What's wrong with this setup?

[masraum]

They LOOK great, but they hamper performance. They aren't as strong or durable, and because they are heavier and they are unsprung and rotating they hurt acceleration, braking, and handling.

Yes you can feel a difference in acceleration, or, at least, Thom/widebody did.

[Bill Verburg]

A D in wheel weight of ~10# is the equivalant of 1-2hp. If that is the D at each wheel then that is ~4-8hp total. That is starting to get into the range of what the average driver can feel.

A far more significant effect comes from any increase in the tire height at the drive wheels. Here even a .25" D in tire height can easily be felt by a driver with even average sensitivity.

If it were my car I would make every effort to keep tire heights ~25" unless significant hp or gearing changes have also been made.

Of course there is always the special case where someone has a specific need in which case any change needs to be aimed at addressing that need. For example someone that wants a more relaxed rpm at freeway speeds might want a 25.7" drive tire.

[JeremyD]

Scooter - you have to do what you like. It's your car - popular opinion aside - it's still your car. Most folks do not explore the limits of their car, on the street or track, make it yours first.

[Kevin Stewart]

I wish we could put this wheel weight thing on myth busters, I have been in wheels 22 years and yet to see any amature tell the difference in a15lb wheel verses a 25 lb wheel, IT didnt show any differenace on the track if any the bigger wheels had better times from wider tires, I race cars also and had this very conversation with a friend the other day, his answer was I have so much hp i can spin them anywhere now, why do i need lighter wheels, it seems the porsche guys answer to speed is lighter wheels, you would be better off if you were gonna spend tons of money on wheels to (kenesis etc)buy sway bars bushings and a corner balance, turbo tie rods, torsion bars, hp brake pads, Kevin

[Bill Verburg]

Kevin I disagree w/ you. Though not as important as the diameter issue a10#/wheel is just barely perceptible in acceleration and more so in response to irregular pavement on a 200hp 2600# chassis.

I do agree that the more hp/torque that is available the less this is important, 8hp out of 200 is more significant than 8hp out of 400 afterall. Alos the ratio of sprung to unsprung weight is an important issue. An extra 40#s on a 1500# cchassis is far more significant/perceptible than 40#s on a 3000# chassis.

I guess that along w/ everything else every statement needs the full set of related quantifiers, qualifiers and related data

[kees]

I love my Porsche and it's some kind of sport to keep it completely original and time-correct. Call it whatever you name it (purist), but that's the way I am.

Not only for the Porsche, but also for my daily driver (Jag).





Kees.

carrera coupe 1985

[DIANA]

A 911 it is for modification.It is one of the cars with more modifications of history.
Your car is beatifull today and tomorrow too.
Porsche change your models.You too.
Your car today have more price.Your car have 2 type of wheels.

Regards

[Kevin Stewart]

Bill I turely understand what your saying, You cant convience me that an amature driver is going to tell the difference,

someone mentioned widebody noticed the differance sure he did, but I believe he noticed more then anything the wider wheels and softer compound tire

everytime someone states they noticed the differance they also put on a008's or the GS or something simular and compare them to a two or three year old (could have no miles) that has a hard compound and is getting harder every day,
another thing i have noticed is the guys will buy the lightest wheel available then put a cheap race tire on it that is 5-6 lbs heavier a tire, go figure,

last comment if you breaking a tire loose then you have to much power weather its a 200hp car or a 100hp car, I have seen this and sold to many tires and you cant convence me, looks good on paper but in realty is just not there, what i mean is they tell me thier times with the new wheels not tires and its the same within a .100 and there are tons of ways to connect the power, the first step is we always back the cam timming down (not the distributor timming) so we dont have an instant on motor, even if the cam comes in at 3500, Kevin

[DavidI]

I think the Cup wheels look great. They give the SC an aggressive look. Do it up!

[Bill Verburg]

Kevin I agree that the way most people do this is irrelevent, the difference between one brand and another, between old rubber and new etc is just too great. But I have seen on a dyno the #s I quoted, same tires mounted on ~10# different wheels, back to back runs.

[Kevin Stewart]

Bill I totaly agree with you about a dyno, but the dyno is not the race track, the lighter wheels dont add hp, just frees up hp, but still its not really seen on a track, Kevin

[Elombard]

They look great on the 74 - 89 cars (bellow bumper) but to me they look weird on the earlier cars?? I especially like the cup 1s, one of the best looking OE wheels ever made IMHO.

[Eric Coffey]

Originally posted by Kevin Stewart
Bill I totaly agree with you about a dyno, but the dyno is not the race track, the lighter wheels dont add hp, just frees up hp, but still its not really seen on a track, Kevin

You make valid points Kevin, but I have to disagree a little with you there. True, lighter wheels don't add HP, but taking away weight (especially un-sprung rotating mass) helps in ALL areas of performance. Adding HP does not. The lighter wheel improves suspension response (modulation?) and allow the brakes to do their job more efficiently (faster). Also, that extra 7 pounds +/- at each corner is at the very end of the (sprung) suspension arm which magnifies the problem. Imagine trying to stop a golf swing mid-stroke while holding a 2 pound weight in your hands, not too hard. Now imagine trying to stop it with that weight taped to the club head.

[350HP930]

Originally posted by Eric Coffey
True, lighter wheels don't add HP, but taking away weight (especially un-sprung rotating mass) helps in ALL areas of performance. Adding HP does not.

Wanna race?

[Kevin Stewart]

All I ask is that you guys in the no, show me you track slips with the same tires and lighter wheels, no more to be said, Kevin

[krichard]

So is this gonna be the new contraversy that takes the place of the chip one. I'm just waiting for loren to pipe in.

[JeremyD]

yeah, dynos or ban!

[89911]

I thought the biggest issue with "cup" wheels wasn't whether they looked correct or not, but that the replicas suffered from poor manufacturing (Mikkels car). Also the production of a cast alloy compared to a forged aluminum gives up some strength and weight. They look fine.

[Bill Verburg]

I thought the biggest issue with "cup" wheels wasn't whether they looked correct or not, but that the replicas suffered from poor manufacturing (Mikkels car). Also the production of a cast alloy compared to a forged aluminum gives up some strength and weight.

That is the issue w/ replicas, they are very heavy and very weak relative to factory wheels. The initial discussusion was about factory wheels which are certainly light and strong enough but have the wrong o/s

Any time the wheel is accelerated that includes &#177 accelerations as well as up/down accelerations and left/right accelerations a heavier wheel needs more energy, the energy has to come from someplace and go to someplace

[Scooter]

Originally posted by Bill Verburg
The initial discussusion was about factory wheels which are certainly light and strong enough but have the wrong o/s

This is correct. I was asking about Porsche factory wheels with spacers/adapters strictly for street use, not for the track.

Sounds like some interesting opinions. Thanks for the input.