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

That’s easy UCI banned it as they wanted DH to appeal to the gnar-rad-shred skater brigade. And it worked!

gnar-rad-shred skater brigade

I like that description 😆

lunge – I agree with you in that at the pointy end of xc racing yes those few seconds mean the difference between winning and loosing. To the rest of us mere mortals, no-one cares.

Yes you could put out a few extra watts, but so could the other guy. The speed is so low it makes very little difference.

To the rest of us mere mortals, no-one cares.

Strava disagrees with you 😆

To the rest of us mere mortals, no-one cares.

Not true at all, when you’re on a long day out, still 50mi from home and know you’re going to be grinding into a headwind for the next 3 hours then making yourself a bit smaller makes a lot of sense.

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

I can believe that. When I built up my fatbike with 4.8″ Jumbo Jims I was amazed to find that I was setting PBs on fire road climbs (on a bike that weighs 35 lb). OK, I’ve never ridden a full on race bike, but still I was beating times set on a variety of 26″ and 29″ hardtails and full suss trail bikes. It made me realise that tyres are more important (and weight less important) than I’d realised.

Now it’s winter and I’ve switched to Bud and Lou tyres, the average speeds have dropped significantly. Yes the Bud/Lou weigh more than the JJs, but I’ll bet it’s not (just) the weight that’s making the difference.

When I built up my fatbike with 4.80″ Jumbo Jims I was amazed to find that I was setting PBs on fire road climbs (on a bike that weighs 350 lb)

Me too!

A big factor is how the bike makes you feel when you’re riding and pedalling. You could have the most efficient, smooth bike in the world, but if it doesn’t make you go “YEAHH!!!” when you’re winding it up, you may as well just sit and twiddle. Unless you’re a roadie in disguise and only mtbing for the exercise/suffering. Or you’re racing.

Just taken the bold step of reading the OP

what sort of bike lets you cover lots of ground in a day?

So ignore my previous post!

If we’re talking “big day out for average joe, ie SDW” A well-fitted comfy, smooth, efficient bike that means you’re fresher for longer is going to be the winner. cush over ultimate lowest weight, relaxed riding position over arse up, head down racey position.

If you’re Ian Leitch setting a SDWD record, you’re back into xc race machine territory.

I read a study a few years ago where they compared hard tails and full-sussers over a rolling XC course – it effectively came down to what was gained by the lighter hardtail on the climbs wasn’t recovered on the downhill by the full-suss.
Climbing speed often comes down to the ability to getting the power through the tyres and this is where a fatter tyre wins, plus they have lower rolling resistance than a skinny tyre, so win+win.
I’d say a carbon-framed and rimmed fatbike with 4″ JJs would be a killer XC weapon – certain outclimb anything and big tyres means means you can go scary-fast on the downhills.
Aerodynamics are insignificant for XC.

So the answer is a fatbike ridden by someone in baggy kit.
Or an xc hardtail ridden in lycra with an aero helmet.
Or an orange 5.
Or a specialized epic.

Take your pick OP ! Winners – the lot of them 😉 😀

Despite my previous post, my 29er XC Carbon FS with proper XC tyres (2.2″ vittoria Mezcal g+) set up tubeless is silly fast, I’ve set pr’s everywhere I’ve ridden it both up and down hill on natural stuff and round trail centres.

As fast up hill as my previous 29’er XC HT with fast tyres but significantly faster down hill and traversing, especially on rooty and rough ground. It’s also more comfortable so I can ride faster for longer.

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

Have you not read dirt mtb mag? All bikes are rubbish apart from wor Eva is flavour of the day.

lots of different bikes are fast. DH, Enduro, XC fs and XC ht are all fastest depending on the relevant race/ terrain.

what sort of bike lets you cover lots of ground in a day?

Climbs make more difference than descents so a XC bike will be faster than a heavier bike in nearly any situation.

I would have thought a XC fs bike would be the most efficient bike for a day out.

Tyres make the biggest difference for me.

Different frames and forks make some differences but tend to offset each other in my experience. Take a lap of a fairly mixed trail centre and I’ll be slightly quicker on the downs on my trail bike but I’ll be quicker on the ups on my lightweight carbon 100mm forked hardtail. Over a day they would kind of even out.

The answer to this is very easy, if we read the OPs posts;

deejayen

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?

