driveshaft

[TheSnail]

I will get one. Weight reduction overall is great, but I highly doubt the rotational mass aspect will be noticeable being such a small diameter. I would imagine that the impact of felt performance would be most due to the fact that it is a one piece drive shaft with two joints instead of a two piece three joint unit. With the stock unit, you have an additional joint, and a small amount of bearing resistance. With a one piece, its as direct as possible. The only down side that I can envision with a 1 piece is a little bit more vibration. As the engine torques, and moves around very slightly the angle from the trans side driveshaft yoke to the diff will change very slightly. A two piece drive shaft will better dampen those angle changes at the cost of more weight, complexity and drive loss.

[Hujan]

Originally Posted by TheSnail

I will get one. Weight reduction overall is great, but I highly doubt the rotational mass aspect will be noticeable being such a small diameter. I would imagine that the impact of felt performance would be most due to the fact that it is a one piece drive shaft with two joints instead of a two piece three joint unit. With the stock unit, you have an additional joint, and a small amount of bearing resistance. With a one piece, its as direct as possible. The only down side that I can envision with a 1 piece is a little bit more vibration. As the engine torques, and moves around very slightly the angle from the trans side driveshaft yoke to the diff will change very slightly. A two piece drive shaft will better dampen those angle changes at the cost of more weight, complexity and drive loss.

Interesting. I wonder if a single-piece CF shaft would be problematic for those of us with solid-mounted drivelines (i.e., solid subframe and delrin diff bushings). My differential moves a heck of a lot less with the new bushings than before on the stock ones. If the engine flexes and neither the drive shaft nor the diff can move with it, that might not be good.

[pbonsalb]

I have noticeably more vibration with my chromoly DSS one piece DS in place of the stock 2 piece on my turbo E36M3. The car does 134.54 in the quarter and I had no other readily available options after breaking two stock DS, so I will live with it. I have poly motor mounts, trans mounts, subframe mounts and diff mounts on that car. Not sure how it would be with stock mounts, but probably better.

[Malek@MRF]

Originally Posted by Hujan

Interesting. I wonder if a single-piece CF shaft would be problematic for those of us with solid-mounted drivelines (i.e., solid subframe and delrin diff bushings). My differential moves a heck of a lot less with the new bushings than before on the stock ones. If the engine flexes and neither the drive shaft nor the diff can move with it, that might not be good.

The drive-shaft is coupled with a flex-disc at the transmission and coupled to the differential with a CV joint. In fact, the less deflection from drive line components yields better results. If one was to upgrade the transmission and motor mounts to stiffer units, then it only gets better from a performance aspect.

[pbonsalb]

The one piece DSS DS that I have on my E36 eliminates the flex disk. I believe the one piece CF DS that BMW uses on the 2015 M3 retains the flex disk. Not sure what DSS will do for the 2008-13 M3, but suspect the flex disk will go and that vibration will increase. How much remains to be discovered.

[roastbeef]

i got this response from them via email;

"Carbon shafts like this usually are not much lighter, only about 2lbs
Removing the Guibo and the soft hanger makes the car more responsive
and connected, this and the fact that the carbon torsional movement is about
30 degrees makes a very big change in the car. cost will be 1499.99"

[OM VT3]

Originally Posted by roastbeef

i got this response from them via email;

"Carbon shafts like this usually are not much lighter, only about 2lbs
Removing the Guibo and the soft hanger makes the car more responsive
and connected, this and the fact that the carbon torsional movement is about
30 degrees makes a very big change in the car. cost will be 1499.99"

When are they making them?

[okusa]

Originally Posted by roastbeef

the fact that the carbon torsional movement is about 30 degrees makes a very big change in the car."

What in the world does that mean?

[Hujan]

Originally Posted by Malek@MRF

The drive-shaft is coupled with a flex-disc at the transmission and coupled to the differential with a CV joint. In fact, the less deflection from drive line components yields better results. If one was to upgrade the transmission and motor mounts to stiffer units, then it only gets better from a performance aspect.

