Backspacing and offset question

95XL · Dec 16, 2007

Ok, I'm working on turning my Ranger into a dually. I'm making 5 to 8 lug adaptors and I'm going to use F-350 rims (dually ones, obviously). I went to the junkyard this weekend and found an older F-350 dually and took all of the measurements I needed (backspacing, etc...). My question is, I figured out how thick to make the adaptor for the front to put the center of the dually rim where the center of the ranger rim used to be. My question is, should I make the same adaptor for the rear? If I make the same adaptor for the rear the inner rim will have the same offset as the stock ranger rim, then the outer rim will just sort of be floating out there. Or should I try to make the adaptor as thin as possible to try and get the center of the duals to be where the ranger rim should be?

Thanks for any help.

95XL · Dec 20, 2007

Anyone?

metalmacguyver · Dec 20, 2007

with this kind of custom fab, the best person to answer your questions is yourself. as far as where the wheels will end up, i think that will depend more on the axle your using.

86ford · Dec 21, 2007

you are seriously concidering puting a dually setup on a 4cyl truck that i assume has a 7.5 rear? you have a whole lot of thinking and planning to do. i honestly think your crazy. if you are keeping the 7.5 rear end you will most likely end up snaping axles if you are even the slightlest bit hard on it because those heavy tires and rims will put alot of stress on your axles just like someone who put 35s on a d28(i am not talking about a mall crawler here). you will have similar issues with the front d28 or d35 if you ever engage the 4x4. you will need to GREATLY increase your gearing to even be able to move those heavy ass tires. your front and rear will also very possibly have serious clearance issues. i am not saying it cant be done but there a whole lot more to it than just making adapter plates and slaping dually tires and rim on it.

86

95XL · Dec 29, 2007

Well, I understand where your coming from, but I have done my homework. You are correct to assume that I currently have a 7.5", but I have 4.10's from the factory, so turning the wheels shouldn't be a problem. The F-350 dually rims are a 16" rim, vs our stock 15" rims. The stock tire size on F-350 dually's are a 215 85 16, which if you use the metric to inch tire converter in the tech library turns out to be about 30" tall, which is what I currently have on my truck right now, and is only about an inch larger than the stock ranger tire. Back to the rear end issue, I am also currently setting up an explorer 8.8 with a l/s. So, after this winter I should be swapping that in, and that would greatly increase the strength of my axle.

And I explained in my previous posts that I've already calculated the adaptor thickness to give me the correct backspacing an offsets for the front, so as not to place extra strain on the wheel bearings. That should also clear up any clearance issues, because the center of the rim is going to be in the same exact place as the stock ones, and my tires don't rub right now?!?

As far as engaging 4wd, the front end wouldn't be turning any heavier wheels and tires than it would be normally if someone had steel rims would it?

So, to answer your original questin, yes I am serioulsy considering putting dual wheels on my 4 cyl., and I have thought it through, and basically all it really is, is slapping some adaptors and some dually rims and tires on it.

94STXRanger · Dec 29, 2007

Isnt this for a school project? I thought i read that it would only be like a temporary thing, not permanent. Have big 350 wheels on there and tires would look cool though i think.

95XL · Dec 30, 2007

Yes, it's for my senior project, so each individual student has to come up with their own project, and we have to buy all of the materials ourselves. I was thinking about making it temporary, but I've already taken out a loan to buy the materials and outer fenders from JC Whitney, so I'm pretty much committed now.

I could always take the adaptors off and put my stock rims back on, but I would have some extremely funny looking fender flares over my rear tires.

86ford · Jan 1, 2008

i was thinking about this and realized that duallys typically have full floating rears to keep the weight of the load off the axles. i still think you are going to be putting to much stress on the bearings and axles. as for the front tires, wheel spacers are also hard on bearings because they move the weight out farther and allows the weight to have more leverage going against the bearings. since you have so much time and money into this i hope it works! it sounds like you did your homework but i think its going to be a long term PITA.

86

krugford · Jan 1, 2008

If he's already taking into account the thickness of his wheel spacers for the front when determining the wheel offset, then it won't put anymore strain on the bearings than what's there now.

Dual rear wheels can be set up to not put anymore strain on the rear as well. With a dually, you have two contact patches instead of one per side. As long as the point midway between these two contact patches is in the same location as the original single contact patch, then the loads imparted to the axle would be the same for normal driving. Full float axles are used as a result of the loads carried by these trucks, not the number of tires bolted to it. The number of tires bolted to it is also a result of the load carried, not the other way around.

The conversion is going to be for looks only. Putting dual rear wheels on a semi float axle in no way will raise the maximum load rating of the axle.

JoshT · Jan 1, 2008

Sounds like a cool project to me, wish my high school had them. If it had my 84 might have a V8 now, naw I didn't have the money to do it.

95XL · Jan 2, 2008

Krugford, you're saying that I should try to get the center of the duals in the same location as the center of my stock rim? Thats the answer I've been looking for, and the reason I started this thread.

JoshT, I also wish my highschool had projects like these, unfortunately I'm in college for machining, so on top of having to pay for materials, I also have to pay 10 grand a semester to make them.

Just a general question, I've seen C-clip eliminator kits floating around online. What do they do?

Backspacing and offset question

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