Brake line expansion ?

[Kaiser2boy]

Does anyone know how much if any the flex brake lines should expand when the brake is pressed ?

I had some one press the brake pedal while I held the flex line in my hand. I could feel a tiny bit of expansion , I am wondering if its normal.

[Gordon Maney]

Does anyone know how much if any the flex brake lines should expand when the brake is pressed ?

I had some one press the brake pedal while I held the flex line in my hand. I could feel a tiny bit of expansion , I am wondering if its normal.

They will do that. Hose containing stainless mesh is less inclined.

[712edf]

In time, the inner wall of the flex line will break down (crack). The line may look fine on the outside, but will expand considerably when pressure is applied. This has been a cause of many spongy brakes & likewise some headscratching, as everything else will be have been looked at & leaving no apparent reason for the sponginess.
But like Gordon said, even healthy lines can be felt to expand when in use.
I probably should replace the lines on my W600, as I have no idea as to their age.

Bucky