Why's my back brake so rubbish?

[nirakaro]

OK, a shiny new cable, bit of lube, and some careful adjustment and it's fixed. I'm puzzled by this post though –

Front brakes are always more effective than back. IIRC about 2/3 of braking force is supplied by the front brake & only 1/3 by the rear.

I know this is the case, but I'd understood this only applied when using both brakes, since the action of the front brake tends to lift the back of the bike. I'd assumed that the back brake used in isolation would be roughly as good as the front brake used in isolation. Is that incorrect?

[Samuel D]

No, because the rear brake used on its own also throws weight onto the front wheel and therefore reduces its own maximum braking force before the rear wheel locks up.

The balance Audax67 mentioned is only a rule of thumb, and practically a useless one in my opinion since it varies so much depending on the conditions.

At maximum braking in a straight line on dry tarmac, all of your weight is on the front wheel and therefore all of your braking comes from the front brake.

The slippier the surface and the more you’re turning (which eats into the tyres’ traction budget leaving less for braking), the more the rear brake contributes to maximum braking until the extreme case where braking approaches zero when the dynamic and static weight balance are the same, in which case the rear brake contributes more to deceleration than the front brake in proportion to the weight on it, typically around 60% on a road bike with the rider in the drops.