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How Much Faster Is A Road Bike Than A Mountain Bike… Part II – It’s Not Just The Tires

June 2012
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I spent some time looking back at some of my most read posts and at the top of the list was, How Much Faster Is A Road Bike Than A Mountain Bike?  Initially I got the idea for writing the post as I was comparing results on Endomondo between the two after I put some miles on my 5200.  The difference between the two bikes is profound, obviously, but I decided to click on some of the other links that show up on a search of the subject and came across this reply to the question:

“take it from someone who knows… the aero benefits of a crouched riding position @ 15mph for 20mins are miniscule compared to the gains you would get from slick tires on a mountain bike in less rotational inertia and rolling resistance.
This isn’t to say that the road bike isn’t going to be faster. It defintely will, but it won’t be because of the aero benefits of a different riding position (which equally apply on and off road… same air after all).”

Now this is an interesting take – and not without merit, though not exactly based on reality either…  And it just so happens that I have data on changing to slicks as well, because I did exactly that for two Olympic Tri’s last year.  I trained with standard knobby tires, and then two days before the first event I switched to the street tires (Specialized Nimbus Armadillo) and left them on for a month or so.

My average was 17.3-17.5 mph with the street tires on a hard tail (front suspension only) Trek 3700.  I weeded out the slower, recovery ride, days because they skew the picture.  The best I ever did on a mountain bike with street tires was 18.7 mph over 10 miles, on paved roads:

Cycling, sport
Start Time
Jul 28, 2011 3:08 PM
Distance
10.20 miles
Duration
32m:42s
Avg Speed
18.7 mph
Max Speed
24.2 mph

I can remember this ride – I wanted to see, specifically, how fast I could push it for 10 miles on my mountain bike.  The weather was perfect, low 80’s and sunny, and those are my results.  I’m in a little better riding shape today than I was back then, but I was still in Olympic Tri shape – in other words, I was in pretty good stinkin’ shape when I took that ride.  If I deduct the two tenths I was at 31:35

To compare today’s results is a little skewed as well – I wouldn’t bother with a 10 mile ride anymore, I’m more about the longer distances now (16 being my easy days, 25 as my normal everyday ride and 50 for my longer days), but let’s take my best 10 mile performances from 25-30 mile rides (I left out my personal best of 26:33 which was due to a nice 15 mph tailwind) and I’m looking at 27:58.

But let’s do away with the bests and look at averages, because that’s what is important.  Today, on my 5200, 18.7 mph is a little (a few tenths) better than a recovery ride over 25 miles (I had a 50 mile ride planned for the next day):

Sport
Cycling, sport
Start Time
Jun 15, 2012 1:48 PM
Distance
25.51 miles
Duration
1h:21m:55s
Avg Speed
18.7 mph
Max Speed
25.5 mph
Calories
1400 kcal
Altitude
650 ft / 860 ft
Elevation
381 ft ↑ / 236 ft ↓

So let’s look at averages:

My average with slicks was around 17.5 mph (1.5-2 mph faster than with knobbies).  The average on my road bike over a distance double the mountain bike is 20 mph.  The tires are obviously thinner on my road bike and offer less rolling resistance than the mountain bike with street tires, but aerodynamics has just as much to do with the increase in speed.  Anyone who has ridden for any length of time will tell you there’s a big difference between riding with your head up and head down on a road bike, let alone riding upright vs. tucked.

Though the physics may not show much on paper, in reality the difference is huge – and we haven’t even discussed riding into the wind yet.  I can hold a 20 mph average easily enough into a 5 mph breeze – there’s no way I’m maintaining 17.5 over the same distance into a breeze…  But let’s go to the cycle computer app for the definitive power numbers on that, shall we?

Road bike, hands on hoods, 0% grade, 10 miles, 5 mph headwind, 20 mph:  303 watts

Under the same conditions, with a hybrid which has slightly better tires than the mountain bike with slicks, that same 303 watts produces a speed of 18.2 mph.

That 1.8 mph difference is mostly aerodynamics folks.  Road bikes are meant to do one thing well, get your butt down the road fast – and they are exceptional at that task.  Flat bar hybrids and mountain bikes with road tires are meant to increase your speed, but the notion that the average rider will keep up with the average roadie on a hybrid is silly – ain’t. no. way.

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15 Comments

  1. Sandra says:

    Indeed. My cycling coach told me that in the end, it depends upon fitness level. A well-tuned cyclist on a hybrid/crossfit could easily outpace someone who is not quite as fine-tuned on an expensive road bike. I don’t mean to say you on a mountain could kill me on a Felt, that’s a major duh. :-). But at high levels of performance, indeed, i would like to continue that conversation with him! I rode so much slower on my Giant hybrid than my new road bike it was ridiculous. Great post!

