stripling

I read this rock-on article extoling the virtues of carbon fiber wheels!

1) improved torque and horse-power 8-10%! :o accel & top speed :o
2) improved gas milage equally as much
3) improved stopping power 5% distance shortening
4) improved handling
5) improved g-turns
6) lightend un-sprung weight

it's making my mough water! Questions are these:

1) how much do stock wheens weigh?
2) how much do carbons weigh (18" say)?
3) the big Q!! HOW MUCH DO THESE things COST! :o ?????

i want 'em so bad i want 'em i want 'em i want 'em .....

dradon03

iTrader: (2)

Well just to let you know for my old GSXR750 project the Carbon Fiber wheels were 10,000$ Canadian so lets say round 8,600$ U.S and that is only for two realitively thin wheels. There are alot of places that make carbon covered wheels.

But authentic carbon fiber wheels, look at formula one and the new Koenigsegg CCX.

Good luck, I think you will find your cash better spent elsewhere to answer these queries,

Alex

21K95RX7

didnt realize wheels increased hp and torque l

-efini-

it doesnt. its less rotating mass, then say a heavier rim, so theres less loss of hp/torque to the road. why dont you just get some light weight fordged rims?

21K95RX7

i know i was being sarcastic

21K95RX7

also, i dont believe that carbon fiber wheels are 100 percent carbon fiber. well for a car atleast, they use an alloy first then wrap them in carbon fiber

GUITARJUNKIE28

you don't buy in to any of that ****, do you?

stripling

1) lighter wheels don't increase engine torque and hp, but to the road it does.

for example, assume your wheels weighed 400 lbs a piece and were made outta solid Pb. Yeah, little 255hp engine would be kickin' 255hp and 190 tq to the shaft, then the shaft and diff take their cut but the wheel weight (translated into inercia) take a cut too. a big one stock, and pretty much everything on a 400 pound wheel. 800 pouds worth of rear-wheel weight would take that 190tq down to about 10

so, going to extreems sometimes helps understand physics. i didn't mean to imply it increased engine hp, but instead "useful" hp from what i've read it's about 8% increase in tq & hp

2) i found BST 100% carbon fiber wheels for my Hayabusa (love it 1% more than my FD) front and back for $3,300 US and $3,600 US comp wheels... http://www.ram.mc/wheels/BST/gallery/BSTgallery.htm
I think the price on carbon wheels is coming down! I'm thinking in the next couple years, if you can get 10% tq gain from an FD and carbon wheels hit, say, $2500 for all four (don't wake me up then it might be worth putting in the top 10 FD upgrade list.

BUT: I'm not sure, 'cause I don't know the WEIGHT of the FD wheels OR of the carbon wheels! I mean, hey, if you don't save more than 40% you're not gonna hit that 10% mark IMHO.

3) ...uh... there is no 3... i just like making lists of 3 or more!

carbon man

Carbon Fibre wheels do have the advantage of weight but they do also have the disadvantage of heat disapation,
If your brakes use the wheels to diapate some of their generated heat then fitting Carbon Fibre wheels would then create on overheating problem for the brakes, Carbon Fibre does not conduct heat.
The other problem is your Tyres, an alloy wheel will conduct brake heat to the tyre case, if you can keep the tempreture in your tyre case your grip level is kept up.

I have not made carbon fibre wheels for cars but I could, I have made some Go-Kart wheels in carbon fibre and they are around half the weight of the original alloy wheels.

Ian.

GUITARJUNKIE28

for the many thousands of dollars you could buy carbon fiber wheels for, just imagine the mods you can do to get more hp...

Heisenberg

iTrader: (3)

How big of a weight difference is there compared to Magnesium wheels??

melicha8

iTrader: (1)

Haha the welch's grape juice refercence makes me laugh

stripling

good catch on the "weltches"

dude, your carbon go-cart wheels are freakin' cool! you could REALLY do that in a car wheel? Would home-made wheels be dangerous?

Also, I never notices my wheels were any hotter after using my fd. so, the brakes and calipers conduct heat into the wheels which conduct it into the tires? you sound like a pretty smart guys for real, but that's really reaching in my book... here's why.

Aluminum is one crappy metal for which to conduct heat. so is rubber. for the calipers to transfer heat from them to the spindal to the shaft to the wheels would easily eat-up 90% of the heat, especially with the surrounding air whipping by. then to make the way out the wheels to the tires, from the tire walls to the tire tread? someone straighten me out, 'cause i'm not buying that.

article i read said carbon fiber wheels would:

1) save gas
2) give you one car length in the 1/4 mile
3) give you 8 car lengths in the 1/2 mile!!!!
4) let you stop 5-10% quicker (decellerated inertial mass)

anyway, i would like to know the weight difference 'cause i know those motorcycle racers have been using carbon wheels for a couple years now and i've never heard this "brakes heat up" argument before

hey i know! run a pipe from the radiator to the brakes! water-cooled brakes! yeah, that's the ticket!

and maybe instead of a water-injector to cool the IC use it to cool the calipers! SCORE! i'm rich! i'll race ya to the patent office!

