[JWahlsten]

Flash,



The reason I don't like the repliwheels more-so than cast wheels specifically is the quality control. I don't have any issues with the pressure cast wheels spec'd by Porsche, but I have 3 cracked repliwheels in my garage. It's not my first experience with these cracking either. I had a similar situation in 1997. So, things haven't gotten better. None of these wheels were ever curbed. They were trashed by cornering forces on the track. Same thing is happening to Fuchs wheels now...



I don't have the 993 wheels, but the 964/965 style. Mine are heavier, but I didn't feel like searching out another set yet, and I like them.



Good point on the Magnesium wheels. They are expensive, light, and fragile. I wouldn't want them unless building a 944 Turbo Cup car for the concours circuit which is not my bag, baby.

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[flash]

interesting. i'm almost sure they are made by the same manufacturer as OEM too. there must be a very definite difference in the process, or a very different composition. never really paid that much attention to it.



what kind of lug nuts were you using?

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[Cloud9...68]

[quote name='flash' timestamp='1404326615' post='159462']

the offset is 55 on the 9" wheels. as long as you don't go over 25" O.D., or over 255 in width, they should fit fine. i have a 57mm offset on a 9" rim on the front of my car, with a 255. fits great. obviously a fit check would be in order.

[/quote]

I was just about to dig out the wheel size calculator, but MCL968's question, and Flash's answer, saved me the trouble.



Speaking about tire widths, I read something in Grassroots Motorsports a few months ago that shocked me, but they had the lap times, and their subjective observations, to back it up. They were evaluating the relationship between wheel width and tire section width, using the same tire model, the BF Goodrich G-Force Rival, currently the top-rated extreme performance summer tire, for all their tests. They started with a 205/50-15 on an 8" wide rim (already a very wide wheel for that size tire), and then put a set of 225/45-15's on the same rim. This was on a Honda CRX, so obviously a completely different car than a 968. They said that in some respects, the wider tire improved the subjective cornering performance (aka "handling"), and in others, they actually degraded it, and the lap times with the two combinations were exactly identical. Then they took the same 225/45-15 tire , and put it on a 9" rim. Their comment was, "This combination was magic". They said it improved the feel and control through the corners in every category, and the lap times crushed those of the same tire on the 8" rim.



Now, it's no mystery that all things being equal, you want the widest possible rim for a given tire. But the thing that amazes me is the sizes they used. I would never have thought a 225 tire would even fit on a 9" rim - the widest rim tire rack recommends for a 225 tire is 8.5". Yet you can't argue with their data. Does this make sense? Does the fact that their test car is very light (although being FWD, it's relatively heavy in the front) skew things?

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[flash]

that one is easy to understand really. a tire that is wider than the rim allows more flex, and therefore more compression under load. this increases tire heat.



this is the same reason that i don't like to see too much camber on a car. while the outside tire may seem flatter in the corner, because the inside tire has almost not contact anymore, it makes the outside tire take the whole load. that means that it gets hotter with the same amount of centrifugal force applied.



stretch the tire on the rim, and you limit tire compression, which evens out the tire temps.



on the street though, this can present a problem, as there will not be much forgiveness, and impacts will transfer quickly to the rim.



for autocross, this is not the best idea either, and some sidewall flex is a good thing, as your tire temps really never get to where the need to be anyway.

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[JWahlsten]

The lugs were always Porsche steel lugs. The set of wheels I recently acquired with the cracks (for the new tires) were also secured with the proper ball end steel lugs. Mine were torqued correctly to 94 ft-lbs. Not sure what the deal was, but they cracked in the center of the spokes. I can shoot some pics.



On the 17x8/9.5s I got from Cole Scroggins at G & W motorsports they ran 245s all the way around...

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[flash]

hmmm - steel should have prevented the problems. interesting.



p.s. - torque spec is 96, not 94

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[JWahlsten]

Whoops. Maybe it was those two ft-lbs...

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[flash]

lol - i doubt it - just wanted to perhaps prevent a booboo later

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[Cloud9...68]

Flash,



I completely understand. But that's not what shocks me about GRM's results - it's the actual wheel/tire sizes they reported on. Would you have thought a 225 tire would perform so well on a 9" rim? I would have though 8" would be about optimal, but the performance on a 9" rim blew it away. Does this imply that the ideal section width for a 968 with a 17 x 9" square set-up is 225? It would be cheaper, and a little lighter, than a 245 or 255. Or is that too much of an extrapolation from a test done on a Honda CRX?



I'm always fascinated when somebody presents hard data that runs counter to "what I've always thought", and this definitely falls into that category, at least for me.

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[flash]

that is really going to depend on the car. keep in mind that the weight is a very real factor, as is the speed of the car. i'd be interested to know what the car weighed, and how fast it was.

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[Cloud9...68]

GRM's test car was a race-prepped 1988 Honda CRX HF, for which Edmunds lists the curb weight at 2103 pounds. It has a full cage, and from the pictures, and the interior doesn't look like it's been stripped (not that there's a whole lot to strip out of that car) , so I'm guessing it may actually be in the 2200 lb range. They swapped the engine out for one from an Acura TSX, which they pretty heavily modified to produce 250 hp at the wheels. They don't give any details on the suspension set-up, but it's a very fast car, for sure, and I'm sure a very capable handler. Not sure how much this helps answer how well GRMs results might translate to the 968.

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[flash]

yeah - 3/4 the car. to follow the same idea, and have the same kind of results, you would need to run a 295 stretched on a 12" rim.

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[steve g]

Andrew, will you change your spring rates when you change from 18 in to 17 in ?

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[Cloud9...68]

My understanding is that I should, but I'm not sure by how much. IF I change (by no means a certainty - these wheels aren't exactly plentiful, and what's out there tends to be in sets of four, with two at 7", and two at 9") to Porsche-style wheels, they will weigh about the same as my current 18" Enkei's. The tires will be lighter, but only by a few pounds.

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[flash]

springs are really to control the unsprung weight. while it may seem like you should adjust the springs for lighter wheels or tires, you are going to be hard pressed to find a spring that will equate to the change. if you make more than a 5lb change, perhaps you should change the spring 25lbs. that may prove difficult, as there are not a lot of choices in 25lb increments. generally a small bump (compression) change in the shock or strut will take care of any weight change at the tire/wheel end.

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[Cloud9...68]

Thanks - good info

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[Cloud9...68]

Getting back to the wheels, I'm pretty sure they were never issued by Porsche in 17", and that they're only available in replicas. They're not on this list of Porsche wheels, which looks pretty complete to me:



http://www.944racing.de/wheelweights.php



I've called several sites who show them, and none of them have any in stock. Among the wheels available in 17 x 9", the most common seems to be the 996 Carrera 2, part No. 996.362.128.00:



http://www..net/forum/topics/set-of-17-porsche-996-wheels-7-and-9-for-sale-889-delivered





Can't say I'm crazy about the looks, but there aren't a whole lot of options, unless, as Flash said in another post, you want to spend upwards of $5K for a set of custom forged alloys.

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