What does ASC REALLY do? - K-Bikes.com - Excellence in Motion
 
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post #1 of 5 (permalink) Old Jul 31st, 2006, 7:08 pm Thread Starter
 
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What does ASC REALLY do?

From my other posts, you may know I'm in the market for a new K1200S, and I'm still on a pretty steep learning curve. I wrestled with the servo vs non-servo assisted brakes and decided to wait for the non-servo. I can continue my suffering by waiting for the ASC option as well. I know what it is, but my question is, what does it really do? Specifically, is it just to keep you from spinning your rear on a hard launch or is it designed to keep your back tire from spinning up firing out of a curve? I don't have a lot of seat time on a bike as powerful as the KS (last one was a '98 Ducati ST2...), so I'd like to know how often that happens in the real world, or does this primarily provide a track-day benefit? Hopefully this will open a discussion that will help folks decide whether this is a nice to have or a need to have... Thanks.
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post #2 of 5 (permalink) Old Jul 31st, 2006, 8:02 pm
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post #3 of 5 (permalink) Old Aug 1st, 2006, 5:55 am
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I know that ABS has been both reviled and praised for the reduction of rider input but on balance in an emergency braking situation the positives may outweigh the negatives. Emergency braking is a much more critical scenario than creating wheel spin.

From my point of view the introduction of further complex systems in the form of traction control / ASC is not at all attractive. Why is this needed when all that is required is decent throttle control by the rider. The "less is more" principle is important at so many levels not the least of which is minimising vehicle mass (braking, handling, power to weight) along with simplicity, durability and reliability. Is it possible that BMW is more interested in controlling the use of their motorcycles than anything else.
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post #4 of 5 (permalink) Old Aug 2nd, 2006, 7:02 pm
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Quote:
Originally Posted by Kalmarjaeger
...I wrestled with the servo vs non-servo assisted brakes and decided to wait for the non-servo. I can continue my suffering by waiting for the ASC option as well...is it just to keep you from spinning your rear on a hard launch or is it designed to keep your back tire from spinning up firing out of a curve?...
I think the current servo brakes are great, especially with ABS. In combination with the anti-dive front suspension they provide the best brakes (by far) I've ever experienced.

That said, they have a few artifacts such as servo sound, sudden boost onset at low speed, no assist with engine off, and what some describe as insufficient feedback. Despite these quirks, IMO the current setup is great but the new one sounds better.

Personally I think ABS is important on either servo or new non-servo brake system. Whether pavement is wet or dry, you only get one chance in a panic stop. It's not just a matter of maintaining control, but wringing out every foot of stopping distance. Without warning in a sudden situation, few riders can instantly snap to 100% braking from high speed. With ABS they can, which reduces the stopping distance on either wet or dry pavement.

Re ASC, I don't get it. It appears to only prevent wheel spin, not prevent the rear from sliding out due to accelerating in a corner. How many accidents are caused by spinning up the rear tire in a straight line? I guess a few, and in that sense ASC might help those. However the bigger problem is the rear sliding out in a curve, possibly causing a high side. I don't think ASC addresses that. It's the old traction pie-chart problem. So much traction is available for lateral and longitudinal (braking, acceleration) use. No motorcycle system can tell how much lateral traction is being used, so ASC can't prevent a slide out.

Honda had an ASC-type system on the ST1100 and didn't put it on the ST1300. I guess if you ride a lot in the rain, ASC might be worth it.

Maybe in the future a combination of yaw sensors, wheel spin sensors and inertial sensors could provide rear wheel slide out control, but I don't think so today for production bikes.

The MotoGP bikes have ASC systems. Even the world's best riders with superb throttle control find ASC useful in that case. However those bikes also have 240 horsepower and weigh about 2/3 the K1200S.
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post #5 of 5 (permalink) Old Aug 2nd, 2006, 8:29 pm
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Quote:
Originally Posted by joema
...... Without warning in a sudden situation, few riders can instantly snap to 100% braking from high speed. With ABS they can, which reduces the stopping distance on either wet or dry pavement.

......Maybe in the future a combination of yaw sensors, wheel spin sensors and inertial sensors could provide rear wheel slide out control, but I don't think so today for production bikes.

The MotoGP bikes have ASC systems. Even the world's best riders with superb throttle control find ASC useful in that case. However those bikes also have 240 horsepower and weigh about 2/3 the K1200S.
Absolutely agree!

Perhaps there is some benefit for traction control for cars in low drive environments but given the degree of effect rider weight and position has on a bike there is a vast difference between the relative benefits for traction control in a car Vs a bike. Full on race bikes / cars are looking for every bit of drive they can get to WIN hence the justification for many racing innovations. Anyone who has ridden or raced on dirt or ice will understand that "wheelspin is your friend" and is an important element of control for cornering / sliding. BMW will apparently include an on / off switch for the ASC function specifically in the multi purpose models. If ASC is not appropriate for low drive, dirt / ice environments just where (and when) is the effective working environment for ASC.

The Japanese have a word for the unuseless idea - "Chindogu" - it would appear to have some relevance in the proposed applications.
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