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Wheel offset
Can someone explain wheel offset to me.
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1978 924 The Grey Ghost - 18,000 miles and counting 1987 944 Black Betty - Bringing back from years of abuse |
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06-23-2013, 07:37 PM
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Registered User
Join Date: Jan 2013
Posts: 220
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Offset is the distance of the face that meets your hubs from the center of the wheel. If a wheel has a low offset, the face is close to the center of the wheel. If the wheel has a 0 offset, the mounting face is directly in the middle of the wheel. With a negative offset, the face that meets the hub is pushed in towards the car more. Offset is measured in millimeters. Positive offset measures toward the outside of the wheel, negative towards the inside.
Last edited by admiralkhole; 06-23-2013 at 07:57 PM.. |
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06-23-2013, 07:53 PM
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Thank you for that explanation but I still am not getting it. I am trying to understand what people mean when they talk about wheels fitting on a car or not because of the offset.
I am a Design Engineer and former Adjunct Professor but for some reason I can't figure this out. Late offset, early offset, I want to figure this out.
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1978 924 The Grey Ghost - 18,000 miles and counting 1987 944 Black Betty - Bringing back from years of abuse |
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06-23-2013, 08:16 PM
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OK, I looked at some picture explanations on line and I now understand it. And thanks admiral your explanation makes sense to me now. What are Phone dials, negative or positive.
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1978 924 The Grey Ghost - 18,000 miles and counting 1987 944 Black Betty - Bringing back from years of abuse |
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06-23-2013, 08:29 PM
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there are several different phone dial wheels, all of which have a positive offset. '86 and earlier cars have a lower offset. Early phone dials have a 23.3 offset. '87 and on have a higher offset...47 and/ or 52 I believe. If you have an early car, you can fit higher offset wheels with adapters or spacers, but not the other way around.
Last edited by admiralkhole; 06-23-2013 at 08:54 PM.. |
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06-23-2013, 08:52 PM
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Join Date: Dec 2011
Location: Space-time continuum
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The offset was changed to allow room for ABS sensors on the 'late'r cars. Not all later cars had ABS, but all had the extra room for it.
For some reason that I cannot figure out, people think that the fitment of a wheel is entirely dependant upon offset. This of course is not true, being as how offset is a function of the wheel's width (in this situation). Porsche made 15x7 Phonedials in three different offsets, and 15x7 Fuchs in at least two different offsets. Take care, Last edited by FrenchToast; 06-24-2013 at 11:08 AM.. |
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06-24-2013, 11:04 AM
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Steve Sims
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This is the most straightforward "offset" explanation I've seen: Wheel Tech - Offset
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Steve Sims '87 924S (Project Car) |
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06-24-2013, 04:43 PM
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Proprietoristicly Refined
Join Date: Jul 2001
Location: ~Carefree Highway~
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This picture "shows" position of negative and positive off set --American Racing
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1988 924S, 85,750K ..+ 1987 924S, 154K DD (+15K est. bad odo) |
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06-24-2013, 05:00 PM
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OK, so then if I were going to buy a new set of rims for my 87 944 what would I have to know, or how would you know if they will fit the car. Would any potential new rim have to have the same or near the same offset as my current rims.
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1978 924 The Grey Ghost - 18,000 miles and counting 1987 944 Black Betty - Bringing back from years of abuse |
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06-24-2013, 05:12 PM
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Registered
Join Date: Jan 2004
Location: Northern Virginia
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You would want a "late offset" wheel.
Factory wheels, base and S (not turbo) in 1987: 7x15, ET 52 (Where ET is offset, and in modern wheels if often stamped ON the wheel) If you are looking at new "Porsche" rims, wheels from a Boxster, 993, 964, 996 all have the potential of being "direct bolt ons".. ie, they have offsets in the 47-52mm range that work with no additional effort. I can't find it off hand, but a place like Wheel Enhancement has a great list of "Porsche" wheels and can be a useful reference. Also, Porsche wheels have a part number stamped in the back, in one of the spokes. You can cross ref. the part number with some of the websites that list the wheels and their dimension and if they would work or not on your car. If you are buying an aftermarket rim, you also need to be aware of your "bolt pattern". They are "5x130". Meaning, 5 holes, 130mm apart. Not all brands of wheels may be available in your bolt pattern.
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1970 914-6 Past: 2000 Boxster 2.7, 1987 944, 1987 924S 1978 911SC, 1976 914 2.0, 1970 914 w/2056 |
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06-24-2013, 05:56 PM
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