker of 8600 lbs, but over my paid for license of 8000 lbs. Or it can go the other way as noted above re in my dumptruck one day.

marty