[johmei]

650 newton meters is like 480 feet pounds..

[idnan]

I broke my driveshaft joint on my 6mt a few months ago but I was FBO with RBs and meth and I had done many datalogs previously in the day. Came onto a main road and nailed it and heard a pop and lost drive completely.

I only had an open diff so got a custom driveshaft made up and fitted an m3 rear subframe w/ oem LSD

[Yeoman]

Pay to play.. I don't know why people are surprised that stuff breaks when you push it beyond what it was designed for.

[ragingpanda]

Why did you stay on it if you were experiencing wheel hop?

[cstavaru]

Originally Posted by BuraQ

It was a matter of time when it was going to happen. With the addition of aftermarket downpipes came the increase in torque.

So yes, and becareful, 450 wtq is the shaft breaking point.

I broke mine tonight at the track perhaps mostly due to wheel hop

Sorry to hear this. Drag racing is really costly, unfortunately.

I found out that if I lower the tire pressure to 1.4 bar, I have no wheelhop whatsoever, and the traction is great. But I do have M3 subframe bushings installed.

EDIT: You said driveshaft, not half-shafts ? Can you post some pics ? What exactly broke ?

[BQTuning]

Originally Posted by Former_Boosted_IS

I am sorry about the misfortune regardless. We all know it sucks when things unexpectedly break. Wheel hop is brutal on this car.

Out of curiosity, where did the failure occur? U-joint, diff, or snapping the actual shaft? Did it damage anything else?

I checked the short shaft they are fine, the "tumbling, and grinding noice'; is coming from in front of the diff

Originally Posted by GeorgiaTech335coupe

Do you use any form of NLS?

I dont think that applies to me, my car is DCT

Originally Posted by ragingpanda

Why did you stay on it if you were experiencing wheel hop?

I didnt, I have wheel hopped many times and feather off the gas. It was one hard knock, not multiple, and it was over with. By time I reacted to it the damage was done.

Originally Posted by cstavaru

EDIT: You said driveshaft, not half-shafts ? Can you post some pics ? What exactly broke ?

Correct the driveshaft, wont have pics till I found out who is going to fix it

[BQTuning]

Got word back today I need a new differential and driveshaft. Appearantly the driveshaft input to the differential is what took a hike

[Former_Boosted_IS]

Originally Posted by BuraQ

Got word back today I need a new differential and driveshaft. Appearantly the driveshaft input to the differential is what took a hike

Get yourself some delrin diff bushings while you are in there. Upgrade the rear guide rods as well.

[M3coupe]

OP, were you running stock clutch in DCT. Trying to get real world idea of what 335is DCT stock clutch can take

[GeorgiaTech335coupe]

Originally Posted by BuraQ

Got word back today I need a new differential and driveshaft. Appearantly the driveshaft input to the differential is what took a hike

That's where mine broke too, but I didn't need a new differential. I'd double check that before you spend the money.

[BQTuning]

Originally Posted by M3coupe

OP, were you running stock clutch in DCT. Trying to get real world idea of what 335is DCT stock clutch can take

Its handling 450+ wtq atm .....

Originally Posted by GeorgiaTech335coupe

That's where mine broke too, but I didn't need a new differential. I'd double check that before you spend the money.

Its all being covered under warranty

[Ulrich]

I found this information...
Maybe the gurus can comment about it...



mc²racing

What is wheel hop?
Wheel hop is a nasty action whereby the driven wheels of a car voilently shake, vibrate, hop, grab, and/or thump upon acceleration. It's usually quite obvious when your car suffers from this condition, for it sounds and feels like your car fell off a garage lift three times every second. Wheel hop doesn't just feel bad - it's bad for your car, too. For reasons that will be explained below, wheel hop can lead to broken drivetrain parts, including axles and rear differentials on a rear-wheel-drive car, and axles and transmissions on a front-wheel-drive car. If your car wheel hops - get it fixed!

What causes wheel hop?
A lot of people don't know why wheel hop occurs, which often leads to them throwing the incorrect parts at the car in an effort to eliminate the issue. Fortunately understanding (and correcting) wheel hop is not difficult. Here is what happens. When a car accelerates, you can picture the forces involved as something (the ground) pushing the driven wheels of the car forward. Obviously if you push the wheels forward, the car is going to move forward also. However, the wheels are not rigidly fixed to the chassis, so when the ground pushes on the wheels, they move forward a bit in the wheel well. Normally a car's acceleration is so small that this motion is negligible, but when a car accelerates quickly, especially during a launch, the wheels can move forward quite a bit in the wheel wells. As the wheels move forward, significant toe changes occur. Now, everybody knows that a tire can provide the most grip when it is perpendicular to the ground, parallel with the acceleration, and pressurized to provide the optimal contact patch. That being said, if the toe of the driven wheels changes during acceleration, the grip of the tire must be changing. Wheel hop is a result of this change in grip. Here is the sequence of events:

1.) Acceleration begins with good grip.
2.) The wheels move forward, toe changes, and available grip is reduced. Wheelspin occurs.
3.) During wheelspin, acceleration is very small. The wheels move back again, toe changes back, and the tire regains grip.
4.) Acceleration begins again, and the process repeats itself.

