>>1527007on a 21 speed bike .eg 3 chainring's x7 sprockets
you can use the two smallest chain rings up front with the four largest cogs at the back
for the largest chainring its best to use the four smallest cogs at the back
,tldr keep the chain in a farely strait line
or keep the FD on 2 and the RD on 4 most of the time
>which brake is primary,in good conditions mostly use the front brake
the front brake can do around 70% of the stopping
but since the front wheel is what keeps you upright you have to be very careful not to loose traction
the back brake can not do much, as slowing down takes weight off the back wheel,
you can delay the rear wheel loosing traction by leaning back but that's advanced method.
the back wheel can loose traction without causing you much trouble.
>left or rightdepends on where in the word the bike was sold
some places have the brake lever on the left operate the front brake (to stop people flipping over the handle bars I guess)
but in most places the right hand lever works the front brake (most people are right handed, so its the stronger hand)
>when do I use both?when there is less traction, such as in rain / mud / gravel
or you need the bike to be more stable apply the rear brake slightly before the front brake
in general there is no reason not to use the rear brake, just use it lightly