Road vs MTB - effort/pace/power

larkim

For reasons known only to myself, last Monday night I went out for a 15.8 mile ride at about 8pm. This was on my heavy, cheap, Decathlon MTB (Rockrider Big RR 5.3 - 29er) which I reckon weighs in at about 15kg.

It took me 1hr2m58s and averaged 15.1mph. Conditions were fairly still, cold and dry. https://app.strava.com/activities/249633873/overview

Last night, I did the same route. Same clothing, almost identical weather conditions (perhaps a couple of degrees warmer), but this time on my light(er), cheap, Decathlon roadie (Triban 3).

This time it took me 55m28s, averaging 17.1mph. https://app.strava.com/activities/252729249

My perceived effort levels I would reckon were about the same, though having spent much more time on the MTB recently my back was a little stiff riding the Triban.

Anyway, what I can't quite understand from Strava is the difference in their calculated power - on the MTB it reckons 223w average, on the road 145w average. Implying (how dare they!) that if I'd applied the same amount of power on the road bike I would have been a lot, lot quicker!

As an objective comparison between two rides I reckon this was a fair assessment of the difference for a relatively inexperienced rider (on both bikes) between road and MTB - might be of some use to someone!

ai_1

I don't use Strava so forgive my ignorance but what does it take into account when calculating average power? Do you tell it your weight, the type of bike and weight of the bike or what?

There is one variable you haven't mentioned which to be honest makes all the rest irrelevant - Tyres
If you ride a MTB with slicks I reckon it would likely be more comparable to a typical road bike than it would be to an identical bike with knobbly tyres.

An aggressive knobbly thread makes a huge difference to the effort needed to maintain a given speed on the road. On the flat it's massively more important than weight and at lower speeds it may even be as important as aerodynamics.

t4tomo

ignore strava power readings, they mean nothing.

larkim

t4tomo wrote:

ignore strava power readings, they mean nothing.

I hear what you're saying - but I would still have thought that the average numbers would be signficantly closer than they were. Strava themselves reckon that their algorithm (which takes into account bike and rider weight, and I suspect an aero coefficient based on whether the bike is a roadie or a MTB) comes out fairly close (at least close enough) to power meters to have some worth.

As for tyres, of course - this was a straight "MTB with MTB tyres" vs "Road bike with road tyres" comparison - though the tyres on my MTB aren't particularly nobbly and were pumped up firmer than I might have them off road.

slowbike

larkim wrote:

though the tyres on my MTB aren't particularly nobbly and were pumped up firmer than I might have them off road.

And there's the next variable ..

It's Strava Power - it's not right and it's not comparable between bikes or in different weather conditions ...

What do you think it would do if you ended up drafting someone else (or a vehicle) - it doesn't know you've done that does it ...

If you want power, get a power meter.... they're dropping in price ...

markhewitt1978

Yup Strava power estimates are just a stab in the dark, much like calorie counts, pretty much meaningless for most purposes, interesting but that's about it.

Power meters might be coming down in price but for £700 they are still off most peoples lists unless you're seriously into racing.

larkim

Slowbike wrote:

larkim wrote:

though the tyres on my MTB aren't particularly nobbly and were pumped up firmer than I might have them off road.

And there's the next variable ..

It's Strava Power - it's not right and it's not comparable between bikes or in different weather conditions ...

I agree!!

But doesn't anyone think that the gap between the two reported figures is just *too* large?

Anyhoo, it wasn't really the power I was wanting to focus on, more the difference between riding a heavy MTB and an entry level roadie - 2mph higher average on an hours riding. Does that fit with others experiences (or perhaps better expressed as a 13% improvement in average speed)?

markhewitt1978

Sounds about right to me!

ai_1

larkim wrote:

Slowbike wrote:

larkim wrote:

though the tyres on my MTB aren't particularly nobbly and were pumped up firmer than I might have them off road.

And there's the next variable ..

It's Strava Power - it's not right and it's not comparable between bikes or in different weather conditions ...

I agree!!

But doesn't anyone think that the gap between the two reported figures is just *too* large?

Anyhoo, it wasn't really the power I was wanting to focus on, more the difference between riding a heavy MTB and an entry level roadie - 2mph higher average on an hours riding. Does that fit with others experiences (or perhaps better expressed as a 13% improvement in average speed)?

