What makes a bike slow? Find out how to reduce drag, rolling resistance and the effect of gravity for a more efficient ride

It's that nagging question that many cyclists may have asked themselves at some point: "Why is my bike so slow?" And while of course, the rider is more important than the bike, could there be a reason your bike feels sluggish? 

A bike's speed is influenced by a combination of factors related to the bike itself, the rider and the environment. Aerodynamic drag is one of the main forces that slow you down, while other forces include rolling resistance and the effect of gravity.

Making your bike faster is a topic that most cyclists can relate to. While working on yourself by improving your power-to-weight ratio, fuelling properly and getting better at riding up hills is obviously going to be the most effective way to increase your cycling speed, there are some things you can do to make the most out of your bike, and your cycling fitness. 

Thankfully, some of these factors can be altered through slight modifications, while others require a bit more work. Here are six tips to consider...

1. Your tyres need upgrading

One of the most cost-effective upgrades you can make to a bike when you're searching for 'free' speed is upgrading to some of the best road bike tyres.

If you want to cycle faster – or ride at a given speed for less effort – you need to choose your tyres carefully and set them up right to minimise rolling resistance. 

Rolling resistance refers to the force that opposes the tyre's motion and acts to slow the bike down and decreasing this is vital to making your bike faster. A tyre with a high rolling resistance demands more power to travel at the same speed, whilst a low rolling resistance tyre requires less power.

> Best winter road bike tyres

Jan-Niklas Jünger, bicycle tyre product manager at Continental said, “At typical road bike speeds aerodynamic drag might account for 70% of the effect holding you back, with about 20% down to rolling resistance."

When selecting the right tyre, it's crucial to factor in your intended usage. Opting for the fastest tyre with the lowest rolling resistance might not always be suitable. For instance, the Veloflex Record tyre, known for its speed, is designed for time trials and track racing, making it less ideal for everyday riding.

2. You're using standard butyl inner tubes

> Butyl v latex v TPU inner tubes: which should you choose?

Once you've chosen the right tyres, it's also important to consider what inner tubes you're using, if you use a wheel/tyre system that takes inner tubes. 

The best bike inner tubes do quite a lot more than just hold air in your tyres, as they also play a role in influencing rolling resistance. 

When considering which inner tubes to buy, there are numerous factors that may affect your decision, such as air retention, durability and rolling resistance. 

Vittoria released a white paper that shows several charts comparing the characteristics of the three inner tube types - butyl, latex and TPU (thermoplastic polyurethane) - revealing significant differences in their rolling resistance. 

Standard butyl inner tubes exhibit the highest rolling resistance, resulting in slower performance compared to latex or TPU tubes.

To show you how this might affect you in the real world, Aerocoach performed tests on a large number of different inner tubes, finding that latex tubes with the lowest rolling resistance resulted in savings of more than seven watts when compared to a standard butyl inner tube at a speed of 45kph. 

"At 45kph, the difference between the fastest and slowest inner tubes would equate to around 12sec over 16km/10 miles," Aerocoach says. 

3. (You) and your bike aren't aero 

> Has aero gone too far? 

Aerodynamics plays a significant role in cycling speed, especially at higher speeds. As previously mentioned, aerodynamic drag is said to account for 70% of the effect in holding you back at typical road riding speeds. 

When you're cycling, your body and bike encounter air resistance, which increases with your speed. If your bike and riding position creates a lot of drag, it can slow you down. Therefore, the more aerodynamic you are, the faster you can ride with the same power output.

Aerodynamic drag is measured in CdA. Aerocoach says: "A small reduction in aerodynamic drag can have a large impact on your race performance - for example, a rider completing a 25 mile/40km time trial in 1hr will reduce their finishing time by around 30sec for just a 2% reduction in their CdA."

Generally, more aerodynamic bikes can be faster, especially under certain conditions and at higher speeds. However, it's essential to consider various factors that affect a bike's overall speed, such as your riding position. 

Improving aerodynamics doesn't necessarily require purchasing a new bike, and you may also want to consider optimising your body position on the bike and your choice of clothing. 

4. The effect of gravity 

> Does a heavier cyclist descend hills quicker? 

There is a constant debate around the trade-off between weight and aerodynamics, where riders may prioritise aerodynamics at the cost of adding more weight to their bikes. 

On a flat route or at speeds of over 20kph, aerodynamic drag accounts for the majority of speed loss - but when cycling uphill, gravity acts as a resistive force, opposing your forward motion.

The steeper the incline, the greater the force of gravity working against you, and you'll have to exert more effort to overcome gravity's pull to maintain your speed. 

> Best lightweight road bikes

In addition to this, the heavier your bike and its components, the greater the gravitational force working against you. To maintain your speed, you'll need to generate more power to overcome the increased gravitational resistance. This extra effort can result in slower speeds. 

Whether it's more important to have a lightweight or aero bike will depend on your cycling goals, riding style and the terrain you typically ride on. 

5. Your chain needs lube

> Best bike chain lubes

An old or poorly lubricated chain can significantly reduce a bike's efficiency by increasing friction and drag in the drivetrain system, which can result in a loss of power and decreased performance while cycling. 

Modern drivetrains are designed to be highly efficient, and a well-maintained drivetrain can typically achieve efficiency levels of around 98%. 

A chain that is either unlubed or worn can reduce the efficiency of the drivetrain. An unlubed chain is said to experience an efficiency loss of around 2-4%, while a moderately worn chain can reduce efficiency between 3-5%. 

> Should you run a 1x set-up on your road bike?

Another area that could reduce drivetrain efficiency and make your bike feel slower is bearing resistance in the bottom bracket and hubs. 

Regular maintenance, degreasing and lubrication of your chain and bearing replacement can help to maintain your bike's efficiency.

6. Stiffness

Bike manufacturers often emphasise three key factors when introducing new road bikes: aerodynamics, weight, and stiffness. While aerodynamics and weight are easily quantified, stiffness is a bigger can of worms. 

When Specialized released the Tarmac SL8, it said the bike has an improved stiffness-to-weight ratio to the tune of 33%. What exactly does this mean in terms of speed, though?

In theory, a stiffer frame should be faster as less flex in the frame means that more of the rider's energy is directly transferred to the wheels, resulting in faster acceleration and higher speeds. 

However, this isn't always the case. On smooth roads the benefits of a stiff frame in terms of power transfer are more noticeable, but on uneven surfaces, the absence of frame flex may prove detrimental. A frame that offers both stiffness and compliance is crucial for maintaining control. 

A stiffer frame may also result in reduced comfort, as it tends to transmit more road vibrations, potentially leading to fatigue and subsequently affecting your riding speed.

So, the answer isn't to purchase the stiffest bike available. Instead, you should consider the type of rider you are and the type of riding you're doing, as comfort and ride feel are very personal. More powerful riders may benefit from stiffer frames, while lighter riders may benefit from some more flex. 

What will you be doing to make your bike faster? Let us know in the comments section below...