    • bgddyjim says:

      Thanks. I just set out to provide a baseline and some understanding into the different styles of bikes as to what one can expect. Now that I’ve been around the block a few times I can answer a lot of questions I had when I started out – I figure if I wondered I might be able to help other people that might have the same questions. 🙂

      • Sandra says:

        Indeed! There will always be people with less experience, every step along the way. It’s awesome to learn from each other!

  2. beechcreekproject says:

    I only own a mountain bike so I have no experience to judge the difference but aren’t road bikes considerably lighter bikes than mountain bikes on the average? I’d have to think that would play into the speed difference quite a bit as well. Love the post and it makes me feel better about my slow pace on my mountain bike. 🙂

    • bgddyjim says:

      Weight depends on the bike – big time. My buddy Tim has a Cannondale Lefty mtb that only weighs four pounds more than my road bike. On the other hand, my 3700 weighs about 9 more. Weight plays into the equation a bit for sure, but not as much as aerodynamics. In fact, my old Cannondale weighs 2 pounds more than my Trek and there was no speed difference between the two. The Trek fits me better so it is more comfortable but I could still push that thing down the road pretty good… According to the cycle computer a 4 pound difference means an increase in speed of one tenth of one mph – not much.

      As far as speed goes, I like to write about it as it relates to different bike styles because most people don’t really know what is considered fast and what is slow. 15-17 mph on a road with a mtb and knobby tires is pretty good. Everyone is different, but I try to provide a decent baseline.

  3. michcyn1 says:

    The one advantage I see in a mountain bike is the safety factor when its a little more slippery out. I am more likely to ride a mountain bike on the trails near my home despite the conditions with a MTB. Whereas a road bike might not be as safe under some conditions…

    • bgddyjim says:

      I agree wholeheartedly, mountain bikes are, without a doubt, much more versatile, stable and safe. Simply looking at geometry alone they’re safer – because you sit more upright you can see better, farther and do so more comfortably. Factor in speed too and it’s not even a question.

      That notwithstanding, they’re 20%-30% slower and that’s what I sought to show with this post. I wrote it because I rode my first year on a mountain bike before buying a roadie and I had the data…

  4. […] UPDATE:  I have a second, companion post, to this one in which I explored the difference between typical mountain bike tires and slicks here. […]

  5. […] How Much Faster Is A Road Bike Than A Mountain Bike… Part II – It’s Not Just The Tires […]

  6. m0tm4t says:

    Old article, yes, but I wanted to point out a couple things for passerbyers. I noticed the link provided for the Specialized Nimbus Armadillo tires were 26. This doesn’t compare with 29/700c on a road bike. Also, the gear ratios are different. The rear cassette may have similar gears, but the front chain ring on your road bike likely has more teeth. You can’t accurately measure differences between your mtb/hybrid VS road regarding riding position/geometry until you also attempt to match wheel size (diameter and width) and gear ratios. Side note, though, installing a larger front chain ring on a mtb is doable, but not practical if you ride trails since you’ll have less clearance.

    • bgddyjim says:

      The differences that you point out are minimal. Take the gear ratios… All mountain bikes back then had a 42 or 44 tooth big ring and an 11 or 12 rear cassette… Doing the math, you’re looking at a top speed of about 24-1/2 mph if you go on the low side (42/12) at a 90 cadence. If you can gear out a mountain bike on the flat, carrying a 24-1/2 mph top speed, you belong on a better bike, in a peloton somewhere.

      As for the bike calculator stats, between the hybrid and the road bike… I didn’t change the tire size for the post. A hybrid is almost 2 mph slower than a road bike, and that’s all aerodynamics.

      I appreciate your clarifications though. Either way, I’ll leave my mountain bike for the trails, all the same.