A MTB would be expected to be slower.
How much? Well that depends, as already mentioned, on lots of other variables including route profile, tyre type, tyre pressure, weight and riding position. Have you any evidence you used similar efforts for both rides? What impact did weather have (wind, atmospheric pressure, etc)? If you told me you rode two bikes back to back with similar effort, one a MTB with off-road tyres and the other a road bike on slicks on flat or rolling terrain and you gave me these figures (15.1mph and 17.1mph) I would not be overly suspicious. They're feasible. I don't think anyone can tell you more than that.

tangled_metal

Not the same but I used to do a test on my hybrid. My commute is a gentle route with the highest point halfway. A lot of it is flat. My test was to ride a distance on the flat as a constant effort level in the normal position then repeat with a lowered position (arms bent so my head was a lot lower). I got the difference in speed down to 2.1mph different typically, with the faster speed being the lower position. I only say this because I am guessing the road bike is more aerodynamic so could account for a lot of the difference in speed.

On the same run when i used to do it with my road bike it was about 10 minutes quicker over 7 - 7.5 miles on my road bike (IIRC 21mph door to door average speed including stops at lights compared to 16mph now). Although I was a lot fitter back then so not all that speed was down to the bike position but a lot more was pure lack of fitness these days.

larkim

Ai_1 wrote:

If you told me you rode two bikes back to back with similar effort, one a MTB with off-road tyres and the other a road bike on slicks on flat or rolling terrain and you gave me these figures (15.1mph and 17.1mph) I would not be overly suspicious. They're feasible. I don't think anyone can tell you more than that.

Glad I'm not being suspicious!

I suppose the main reason I posted it was to show something of a real world answer the sort of question which was bubbling around in my head before I decided to get the Triban - "I know a road bike will be faster than my MTB, but how much?"

Obviously everyone is different, and my experience will not be unique and subject to many more variables than I am able either to report or control. But as an anecdote with at least an accurate Strava trace behind it, it has some merit! (Both bikes ridden with SPDs by the way)

tangled_metal

Download the Thorn Cycles pdf brochure there is some interesting info and opinions on there about bikes that you might be interested in. I think the guy who wrote them is an experienced cyclist and tourer who knows a bit about bikes too. The parts of the brochure of relevence is the opinions on the performance of bikes. Choice of tyres, type of bike, aerodynamics, air temperature, rolling resistance, etc. Basically all the factors that affect performance. Interesting his opinions on tyres I thought.

markhewitt1978

I did watch a video (I forget where now) where they did back to back tests of a MTB and a road bike. On the road as expected the road bike was fastest. However in the forest, off road, a little rooty but no jumps etc they did the same test, and the road bike actually matched the MTB, although it was being ridden by a very experienced mountain biker.

ai_1

larkim wrote:

....I suppose the main reason I posted it was to show something of a real world answer the sort of question which was bubbling around in my head before I decided to get the Triban - "I know a road bike will be faster than my MTB, but how much?"

Do two rides on the same bike on different days and I reckon you'll get a different average speed too. It's a largely pointless activity unless you do it several times on each bike in pretty consistent weather and going flat out or using a power meter or HR monitor each time to try and keep effort close to equal. Avergae this and the error should not be huge but it's still not a precision test. Basically, why bother?
So in order to try and answer your question but without attempting to put figures against it lets do this. Let me assume you're not in a terribly aggressive position on the MTB and will be in a typical road bike position on the new bike. And also assuming that the gearing on either bike is not a factor in performance:
1. MTB with off-road tyres will be noticeably slower, less comfortable and poorer grip than same MTB with slicks on all road rides.
2. MTB with slicks will be slower than road bike. On flat roads this will be due mostly to rider position and on hilly routes due to combo of rider position and weight.
3. In all cases the difference between road and MTB will be bigger the faster your average speed. MTB with slicks may not be dramatically slower at low speeds but will lose out at higher speeds when aerodynamics become totally dominant.

keef66

Last year I happened to do the same circular route a couple of days apart and in similar weather conditions. Once was on my wet weather alu bike with mudguards etc, the other on my lighter dry carbon bike. I felt I'd done both rides at a similar tempo, and was astonished to find I'd recorded exactly the same time and hence average speed.

