How do on-road mountain bike speeds translate to road bike speeds?

Question

When cycling on roads on my mountain bike, I generally get around 10-12 miles per hour on a flat surface.

What sort of speeds can I expect to get on a road bike?

Answer 1

On my reasonably flat commute I average around 16 mph on my road bike, but your average speed is dependent on many different factors. A general rule of thumb is that if you are switching from a mountain bike with knobbies to a road bike you will be between 15-20% faster at the same watts/effort. Typically that's only a change of 2-3 mph.

I teach a bike commuting workshop, and one of the most common questions is whether to switch from a mountain bike to a road bike in order to increase speed. Typically, I tell people to try three things first:

1. Swap out your knobby tires for high pressure slicks. You can find 1.25" -1.5" slick tires that fit mountain bike rims and run at between 75 - 90 lbs of pressure. These will dramatically reduce rolling resistance.
2. If you have a suspension either lock it out, or set it as stiff as you can. Locking out your suspension will cause more of your effort to be transferred directly through the drive-train and translate into less loss of momentum from shock absorption.
3. Try clipless pedals. Your pedal stroke will be more efficient, again resulting in an increase in speed.

If you do those three things the only real differences between a road bike and your mountain bike will be the weight (which matters a lot more when accelerating than it does when you are already rolling) and surface area resistance from riding in the drops. But most road bikers don't spend much time in the drops.

Finally, your weight and fitness make a huge difference. I frequently pass road bike riders while on my commuter rigid frame mountain bike with high pressure slicks.

Answer 2

The average speeds that can be attained on a road bike (or any bike) are determined by several factors:

• Distance covered
• Road surface
• Wind
• Equipment, meaning the bike and components
• Terrain
• Age and fitness of the cyclist
• Teamwork

Based on observation and considering all that, on primarily flat, non-windy, terrain, on a decent road bike, my estimates would be:

• Novice cyclist - a short distance (10-15 mi): 10 - 12 mph
• Casual, fit, cyclist - a short/medium distance (~25 mi): 15 - 16 mph
• Average club cyclist/fitness cyclist - a medium distance (+/-40 mi): 16 - 19 mph
• Experienced club cyclist/amateur racer - a medium/long distance (+/-55 mi): 20+ mph
• Pro cyclist - long distances: 25+ mph

Anecdotally... on one of my frequent rides through some farmland, there is a 12 mile, mostly flat stretch. With a tailwind, I'm a pro. A headwind, I'm a novice. With no wind, I'm somewhere in between, depending on the day.

Another anecdote... In my area I frequently use a particular paved bike path on both a road and mtn bike, mainly because it leads to a park full of single-track, and beyond that to nice countryside for road cycling. Anyway, I have 8 years of ride data for that route. Along that path there is a 6 mile, flat open, stretch that was repaved 2 years ago; originally it was very rough, chunky asphalt and upon repaving it was converted to very smooth asphalt. Lo and behold, after the repaving, my average speed on both bikes jumped up ~4 mph.

Answer 3

The biggest difference between a mountain bike and a road bike is gear ratio.

Any other difference can be overcome. You can change tires, increase pressure, lock out your suspension, and use clipless pedals, but if you are on a typical mountain bike, your gearing will still limit you to a speed which is roughly 30% slower than the same effort will produce on a mountain bike.

For instance, the typical top end MTB gearing, with a 44t big ring and a 12t rear, and a typical cadence of 90 RPMs gives you a speed of 26 mph possible. See the chart below for the speed of each gear combination with a typical MTB gearing.

The same cadence in the top gear of a compact double road bike, a 50 x 11 usually, gives a possible top speed of 33 mph, at the same level of effort.

Standard 53 x 12 is about 32 mph, with all else equal.

Of course, you need to be fit enough to maintain that pace. But since you're comparing the same levels of effort, that's a bit more than 2-3 miles an hour. More like 9 mph faster.

Which on a 20 mile commute = 46 minutes on the MTB, versus 33 minutes on a road bike, at the same level of effort.

This is strictly a matter of gearing and mechanical advantage, for a roughly 30% increase in speed.

BTW, all of the math here assumes the same tire diameter, which is not typical. (See the Charts for complete and accurate differences, with crank lengths, tire size, and gear spread accounted for)

The difference in wheel size alone, assuming high pressure slicks, is worth the 2 mph difference that @Gary.Ray claims in his answer above. This last chart is identical to the MTB chart above, except I've changed the wheel and tire size to match a road bike. RPMs, gearing, and pressure are identical to the first MTB chart. The difference in gearing from the wheel size change is 2 MPH.

By the way, the app I used to do the calculations and the charts here is called Gear Head, it's on the app store for iPhone and iPad, and it's the best tool I've found for these kinds of calculations. I like it, but I don't have any other connection to it, just for the record.

Answer 4

At those speeds on flat terrain there are other factors that will impact average speed far more than bicycle type.

In particular, stopping at intersections in an urban area will cause your average speed to plummet. 12mph average is actually reasonable for a dense city area and is not much slower than what cars average.

If you're talking about riding in areas without stopping, getting faster than 12mph average is easy with a little more experience.

Answer 5

As noted...It's mostly the motor... On nice flat roads with a good roadster...20+ even at my age. However, throw in some hills and a headwind and the average plummets. I have a 2-mile road course around the local park that incorporates 2 hills on each leg. When I was 15 years younger and in good shape, I could maintain 18 around that.
Not now...

Answer 6

20 to 22 mph average over 40 miles with a light road bicycle, bicycle shorts, clipless peddles, proper bicycling shoes, a helmet, excellent fitness, and a lot of practice. Peak speeds can be as high as 30 to 35 mph on the flats in a tight group of 6 or eight riders or so.

Answer 7

Fitness is the biggest factor in how fast you can maintain. To provide a point of comparison, a local club here in the Seattle area holds an early spring Time Trial (race against the clock) every March. Looking at the results--and keep in mind, these are racers going all out, just short of barfing when they finish--those that competed averaged from 20 mph to 30 mph. Personally there is no way I can maintain 20 mph on the flats due to my lack of conditioning.

When The Fat Cyclist wrote about riding in the team car for a stage of the Tour of California, he got to follow one of Team Radio Shack's riders. His rider was planning on making it an 'easy' day, and was riding around 30 mph.

In conclusion...Your Mileage May Vary!

edit: btw, my personal speed (48-year-old dude, about 30 pounds overweight) is about 16.5 mph on smooth flats with no wind. Overall speed for a long ride, counting little stops to make a phone call, fill a water bottle, etc. averages about 13.5 mph.

Answer 8

On my hybrid (think Mountain bike style but with thinner wheels) I average about 12-14 mph around Bolton (lots of hills) when I go out at my in-laws (in Doncaster where it's fairly flat) I average 15-18mph.

On a road bike you'll be faster still as it's lighter and built for speed.