Larz

Is there a downside to using a carbon fiber drive shaft. I know it should increase engine response, but will it affect drivability on public roads?

David Beale

You shouldn't even notice it's different. Don't hit it with a large rock etc. It may break. They are quite brittle. There are warnings of this in the RX-8 manuals. Luckly, the driveshaft on our cars is well protected by the PPF.

rotorbrain

i doubt itll hurt you anymore than getting a really light flywheel. street cars dont really need a carbon fiber d-shaft to be honest. when over torqued. . . they shatter. . . and all youre doing is lightening the rotational mass of an already balanced and small cylinder. i dont think its worth the money. you could spend that 500+ on something else. . . like an intercooler. . . or a better set of tires. if you want the driveshaft to be a nice piece of equipment you should have it professionally balanced.

paul

Larz

Thanks for the advice. I didn't realize they were so brittle. I work on jets covered in carbon fiber. I've dropped plenty, and have yet to break one.

Mahjik

iTrader: (1)

Have you ever felt the stock driveshaft? It's pretty darn light. I doubt you'll gain anything by that modification alone.

rotorbrain

im sure you can assume that aviation carbon fiber/kevlar is of a higher quality than lowly "road worthy" carbon fiber. a lot of people like a carbon d-shaft "because" they shatter. rather than a large metal shlong running up your *** at 100+ mph your undercarriage gets sprinkled with carbon fiber shards. . . . quite a bit safer if you ask me. . . but thats for racecars. . . how many street cars do you know of that mess up driveshafts?

paul

Larz

So what causes one to twist, or deform? A hard impact by running something over?

racer1

Thats maybe the last mod anyone would think of.

It's a waste of money. Have you done everything else?

Tim McCreary

Highly modified engines can cause too much torque to sustain the proper shape of the driveshaft causing it to disintegrate or break.

If the front universal joint fails, a metal driveshaft will act as a pole vault for the car assuming it drops to the road (which it wont because of the PPF). Carbon fiber will disintegrate once it fractures.

Carbon fiber has much better internal strength and less flex with the high torque, but the cost is only outweighed by safety, not by performance gains.

Tim

turbojeff

iTrader: (30)

IIRC I posted a while back that the stock driveshaft weighed 14lbs. Why bother.

Larz

Just wondering. I had nothing better on my mind.

Tim Benton

iTrader: (1)

carbon fiber drive shaft weighed just barely over 11 lbs. I got one since it the last thing I could think of for my car....I didn't notice a difference other than knowing it was there and saving about 3 lbs. The price is actually around 900 from ACPT.

Tim

rotorbrain

wow tim. . . you coulda finished my intercooler installation for me!!!!! come on, now. . . start using your head.

paul

Ghostrider7

why are you acting like you could afford a carbon fiber driveshaft you know you are going to put carbon fiber overlays on your driveshaft and think that you are the **** when in reality you are a **** sucking fagot ok larz

clayne

A custom manufactured aluminum driveshaft will be cheaper.

Mahjik

iTrader: (1)

This is a warning. Next time will be a ban.

Check the club FAQ for conduct:

https://www.rx7club.com/misc.php?s=&...page=4#conduct

This is a technical forum, not a flame forum.

Want2race

I dont think I have read such crap in a while of being here...

Dump trucks and MANY Semi tractor trailers have CF driveshafts.. Somehow they dont shatter.. Odd isnt it ?

CF is strong on 2 axis.. Usually that 3rd is very weak. But it shouldnt be stressed in that direction!

pp13bnos

iTrader: (1)

I was told that a CF drive shaft makes the car feel alot smoother. Any first hand exp. Tim? CJ

RX7SpiritR

iTrader: (1)

the driveshaft on an automatic FD is about 15 pounds! It's probably lighter on a 5-speed, and a CF weighs in at about 9-10 pounds. So really you wont gain anythingIMHO.

RX7SpiritR

iTrader: (1)

What's his problem? Do I sense Jealousy?!

diablone

iTrader: (2)

Someone pointed out that he's unexperienced.

https://www.rx7club.com/showthread.p...hreadid=252639

Tim Benton

iTrader: (1)

I honestly couldn't tell anything about the CF being smoother than the stock piece. It truly is a modification of last resorts and it's either spend the money on something you love........or your wife

Tim

AgentSpeed

Good point! The car it is!

DigDug

Racing item...

Ideally, as you optimize more and more aspects of the vehicle, you will gradually experience increasingly-diminishing returns - each subsequent modification you do gains you less than the previous one (provided you perform them in logical order). A carbon driveshaft is one of the last items you would address - you're not really going to gain anything in terms of cornering or braking, but you stand to gain a small amount in reduction of rotational inertia along the driveline - an acceleration/response benefit. Honestly, I doubt you would even notice on the FD, because the stock shaft is plenty light as is, even for competition. A suitable carbon equivalent would end up weighing almost as much as the factory piece, so you don't stand to gain much overall. Mazda did their homework.

The flexibility (or inversely, "brittleness") of a carbon piece is based primarily on the organization of the fibers, and in close relation, what type of force you are applying. Obviously, carbon driveshafts are made in the way most appropriate for their use, and as such they are relatively strong in response to torsional force about the shaft's axis. However, you will find that the piece is not nearly as strong if you apply a torsional force about a perpendicular axis - and we're talking orders of magnitude here!

DigDug

Oops, I had overlooked this comment:

This is the basic premise of my previous post. However, I would note that the number of axes really depends on the construction.

Not really. They are designed to be adequate for the forces applied to them. The manufacturers obviously have the necessary engineering resources to design a production-quality component that can stand up to the torsional loads produced by those diesel engines.