Lance was clearly on to something when he said it's not about the bike.

Made me realise that I'd be wasting money going for anything lighter unless it was me.

ForumNewbie

If you tried a Heart Rate Monitor that would show the effort you put in on each ride, and may give you a better comparison than Strava power averages.

w00dster

Just to contradict the post about not about the bike...
I have a 12kg cross bike and a 7kg road bike (good lite wheels running bontrager R4 tyres).
I'm a fairly strong rider who gets out quite a lot. I can tell you now I can't keep up with fellow A group riders on my heavy cross bike (knobbly tyres running about 60psi). I get dropped when the speeds go up. On my road bike I have no problem keeping up the pace, in excess of 23 mph and the watts needed to maintain that speed on that set up are too high.
On my MTB I wouldn't even dream of trying to keep up normal road speeds, it would kill me!

It's not all about the bike, but it does play a significant part. Over a flattish small distance it may not be as noticable, throw in some hills and a big distance and I think you will notice a difference.

meanredspider

I'd agree that the bike does make a difference - I've even measured differences between tyres and tyre sizes.

As for Strava - it can only make wild guesses at power. If you tell it you have an MTB it will probably assume you are using MTB tyres and dressed in MTB gear and may even assume you're riding off-road. It will obviously assume very different things when you're riding a roadie. My experience of Strava's powrr estimates (even when riding a roadie on road in roadie gear - possibly the most predictable set of conditions) is that the power estimates are way too low - possibly only 60% of the number I get when I ride with a power meter - so the figures are junk.

ai_1

w00dster wrote:

Just to contradict the post about not about the bike...
I have a 12kg cross bike and a 7kg road bike (good lite wheels running bontrager R4 tyres).
I'm a fairly strong rider who gets out quite a lot. I can tell you now I can't keep up with fellow A group riders on my heavy cross bike (knobbly tyres running about 60psi). I get dropped when the speeds go up. On my road bike I have no problem keeping up the pace, in excess of 23 mph and the watts needed to maintain that speed on that set up are too high.
On my MTB I wouldn't even dream of trying to keep up normal road speeds, it would kill me!

It's not all about the bike, but it does play a significant part. Over a flattish small distance it may not be as noticable, throw in some hills and a big distance and I think you will notice a difference.

The bike as a whole makes a big difference but generally weight is not a big factor. The tyres and position are. I suspect an aggressively set up MTB with slicks wouldn't lag too far behind a road bike in most conditions although I'd still want a road bike if only for the drop bars!

Anonymous

markhewitt1978 wrote:

I did watch a video (I forget where now) where they did back to back tests of a MTB and a road bike. On the road as expected the road bike was fastest. However in the forest, off road, a little rooty but no jumps etc they did the same test, and the road bike actually matched the MTB, although it was being ridden by a very experienced mountain biker.

Why does that surprise you/anyone?
Unless you needed the MTB for the reasons its an MTB then why would the road bike be slower?

Do not think the rider being MTB experienced made much difference (being faster on the road bike off road) as a non experienced MTB rider would be slower on the MTB.

In the real world people would probably be slower on their road bike off road, than on an MTB, but thats mainly because they would A/ find it odd/very uncomfortable, and B/ not want to bugger up their road bike.

A lot of the differences on an MTB bike are there for the comfort/convenience of the rider.
Road/hybrid/non suss MTB's can cope with quite a lot of abuse.

markhewitt1978

Yes; it's certainly true that the mountain biker didn't care one bit during the test if they broke the bike or buckled the wheels etc.

IShaggy

When I got my first road bike, upgrading from my MTB, I thought I'd be a god. But I was sorely disappointed after my 1st ride, as I was only marginally faster. I thought that roadies were really quick because of their bikes. I didn't realize that most of the speed was a result of training hard.

As for the Strava power estimates. Ignore then. If you're perceived effort was the same for both rides then the power won't be far off.

Schoie81

larkim wrote:

Anyhoo, it wasn't really the power I was wanting to focus on, more the difference between riding a heavy MTB and an entry level roadie - 2mph higher average on an hours riding. Does that fit with others experiences (or perhaps better expressed as a 13% improvement in average speed)?

