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What is the difference between early 70s and mid 70s or later 15X6 Fuchs wheels? Are they the same offset?
Thanks.
Thanks.
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Last edited by GT3Racerich; 06-15-2022, 08:35 AM. -
Same offsets and overall appearance. You have early versions with hearts on the window at the valve stem, and early versions without hearts. These are lighter than later versions and use a 3 prong early style center cap. This changed after 7/73 with the introduction of MY74 and they started using the later ring style center caps. -
Actually, the overall appearances are different between the 'Deep Six' of '69-'71 and the later 'Flat Six' of '72-on. This, independent of the valve stem supports and the hub opening change.
I've never heard about the weight differences between the Deep and Flat 6. This doesn't include the early 6R because we think that the 6R was actually drawn out of the 5.5 blanks.
Anyone have weights of a '70 Deep 6 and a '72 Flat 6 to compare?Comment
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I believe the last run of early wheels is 5/73 (which is the same as saying the 7/73s are later, as they made the fuchs in batches and I don't think there are 6/73s?), and thereafter they go to the bigger 71mm openings. I think the later 7j and 8j wheels are a tad bit heavier because they were made more robustly. Per Harvey, the early wider wheels used for racing were intended to be "disposable" - used for a race or two. He told me not to track mine for this reason. The 944 7j and 8js are definitely heavier. I can assure you no one will know the difference between the early '70s and mid '70s when they are on your car, and the three prong caps can easily be caulked to a later rim to fully replicate the look.Comment
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Thank you guys. That is the info I was looking for.
As far as "Deep 6" and "Flat 6", what is that referring to if the offset is the same?
Also, it seems that the later 15x6 wheels are a lot more expensive than 7s or 8s? I wouldn't have thought that. Can you tell from this photo if this wheel is a deep 6 or a flat 6?
Thanks again.
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That's a flat six and Ben's picture is a really good pictorial. What I look at is the cutouts between the spokes. On the Deep six the cutout opening bends down into the depth of the lip reveal. The Flat six cutout is, ummm,,,,,flat.Originally posted by GT3Racerich View Post
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Thank you all. I really appreciate it.Comment
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That's a great illustration. Thanks for posting it.Originally posted by gtBen View Post
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A similar question might be:
"What is the difference between a man and a woman?"
Study them for about one second and you will notice subtle differences.
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Can deep 6s identify as flat 6s and vice versa?Comment
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In this day, even a 5.5jx14 can pretend to be a 7r.
I think the flat 6s were produced in fewer numbers, perhaps a year less and presumably more E's sold with cookie cutters during that run, plus a few more 7j's that deep 6s wouldn't have needed to compete with. Has anyone tried to estimate wheel production figures? 6r's the fewest?Comment
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Ha! Frank checking for bulges, LOL.... If we ever meet in person, you'll notice that mine ain't subtle.Originally posted by Frank Beck View Post
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The earlier wheels were designed to be used with tubes and may be unsafe when used with tubeless tires. At what point was the 6X15 rim changed to accommodate tubeless tires?
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dhoComment
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Porsche and their preferred tyre manufacturers did not recommend tubeless with earlier rims. They issued technical bulletins about topic that are unambiguous.
Just for hobby interest I’ve attached image of one such bulletin from around mid 70s that sets out the reasons Porsche policy was not to do it at that time (with a Google translation of same). Not just the attached but many of the tyre companies published similar viewpoints at time that I’ve seen.
Maybe some owners with older rims without safety jumps are unaware or if aware maybe simply ignore the fact it is not a permitted combination of rim and tyre-type.
I wonder if it could even create a liability in event if an incident/ accident and the prohibited combination were found to be on a car ? Might it invalidate insurance in event of an incident if combination was not declared when seeking cover — ignoring long standing published OEM and tyre supplier policy . Similarly it is not clear what liability could arise for workshops tyre fitters etc who choose fit the rim/ tyre combinations in breach especially with the technical position being a matter of record for four decades? Might such businesses have less wiggle room than a customer if pleading ignorance of the OEM and tyre company policy position and criteria ?
Personally I wouldn’t fit tubeless to the older rims. The “flat six” with safety humps on rims and correct tubeless valve seating were introduced before the adoption of tubeless by Porsche. The use of flat rims preceded adopting of tubeless by factory by a year or two. Porsche seem to have design the layer rims to be safe for the emerging tubeless trend. Tubeless fitment by factory didn’t seem to happen until the G series, roughly mid 70s. If important I have a note of exact dates when Porsche earlier use of tube type tyre changed over to tubeless for several major tyre brands they used at time.
I expect some folks here have all the old bulletins among their literature collection. If so please post a clearer image than the blurred example I’ve attached. Also the other bulletin group 6 no 12 10.10.1974 as referenced in the attachment. On my view would be interesting to upload too so that owners at least have the historic policy and criteria back in the day.
I’m not an expert on wheel and tyre design and this historical content may not be the latest position or be applicable to all regions so I recommend to always get qualified advice on safety critical matters like criteria when choosing wheel and tyre combinations.
SteveAttached FilesLast edited by 911MRP; 06-18-2022, 11:25 AM.Comment
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