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    Unsprung weight on 19" 997 S wheels?

    Which of the 19" wheels for the 997 S has the LEAST amount of unprung weight (i.e. weighs less)? Stock S wheel, Carrera Classic, Sport Design or new XRR wheel? Excellence Magazine stated that the Sport Design wheel (standard on the 997 S X51 Club Coupe) had the least amt. of unsprung weight. From appearances, it would seem that the Carrera Classics weigh less (more open space between spokes). Anyone know for sure?

    Re: Unsprung weight on 19" 997 S wheels?

    What I heard from a person the weight of the S wheels is light than other stock wheels, which is around 21 lb

    Re: Unsprung weight on 19" 997 S wheels?

    I remember reading someplace that the SPORT DESIGN WHEELS are the lightest you can get from the factory. I will look around to verify..

    Re: Unsprung weight on 19" 997 S wheels?

    stock S wheels weigh 25.5 rear and 22 front. I don't have other weights.

    Re: Unsprung weight on 19" 997 S wheels?

    This has been an ongoing question for some time; both here and on the rennlist. No one seems to have the real answer. Obviously, to a bunch of us it is important. Dealers, too, don't know the answer. Would be nice if Zuffenhausen would publish that data for us through PCNA.

    Dan

    Re: Unsprung weight on 19" 997 S wheels?

    However, I think lighter the wheels are not always the best. I just the the original S wheels to a super light sportec wheels (only 8kg), however I don't really like the feel of the sterring wheels when I drive fast.

    Unsprung weight is key!

    The lighter the wheels and tires the better - within margins of safety. Helps the car handle better (faster steering) and helps improve the ride.

    If you have high speed instability check tire pressures to see if they are correct.

    If they are, try and drive someone else's 997 to see if it feels the same as yours.

    If it feels the same then you have discovered the beauty of the 911 having less weight over its front wheels - in other words it's an inherant part of the design.

    If it feels different take it to the dealer for an alignment.

    Re: Unsprung weight on 19" 997 S wheels?

    Quote:
    Sun Gor said:
    However, I think lighter the wheels are not always the best. I just the the original S wheels to a super light sportec wheels (only 8kg), however I don't really like the feel of the sterring wheels when I drive fast.



    The potential problem with lightweight wheels is generally considered to be their inability to withstand damage from hitting potholes or from riding over kerbs.

    The phenomenon you describe sounds like it is more likely to be caused by some other problem, not just by the low weight of the wheels.

    Re: Unsprung weight on 19" 997 S wheels?

    One thing seems for sure: the XRR is NOT going to be the lightest of the bunch.

    One other certainty: 18 inchers are going to weight less than the 19's.

    Re: Unsprung weight on 19" 997 S wheels?

    Quote:
    fritz said:
    Quote:
    Sun Gor said:
    However, I think lighter the wheels are not always the best. I just the the original S wheels to a super light sportec wheels (only 8kg), however I don't really like the feel of the sterring wheels when I drive fast.



    The potential problem with lightweight wheels is generally considered to be their inability to withstand damage from hitting potholes or from riding over kerbs.

    The phenomenon you describe sounds like it is more likely to be caused by some other problem, not just by the low weight of the wheels.



    In contrast to that statement we have the reality of forged rims (which Porsche has migrated away from) which provide incredibly strong wheels AND lightness. So,--that sort of flies in the face of that statement about lightweight wheels.

    dan

    Re: Unsprung weight on 19" 997 S wheels?

    18s may weigh less than larger wheels, however, the respective tire adds more relative weight than the wheel.

    Re: Unsprung weight on 19" 997 S wheels?

    Quote:
    Dan L said:
    Quote:
    fritz said:
    The potential problem with lightweight wheels is generally considered to be their inability to withstand damage from hitting potholes or from riding over kerbs.

    The phenomenon you describe sounds like it is more likely to be caused by some other problem, not just by the low weight of the wheels.



    In contrast to that statement we have the reality of forged rims (which Porsche has migrated away from) which provide incredibly strong wheels AND lightness. So,--that sort of flies in the face of that statement about lightweight wheels.

    dan



    OK, allow me to amend my original post to:

    "The potential problem with lightweight wheels is generally considered to be their inability to withstand damage from hitting potholes or from riding over kerbs , unless of course you include well-designed forged wheels, which due to the improved properties of certain aluminum alloys when they are forged tend to more resistant to abuse, despite also being lighter than cast wheels with flow-formed rims. Forged wheels are relatively rare because they are much more expensive to produce than conventional alloy wheels both in terms of tooling costs and manufacturing costs.

