Quick Backspacing Question

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70Dart340V8

70Dart340V8

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I'm planning on buying a set of rims for my 1970 Dodge Dart 340 soon. I've looked around and have seen that people really like to run 15x7 rims with 4.5" of Backspacing. For my front wheels I plan to have a 15x7 with 4" of Backspacing with a 215x60R15 tire. I feel like this should fit fine. If worse comes to worse I have a fender roller that I can use. For the rear I'm planning on a 15x8 rim with 4.5" of Backspacing with a 225/60R15 tire. Has anyone run anything similar to this before? I'm unsure that if since I'm using the 8" rim in the back if I should give it a little less Backspacing seeing how I have a fender roller I could use. Just to be safe and to avoid having the inside of the tires rub.
 
You'd be better off with more backspacing in the front and the back. Stock BBP 15x7's had a 4.25" backspace (+6 offset), and running them on my Duster with 225/60/15's there wasn't any extra room to the fender. The 215's would be close with a 4" backspace, but they should fit.

In the back I'd say the same, a 225/60/15 will fit just fine on a 15x7 and the stock backspace would be 4.25". Most have found that getting the max tire out back with a BBP axle means more like 4.5" of backspace on a 15x7", a +12 offset. With a 15x8 that works out to about 5" of backspace. Again though, with a 225/60/15 the rim you listed should work, but it will be close, and you won't be able to run anything bigger than a 225 in the back. Which is a shame because with the proper backspacing most folks can run a 245.

The only thing you didn't mention was whether or not your car still has the SBP or has been converted to BBP. All of my recommendations are for BBP, because the BBP brakes and axles add track width to both the front and rear. With a SBP set up you'll have more room. I still wouldn't say those wheels would be ideal, but your clearance would be a lot safer than if you're running BBP.
 
On my 73 Swinger I have 215/70/15's on 8 inch rims and have about 1/2 or less between the tire and the springs, but more than an inch between the tires and the fenders.

The rims are 4.5 backspace so if I put on rims with a 3.75-4 backspace I could run 225's

Don't know if this helps or just confuses more. :D
 
What 72 said, you need more backspacing if your BBP swapped. Good luck finding rims that will fit and not require spacers, modifying your hubs or look like they belong on the neighbor kids Civic.
 
is it BBP swapped?

I've got 2 BBP 15x8 5" BS steel wheels that would work if you are BBP.
 
Im running sbp axles with a 1 inch billet aluminum adapter to go to bbp wheels, the 1inch adapter gives me more room to my leafs, im running a 275/60r15 on the rear and have about 3/4" of clearance between my sidewall and leaf and about 3/16" to my quarter lip. If i didnt run them id be limited in rear tire width, still thinking i could squeeze some 295/50r15's on there but wheels arent wide enough lol
 
I recommend a 4.25" back space on a 15 x 7 rim.
Tires, depends on the condition of your suspension.
Wore out springs, etc will make the tire sizes vary.
 
71DodgeDemon340 said:
Im running sbp axles with a 1 inch billet aluminum adapter to go to bbp wheels, the 1inch adapter gives me more room to my leafs, im running a 275/60r15 on the rear and have about 3/4" of clearance between my sidewall and leaf and about 3/16" to my quarter lip. If i didnt run them id be limited in rear tire width, still thinking i could squeeze some 295/50r15's on there but wheels arent wide enough lol
Click to expand...

The 1" adaptor doesn't give you any more room, it just changes the amount of backspace needed. And since you didn't mention the backspace you have, the presence of an adaptor doesn't mean anything to us. If your wheels fit, you obviously have about 1" more backspacing than you would need if you didn't have the adaptors.

Also, Dart's do not have the same size wheel wells as Dusters/Demons/Dart Sports. Without moving the springs you can't get anything bigger than a 255 on a Dart, and most people find that even a 245 is cutting it close for clearance even when everything is centered perfectly.

On a Duster/Demon/Dart Sport 275's are easy with the stock spring locations. A 295 requires a 1/2" offset and a quarter lip trim if your wheels are actually inside the wheel wells. If you're running SS springs or have the back end of the car jacked up then it doesn't matter as much since the quarters will be well above the tires anyway. But that's not the same as fitting.
 
Oh lol my bad, i forget that they are different. Im running 15x7 rallye wheels with i believe 4.25 or 4.5 backspace. I hear dart and automatically think they are the same but only thing that is identical is the front, now if he was talking about a duster tgen my input would be a lot more practical lol sorry bout that
 
Why do you want to put a 225-60-15 on an 8 inch rim? A stock 6 inch rim will suffice for that size tire. Are you looking for the fartcan look? Just remember if you put a tire on a wheel wider than the tire, if you scuff a curb or pothole you ruin the wheel and tires are generally cheaper to buy then wheels. I like a little side wall bulge to protect the rim. I run a 255-60-15 on a 7 inch rim with 4.5 inches of backspacing with no rubbing and no ill handling.
 
Dart66, Are you running a stock rear suspension? No wheel tubs or leaf spring relocation? Also is this on a 70+ Dart or a pre-70? I may be wrong but I read somewhere that the older model darts had bigger wheel wells. I may be wrong on that though. If so I'd like to run that. I am just trying to fit a comfortably big tire in the rear with no modification to the tubs or having to relocate the leaf springs. I read a 225 would fit flush on a 8" wide wheel.

As for the bolt pattern, how much would it roughly cost to do a complete swap to a bigger bolt pattern? (roughly)
 
Yes the back half of my 66 Dart has not been altered at all. It has caltrac 1 inch lower mono leafs and bars in the stock location. As far as wheel wells go I think they are pretty close in size with nod to the newer Darts for the bigger wheel wells. I have a buddy with a 69 Dart with 275-60-15 on 7" wheels with 4 3/8 back spacing but his car sits slightly higher then stock, those will not fit my dart. As far as the bigger bolt pattern goes the inexpensive way to do it is to have the stock axles and brake drums redrilled or you would have to buy new axles. Price of both very by machine shop or manufacturer. Axles would run about 3to4 hundred, redrilling should run a hundred or less. The front end would be the cost of a big bolt pattern disc brake swap, but I have seen cars with the front hubs and drums drilled out.
 
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