When will we see an entry level full CF Ferrari ?

Well, it's a bit like having a thread about a carbon fiber tub (which you're on). You save a little weight, you go a little faster.

 

CF tubs are a lot lighter, not merely incrementally, then an equivalently rigid chassis made of other materials.

 

You're quibbling about percentages, but to go with your line of thought simply answer: "How much does an Enzo (and F50) weigh?"

 

I doubt there is a CF wheel that will pass the excessively overcautious battery of tests the OEM's require. I only have direct experience with Honda wheels, but I am sure Ferrari would need to be even more cautious given the higher speeds involved.

 

This thread is about "when."

 

The TR 512 is a third heavier than the all but identical sized F-50 (2712lbs) and 33% is not a quibble.

Making wheels a few% lighter with a considerable reduction in safety does not make nearly as much sense.

 

The TR 512 vs F50 sprung weight reduction is a fine accomplishment...but reducing unsprung rotational weight would make even larger improvements upon performance.

So what would you say if wheels could be safely reduced in weight by 30%?

 

References, please.

I'd first ask for a definition of "safely".

 

Lets look at the math.
The kinetic energy of an object in motion is:

E = ½mv2
Where E is kinetic energy in joules, m is mass in kg, and v is velocity in meters per second.

Now, for a rotating mass (such as a wheel), the formula is:

E = ½Iw2. I = mr2, w = v/r
Where I is the moment of inertia, w is the angular velocity in radians per second, r is the radius in meters. Of course, when a rotating mass is moving down the road, then E is the KE of the mass at speed *PLUS* the KE of the rotating mass.

Since a wheel is rotating at the same speed the car is traveling, the KE of this wheel is now:

E = ½mv2 + ½Iw2
substituting for I and w, we get: E = ½mv2 + ½mr2v2/r2

the r2 term cancels, and we finally get: ½mv2 + ½mv2 which simplifies to just E=mv2

In other words, twice the KE of a non-rotating mass on the car (E = ½mv2).

This is the kernel of truth in the old saying that "A pound off the wheels = 2 pounds off the frame."

 

http://forums.corvetteforum.com/showthread.php?p=1559309462
Let me describe an experiment performed in Norway a number of years ago. It might be of interest in this tread.

First, the weight of the wheel affect unsprung weight. But if we talk rotational inertia, which is something different, It is NOT enough to put the wheel on a scale. We must take in to account WHERE the weight is located on the wheel. This is the same phenomenon as a mid-engined car compares to a nose and rear heavy car.

An experiment shows the following. If we let a wheel roll down a board,
the wheel has a linear acceleration. It also has a linear acceleration around its own axle. Both require energy. The energy to rotate the wheels is given by Kr=(I * w^2) / 2.
The ”straight line” acceleration is Kv = (m * v^2) / 2,

We have a 10,89 feet long board raised 5 feet (26,377 gdr) in one end, and the other end resting on the floor.
A downhill “road” situation. We have three wheels.
A, 8x17 with 235/40 tires weigh 44p,
B, 15 inch with 205/60 tires weight 35 p, and
C, 14 inch with 195/60 tires weight 32p.
We will take each wheel, hold it on top of the board, and let it roll down by gravity to the floor. Measure the time with a photocell. A tire with higher rotational inertia will then take MORE energy to start to turn around. That energy loss will make it take a longer time to roll down the board. Here are the numbers.
A 1,61 sec. Moment of mass 1,272 Virtual mass 75p.
B 1,59 sec. Moment of mass 0,946 Virtual mass 57p.
C 1,56 sec. Moment of mass 0,704 Virtual mass 51p.



A car that weights 2200 pound (1000kg) that does 0 to 60 mph at 10 sec will loose 3 tenth of a sec, using the 17 incher used in this example!!!
A 10 sec quartermile car will lose about 25 horses!

Goran Malmberg

 

isn't the Dymag CF/Magnesium hybrid quite a bit lighter than OEM wheels of equiv size??? 19x13 wheel is a touch less than 19lbs, 19x9 is 16lbs, for the Dymag hybrid...how much does an OEM Ferrari wheel come in at???