Bob_760

Crappy metal for which to conduct heat??????
Well maybe if you are looking to compare them to wheels made of Gold, Copper, Silver or Diamond.... Besides those its pretty much the best..

Also keep in mind, the calipers get hot, the rotors also get hot. Have you ever stopped hard then put your finger on a rotor? It gets pretty hot, I think it's a bit silly to think a GIANT PIECE OF ALUMINUM thats bolted DIRECTLY to a very hot piece of metal wouldnt conduct any heat. If you've ever done any racing you know that you frequently brake very hard, it generates ALOT of heat which has to go somewhere. After just a short roughly 1min long 45mph max speed autoX a set of aluminum wheels will be nice and warm. At the track it dosent take long to accumulate alot more heat.

maxcooper

Aluminum is a great conductor of heat. That's why they make CPU, stereo amplifier, and just about every other kind of heat sink out of it (with a few esoteric exceptions using copper). Heat from the brakes conduct into the wheel and then to the air that is flowing around the wheels; a positive side effect. Heating the tires and the air in the tires is a negative side effect.

It would be overkill, but there are brake systems that circulate the brake fluid (the calipers are not a "dead end") to keep the fluid from boiling in the calipers.

You will only stop faster with lighter wheels if your brakes can't maximize the traction of your tires (i.e. you can't lock the wheels while braking).

Note that tires typically weigh more than wheels, and most of the tire weight is concentrated at the outer diameter. When considering the weight and rotational inertia of your wheels, tires are more significant than rims.

I am all for "adding lightness", but the cost/benefit ratio of carbon fiber wheels is very hard to justify at current prices. As an alternative, I recommend some 1-piece forged aluminum wheels instead.

-Max

carbon man

depending on the mass of the magnesium wheel to compare with the weight of the carbon fibre wheels could be, if a wheel is made with bulky spokes or thicker walls for strenght then it is heavier than a normal wheel. Some racing rims are made in magnesium and very thin walls which make them very light, where a production car alloy wheel for road purposes is usually a bit heavy. I made the carbon fibre go-kart wheels and as a comparison the carbon fibre wheels are less than 50% of the weight of the alloy originals (same dimensions)
Ian.

Narfle

iTrader: (16)

make this ricer wet dream thread go away

fd_neal

iTrader: (4)

When you can buy 10lbs aluminum wheels and a typical tire is 25lbs im not sure what actual benifits a 6 or 7 lbs carbon wheel is gonna give ya.

And for the record FD wheels are decently light at 14-16lbs already

carbon man

Dangerous wheels, the only fear I would have is if they hit solid objects like hitting kerbs hard. I do make carbon fibre parts for a living so I don't believe I am exactly a back yard operation, I have and still do build parts for car and motorcyle manufacturers as well as a few motor racing teams. Yes I could make car wheels if I had a customer that could afford them.

The reference I made to the brake tempereture problem is with cars not motorcycles, cars have more mass to stop and generate a lot more heat during braking and a car that has allready a brake fading problem due to heat will have a bigger problem when part of the heat can't be disperced through the alloy wheel.

I have set up water cooled the brakes by spraying water directly on the disc for race cars, I also set up a cooling system for a truck for truck racing where they spayed water in the brake drum to cool the brakes, this truck I also set up water cooling for the shocks.

Ian

carbon man

The benifit of any weight reduction on "un-sprung" weight is huge. A lot of motor sport catagories have minimum wheel weights limits for both safety and equality issues. Lighter the un-sprung weight the more grip you gain, the easier it is to control the suspension movement.

Ian.

KeloidJonesJr.

iTrader: (8)

what about a turbo?

fd_neal

iTrader: (4)

Yes i know this
The point I was trying to make is when youre looking at a total package of 32lbs vs 35lbs the benifits are minimal. For the money spent there are 100's of better mods that will create a larger benifit.

stripling

wow, i profoundly mis-spoke... al is indeed an excellent conductor.

what i'd REALLY like to know is the breakdown here...

HOW MUCH does the stock FD wheel weigh?

HOW MUCH does the stock FD tire weigh? (or a modern equevilancy)

HOW MUCH does the SAME carbon wheel weigh?

WHAT is the inertia of the "stock" combo at 60m/h?

WHAT is the inertia of the carbon with same rubber?

I have been told the FD wheel is about 15 pounds and the tire is 8.

That's 23 pounds.

I have been told a 16x8.5 carbon super-expensive $2500 wheel is 8 pounds.