Thanks for that. I had a feeling you'd have something insightful to say on the issue. That's good to know. Now the question is: How much extra vibration would a one-piece CF driveshaft entail compared to a two-piece steel version, especially on a car with a solid driveline?

My understanding is that carbon fiber actually has some vibration damping effects. For example, a bicycle frame made of CF will translate a lot less road feel and vibration to the rider than would an identical frame made of, say, aluminum or even steel. This is true even though CF would be just as, if not more, stiff than even aluminum.

If this is correct, then I would think a CF driveshaft would mitigate some of the vibration inherent in the drivetrain.

[roastbeef]

Originally Posted by leigh

When are they making them?

They have prototypes right now.

[PrimeBMW]

This CF drive shaft is for my e46 M3 race car with a S62 (M5 trans). It is about 3 lbs. lighter than a custom steel shaft built for a 5-speed swap. Everything is hard mounted: engine, trans, diff, subframes.

[pbonsalb]

Originally Posted by roastbeef

i got this response from them via email;

"Carbon shafts like this usually are not much lighter, only about 2lbs
Removing the Guibo and the soft hanger makes the car more responsive
and connected, this and the fact that the carbon torsional movement is about
30 degrees makes a very big change in the car. cost will be 1499.99"

I read that BMW has reported a 12 lb savings with the CF driveshaft over a standard driveshaft.

[roastbeef]

Originally Posted by PrimeBMW

This CF drive shaft is for my e46 M3 race car with a S62 (M5 trans). It is about 3 lbs. lighter than a custom steel shaft built for a 5-speed swap. Everything is hard mounted: engine, trans, diff, subframes.

nice! did you notice a large difference with the hard mounted engine, trans, diff, and subframes?
do you feel the carbon driveshaft is a worthwhile mod for responsiveness and getting rid of the guibo helped with the overall feel of the car?
i want to do all of the above to my e92 m3. it isn't a track build, but i love functionality. i just don't want it to be too uncomfortable on the street.

any opinion on increased wear on the drivetrain from a more rigid setup?

Originally Posted by pbonsalb

I read that BMW has reported a 12 lb savings with the CF driveshaft over a standard driveshaft.

i doubt we will save that much, like quoted above, its only going to be about 3-5 lbs, but there are other benefits as well.

[Disturbed]

Originally Posted by Beemdog

Well, the driveshaftshop.com has 'em for all the older M3s at $1399 each. Maybe the E9x is in the works? They do customs as well. I knew a guy with one of their carbon fiber driveshafts on his Viper.

That guy would be me. :-) But I got my parts from PST in FL.

I sold my rights to the Viper CF stuff when I sold my CF company. Don't forget to check out PST I recogmend them. 1st class all the way with them.

[Disturbed]

As far as the other Benifits of CF over metal Driveshafts is that they ABSORB then Release Energy. On the Vipers this aided tire hook up on hard launches then on braking it absorbed some driveline shick and helped with tailwag. The last Benifit was shifting. Made it smoother when rowing gears.

[In33anity]

Originally Posted by Beemdog

Well, the driveshaftshop.com has 'em for all the older M3s at $1399 each. Maybe the E9x is in the works? They do customs as well. I knew a guy with one of their carbon fiber driveshafts on his Viper.

They just built me a custom cf driveshaft for my S65 based '33 Ford Hot Rod, went in this weekend, see pics installed at http://www.m3post.com/forums/showthr...=947904&page=5



They now have my e90 OEM as a reference in their collection. Frank's a great guy. Call him!

[PrimeBMW]

The driveshaft shop was very easy to work with which is not the case for many other race venders. Good for them. Our cf drive shaft is combined with a light weight flywheel and clutch so I am sure the response will be ideal. First start up won't be for a couple of weeks so I don't have any experience with the cf ds yet.
Hard mount engine, trans, diff and subframe: These are all great things for a race car and not so good for a street car. At most one "might" consider subframe brushes on a street car but would be overkill for a dd car.

