Pedal Talk
What is Pedal kickback
TECH TALK
1/9/20263 min read
Pedal Kickback Explained
That strange feeling when your pedals push back at you
Modern mountain bikes are incredibly good at riding over rough ground. Their suspension allows the rear wheel to move up and down, helping the bike stay in contact with the trail.
But sometimes, when the suspension moves, you might feel your pedals suddenly try to turn backwards.
This is called pedal kickback.
It sounds complicated, but the basic idea is quite simple.
What causes pedal kickback?
When your rear suspension compresses, the rear wheel doesn't always move straight upwards. On many bikes, the rear axle also moves backwards as the suspension goes through its travel.
When the rear wheel moves away from the bike, the distance between the rear axle and the crank can increase.
The chain connects these two points.
So, as the rear wheel moves backwards, the suspension can effectively pull on the chain.
If the drivetrain is free to move, some of this movement can be absorbed by the freehub in the rear wheel.
But if the rear wheel is being slowed by the brakes, the drivetrain can't move as freely.
The result can be the chain pulling on the cranks and causing your pedals to rotate backwards.
That's pedal kickback.
Why would the bike do this?
This is where things get interesting.
The same suspension characteristics that can cause pedal kickback can also help a bike pedal efficiently.
When you pedal hard, the chain pulls on the suspension system. Engineers can use this force to help stop the suspension from bobbing up and down while you're climbing.
This is called anti-squat.
A bike with more anti-squat can feel very efficient when you're pedalling.
The downside is that the drivetrain can have more influence over the suspension when you hit bumps.
So, very simply:
More anti-squat can mean more pedal kickback.
But that doesn't mean more is always better or worse. Bike designers have to find a balance that suits how the bike is intended to be ridden.
When do you notice it?
Pedal kickback is most noticeable when you're riding through a rough section of trail while braking.
Imagine you're descending a steep, rocky trail. You're standing on the pedals and braking hard. The rear wheel hits a large rock and the suspension compresses.
The wheel moves upwards and backwards.
Because you're braking, the rear wheel isn't able to rotate freely.
The resulting chain movement can rotate the cranks backwards.
You may feel this as a sudden tug on your feet.
On smaller bumps, you might never notice it at all.
How have mountain-bike companies reduced it?
Bike designers have come up with several ways to reduce or control pedal kickback.
One of the biggest developments has been the high-pivot suspension design.
On a high-pivot bike, the main suspension pivot is positioned higher in the frame. This allows the rear wheel to travel backwards as it moves through its suspension travel.
That can help the wheel move out of the way of big obstacles.
However, there is a problem.
A rearward-moving wheel creates more chain growth, which could create even more pedal kickback.
So many high-pivot bikes use an additional pulley called an idler.
What's an idler pulley?
An idler is simply a small extra wheel that the chain runs around.
It changes the route the chain takes through the bike.
By carefully positioning the idler, engineers can allow the rear wheel to move backwards without transferring all of that movement directly into the pedals.
This means they can get some of the benefits of a rearward axle path while controlling pedal kickback.
You'll see this system on many modern enduro and downhill bikes.
Can pedal kickback be eliminated?
Not completely — and engineers don't necessarily want to eliminate it entirely.
Pedal kickback is connected to other characteristics of the suspension, particularly anti-squat.
Instead, modern bike designers try to control how much kickback there is and when it happens.
Some bikes prioritise efficient pedalling and therefore accept a certain amount of kickback.
Others, particularly bikes designed for aggressive downhill riding, prioritise suspension movement and traction.
There are also aftermarket systems that can reduce the amount of drivetrain movement reaching the rider. These include systems such as Ochain, which allows a small amount of movement between the crank and chainring.
Should you worry about it?
For most riders, pedal kickback isn't something you need to obsess over.
It's simply one of the compromises involved in designing a full-suspension mountain bike.
If you're new to mountain-bike technology, the easiest way to remember it is this:
When the rear wheel moves backwards during suspension compression, it can pull on the chain and cause the pedals to rotate backwards. That's pedal kickback.
Modern suspension designers have developed clever ways of managing it, particularly through suspension geometry, high-pivot designs and idler pulleys.
And the more you learn about mountain-bike suspension, the more you'll realise that almost everything is a compromise.
The trick is designing a bike where those compromises work together to make the bike feel good on the trail.