I know speed isn’t everything, and some mountain bikes can be ridden on terrain where others will be being pushed or carried, but what sort of bike lets you cover lots of ground in a day?

Is low weight (for climbing), skinny tyres and narrow bars (for aerodynamics) where it’s at? Mountain bikers don’t seem too bothered about this kind of thing, but there must be some sort of bike which is easier to keep rolling at speed, with less effort/energy expenditure.

It’s not about the bike is the short answer.

The person stealing it

Given the same rider then it is likely a carbon hardtail with skinny tyres on and a big ring up front would be the fastest in my opin. I don’t think the width of the bars would make any difference, well maybe a little but minimal.

I don’t know the answer, but I do think that the importance of weight in a mountain bike is over-exaggerated. Probably just because it is easy to measure and simple to market. But a bike that is more efficient (e.g. stiffer, lower rolling resistance etc) will usually beat something that is just lighter. Weight matters when you are lifting the bike (over a fence, onto the car, or just onto your shoulders), but other than that I think it should be lower down the list than it seems to be.

Legs->Tyres->Weight->Aero

A proper fast XC tyre makes a world of difference – especially to lighter or less fit riders that really don’t have an extra 50w to spare on rolling resistance.

Mine for example was a Giant XTC29, really good at covering ground well with something like the old Racing Ralphs installed. I still struggle to get near my PBs on many of the faster Ridgeway type trails.

the rider

Are you talking about canal tow paths, riding around a muddy field here… ie glorified road cycling.

If you mean proper MTBiking then Surely rider input verses a tool for the right type of terrain.

an electric motor and a battery?

KTM Aera comp 29er is electric quick. Carbon fibre, stiff rear end, 29inch wheels and tripple chain ring all add up to a very quick xc mountain bike. I think a lot is about gear ratio and crank arm length.

29″ wheels seem to be quite a bit faster for covering ground than 26″.

Rider
Rider weight
Riders weight to power ratio

Terrain
Conditions
Distance
Then the bike ….

Weight is a falsity in some cases,

A pub with a big log fire and loweswater gold on?

Fastest in what respect Up? Down ? XC ?

Down a full bounce with loads of travel good wheel set up and brave rider big conkers

Up , Lightweight plus bike with good gearing and big lungs

Xc , carbon 29er no weight big legs and lungs and a full English

Terrain
Conditions
Distance
Then the bike ….

Weight is a falsity in some cases,

I get the feeling you’ve never actually ridden a fast MTB.
Give me an XC race bike and i’ll knock out faster times over any kind of distance than a trail/enduro bike with burly tyres on regardless of the conditions.

After legs, I’d guess at a 29er with fast tyres (but crucially still able to hook up and give a level of confidence) on something with 100mm of travel and ‘average’ geometry, to give a bit of cushioning and all day easiness to allow the rider to just keep pushing the pedals.
Having said that, I’m always amazed at how different a bike can feel without it making a blind bit of difference to how well I cover ground or how fast I go.

People under-estimate the importance of aerodynamics when riding mountain bikes IMO.

can’t remember figures (wich will vary from case to case anyway) but its a fairly low speed at which overcoming aerodynamic drag uses up a lot of you power.

So narrower bars and a good body position do make a big difference. tuck in those elbows!

Whatever Nino is riding

Get rid of the flappy clothing, Enduroists head to toe in lycra a marketing mans dream!

People under-estimate the importance of aerodynamics when riding mountain bikes IMO.

can’t remember figures (wich will vary from case to case anyway) but its a fairly low speed at which overcoming aerodynamic drag uses up a lot of you power.

So narrower bars and a good body position do make a big difference. tuck in those elbows!

I think its around 18mph, so pretty quick for an MTB, hence no-one is really bothered about it

I get the feeling you’ve never actually ridden a fast MTB.
Give me an XC race bike and i’ll knock out faster times over any kind of distance than a trail/enduro bike with burly tyres on regardless of the conditions.

Well done but terrain plays an important issue, but then it comes down to rider ability….surely.

I think its around 18mph, so pretty quick for an MTB, hence no-one is really bothered about it

See I thought it was 18kmh, which even for a below average sport cat rider such as myself is about average speed when racing on flatter courses

I’m more of a road cyclist (audax in recent years, but on various bikes including fixies and recumbents). As you say it’s difficult to pinpoint what works, but I try to pay attention to rolling resistance, drivetrain friction, aerodynamics, and frame stiffness (up to a point). I’m not too bothered about weight within reason, but some mountain bikes do seem to weigh a ton. I don’t ‘race’ as such, but I like to be able to go at a decent pace, and having an efficient bike is less tiring to ride, and lets you conserve energy while keeping up with other riders.

