15x8 Backspacing Question

LewisL230

Not-quite-so-new-guy
Dec 23, 2007
15
3
Nashville, TN
So I’m going to buy the jegs set spike wheels for my 4 door Malibu. I’m getting 15x4s for the front and wanted 15x8s for the back. The problem I see is that the 15x8s only come with 4.5 and 5.5 backspacing. They also have a 15x7 and a 15x10. The tires I’d like to run are either a 255/50/15 or a 275/60/15. More than likely a drag radial. I’d rather not run spacers as I’ve seen those cause some problems.
 

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565bbchevy

Geezer
Aug 8, 2011
8,333
113
Michigan
Consider doing a frame notch and either one of those back spacings will work.
 

UNGN

Comic Book Super Hero
Sep 6, 2016
3,061
113
Southlake, TX
Around 3.7 - 4" is Ideal with an 8" wheel on G-body

Depending what the back of this wheel looks like, You may consider using 1" - 1.5" Wheel Adapters.

Spacers are death, Wheel adapters are pretty strong and probably won't break without huge power. I wouldn't worry about wheel adapters until you are pulling the Front tires off the ground.

Both 255/60 and 275/60 Drag radials work OK on 7" rim, though they work better on an 8" rim.
 

UNGN

Comic Book Super Hero
Sep 6, 2016
3,061
113
Southlake, TX
You have about 5.5 inches of BS to the frame. the section with of the 275 60 15 is 11.4 inches. That means 1.7 inches of the tire is wider than the 8 inch rim on both sides. Do the math and the tire will hit the frame w/ a 4 inch backspace. You need 3.5 BP with that tire.

View attachment 153887

You have to add another 3/8" - 1/2" to this to account for the rim wall thickness. The 8" is inside the rim, But BS is measured outside the rim (and some people measure it at the Rim lip adding another 1/8" - 1/4" to the rim thickness.

If BS were standardized to the back inside wall of the rim, only the guys who stretch 195's onto 9.5" wide rims would be screwed. The rest of us would know where the tire was vs. the frame.
 
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LewisL230

Not-quite-so-new-guy
Thread starter
Dec 23, 2007
15
3
Nashville, TN
It’s still the 7.5. The next thing I touch will be new rear end. With the stock 305 I don’t plan to do a burnout at the track. Hopefully it’ll last until I can get another rear end built.
 

lilbowtie

Comic Book Super Hero
Jan 7, 2006
3,462
113
Canton Mi
You won't hurt it with a stock 305. If you run stock tires which shouldn't spin it will help your rear end ratio instead of a 28 tall radial. Don't expect much (around 18) but have fun !!
 

LewisL230

Not-quite-so-new-guy
Thread starter
Dec 23, 2007
15
3
Nashville, TN
I’m thinking I’m gonna go with a 255/60 drag radial. Just because it is a a little shorter. We only run 1/8 mile around here so I’m just hoping for 11s because that poor 305 has no power at all. I may put a gear in the 7.5 just to make it a bit more fun to drive while I’m saving money to put a 9” in it. Then once the 9” is in. I can start deciding on which direction to go with the engine.
 

lilbowtie

Comic Book Super Hero
Jan 7, 2006
3,462
113
Canton Mi
That tire only has a 10.1 sec width so you could go with a 4 inch bp. If you want to make some good power reasonable w/ a 350 I can give you some ideas
 
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