[Hujan]

Originally Posted by PrimeBMW

The driveshaft shop was very easy to work with which is not the case for many other race venders. Good for them. Our cf drive shaft is combined with a light weight flywheel and clutch so I am sure the response will be ideal. First start up won't be for a couple of weeks so I don't have any experience with the cf ds yet.
Hard mount engine, trans, diff and subframe: These are all great things for a race car and not so good for a street car. At most one "might" consider subframe brushes on a street car but would be overkill for a dd car.

In my limited experience, solid subframe bushings add zero NVH. Combined with solid subframe bushings, solid diff bushings add a little diff whine, particularly at freeway speeds.

[Hujan]

Looks like The Driveshaft Shop now has a CF driveshaft for E92 M3:

http://www.driveshaftshop.com/import...th-double-cv-s

They list it for the manual versions. I didn't realize there was a difference in the driveshaft between the two transmissions.

Also, they list it at 20 lbs. Seems heavy for a CF driveshaft and makes me wonder how much the OEM shaft weighs.

[ashtaron14]

I just sent them an email to ask for clarification. Heck I don't even know there's a diff in driveshaft length b/t the Coupe and the Sedan (it's listed for the Coupe)

[M33too]

I really wanted to buy one of these for weight savings but for the money I felt like it wasn't enough of a savings. Read somewhere that the stocker is around 29 lbs. Can someone confirm?

[ashtaron14]

From the Driveshaft Shop

The weight is not the real advantage that Carbon can or will give, in fact any vehicle will see quite a difference when launching.
This is some info we we share on this subject (not trying to sell just letting you know the weight thing is not its real value) what
most don't know is the Carbon end is allot heavier due to the bond area and what you save in the tube sometimes can be given back in
the ends.

Picture (3) 36" long pieces of tube in front of you, one steel on aluminum and one carbon. You pick up the steel tube with your index
finger and thumb and strike it with a screwdriver, this will ring like a bell and resonate for some time. Pick up the Aluminum tube and
you will get about the same, but it will not ring as long or as much. Then pick up the Carbon and it will just make a Click sound when
its struck, you see the material is much better at "NOT" transferring noise/Harmonics from the drive train to the cabin, This may be an
issue if you have a bad Diff or solid or poly mounts in the Vehicle.

The real advantage of the Carbon comes from its Torsional property's, When launching a vehicle either on the street or on the track
something happens that most are not aware of, all Drive shafts will torsionally twist. A steel shaft will twist from 5-7 degrees an
Aluminum about 20 degrees and then you have the Carbon at an amazing 30 degrees. This may not seem all that amazing but what happens
next is, when the steel shaft releases its like a spring unwinding it will come back at the same force and will not only help to break
the tires loose it can also send a harmful shock in to the drive train from this forward to reverse shock. Then we have the Aluminum, it
will twist up the 20 degrees and also releases like a spring but not as harsh or as fast (best bang for the buck as long as the tube will
handle the HP). Aluminum does not transfer as much NHV as steel and its light.

Then we move to the Carbon it will wrap up 30 degrees but its ability after this is what makes it work so well, it will release the
energy over time as it un-winds and will not give the reverse shock of the other materials, in testing what we have found
(this has been proven over and over) is the shaft will slow down the harmful shock that will damage the drive train AND will also
help the 60ft times by not reverse shocking everything its attached to. in private testing we have seen from .1 to .3 gain on 60ft times
depending on the shaft coming off of the vehicle, this will also relate to a smoother drive train, much less harmonic transfer and
be easier on any and all other parts that may not be up to par (weak diff/trans ect) I just wanted to let you know that weight is not
the real advantage here, when comparing shafts take all of this into consideration for a better build.

Now I just need to know if Sedan & Coupe have the same driveshaft.