BMW explains why it’s manual transmission E60 BMW M5‘s DSC stability control cannot be disabled. The issue is with the huge amount of power and torque that the engine outputs – it causes excessive axle tramp.
What is axle tramp exactly? Axle tramp is when a wheel moves up and down very very violently, with such force that it actually leaves the ground – like a car hopping. A problem with putting power down to the wheels, worse than torque steer. It is caused by the axle rotating slightly with the wheels then springing back repeatedly.
With the 7-speed SMG III-equipped E60 BMW M5, BMW could fine tune the operation of clutch plates to combat axle tramp during crazy tyre burning starts even with DSC off, but this was just not possible with a pure manual gearbox with a pedal-operated clutch. BMW’s solution – leave DSC permanently on but offer a mode that is less intervening called M Dynamic. Which makes me wonder, why not somehow set up the engine to limit torque delivery in the first gear, so that traction control can be fully off in all the other gears? Did BMW’s engineers miss something here?
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Axle tramp, axle beggar, axle hobo, whatever – if the M3 doesn't come with a proper manual and fully switch-offable traction control, I'm going to summon Voltron to go and lay the smack on some BMW engineers. If Audi can do it, they better be sure that they're expected to do it too.
A good reason for BMW to show the world that SMG-III is the only choice for pure fun on the track. Probably the manuals are designed for soccer mums who likes to drive fast, but not too fast to go sideways. So, there you have it. The fun tyre burning SMG M5 & the not-so-fun but safe clutch manual M5.
Heard from a Bavarian engineer
" Ve hav found ze problem and fixed it. Dis ist our vay and you vill make noize. No. Psbbbbbt!"
Turns around and laughs while he goes for another exactly-poured-half liter.
Paul, unfortunately the solution isnt quite as simple as you explained unless you limit the torque output in ALL the gears. This is because being in a higher gear other than first doesnt make the monster torque dissapear. All that does is reduce the multiplication factor of torque to the wheels. So the tarmac sees less torque, but the engine is still producing the same amount of torque, which is stressed onto the drivetrain.
It's like when you ride a bicycle, the higher the gear you're in, it feels heavier to pedal, but in fact the chain tension is higher. Same principle applies. It is this tension that causes the axle to "tramp".
Engineers in the 70s had a solution for a certain German car manufacturer for this problem which was called "wheel hop". They balanced the entire brake drum together with the wheel and tyre. It managed to reduce the problem.
For the modern car using rear discs, it would probably involve the centre hub and disc bolted to the wheel and tyre. Doesn't sound practical though. A few hours on Malaysian roads (maintained expensively by our road tax money) would be enough to bash it out of balance again.
normal_user,
Um…manuals for soccer mums? I think it's normally torque converters for that lot. In any case, this is not about track shenanigans, very few people are likely to take their M5s on track anyway, and I'd empathise with that considering how much they cost. And going sideways on most roads is just irresponsible. This is about the tactility of having a couple more levers at your command, being the brains of the operation and keeping the engine on the boil of your own accord, once in a while finessing a heel-and-toe so slick and seamless that you have a warm glow in you after. It might not be the fastest or most efficient way, but in many ways it can be the most fun.
Another technical issue from the Bavaria Motor Workshop..
This happen when performance doesn't neat the practicality.
Let it to the engineers to think over.
axle tramp is the same with wheel hop right? If that's the case, then the DSC is meant to protect the car from inexperienced drivers whoare a little too eager to let the tail step out , or burn rubber for spectacle.
A good driver would put in just the right amount of torque to let the car dance a bit or power oversteer out of a fast corner..
darylchan: isnt the axle after the gearbox, which means differnet gears would put different torque onto it?
or it might affect the 0-100km time , which is essential marketing wise not to be slower than rival cars that the m5 is competing against….another suggestion is,y not put the x-drive found on the x5 into the m5…4-wheel drive silimar to the audi quattro…wd manage torque much better…
put water before the dash, like funny car drag,
or if want to mantain RWD, move the transmission to the rear, to gain some weight thus prevent 'hopping', and got the superneutral handler at 50/50 weight distributiom, like a classic porsche 924 turbo,
The RWD E60 BMW M5 engine produces 520 Nm of torque at 6,100 RPM. The AWD Nismo Z Tune GT-R RB26 unit produces 540 Nm of torque. Whats wrong with this picture?
Although they are have different drive-trains and gear boxes (M5 transmission done by the M Division and the Z Tune is by Getrag), I'm pretty sure that there are plenty of other cars of the RWD class that can support that amount of torque without the worry of axle tramp.
Come on M, you know you can overcome this.
I really hope Jeremy Clarkson drives this and try disabling it.
maybe they understood that most m5 owners arent going to be so careful with thier footwork. if you're gonna spin your wheel everytime in first gear when just trying to do a normal start then its not going to be a fun drive. its not something the executive owner wants. most of them are rich mid or late age drivers who just want a fast sporty luxury cruiser for road use.
dangerous part is that when the person spins the wheels and wants to regain traction by easing on the pedal with the brakes off. when those thick rubber gain traction and bite the ground its gonna fling the car forward and you dont want to ram your spanking new M5 into another cars 'protection' tow bars.
besides the manual loving enthusiast crowd will be served by the M3 unless they decide the new SMG gives them better real world figures and bragging rights.
For pure un-adultered fun, huge torque, manual, no computers = American Muscle Car.
BMW's engineers are bullshitting. They just doesn't want people (Especially Americans, largest market of M5s) to do their usual wakeup-brushyourteeth-BURNOUT routine, and as all know, America's governed by lawyers…. so to avoid lawsuits, claims or warranty cost to go AWOL…. they told this stupid lie bout thumping cars.
That's just my stupid, pointless rants. :)
a simple google search on axle tramp and it gives results on ye-old-leaf spring set up!!! ahahaha
alot of debate on this on other car forums.. but who cares.. how often u gonna make elevens.