Help with technical stuff like backspacing and offset

usurp · 10-26-2009, 01:18 PM

Hey guys, my OEM z4 wheel cracked and another is dented so i decided to order some new wheels from tirerack. Now I put in all the details 2005, BMW, Z4 3.0 and its displaying a bunch of wheels for me. I am stick to 18" but every wheel i click seems to have a different offset and backspacing. What do they mean?

I found for example some BBS RX with the following specs:
Offset: 38mm Backspacing: 6.0" Bolt Pattern: 5-120

I then checked the BBS CK and it had the following specs:
Offset: 45mm Backspacing: 6.29" Bolt Pattern: 5-120

What does it mean?

thanks!

nickpapa · 10-26-2009, 02:15 PM

backspacing is the distance from the inside face (the part pressing against the rotor) to the inside edge of the rim.

so for the example above, the RX will stick out more than the CK (if they are the same size and width)

usurp · 10-27-2009, 11:19 AM

Ah cool thanks. so whats the OEM backspacing or offset?

nmulax · 10-28-2009, 12:57 PM

Quote:

Originally Posted by usurp

Ah cool thanks. so whats the OEM backspacing or offset?

Which OEM wheels do you have?

You can find the offset on RealOEM.com

Click here

usurp · 10-28-2009, 01:00 PM

I have these
http://www.realoem.com/bmw/showparts...43&hg=36&fg=15

02 TWO-PIECE LIGHT ALLOY RIM 8JX18 ET:47
02 TWO-PIECE LIGHT ALLOY RIM 81/2JX18 ET:50

usurp · 10-28-2009, 01:02 PM

damn, my OEM's cost over $800.. thats crazy

10-26-2009, 01:18 PM	#1
usurp Private 7 Rep 52 Posts Drives: 2005 BMW Z4 Roadster - 3.0i Join Date: Apr 2008 Location: Kuwait iTrader: (0)	Help with technical stuff like backspacing and offset Hey guys, my OEM z4 wheel cracked and another is dented so i decided to order some new wheels from tirerack. Now I put in all the details 2005, BMW, Z4 3.0 and its displaying a bunch of wheels for me. I am stick to 18" but every wheel i click seems to have a different offset and backspacing. What do they mean? I found for example some BBS RX with the following specs: Offset: 38mm Backspacing: 6.0" Bolt Pattern: 5-120 I then checked the BBS CK and it had the following specs: Offset: 45mm Backspacing: 6.29" Bolt Pattern: 5-120 What does it mean? thanks! __________________ 2005 BMW Z4 Roadster - 3.0l, SMG, M Seats, Eisenmann exhaust and Hardtop.
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10-26-2009, 02:15 PM	#2
nickpapa First Lieutenant 23 Rep 374 Posts Drives: Z4 3.0 Join Date: Oct 2008 Location: North Jersey iTrader: (3)	backspacing is the distance from the inside face (the part pressing against the rotor) to the inside edge of the rim. so for the example above, the RX will stick out more than the CK (if they are the same size and width)
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10-27-2009, 11:19 AM	#3
usurp Private 7 Rep 52 Posts Drives: 2005 BMW Z4 Roadster - 3.0i Join Date: Apr 2008 Location: Kuwait iTrader: (0)	Ah cool thanks. so whats the OEM backspacing or offset? __________________ 2005 BMW Z4 Roadster - 3.0l, SMG, M Seats, Eisenmann exhaust and Hardtop.
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10-28-2009, 01:00 PM	#5
usurp Private 7 Rep 52 Posts Drives: 2005 BMW Z4 Roadster - 3.0i Join Date: Apr 2008 Location: Kuwait iTrader: (0)	I have these http://www.realoem.com/bmw/showparts...43&hg=36&fg=15 02 TWO-PIECE LIGHT ALLOY RIM 8JX18 ET:47 02 TWO-PIECE LIGHT ALLOY RIM 81/2JX18 ET:50 __________________ 2005 BMW Z4 Roadster - 3.0l, SMG, M Seats, Eisenmann exhaust and Hardtop.
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10-28-2009, 01:02 PM	#6
usurp Private 7 Rep 52 Posts Drives: 2005 BMW Z4 Roadster - 3.0i Join Date: Apr 2008 Location: Kuwait iTrader: (0)	damn, my OEM's cost over $800.. thats crazy __________________ 2005 BMW Z4 Roadster - 3.0l, SMG, M Seats, Eisenmann exhaust and Hardtop.
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