I'm sorry but a CF rim would weigh more than 2 lbs. Just look at how much a hood weighs. There is ALOT more CF needed in a rim than in a hood. Your friend with the RX7 "CF" rims is full of poo.

Your first mistake was when you said Yeah talk to me online and I'll tell you about my Saleen S7 TT that I use as my daily driver and my very own personal Milennium Falcon that I use for longer trips...

 

speaking of the s7 lol have you noticed all the cf in thoughs?? there is a big car deal for saleen and lambos in naperville ill and the s7 they have has cf headlight housings and every body panel is cf its crazy

 

Usually, yes you are right. But when someone provides not only pictures of his rx-7, pictures of him working on it, friend in another car taking a few of him driving, and also a picture of the rim on a scale showing "2.3lbs", you typically go ahead a believe them. Sure, he could be lying and just found a bunch of online pictures, but whoever's rx-7 that was the rims were weighed at 2.3 according to scale. (per rim)

 

Speaking of CF hoods, mine weighs 10.

 

If anything it was kg, not lbs. There is no way an 18 inch rim could weigh 2.3lbs and hold any weight.
You spin a piece of metal fast enough and you can cut it with a piece of paper or a human hair.

Oh and on the slim chance that the scale did say 2.3 lbs ever hear of photoshop? Just from an engineering standpoint its too improbable to have a rim weigh 2.3 lbs, be 18 inches, carbon fiber and only cost $1400 per rim.
As it was said earlier, bikes that are made of CF cost $3000 and they use less CF than a rim would need. (oh and those bikes with just the frame weigh more than 2lbs)

 

DUDE.. THERE IS NO SUCH THING AS A 2LB CF WHEEL.. LIKE IT OR NOT.

 

I doubt there is a true CF wheel. The torque would probably snap the splines on the rim. CF doesnt last long when its twisted or torqued...

 

^^^ Wrongo!
Black Stone
DyMag
Lovely!

Scott

 

Heh, ok ok you got me, but I wasnt specific enough.

Moving a motorcycle is alot less stress than moving a 2000+ lb vehicle. 200 ft/lbs tq moving 500lbs is alot less than 200 ft/lbs tq moving 2000+ lb. The weight difference would make a huge impact on the life of a CF rim.

Anyways just to make a point even more pronounced those wheels all cost at the cheapest around $2500

And thats for less material needed for a bike rim, not a vehicle rim!

 

I'm just stating what i saw, if you guys want to argue about it with someone take it up with someone else other than me. I know photoshop, i used to design websites for people with dreamweaver as well as numerous other things.

 

^ ^
Point to that was it wasn't altered imaging. It could have been 2.3kg, but i'm assuming it was lbs since the guy lives here in the states. Of course, again, assuming these pictures are truly his and didn't just pick random google or yahoo images.

And it is possible to get these rims for $1,350 with a half sponsorship deal, or knowing someone in the business. Of course, i dont know if he did or does or not. I didn't talk to him that long to find out every detail.

 

oh and about twisting forces. how come they make cf driveshafts then? that's a lot of twisting right there.

 

Exactly.

Cf blended with the right compound can be extremely sturdy and handle a ton of pressure/twists/whatever.

 

x2 - some people here talk 'bout ____e they know nothin' about. It's better to ask and learn than to stick foot too far into mouth!!!

SCOTT

 

Which is part in reason why i asked to see proof of the rims weighing so light. If i can contact him again, i will ask if those pictures were in 2.3kg or 2.3lbs. I do realize how light those are, i'm not making "ignorant" assumptions, i'm just providing past down information sort of speak. So as i stated before, don't yell at me for incorrect information if it happens to be incorrect, these are not my rims nor will they be.

 

CF drive shafts?

It's the direction of the twisting.

For a drive shaft, the twisting would occur parralel to the weave whereas on rims, the twisting would occur perpendicular to the weave.

Also, with a drive shaft, all of the torsion is applied in a tight area instead of on a wheel where the torsion is multiplied by 18". Add to that, the amount of work required to move 3000 lbs of car 100 ft - you got some serious leverage and torque being applied to not so strong parts of a wheel.

All of that torque would then be centered on the very ends of the drive shaft but those ends are reinforced with non CF parts anyways.

I think.

 

the driveshaft experiences more torque than the wheel.

 

Of course it does.

However, the torque applied to the drive shaft is in the same direction of the weave of the CF.

On a wheel, the weave would be experiencing torsion in two forms - torque from the drive shaft and torque from the ground. The friction required to get the car moving becomes a retarding torque applied to a relatively narrow and weak pillar or CF.

Consider a bike wheel. I'm not talking about a motorcycle, I'm talking about a bicycle. The brakes on a bicycle are really weak - if you apply full brake pressure you can still pretty easily push the bike. Now, if you go really fast and then brake only the front brake you'll flip over. If the brakes are weak than why would you flip over? Torque. The longer the distance from the center a force is applied to a circular moving object, the greater the force is multiplied.

This is the same concept - I don't even know if it applies properly. I don't know the very nature of CF.. CF can be stronger than steel - I do know that.

 

its actually the opposit of that concept. All of the torque would be at the center of the wheel, but maybe thats what you were talking about. Oh and you can make the weave go any direction u'd like.

 

What you can't do is make the weave go in two directions.

It's probably incorrect to say that the drive shaft experiences more torsion.. it'd be more correct to say it experiences a greater torsion. The wheel actually experiences two different forces. One force comes from the drive shaft while the other one comes from the ground.

EDIT: I think the point of my argument may have been skewed slightly. I was just explaining how it would be possible that CF wheels break - not that they WILL break. If you look at the design of the CF wheel above, you'll see that each spoke reinforces the next one and that the spokes are somewhat diagonal of what you'd - in the direction opposite of the torque that will be applied via the the engine. This design eliminates the weakness of single directional weave. I'd imagine, though, that if the wheel were designed in a conventional 5 spoke star design, the potential for breakage will be greater.