This rapid switching between grippy acceleration and wheelspin is wheel hop. My above description of the wheel hop process sounds tame, but the frequency of the grip changes and the magnitude of the forces involved is what makes wheel hop so violent. Race tires can prevent wheel hop since they have more grip (i.e., they don't lose grip even with the toe change), but cars that wheel hop with race tires will do so in a much more violent fashion.

How do I get rid of wheel hop?
Getting rid of wheel hop really isn't difficult. If you can limit the motion of the wheel with respect to the chassis, then the toe changes during acceleration will be small and the tire will not suddenly lose grip. If the tire does lose grip (common on a high-HP car of course), then it won't suddenly regain grip due to the wheel moving back to it's static position. How do you keep the wheel from moving with respect to the chassis? Well, assuming your car has reasonably rigid suspension arms, then all you need to look at are the suspension bushings! The wheel can move with respect to the chassis because the bushings flex...especially old, stock rubber bushings. Sometimes simply replacing old rubber bushings with new rubber bushings is all that is required. However, on a modified car that posesses more horsepower than the designer's intended, upgrading to stiffer materials like nylon or polyurethane may be required. The ultimate solution is to use rod ends or spherical bearings at every suspension joint, but that is unreasonable unless your car will never again see public roadways. Anyway, by simply upgrading your bushings, the suspension bushings will not flex as much under strong acceleration, the wheel will not move far forward in the wheel well, the toe of the car will not appreciably change, and your tires will not lose grip. Wheel hop will have been eliminated.

In some cases weak shocks can allow a perturbed wheel to continue hopping up and down since the motion is not damped. This is a less likely scenario, but shocks should not be ruled out as a potential culprit.

What doesn't get rid of wheel hop?
As mentioned earlier, a lot of people throw the wrong parts at the car in an effort to eliminate wheel hop. First, springs and sway bars will generally not do anything to promote or prevent wheel hop. Additionally, suspension settings, such as camber and toe, will generally not help the issue. It is the change in toe that leads to wheel hop, not the static setting. Tires do not cause wheel hop, though they do determine the grip level at which wheel hop occurs. For example, race tires, with their increased grip over street tires, will not break traction until you reach a higher level of acceleration. Some people might think that race tires solved their wheel hop problems, but in truth they merely changed their "wheel hop acceleration threshold" from a level below their launch acceleration to a level above their launch acceleration. Once they increase their horsepower to the point where they can accelerate enough to once again reach that threshold, their wheel hop will return.

Limited-slip differentials will also not prevent wheel hop. They may increase the acceleration threshold at which wheel hop occurs (much like installing race tires), but once again an increase in horsepower will eventually reintroduce the problem.

Check your shocks. If they are not malfunctioning, then you need to increase your bushing stiffness.


http://www.mc2racing.com/tech/20061012a/index.html

[tphss]

The dealer doesn't give you problems with replacement under warranty with the mods? I know my dealer here would be all over that to avoid fixing.

[onebadmofo]

My failed DS.


Notice that the splines go like this /l/l/l instead of /\/\/\

[BQTuning]

Originally Posted by tphss

The dealer doesn't give you problems with replacement under warranty with the mods? I know my dealer here would be all over that to avoid fixing.

Depends on your SA and you relationship with him/her, depends on your SA's relationship with the shop forman, techs, and it depends on the attitude of the customer.

Delears make money off of warranty claims. If a "work around" is possible then you can figure out the rest


Getting the right SA is a crapshoot. If ever lose mine then no more BMWs for me.

[BQTuning]

Originally Posted by tphss

....Sometimes simply replacing old rubber bushings with new rubber bushings is all that is required. However, on a modified car that posesses more horsepower than the designer's intended, upgrading to stiffer materials like nylon or polyurethane may be required. ...... simply upgrading your bushings, the suspension bushings will not flex as much under strong acceleration, the wheel will not move far forward in the wheel well, the toe of the car will not appreciably change, and your tires will not lose grip. Wheel hop will have been eliminated.

That was dead on.....thanks for the info

[BQTuning]

Got my car back yesterday and just going to chill till I get a suspension and bushings upgrade.

Will also get a Differential Brace added when LSD gets installed. Thanks to *********** for the reference on this

Other wise, be careful launching these cars on the drag strip on stock suspension when you have increased significantly the power

[GeorgiaTech335coupe]

Originally Posted by BuraQ

Got my car back yesterday and just going to chill till I get a suspension and bushings upgrade.

Will also get a Differential Brace added when LSD gets installed. Thanks to *********** for the reference on this

Other wise, be careful launching these cars on the drag strip on stock suspension when you have increased significantly the power

Not sure what tires you run, but when I switched to drag radials (NT555R), most of my wheel hop (80-90%) disappeared.

[BQTuning]

Originally Posted by GeorgiaTech335coupe

Not sure what tires you run, but when I switched to drag radials (NT555R), most of my wheel hop (80-90%) disappeared.

I am running NT555

[Black Sheep]

I just broke something in my car last night in the rear end, awaiting on what exactly I broke. Car would not move at all... Heard some nasty grinding in the diff so will see.

[Black Sheep]

Driverside half shaft broke, they wont cover it under warranty for me...

[GeorgiaTech335coupe]

Originally Posted by Black Sheep

Driverside half shaft broke, they wont cover it under warranty for me...

What were the conditions in which you broke it?