I have gathered some info from the site, but not finding specifics. I would like to hear from others who have upgraded a dually to larger tires. I've discussed this with a local ford truck shop and they seem to have the knowledge.

My Goal: Increase tire size for improved look, but not compromise truck warranty. I want to install 285/70R17 to increase diameter and width

1. I want to stay with my stock wheels (stock tire is 245/70R17). Steel inner on rear (2X), Aluminum all other (4X)
2. I will install rear wheel spacers(probably (1.75 or 2.0 inch)
3. I will install a leveling kit on the front
4. I know my 4:30 gear ratio will drop accordingly with the increased diameter
5. Some say Ford can change ECU to reflect one of the factory gear ration settings (not sure I need to technically do that for warranty reasons).
6. Some say the change in diameter will effect some ECU settings and thus truck performance (not sure that is true?)

I would really appreciate any lessons others have learned and if anyone else has installed this tire size on a dually.

Mark

 

I should have added that I do tow a toy hauler at about 17K-18K loaded

 

One thing to consider with spacers, is how you will mount the rear tires. I am thinking that spacers of thickness over say 1/2" or so will cause you to not have enough stud to mount the wheels safely.

Research the tires you want to use and see what the section width is compared to the current tires. This should give you an idea about spacer thickness.

 

I know you want to stay with your 17" wheels but this what I did. I ordered a '16 F350 Tow Boss and did not like the 17" wheels/tires. Before the truck came in I bought a set (6) of American Eagle 20 X 7.5 wheels for $225 ea.and 6 Michelin Defender 275-65-20 tires. I sold the 17" tires and wheels for $1500.

I didn't need to level or ad wheel spacers, the tires are 34" and lowers the 4.30 gears dow to about a 3.73 as my truck runs 2000 rpm @ 70 mph. As Just Strokin said you can't add thick spacers w/o having longer studs installed. When you add up good quality steel spacers/ longer studs/leveling kit you're going to have quite a bit of money tied up in parts........up to you. Plus these tires don't hang out of your rear fenders......... unless you like that look.

 

Thank you CYNCWBY,

That configuration looks awesome. As for rear spacers, they mfg hub centric spacers that bolt on with studs in them. That is the typical way to handle the spacing in the rear. However I think what you did is more appealing in terms of minimizing changes.

Question: Did you have the dealer change the gear ratio setting on your ECU.

Thanks for the information and great pictures!

 

The thicker spacers mount to the existing studs, and have studs mounted offset from the bolt centers to mount the outer wheels. The spacers actually MOUNTS to the factory studs, and has its own studs for the outer wheel.
Example
8X200 TO 8X200 WHEEL SPACERS | ADAPTERS | FORD F-350 SUPER DUTY DUALLY | 3" INCH - Wheels

 

Yes since the Michelins were a stock 34" size they reset the computer very easily. I see what you mean on the rear, seems to me that they would stick out waaaay too far.....dunno. Some guys like the tractor look, I don't. Plus the way I did it minimalizes a lot of extra work, besides I always liked the looks of the older F450 with the 19.5 wheels. With the new Bbilstein shocks and this tire/wheel package it rides like a dream........ for a big dually truck.

 

To CYNCWBY,

Can you confirm how much gap you have between the rear tires? Here is why I ask.

If the new wheels you bought have the same offset as stock, then tire calculations from my stock tires 245/70R17 to the tire you selected 275/65/20 shows the width to be 9.6 inch vs. 10.8 inch respectively. That is a difference of 1.2 inch. The gap on my current tires is 1.3 inches. That leaves little (0.10 in) or no gap. When loaded with a trailer, then for sure they would rub.

I hope you can clear this up for me. I assume I have missed something.

Thanks,

Mark

 

Well I don't know if this will clear it up for you or not. I'm not aware of this specific wheels back spacing but if you contact American Eagle Industries in Chino, Ca. I'm sure they could give you the specs for the #058 wheel.

I really don't think they are the same due to the measurements you figured out. Here's a pic I just took of my trucks rear wheel spacing, as you can see there's plenty of room, the 2x4 is 1 1/2" wide and give it another 1/4" or so. I probably could run wider tires but the Michelin Defenders are perfect for my application. I hope this doesn't add to the confusion.....Dave

 

I really appreciate that. You have confirmed things. I agree the 20", 058 wheels have a different offset from the Ford Factory 17" wheels to provide that clearance. I agree that the tire could even be a little wider and no issue. Thanks so much, this really cements things for me.

The only downside is my local supplier says this exact wheel is on BO with no timeline. I just may have to wait. Not able to find something else in this style and size.

Thanks,

Mark

 

Not to worry.....I bought mine from a long time seller on ebay, he goes by "cinimus" but his name is Jon Keimach and he owns JK Motorsports in Riverside, Ca. Phone is (909) 245-1165. he is basically a wheel broker and usually has an ample supply of these wheels.

You can find his ebay add by typing in "Eagle 20x7.5 dually wheels" and just scroll down to the pic of the 058. I paid $225 ea. with lugs and cap, luckily I was able to pick the wheels up as we were going down to So. Cal. to see the kids anyway so I saved the $40 ea. for shipping. I bought the Michelin Defenders from Discount Tire Online, paid $261 ea. with free shipping, best deal I could find. Hope this helps.......Dave

 

You can use Forscan, a windows based computer, and an OBD II programmer (ELM 327) adapter and change all kinds of things.

What I see in the computer are gear ratios and tire sizes. I'm sure between the both you could get your new tire size dialed in pretty darn close.

 

 

I was also looking recently as the clear on my factory wheels is peeling................again. It appears that Eagle Alloys went under. 4 Wheel Parts has them all listed as NLA and their website is gone.

 

The Toyo Open Country 255/80/17 Installed

Plenty of turning radius

65psi no load same clearance as stock

Ride and handle well, I think I made the right choice

I will post more pics when I hook up the trailer with 4200 lbs of pin wt.

Toyo AT 2 255/80/17