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RLM4x4 · 08-13-2013, 02:57 PM

I have a 2007 Ford f-250 crew cab diesel. It came factory with 17" tires but when I bought it someone has put 20" tires on it. My question is as far as towing a fifth wheel should I keep the 20's or go back to the 17's? getting ready for some new rubber and was just wondering pro and cons of the difference.
Thanks
All opinions welcome. LOL

Mr_D · 08-13-2013, 03:05 PM

Probably check with Ford but as I understand it the certifications for towing are made with the OEM tires and wheels. Changing to a different size without factory approval probably would not be advisable.

BFlinn181 · 08-13-2013, 03:20 PM

I agree with Mr._D, height, rear end ratio, etc. all set up for the shorter tires. Larger tires will effect your towing ability and speedometer reading.

powerboatr · 08-13-2013, 03:21 PM

you can go to fords vehicle site and check, but 17" usually carry the higher capacity than the 20" tires and wheels

not sure why....may have to do with sidewall loads or something

https://www.fleet.ford.com

jesilvas · 08-13-2013, 06:07 PM

I'd compare rim weight ratings. If they are the same or better and cover your rear GAWR, I'd just go with what you want. You can get a tire for either one to make them basically the same gear ratio in the end.

sswilson · 08-13-2013, 07:43 PM

If I am correct, your 20" wheels probably have low profile tires on them and realistically are the same circumference as the old 17" wheels and standard tires. This should not affect your speedo. The 20 " are probably passenger tires rather than LT (light truck) tires which would give you better control and weight capacity. I have a F150 and I really noticed the difference when I went to oversized LT tires. I carry a heavy Goldwing in the back and don't feel the weight like I did with passenger tires. Albeit my speedo is now out but I know how much.

JIMNLIN · 08-13-2013, 08:09 PM

Ford has a 20" option for the F250 and F350 SRW for '07 model year.
The tire is a LT275/65-20" E at 3415 lbs capacity on 20" wheels rated at 3525 lbs capacity.
These 20" LTR E tires are not a 20" P tire. Apples vs oranges. You didn't give any size and load range . These tires are heavy and will have more parasitic drag over say a LT265/75- 17" E tire. Some guys like the big tires for looks or the higher load rating.

They are a upgrade in capacity however they are expensive to replace. Your call.

wandering1 · 08-14-2013, 06:48 AM

Real simple, look at the plate inside the door frame and that will tell you the size tires your truck are supposed to have.

RLM4x4 · 08-14-2013, 07:28 AM

Jim is correct. Whoever put the 20" on used OEM fords rims with Goodyear Wranglers. My thing is the price of the tires 20" run approximately 300-375 a tire while 17" run 140-180 a tire. If the speedometer reads 60 I'm actually doing 64. The tire experts (Big O) tell me the 20" would be better. Having problems finding a used set of OEM 17" rims

Dutch Star David · 08-14-2013, 07:38 AM

Tires 20" run approximately 300-375 a tire while 17" run 140-180 a tire. The tire experts (Big O) tell me the 20" would be better.

Which would you rather sell if you're the tire store even if markup is the same for each? And I'm pretty sure the markup % is at least as much on the 20's as the 17's-probably more.

RLM4x4 · 08-14-2013, 07:54 AM

I agree. That's why I'm really considering going back to 17" tires . Just having trouble finding some OEM rims

Dutch Star David · 08-14-2013, 09:07 PM

Quote:

Originally Posted by RLM4x4

I agree. That's why I'm really considering going back to 17" tires . Just having trouble finding some OEM rims

Salvage yard? Can you find original owner? They are probably in the back of his garage.

Grimesy · 08-14-2013, 09:22 PM

Haven't talked about gear ratio so here goes if the circumference of the 20's is greater you will have higher gear ration with less pulling power. Usually a ratio in the 4's has more pulling capabilities than one with a lower number, say in the high 3's. I just reread what I wrote and now I am confused as well.

Don G.