I had a mountain bike lesson, and the wide bars, flappy clothes, and sticky-oot knees go against what I’m used to. Some of the bikes seem pretty hefty as well. I don’t suppose there a lot you can do about rolling resistance – you probably just have to run whatever tyre gives you grip. Also, I imagine a really light bike would be a handful on the descents.

As for terrain, I was thinking of a mixed bag – maybe a coast-to-coast over a day, or some longer distance routes in Scotland, or even the North Downs Way – which I once did on my 90’s rigid bike when lightweight mountain bikes were the order of the day!

See I thought it was 18kmh, which even for a below average sport cat rider such as myself is about average speed when racing on flatter courses

In a xc race env then yes, lycra all the way. But for most recreational riders (which is everyone who doesnt enter races) its not important.

Aerodynamics do come into play at lower speeds, though. It’s a combination of your speed and the wind speed, so if you’re riding at 8mph into a 10mph headwind it wouldn’t hurt to tuck yer elbers in!

I’d say a xc marathon type bike with 90/100 mm travel both ends, good fast tyres if we’re talking purely in bike terms.

Slightly left field bur my fat bike with 4.0″ jumbo Jim’s rolls faster than my mates Scott Genius with 2.4″ advantages. We tried it on a long steady down slope from a rolling start and no pedalling. I hit 39kph and him 34kph. We weigh the same and the bikes pretty much do, there’s no way that a JJ is moar aero than an advantage

Aero is surprisingly important, GMBN did an interesting video on it.
[video]https://www.youtube.com/watch?v=Loi3L_Uai9o[/video]

I think a lot is about gear ratio and crank arm length.

PLEASE tell me that was a joke!

What makes a fast mountain bike?

Marketing and naivete

Lunge – not the most scientific test and only an 8 second difference. I`m still not bothered about aerodynamics on my MTB

Aerodynamics do come into play at lower speeds, though. It’s a combination of your speed and the wind speed, so if you’re riding at 8mph into a 10mph headwind it wouldn’t hurt to tuck yer elbers in!

Bull****!. It wont make you quicker it just means you are saving a VERY minimal amount of watts to travel the same speed as someone who isnt as aero.

not the most scientific test and only an 8 second difference.

Well that is still a 6.5% improvement, so quite a lot.

29er disk wheel anyone?

Slightly left field bur my fat bike with 4.0″ jumbo Jim’s rolls faster than my mates Scott Genius with 2.4″ advantages.

This is hardly a surprise.
Its not easy to find rolling resistance data, but what there is available shows that Schwalbe and Conti are light years ahead in rolling speed.
In my experience i’ve found ‘fast’ maxxis offerings to be more grippy than expected, but not actually fast.

Well that is still a 6.5% improvement, so quite a lot.

29er disk wheel anyone?

As i said not very scientific. I bet they could do several runs with same rider and bike and get a 3 – 4 second difference anyway. How much of those 8 seconds was down to being more aero? And how much was down to having a better run, choosing better lines, carrying more speed through corners?

Then see how much of that 8 second advantage you loose trying to turn that 29r disc on the next climb

Everyone I demoed a spesh epic I was amazed that there was no hidden motor – awesome fast bike

To put into context did a demo day with about 20 people. On most bikes I was about 5-8 on climb. On the epic I was first by a country mile – same bike, same rider, same course!

I tried this out on a local loop when I got a new XC 29er full suss, my first run was four minutes faster than my best ever time on my 650b hard tail.

which proves virtually nothing in the real world 🙂

Haven’t read all the answers so may be a repeat but taking the rider out from the equation as obviously Gee Atherton is going to be faster than me if he was on a Brompton and I was on the best bike ever… I would probably say geometry and suspension performance. I have a 29er and I’m no faster on it than I was on my orange 5 26er. The 29er fits me better and hence I’m more comfortable and hence enjoy riding it more but Im not faster. Actually Im less fit now which may make more of a difference!

OOPs sorry, just re-read the title – I though it said who not what 😳

Bull****!. It wont make you quicker it just means you are saving a VERY minimal amount of watts to travel the same speed as someone who isnt as aero.

Or you could put out the same watts and be faster. So yes, it would make you quicker. And whilst the GMBN vid is not a perfect scientific study it does add some weight to the aero argument. You may choose not to be worried about it, that’s fine, but it does make a difference.

Anyway, I believe be followup question to this is “why don’t DHers wear Lycra”.