Spongy brakes and even spongier math

I'll preface this with, yes I need to replace the brake hoses, but intended to get the bike running first...and this exercise is more entertainment than tech.

So, old rubber hoses, bleeding the brake and it's soft no matter what. Pretty confident the air is out. You can feel the hoses move a bit under load, so in a completely useless effort influenced by beer and hot sun, I figured I'd determine how much the hoses affect things.

With repeated caliper measurements, I averaged it to 4 thousandths of swell under load. The reminder of the dimensions are quick estimates based on tape measures held at squinting distance. I did chop a old hose to check the I.D. also. The math tells me this translates into about 7/8" (!!) additional pull in the brake lever, which is all felt as a spring.

 

Don't know about the math, but from my experience replacing original hoses with stainless hoses, I agree that the rubber hoses feel a little softer. I actually prefer the softer feel, but I also like to know my hoses are in good shape.

 

Old hoses will expand more under pressure than new, even if they are of the original type.