Its a shorter ride, but for comparison, over the last two weeks, due to snow and ice on my usual off-road route, I've been riding on the road on my MTB (hardtail with nobbly tires..) on a route I also ride in the summer on my road bike. Its 8.25 miles and includes a 2.5mile long decent - On the road bike I average about 21mins roughly 23mph, MTB - about 27mins roughly 18mph, so quite a difference for me.

cycleclinic

One guy are recent reliabilty ride did it at around 20 mph average on a mtb. He was one of the lead riders and not on a 29er either an old retro with wide know by old looking tyres. Much respect to him he even spent a silly amount of time of the front. I will find out how much junk those strava numbers are when I get my garden pedals. I already know they are junk.

I have only ride my road bike of road once it actually did of I rode in a field too looking for a neighbours dog.

simon_masterson

It depends somewhat on what 'MTB' and 'Road' bike we're talking about - both can be a multitude of different things. A bike that is set up to be good for mountain biking will be a bit slower than a road bike, but one that's more like a hybrid with a larger frame, slick tyres and bigger gears, not necessarily as much. Getting into an awkward Obree-esque (ish) position on flat bars can also be rather aerodynamic, if a bit uncomfortable...

diy

I've always found it about 20% on a hilly ride, much more on the flat. MTBers will get faster at MTBing by road riding, but being a roady wont make you a fast MTBer.

The issue is that a lot more of going quick on an MTB is skill/technique whereas on a road bike fitness makes a huge difference.

awavey

maybe Im just being slow understanding the weight makes no difference bit here or getting completely the wrong end of the stick, but whilst I understand there is more to the differences road vs MTB bikes give you in terms of overall pace etc than just weight, I just cant believe if you said to a road biker, here have another 7kg of weight to carry around with you, theyd turn around and go thats totally fine as the weight makes no difference its all aero.

as when I commute to work on my already overweight MTB (17kg approx) and have had to take my laptop with me, which weighs nearly 2.5kg and sits in my panniers so isnt being aero unfriendly, I can definately feel the difference in weight, that impacts the power I have to push out to get going and maintain a certain pace and the energy level required to sustain it.

when at the weekend I dump all that extra weight Im carrying to work, it feels like a totally different bike in terms of pushing the same physical efforts on the pedals, yet Im going 2-3mph on average quicker, for longer.

if I then swap from my overweight MTB (17kg approx) to a roadbike (10kg approx), ok the road bike is changing alot of the factors which can affect this amount of effort/pace/power, but shedding 7kg has got to make a difference, thats not an insignificant amount of weight to lose simply through different bike setups.

ai_1

Weight is very relevant when you're climbing or accelerating. Accelerating here includes gaining speed, braking and cornering. However when you're cruising at constant speed in a straight line it makes very little difference. Rolling resistance will increase a little but that's not going to make a very significant difference to average speed. If you're continually starting and stopping at junctions or lights and/or have lots of climbing to do then a heavy bike will cost you time and/or effort.

diy

Don't underestimate the impact of contact patch, rolling resistence, the wobbly bits (suspension) and efficient riding position. Weight is less important on the flat.

ai_1

diy wrote:

Don't underestimate the impact of contact patch, rolling resistence, the wobbly bits (suspension) and efficient riding position. Weight is less important on the flat.

I'd forgotten about suspension. I was assuming a rigid MTB. Suspension can absorb a significant amount of energy, that's what the dampers are for, but some of the energy absorbed would otherwise contribute to propulsion. I've no idea on figures for the impact of suspension but it's certainly relevant for a front suspension bike and I assume it's much more significant still for a full suspension bike (I've never tried one myself).

diy

Modern MTBs have all sorts of patented devices to reduce pedal induced bob. However, even with a stiff propedal and fork lock, they still suck huge amounts of power. IME a soft rear is far worse than a soft front on a climb. The torque on the rear makes the suspension suck down changing the angle of attack on the pedals and each stroke gets soaked up by the power stage of the stroke causing you to bob.

Having said that tyres are really the issue. MTB tyres get progressivley worse as you go faster. 20mph even on XC tyres and tarmac is hard work.