The 10 Reasons Why Mountain Bikes Are Slow On-Road

If you often wonder why mountain bikes are slower on the road and why a mountain biker can’t keep up with a road biker, you are in the right place.

In this article, I will tell you all the major factors that impact a mountain bike’s speed on the road and I will give you the results of a test made to see the difference in speed with different tire pressures. So keep reading!

1. Bike’s Gear Ratios

A mountain bike transmission system is designed to offer the best performance when riding on trails and when riding uphill in off-rad conditions. The main reason why a mountain bike can’t reach the same speed as a road bike is that it doesn’t have a high enough gear ratio.

The mountain bike front chainring(s) attached to the cranks aren’t designed to achieve the maximum speed and for this reason, have fewer teeth than the front chainring of a road bike.

MTB on the road

On a road bike, a rider can achieve a speed of 25mph (approx 40 km/h) with a cadence of around 90 RPM, at this cadence the road biker is not deprived of oxygen and he can maintain this pace for a long time.

If you ride a mountain bike it is hard to ride faster than 19mph, this is because the front chainring for an MTB with a one-speed transmission system has 34, 36, 38, or 42 teeth and for a road bike it is normal to have more than 50.

2. Bike’s Geometry

Modern mountain bikes have longer frames designed to be stable at high speeds but because they are met for riding on mountain trails they are designed to offer the rider a more upright position for improved maneuverability, but this has a negative effect on the overall aerodynamic.

Mountain bikes are equipped with long and straight handlebars to overcome the tight turns on trails, this is great for maneuverability but not so great for aerodynamic and speed.

There is no point in equipping a bike for overcoming the challenges on trails with drop bars because a mountain biker can’t ride on trails in the same forward position that a road biker rides.

If you ride bent forward, you will encounter less resistance from the wind, which will positively impact your speed.

3. Bike’s Weight

Mountain bikes are built to be tuff and durable and for this reason, they are heavier than road bikes that don’t have to withstand the harsh terrains on which mountain bikes are ridden. This extra weight is noticed when sprinting or on uphill portions of the ride.

Price RangeMountain BikesRoad Bikes
500 – 1000$31 lb (approx 14kg)
1000 – 2000$27.5 lb (approx 12.5kg) 20 lb (approx 9kg)
2000 – 3000$31 lb (approx 14kg)
18.7 lb (approx 8.5kg)
3000 – 5000$ 30 lb (approx 13.5kg)
17.7 lb (approx 8kg)

In the table above we can see the difference between the average weight of mountain bikes and road bikes.

The difference in weight is significant, on road bikes the more you pay the lighter the bike gets, on mountain bikes the story is a little bit different. The more you pay the more capable to tackle harsher terrain the bike gets (more suspensions, tougher components), weight is not the main concern here.

The weight of a mountain bike is a big disadvantage when sprinting or climbing hills on the road.

4. Bike Suspensions

To be able to be ridden on rough terrain without throwing the rider off the bike, mountain bikes are equipped with front suspension and the more expensive ones have rear suspension also.

Suspensions are a great thing in off-road conditions but when it comes to riding on the road they will slow you down because some of your pedaling power will be absorbed by them.

On mid to high-range suspensions you have the option to lock them, if you what to have more speed on the road I encourage you to do that.

5. Wide Tires

MTB Weel

To have maximum traction on dirt mountain bikes are equipped with wider tires but this is a disadvantage if you ride them on the pavement because you have a greater surface of contact between your tires and the road, this is equivalent to more friction and less speed.

Mountain bikes tires have a 2.25″ to 2.4″ width range compared to road bikes tires that are in the 23 to 28 mm (0.9″ to 1.1″) range.

A mountain bike tire will have more than double the tire width of a road bike, this is because they aren’t designed for speed on the road.

6. Knobby Tires

This is another mountain bike tire feature that is highly needed off-road but is a major disadvantage on the pavement, if you want more speed on the road you need as little traction as possible.

You can change the stock tires of a mountain bike with tires designed for the road but you will lose on the bike’s off-road performance.

7. Tire Tread Pattern

For many years road tires manufacturers have invested a great deal of money in the research on tire tread patterns to improve the overall bike’s speed in any weather conditions.

Mountain bikes do not benefit from all the advancements made for road tire tread patterns because the main focus of mountain bike tires manufacturers is grip and traction, if you don’t lose traction descending on trails you will have more speed. But on-road things are different.

8. Tire Presure

Tire pressure is an important factor that determines the speed and traction of a bike. The less pressure you have the more traction you gain but the less speed you will have.

So to increase your mountain bike’s speed you need to increase tire pressure, but be aware not to go over the maximum limit declared by the tire manufacturer.

To prove this concept I made a test. I have ridden the same road (on pavement) on the same day with the same mountain bike but different tire pressure and the results are:

The results were interesting. On 3 bar tire pressure, the average speed was 10.7 mph and for a 2.2 bar tire pressure, the average speed was 10.3 mph. Not a huge difference but still having more tire pressure improved my speed.

Test conclusions:

  • on a 0.8 bar more tire pressure, the average speed increased by 0.4 mph ( 3.8% )
  • on a 0.8 bar more tire pressure, the maximum speed increased by 0.7 mph ( 2.5% )
  • the ride was more comfortable at a lower tire pressure
  • it seemed to be harder to pedal with a lower tire pressure (more resistance)
  • with higher tire pressure the bike accelerates faster on descents

9. Softer Tyre Compounds

Softer tires mean more traction but less speed and less durability on the pavement. This is just another feature highly optimized for off-road riding.

10. Bad Chain Lubrification

A bad chain lubrification can impact the performance of your transmission system and I previously told you road bikes are more speed efficient because they have a better transmission that is designed with speed in mind.

This is an easy fix, you just need to lube your chain and everything is alright.

Final thoughts

By now you know all the factors that influence the speed of a mountain bike on the road and I hope that now you know what to improve on your bike to gain more speed on the road.

I would not change my mountain bike, because I plan to ride it off-road and don’t want to lose performance there. When I ride it on the road I lose some speed but I am ok with that.

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I started mountain biking many years ago to improve my overall health state. After my first ride, I fell in love with the sport. Now I spend dozens of hours a week researching and training to compete in local XC and Enduro events.