  7. Jesse Kelly says:

    Just came across your blog. I’m an MTB racer and do all my training, including road, on an MTB. It’s out of necessity to a degree but I think it’s ideal for training as it simply teaches you to get aerodynamic and fast on the mountain bike. I just did a 64mile sportif this morning and averaged 17.8mph. I trashed myself! I’ve ridden with numerous roadies and groups and they always seemed surprised to see a full-sus MTB with fat tires in their midst. But I’ve done a lot of things to mitigate the disadvantages and the bike is not as slow as it may seem.
    **Time trail saddle – allowing me to slide forward an back to multiple positions
    **Dropper post, – not sure how anyone would ride without one on the road! It gives me the ability to pitch myself super high (hyper extension height) while climbing and I perch like I’m virtually standing with weight balanced between the wheels. Also great for stretching the legs out for a couple minutes. Also ability to drop it super low while screaming down a 45mph descent, which is great for comfort and confidence
    **Bar position- geometry of all faster mtb riders resemble road geometry. You can always tell a cat 2 rider by the bars being same height as their saddle. Pro riders are all riding much lower up front, which, surprisingly, also lowers your overall center of gravity and I’ve actually found I’m less susceptible to OTB on the XC setup.
    **Top of the line full carbon bike- yeah still much heavier than the average road bike, but kitted out with dropper it’s under 25lb.
    ** Carbon wheelset. – actually my wheelset it probably lighter than most roadie wheelsets
    ** tubeless tires- sure the tires are a massive hit, but along with the lightweight rims the ‘heavy tires are tubeless so we’re talking a about 6-700 grams with sealant. Heavier than a road tire for sure but not outrageous.
    ** I don’t do this but I can run probably down to 32mm slicks on these rims, and right down to 23c if I got a different wheelset. This would be the single biggest improvement I could make if I wanted to do a road event.
    ** As it is the Ultra Cross series in the US has enough dirt and road that results are really a toss up between MTB riders with smaller knobbies (35-40mm) and cross bikes with larger cross tires. Though a couple of the major races have been run on regular MTB tires.
    ***Going back to bar position; we found that when hitting 20mph just moving your hands in from the normal MTB handlebar position to to the stem, saves over .5mph alone. You actually sit higher, but your narrower, and with your arms straight it can be a very relaxing position as well as being faster. If you bend your arms you are faster too, but it’s very tiring. However, if you can drop to your elbows you can gain up to 2mph! I spend 6 months riding with an aero bar, and once I got comfortable down low I can now ride straight road in the aero position with no aerobar. I put some foam pads on the bars where my forearms rest. It’s not quite as fast as TT position of course but you are actually lower than a roadie in the Hoods, Mabye even lower than a roadie in the drops too. It doesn’t work everywhere, but I use the position all the time when it’s safe. In MTB races I can even drop on most smoother fire roads. Some MTB riders have taken to dropping their hands the fork on the road, which I am not comfortable doing. But it is also must faster than conventional position
    **I put a larger 38 ring up front. with ever increasing gear ranges I have enough gears to ride at 26mph comfortably (38×10). I can ride for a while up to 30mph without too much misery, but it gets tough.

    So it’s weird, but having a top of the line MTB makes a difference the faster you go. So if I’m out with my buddies on their regular, decent, MTBs, and were averaging 8mph, they keep up fine with no more or less effort than me. But if we’re average 13mph my bike is built to go faster while theirs lacks in the higher end performance. Basically what I’m saying is someone of my equal fitness has no problem keeping up with me at a lower pace, but when the trail gets faster they suffer much more on a lesser bike. Well, that is the same for the road. I’ve set up my bike so that if a long road ride is average 17-19mph I don’t feel I have much of a disadvantage compared to a roadie. But for me to go a few MPH faster the effort becomes exponentially harder, while the roadie doesn’t need nearly the same extra wattage.

    I was surprised onetime when I went out with a pro triathlete friend. I kept up with him one the flats and if he got ahead I’d suck in behind. On the steep hills I was super fit, the pace was much slower, and his geometry was not set up for the climbs, so I was riding faster than him there. But then I thought I’d just suck in behind him on the descents… not a chance! We’d come over a crest and by the time I got to 25mph he was at 30. When I got to 30 he was a 40. The bike was simply built to go so much faster than my MTB could ever go.

    So basically I reckon narrow slicks make a great advantage to a point, but it all ads up, the weight, the aerodynamics of the bike itself, etc…. To a point I don’t really have a disadvantage, but moving to a faster roadie pace gets exponentially harder. All pretty obvious when you think about it, but interesting nonetheless.

    • bgddyjim says:

      First, thanks for taking the time to write such a comprehensive comment, Jesse. Too cool, man.

      18 mph over 60 miles is mega-tough, brother. I’d love to see what you could do on a $10,000 14 pound road bike!

      Humorously, my friends and I have spent much of this winter on our mountain bikes and I have found that arms bent, hands at the stem position and it’s a lot more comfortable when you’re a roadie.

      I’d like to see how you’d to hanging with my friends and I, at the back of our paceline if we were all working to protect you… You’d get a heck of a draft but we’re 19-22 mph over 80-100 miles.

      Awesome comment, man. One of the best in the history of this blog. Thanks.

  8. Eric Kelsey says:

    Motivation from this post and a few other reasons inspired me to see how fast I could do 20 miles on my fat bike. Best so far after 7 rides over same exact route is 17.6 mph average. Small details include I have a carbon fat bike with carbon wheels so its really light. I have lightest tires available but are still 4 inches wide. One thing I noticed is the rides with very little to no wind are my best. One thing I like is the comfort of the wide tires on rough road surfaces but pushing the wide tires hard would be tough after 20 miles. Im thinking about switching Carbon wheels for the stock ones just to see how I do.

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