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

The answer is, look at what the fastest riders ride of things like the Tour Divide etc. Put it all in a spreadsheet and weight it by finishing time, then check the bikes build out, and average the components.

29er
2.2 or 2.4 reasonably fast tyres. Some people do ok with + or fat.
100mm or thereabouts suspension. Some will be rigid, some 120. Some light XC full sussers.
Something dialed back from full on XC bike, a little more upright

It is probably more down to experience and what you like / are comfortable on / want to ride.

What type of string is the longest?

The one that’s cut that way

Fastest bike I’ve ridden in the Peak District: Yeti 575 with Rock Shox Lyriks.

Fastest MTB I’ve ever ridden elsewhere: Cube reaction GTC 29er

Really depends where you are riding.

Most fun however was a Cotic Soul. Still miss it.

There’s a little rocky downhill strava segment in my local woods that I’ve ridden plenty of times, mostly on my Anthem. Did it a few times on a Cotic demo day and beat by PB on the Flare and Rocket. Went out one night last week on my 26″ Dialled PA HT and beat those times. So that is conclusive evidence that a 26er HT is the fastest bike. QED.

The fastest bike I’ve ridden was the bike I was riding when I was at my fittest. It happened to be a Spesh Camber Comp Carbon 29. I briefly held KOMs on some climbs around Rivington. I’m minutes slower now whatever bike I am on.

Things appear to have moved on though – I’m almost a minute slower than the current KOM on one of the climbs. He was probably on an e-bike though 😉 https://www.strava.com/segments/1451786

On the Ridgeway Double I averaged 11.8mph on a 1×10 FS, Pedalhead averaged 13mph on a rigid singlespeed.

It’s what works for you. For most a short travel FS set up to be comfortable over long periods of time works well.

My ‘fish was/is perfect, my Epic is 3lbs lighter but doesn’t work because the position is too aggressive.

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.

Minimal? Wind resistance goes up with the square of speed, so on a bike with a pretty small power source it is a massively increasing amount that is lost for every mph you go faster.

Fair enough downhill off road there are other things dictating your overall speed. But on the flat into a headwind? I can think of one XC race this year where there was a massive fire road headwind section (the techy return leg was in a cutting so no tailwind benefit on the way back).

The fastest bike is the one ridden by anybody who passes me and frankly it’s an unfair advantage. When I’m doing the passing it’s not about the bike.

What makes a fast mountain bike?

2 pages of answers and opinions and nobody has provided the actual answer…

Red bits.

Just add a few red bits, eg bar ends, grips, pedals, saddle, hubs, etc..a bit at a time until it achieves speeds you can’t control,

Everyone knows red is fastest.

+1 coolhandluke!

About 2000w of #5 and 200mg of nadrolone

Also fast cornering vs fast in a straight line should be considered. Fast in the air? Fast over chunk? So many variables. That said, in the greater scheme there are more straight bits.

I will say I took my 1994 26″ hardtail out for its annual ride last week and was near 2mph up on my average speed compared to my FS, also Rockect Ron vs a DHR II may have had something to do with it. Going though a rock garden prompted the term “bone-shaking” to rattle around in my head. I did feel like I took a more conservative line choice in the rough but if you took the ride as a whole including boring bits I’m sure I was quicker.

It will still be getting tucked away in favour of the FS as I have more FUN on sections of trail I enjoy the most. I’ll take that over average speed anyday.

Just go and drop 6.5k on a cannondale scalpel

It’s interesting that half the answers are actually addressing what makes an MTB more ‘efficient’ and that there’s some debate on what is actually meant by “fast”…

For those that want a bike to be quicker overall i.e. up and down over mixed surfaces and terrain it’s almost sounds like a CX bike (flat or drop bars?) might actually suit better and the compromises when pointed down can be lived with.

Except I don’t think that is really what a lot of riders mean by “faster” narrower tyres rolling better has been reasonably well debunked now, even roadies are going fatter now.

Most ‘lesure’ MTBists seem to want to be able to winch to a trail head comfortably and then enjoy some brakes off, corner carving, wheels of the ground type fun without suffering too much for their kicks… For that I would say weight is a relatively minor factor (lighter is of course nice to have) and it’s geometry, tyres and suspension, in that order, which provide the ability to milk “speed” from a trail… All IMO of course.

on the sort of rides the OP mentions I would say weight has a big effect ‘cos you will spend a lot of time climbing and the downs will not be hugely technical. then comfort, then tyres