Front spacing/Back spacing question

[72chevynoob]

I am switching my truck from 6 to 5 lug in the front, with spindles and rotors from a 1981 silverado. I plan on keeping the rear 6 lug and just running the same brand of rallyes on the rear with smoothie hub caps. i am wondering what the front spacing or back spacing should be for them to look and work the best. The rears will be 15x10 or 15x12 and the fronts will be 15x8 or 15x9.
Thanks

[Pondscum]

bump

[CC69Rat]

Stepside or Fleetside? Lowered or stock height?

[72chevynoob]

Fleetside. Stock height but it will get lowered ptobably 4/6
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[lolife99]

What year truck?

[CC69Rat]

6 lug 72 ? ( .. from his forum name )
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[72chevynoob]

Haha not a 72- a 69. I was looking for a 72 when i joined, though.
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[CC69Rat]

Do you know if it's early or late rear end housing?
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[lolife99]

You have several issues that need to be addressed.
15 inch wheels is the first one.
Your front wheels can not have more than a 4" backspace, and you will probably need to do a little trimming of the lower a-arms to make them work with spindles.
With that said,... I would use a 15x7 wheel to tuck them under the fenders nicely.
The rear will work with a 15x10 with a 4.75"-5" backspace.
Finding tires for a 15x10 or 15x12 might be tough unless you go with a Mickey Thompson tire.
My opinion,... I think a 275/60 looks stretched on a 15x10,... and a 295/50 looks too short.


Your 4/6 drop is the perfect drop!

[lolife99]

Originally Posted by CC69Rat

Do you know if it's early or late rear end housing?
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Should be the early 67-69 (narrower) rearend if it's original to the truck.

[72chevynoob]

Im pretty sure its original, it is a 12 bolt and it has the 6 lug drums. It is quite a bot narrowetr than the front as well, so i think it is.
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[72chevynoob]

What do you mean when you say that a 275/60 looks stretched?

[lolife99]

Originally Posted by 72chevynoob

What do you mean when you say that a 275/60 looks stretched?

In my opinion,... a 275/60 looks better on a 15x8.

[CC69Rat]

If you can, lay under the back of the truck and measure from one backing plate to the other. Is it 55.5" or 57" wide. .. (lolife99's method actually)
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[CC69Rat]

275 / 25.4 = 10.82 in

25.4 cm in one inch. 275 tire is 275cm wide.

Multiply in inches x the aspect ratio to get the sidewall height.

Ex. 275/60/15 would look like this. 275/25.4*.60 = 6.49in sidewall. Top + bottom sidewall + rim size = overall size. 6.5+6.5+15 = 28in tall.

295/50/15. 295/25.4*.50*2+15. 5.8" sidewall but only 26.6" tall. 'Wide and short'

Make sense?
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[72chevynoob]

Originally Posted by CC69Rat

If you can, lay under the back of the truck and measure from one backing plate to the other. Is it 55.5" or 57" wide. .. (lolife99's method actually)
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It is 55.5 inches, so probabvy the original axle
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[72chevynoob]

Thanks for explaining this to me guys. if i went with 16" rallyes from summit could i go with 16x8s in the front without having to trim the a-arms? 15x8s seemed to work pretty good in the truck i pulled the spindles off of, although i have no clue what the backspacing is on those rims.
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[ChevLoRay]

Maybe this'll help....On my '96 GMC with DJM spindles up front, I went with Wheel Vintique 'Vette style rallye wheels in a 16x7 size with a 4-inch backspace. Before that, it had 15x7's up front and 15x8's out back. I had to go with the 7's because a 4-inch backspace would let the inside of the wheels contact the lower control arms when turning. I know some folks don't have any qualms about trimming them, but my thinking is that the engineers designed the shape of those control arms for a specific reason.

On my '69, I went with Early Classic Enterprises and a 2.5/4.0 drop. I kept the 6-lug patter on the disc conversion because of the wheels I had at the time. Since then, I went with Wheel Vintiques 15x8 up front, with a 4-inch backspace and 15x10's out back with a 5-inch backspace. Pre-disc brake steel wheels won't clear the rotors, but 6-lug 4WD wheels will work.

[A.Bursell]

Originally Posted by ChevLoRay

On my '69, I went with Early Classic Enterprises and a 2.5/4.0 drop. I kept the 6-lug patter on the disc conversion because of the wheels I had at the time. Since then, I went with Wheel Vintiques 15x8 up front, with a 4-inch backspace and 15x10's out back with a 5-inch backspace. Pre-disc brake steel wheels won't clear the rotors, but 6-lug 4WD wheels will work.

Is it safe to say no trimming with stock spindles, but lowering spindles will contact or require trimming? This is with a 15x8 wheel.

Adam
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[72chevynoob]

So would 15x7 with 4" b.s. fit on cpp 2-1/2" drop spindles without having to trim or should i go to 16x7?
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[lolife99]

Originally Posted by 72chevynoob

So would 15x7 with 4" b.s. fit on cpp 2-1/2" drop spindles without having to trim or should i go to 16x7?
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You would have to trim.