 

OEM F430 front wheel 19x7.5 is a rather embarrassing 27.4 lb.

OEM magnesium front 18x7.5 F355 wheel is 21.8 lb.

If memory serves, 360 stock one piece wheel is even lighter.

I wrote my senior thesis on carbon fiber wheels, and as No Doubt, said, it's about "when."

Reducing rotating mass (wheels, brakes, tires, flywheels, gears, whatever) makes it easier to accelerate the car. Mass reduction in the wheel/brake/tire area makes braking, steering, and suspension performance more efficient, too. The faster something spins, the bigger the effect of mass reduction on acceleration.

Some of you might be surprised at how lax the "battery of tests" for wheels is. "Passing" those is definitely not the issue here.

Chris

 

While we're talking about wheels, I'll add the factory optional modular wheels are heavier than the one-piece cast wheels. They're for looks, not performance.

 

45 pounds difference from OEM F430 wheels to Dymag CF wheels.

That's 90 pounds of undesired virtual mass. Easily a tenth of a second performance difference 0 to 60mph, perhaps even more.

 

More like 60 lb. Your derivation only applies if all of the mass is concentrated at the rim. That doesn't seem worth the cost. I'm also not convinced of the durability (either to impacts or long-term degradation).

 

Have you priced F430 OEM rims?! CF wheels move more mass to the center, by the way.

It's just a question of "when."

 

well now, i don't think that's merely a pound or two...that's a HUGE difference in weight savings!!! 27lbs for the front wheel? wow, that is terrible. hmm, OEM wheels are pretty darn expensive, so the price of these CF hybrid wheels aren't bad at all. read somewhere a single CGT OEM wheel costs more than $10K!!! ludicrous!

 

"Virtual mass"?

"A tenth of a second...0-60", but at what cost to treasure and safety? One unavoidable pothole and the CF rimmed wheel is "limp home, then trash", if not actually "instant trash"...

So I have to ask again: Why do you shill for CFC wheels?

 

Why do you shill against CF wheels with such urban legends?

 

Why should I price F430 rims? Don't compare an aftermarket price to an OEM. You can buy metal replacement rims that will work on any car for much less than CF ones. I'm sure Ferrari will charge a lot more than the current prices if they ever manufacture CF wheels.

Anyway, you could much more easily eliminate wheel weight by making them smaller. But that's not been fashionable lately.

 

the idea that today's CF products being 'fragile' and prone to catastrophic failure is something i've been following with great interest. i think about all those CF motorcycle wheels on the street--and track--and wonder, as it's nothing new in the world of two wheels. have not seen or heard anything on that front pertaining to 'sudden' failure... this fear/subject is also a popular topic in the commercial air scheme of things...but that's in another thread. as far as CF wheels for cars, i believe it has just been a matter of cost/unit, not a matter of safety or engineering. CF manufacturing has always been expensive due to the labor intensive tooling. RTM and other 'new' methods have greatly helped bring costs down as far as tooling is concerned, but we are still nowhere near the efficiency we're at with alloys. Me, i'm all for new technology, and hope that in the near future the cost barrier will be lowered.

 

if i'm not mistaken, Ferrari does not make their own wheels...they have to make money on top of what it costs them to buy from their supplier...

 

Are those motorcycle wheels durable over long time periods? From what I understand, CF components tend to degrade over time. Will a CF wheel remain safe for decades? Also, cars are driven much more than bikes. Will the wheels last for hundreds of thousands of miles?

The loads cars see aren't quite the same either. Besides the extra weight (which probably isn't important with proper design), the wheels have to be able to rub into curbs every once in a while (possibly at speed) without losing significant safety. Someone might also try to turn a wheel hard into a curb while parking. Partially because bikes don't have PS, I'm guessing that these kinds of issues are much more relevant for cars.

Just to be clear, I'm not really arguing. This is just speculation, and I would love for someone to post something more concrete.

 

Yeah, ok. Still, the OEM profit margins on wheels are probably higher than almost any other part of the car.