These specific conditions up the importance of having a good braking technique. You can slow your bike down even if it’s at an angle when the ground is dry, but if the grip is reduced (wet road, muddy ground, dead leaves, sand or gravel), you must remember to never brake when it’s tilted. Otherwise, you’re sure to lose your grip.
In dangerous conditions, it’s especially important to correctly distribute your braking power if you want to avoid stopping your wheel completely. The 70/30 split might need to become 50/50 on a wet road. And on sand or gravel, you might even need to go to 0/100, i.e. completely ignoring the front brake.
Blocking the front wheel on gravel or sand is often a fall waiting to happen. It’s much better to take longer to brake by using just the rear brake, even if it means risking stopping this wheel, as it is easier to control as soon as your bike is straight again. And if you want to delay the point at which you brake, keep as much weight as possible on the back of the bike.
While riding downhill, it's important to slow down before going into a corner. But often, if you’re on a downhill route that you don’t know, you’ll approach a bend too quickly. If the bend gets tighter or is hidden by vegetation, it could take you by surprise and turn out to be sharper than you thought.
In this case, if you don’t slow down, you’re sure to find yourself flat on your back. To help you with your turns, only use the rear brake once the bike has started to lean. This will help you to turn a little bit more, but remember to use the brake sparingly to avoid skidding.
It’s quite common in a peloton for riders to be only 50 cm away from one another. Therefore, you obviously shouldn’t brake too harshly unless it’s an emergency. If you break too sharply, you could be hit by the riders behind you who weren’t expecting you to stop.
The best thing is to use the rear brake more than the front if you want to slow down. Generally, that’s all you need. If you brake too much, you’ll have to expend much more energy to get going again.