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More brake confusion


PAS

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Morning PAS

 

Yes, that is sort of confusing but there IS merit in that BMW bulletin.

 

Will most riders under normal circumstance notice the difference?-- I seriously doubt it.

 

They mention residual braking & that is not great anyhow so for most riders the quicker pressure spike is a non issue.

 

ON the I-ABS (servo control) wheel circuit side there IS a possibility that a rider m-i-g-h-t notice the change if braking from speed on a very slippery surface. It could cause premature wheel lock up & the rider could go down-- but on a very slippery surface from speed there is a chance the rider could go down even with the correct brake lines in the system.

 

On a motorcycle (single track vehicle) the ABS not only has to prevent wheel lock up but must also read way ahead & predict impending wheel lock up before it even starts to happen. On a motorcycle, on a slippery surface, you can't take the spinning wheels down to lock-up & expect the wheel to regain enough traction to spin back up fast enough to prevent stabilization issues. (on a car if you lock a wheel for an instant no big deal, on a motorcycle if you lock a wheel for an instant you could easily go down)

 

The BMW I-ABS system uses internal pressure switch's & a learnable decal glide that reads ahead & predicts wheel lock up before you even get there. If you alter the spring (brake line expansion) in the wheel circuit side then you can fool the I-ABS system enough to have it not read ahead correctly. Now, obviously the I-ABS controller can be programmed for the brake line change (hydraulic circuit spring change) & I would imagine BMW did that when going to StalFlex brake lines.

 

Is it something I would lose sleep over--NO-- is it something to be aware of--YES!

 

 

 

 

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If you alter the spring (brake line expansion) in the wheel circuit side then you can fool the I-ABS system enough to have it not read ahead correctly.

 

DR,

I get it, but...as the rubber lines break down with age (more springy, I assume), isn't this happening anyway (maybe the opposite direction). Isn't that part of the reason to go to the SS lines?

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If you alter the spring (brake line expansion) in the wheel circuit side then you can fool the I-ABS system enough to have it not read ahead correctly.

 

DR,

I get it, but...as the rubber lines break down with age (more springy, I assume), isn't this happening anyway (maybe the opposite direction). Isn't that part of the reason to go to the SS lines?

 

Afternoon greiffster

 

Sure, too much compliance in the other direction is also not a good thing.

 

The upside of that direction is a little more ABS forgiveness. Probably increase your stopping distance slightly on a poor traction surface but less chance of a premature wheel lockup.

 

In the real world, again, most riders probably can't tell the difference & of those who can, most of those probably don't

depend on the ABS system to "save them" from themselves anyhow.

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