    I don't know what got into me that I should have failed to mention that in my original post.


    PS: I almost forgot to mention: My real point in my initial post was meant to be that I thought it unlikely that the unsatisfactory "feel" in the steering wheel was just a result of using lighter wheels than those supplied as original equipment.

    Re: Unsprung weight on 19" 997 S wheels?

    Quote:
    devo said:
    18s may weigh less than larger wheels, however, the respective tire adds more relative weight than the wheel.



    I don't think that's true: wheel weighs more than tire.

    Ie. total weight of 19's with tire still exceeds 18's with tire.

    Race tuners like Manthey Motors and others (including Walter Rohl himself) have been quoted as saying that the optimal wheel size for a 911 is 18. The GT3 cup car has 18's and has for a long time.

    19's are more for looks (and 20's are just ridiculous). The issue is that the 997 has been aesthetically designed to accomodate 19's - the 18's look too small on a 997.

    Re: Unsprung weight on 19" 997 S wheels?

    ....also, if you are looking for the lightest possible combination, you should also weight the different tire brands, the weight can vary quite a bit, particularly "R-compound" tires.

    Re: Unsprung weight on 19" 997 S wheels?

    Well the wheel issue wells up again---

    Veteran says:
    "19's are more for looks (and 20's are just ridiculous). The issue is that the 997 has been aesthetically designed to accomodate 19's - the 18's look too small on a 997. "

    We just do not understand that ---- the overall diameter of the 18in plus higher profile tire is almost exactly the same as the 19in plus the rubber bands. This keeps the ratio/gears the same.

    But then what counts is whether the wheel design makes the wheel look larger or not ---- if the 'spokes' extend well into the rim,then the wheel looks much larger.E.g. the BBS RS-GTs I use in summer look much larger than the standard 18in Classics. They look like 19in -----

    I just do not 'get' this large diameter wheel fettish ----- the wheel/tire combination is heavier, more unsprung weight, less tire compliance, poorer ride ----- and in the extreme somewhat better steering/handling respnse, although the 18in is rather good --- hardly sloppy!

    I have 17 or 18in on the daily driver Acura TL (6spd, sports suspension) and the 18in is markedly harsher, although they do look much better stylistically, in this case. The 'spokes' extend well into the rims, so my 18in TL wheels look much larger than the 18in 997 wheels (they have the SAME size tires, and are in my basement for the winter.) The TL happens to suit that look very well------

    But then you can tune the ride with tire pressures, each couple or 3 pounds/in.in is equivalent to another set of harder/softer springs. I run the 997 with 6 pounds lower pressure on the nastier city/suburban roads, and only inflate higher for extended high speed runs (no worries, and I did that in the now departed NSX for 7 years)

    Bonne Chance

    KiwiCanuck

    --------------------
    -SB

    Re: Unsprung weight on 19" 997 S wheels?

    Quote:
    KiwiCanuck said:
    Veteran says:
    "19's are more for looks (and 20's are just ridiculous). The issue is that the 997 has been aesthetically designed to accomodate 19's - the 18's look too small on a 997. "

    We just do not understand that ---- the overall diameter of the 18in plus higher profile tire is almost exactly the same as the 19in plus the rubber bands. This keeps the ratio/gears the same.


    I just do not 'get' this large diameter wheel fettish ----- the wheel/tire combination is heavier, more unsprung weight, less tire compliance, poorer ride ----- and in the extreme somewhat better steering/handling respnse, although the 18in is rather good --- hardly sloppy!





    The 18 inch Carrera III wheels look smaller in the 997 wheel well than the 19 inch Carrera Classics, yet the design is almost identical - spokes go out to the rim. The 19 inch wheel just looks better on the 997. While your logic on overall wheel/tire diameter makes perfect sense, I don't think you'll find much debate on the preferred look of the 19 inch wheel on the 997.

    I agree completely with you regarding the issue of weight and performance with 18's.

    That's the dilemma.

     
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