Backspacing and Offset

pontiacgp

pontiacgp

Canadian Prime Minister
Mar 31, 2006
24,190
9,384
113
Kitchener, Ontario
#31
Norrisboy79 said:
I want to go with a 10 inch rear wheel on my 79 cutlass what bc do I need to make it clear everything and not stick out of the wheel well I'm talking about weld prostars by the way. Can anybody help me????
what rear end do you have?
 
83StreetMachine

83StreetMachine

Apprentice
Dec 16, 2011
73
41
8
Central NJ
#33
Last edited:
565bbchevy

565bbchevy

Geezer
Aug 8, 2011
5,824
4,802
113
Michigan
#34
That's much better.
I think everyone is over thinking this. Here's a simple example:
You have an 8" wide rim with a 4" backspace
That is a 0 offset rim. This is because the centerline of the rim is 4" (centerline = rim width/2) and the backspace is 4".
Don't let the metric conversion to mm trip you up.
An 8" rim with 0 offset would about 4.5" of backspace.
 
Last edited:
350Cutty

350Cutty

Apprentice
Dec 20, 2018
56
33
18
Miami, FL
#36
I don't know if it has been mentioned, but for offset, the smaller the number (or more negative), the further out they stick out. Like the wheels on my truck have a -11 offset and I can see them clearly in my mirrors because they stick out a lot. +15 is more of a factory wheel offset and would sit inside the fenders.
 
D

Doug Chahoy

G-Body Guru
Nov 21, 2016
849
553
63
#37
I don't know if it has been mentioned, but for offset, the smaller the number (or more negative), the further out they stick out. Like the wheels on my truck have a -11 offset and I can see them clearly in my mirrors because they stick out a lot. +15 is more of a factory wheel offset and would sit inside the fenders.
I have to say after reading this entire thread INFO OVERLOAD! When the factories started making the wheels more like hubcaps (like a new Camaro) they can't in my understanding be centered. The whole wheel seems to be all B/S the way it sits over the brakes toward the frame.
 
BOXCARS

BOXCARS

Master Mechanic
Apr 29, 2017
322
275
43
#38
Well, I just read the last few comments. My question would be, why don't they just reveal the backspace measurement, eg 5", 4.5", 4" etc.? What good is zero offset, or some other figure that describes offset? Many wheel ads only mention offset. Why would they want to confuse their customers? Wouldn't it be easier to understand to just use the backspace measurement? Inquiring minds need to know.

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