That's 15 pounds vs. 23 pounds or a diff of 8 pounds

8 pounds per wheel is HUGE at high speeds. The inertial average of the FD stock wheel is around 4000 pounds @ 60m/h @ 23 pounds and less than 3000 with carbon.

IF THESE NUMBERS ARE CORRECT! I have NOT weighed them, only taking others numbers.

Now, at 25m/h the inertial mass is not nearly as significant. What's the form to calc rot. inertia? I've been outta college too long...

But I think i blew myself outta the water here... my original hope was to "achieve more torque" and I'm pretty sure lighter unsprung weight, esp. rot. weight, translates to LOTS more HP and LITTLE more tq

and why is this? because, as we all know, to get HP we take TORQUE times RPM div. by 5252 ... or like this HP=TORQUE * RPM / 5252

so, clearly the higher RPM in which we can sustain TORQUE the higher the HP outcome. That's why my gsxr 1000 which red-lines at 14,000 has HUGE HP (165) and tiny torque (78) ... 'cause it makes it all upstairs.

and thus, sigh... since the inertial weight of the wheels gets HUGE once you start getting past 3rd gear, you're not gonna feel those benefits to light weigh wheels and that usable torque until you hit around 70m/h or so.

sigh

i've owned rx-7's for years and years and more years and have always though "wow, what a perfect car... if only it had more torque"

and no, i refuse to stick in a corvette ls1 engine... a wankle is a beautiful thing... just ask my g/f

and no, i'm not gonna stick in a new rear-end or a tranny that converts it down. i don't wanna shift outta 1st redlining at 15m/h

carbon man

I see what your point is and I know what a difference of weight reduction on un-sprung weight can be, for an example grab a quart of milk and shake it as fast as you can and imagine what that enegy is at around 200 feet per second in stead of the 2 or 3 feet per second that you can achieve and this is what weight we are talking about reducing, 3lbs at 200 feet per second to accelerate and then stop is a huge amount of work for a shock and that same energy that we can't control in the tyre. If I had my way I would reduce the un-spung weight if I could, a garanteed performance gain.

Ian.

maxcooper

14-16 lbs, depending on which style (they both look the same). I have personally weighed several that were 15.8 lbs each.

20-26 lbs each. I think the stock tires were 23 lbs -ish.

I will guess and say half, or 8 lbs.

Inertia is constant regardless of speed (until Centerforce makes a wheel, hehe). I don't know the answer, but it would be possible to make a reasonable estimation by adding up some values for various cylinders and discs (a crude model of the wheel [rim+tire]).

Well, lets do a SWAG. The tire is larger in diameter than the rim and weighs a good bit more. I think we could conservatively estimate that the rim accounts for 1/3 of the rotational inertia and the tire accounts for 2/3. The carbon rim would be half the weight but otherwise similar in distribution of mass, so lets guess that the carbon rim has half the rotational inertia of the stock rim. Adding that all back together, I would expect the carbon wheel to have 5/6 the inertia of the stock wheel. A savings of 1/6.

Having weighed both the wheels and tires myself on several occasions (stock and some aftermarket), I can assure you that is not correct.

I agree that 8 lbs per wheel is a big difference. I own two sets of forged aftermarket wheels for my car. I have paid a lot of money to save a few pounds. But spending $10K on stock-ish-sized wheels that are "only" 8 lbs lighter (than stock, and I bet you can get 12 lbs 16x8 alum wheels) only makes sense after you spend an enormous sum of money on other aspects of the car.

The benefits about acceleration that are claimed depend on the rotational inertia of the wheel (rim+tire) rather than the mass. My SWAG for the reduction in rotational inertia is only 1/6 relative to the already-very-light stock wheels. There isn't a lot of bang for the buck here.

Better ways to spend $10K:

- buy light wheels, and light tires (I didn't do so well on this part) with small outer diameters:
my street wheels: http://maxcooper.com/rx7/parts_info/...37k/index.html
my track wheels (lots of rubber, only a few lbs more than stock wheels): http://maxcooper.com/rx7/parts_info/ccw18/index.html

- upgrade the brakes, shedding unsprung weight in the process:
my fronts, 2+ lbs lighter per corner: http://maxcooper.com/rx7/parts_info/brakes/index.html
my rears, 4-5 lbs lighter per corner: http://maxcooper.com/rx7/how-to/brakes/rear/index.html

- install a light flywheel, see this page for my calcs about reduced drivetrain losses in low gears: http://maxcooper.com/rx7/parts_info/flywheel/index.htm

- if you really want torque, install a V8. Or do a purposeful build and tuning of your 13B with the intent to build torque (i.e. there was an FD for sale recently that had a very impressive torque curve as a result of careful upgrades and tuning).

-Max