Agreed. Having seen the guys at the olympics tackle some of the course with silly high seats its clearly not a requirement for everyone, but for those less gifted (ie 95% of riders) it surely makes sense.

I reckon most of those guys could go faster on droppers, even them. Definitely a ‘marginal gain’ though. Mountain bikers aren’t exactly famed for marginal gains, but fashion, is something they definitely are famed for. Dropper seatposts definitely aren’t XC fashion though…

Yes, I completely agree most people might be quicker and the weight of a dropper post brings immediate benefits to control and confidence. My comment about weight was in response to a previous poster’s more general comment about ‘does weight really matter on an mtb’. And in my opinion, yes, weight matters with all other things being equal, but if that is offset by functional advantage then I’d take the weight gain. A bit like having stiffer wheels rather than going for flexy ultralight rims. But generally I’ll take weight-loss where I can get it*

*well, apart from last week’s bout of gastroenteritis 😯

The guy with a dropper needs to increase output by just over a watt to sustain the same relative output as before, that deals with the slowing effect of a adding the dropper. It is de minimis.

I’m not totally convinced of the real world application of the science there, adding 2/3 of pound = 1w additional power required?

By that logic switching to DH wheels (@6lbs heavier) would only require 10w additional power on the climbs?

Everyone seems to be almost desperate to have their own use of a dropper post validated by pro XC riders using one. If they felt it was an advantage, or if they got paid enough by a sponsor, they’d already be using one.

All the above stuff suggests it would be a great advantage, but they can ride well enough without one, as is demonstrated at every race.

Droppers are this seasons fashion for the STW riders; this does not imply a performance advantage for real athletes.

I think this is a good point:

But if the course doesn’t enable you to overtake and make use of the extra speed on the downhills,

Whilst the top guys don’t use the descents to recover, many people (myself included) do, so actually having something which enables you to absolutely hammer the descents when you’re not going to anyway, is even more pointless. I wonder if that accentuates the difference for the DH racers who have a go at XC, who are hammering the descents.

gonna give a dropper a go, mainly for jumping if I get brave. think I would remove for sdw, big dog etc.

may find I dont notice it though.

very undecided about this.

possibly the advantage is on corners where you can drive the weight through the pedals more effectively.

if we are talking marginal gains.

http://www.cervelo.com/en/engineering/thinking-and-processes/aerodynamics.html

why don’t we see aero mtbs i am sure you can get a reasonable advantage by redesigning the forks, wheels etc. For the average bimbler no issue, but once you are unto 20mph which is easy on fire road sections it becomes a real issue.

possibly the advantage is on corners where you can drive the weight through the pedals more effectively.

How?

If you want to drive the weight through the pedals more effectively you are already standing up, so moving something that you don’t actually touch is going to have no effect at all.

If I could get properly fit, I’d be lethal in an XC race

Ha…hahaha….hahahahahaha

Come on then big guns, get fit and ‘be lethal’

Most of the fast lads I know are proper quick both up and down. Winter ‘xc’ races are by no means a measure – a lot of road riders and tt’ers use mtb in winter for training. Mental quick on the fire roads, slower on the single track, mainly because they’re either recovering or because they don’t want to crash wrecking their upcoming season. Additionally gorricks are a free for all, you can pitch up as an expert or elite if you like getting your head kicked in

Do the first national at sherwood, any class you like and see how much ‘bitch braking’ you’re doing then…

why don’t we see aero mtbs

Because the UK mtb market still thinks baggy shorts and baggy tops and Camelbaks filled with ‘life saving’ equipment is the shizzle.

Mountain biking in the UK is a leisure activity rather than a sport for the people who spend money in the high street shops and on the internet.

Because the UK mtb market still thinks baggy shorts and baggy tops and Camelbaks filled with ‘life saving’ equipment is the shizzle.

i know, bit like the hissy fit when riders started using skin suits for downhill.

njee20 – Member
Whilst the top guys don’t use the descents to recover

Really? Why not?

why don’t we see aero mtbs

Because they would offer minimal benefits, even to xc pros.

Because they would offer minimal benefits, even to xc pros.

bit like dropper posts then.

Really? Why not?

because they are hammering it the downhills and uphills because all the other top guys are hammering it on the downhills and uphills too. hence being in the top guy group.

Pedalling hard on the downhill? Really? That hard?

Pedalling hard on the downhill? Really? That hard ?

Given the exertion required for DH racing, I would suggest that this is true.

Do you have any evidence or experience to suggest otherwise?

Pedalling hard on the downhill? Really? That hard?

Could be a headwind 😆

crikey – Member
Given the exertion required for DH racing, I would suggest that this is true.

Do you have any evidence or experience to suggest otherwise?

I’ve raced xc,and not badly. Yup, some descents were hard work. The only ones so hard you couldn’t recover at least a bit on were in enduros.

If only an aero Xc bike could make me an elite… unfortunately though frontal mass might be usefull at 55Kph we still stick a sodding wide number board on the bars.As for standing up round corners in mud,the converse is generally true..

It’s er, not about the bike…?

I run 5mm lower on my xc race bike than I do on the road.

who sits down in the tech stuff anyway?

I’ve learnt to get off the back and hover over the saddle when it gets techy.

the other thing about relative saddle heights between road and xc is that the offset makes a big difference. if you run an in-line post offroad you can run the saddle a little higher than if you ran a setback onroad.

The most obvious problem with an aero XC bike is the current fashion for very wide bars. My mate came over from Aus and laughed himself silly at a few guys we saw tucking down on a fast descent with their arms waaaaaay out in the wind. He rides international MTB stage races…

So here’s a question; IME you tend to see Xc racers using hard tails. I assume that’s for efficiency reasons, so is there any argument that says the less fit you are, and the more technical the course is, that a short travel full sus would allow you to travel over the rough bits easier/faster allowing you to recover a some of your loss on smooth / climbs?

If that’s the case, how does one determine “which bike” assuming both bikes where the same spec yet one HT and one FS?

The most obvious problem with an aero XC bike is the current fashion for very wide bars.

Nope, bars should make no difference. Everyone knows if you’re going to tuck you should have one hand on the stem and the other behind your back, Sean Yates style )

so is there any argument that says the less fit you are, and the more technical the course is, that a short travel full sus would allow you to travel over the rough bits easier/faster allowing you to recover a some of your loss on smooth / climbs?

Look at the London Olympic podium.

http://www.cyclingweekly.co.uk/racing/olympics/kulhavy-wins-mens-olympic-mountain-bike-event-as-killeen-crashes-out-39964

there is no easy answer, there is no “right” answer.

Well, I’m struggling with the transition from an anthem to a scale, ups and downs are fine and actually measurably faster on the scale, it is pedalling in the rougher flat stuff I suck at. If anyone rode the brass monkeys rd 1 back in nov there was a short uphill section with lots of grassy tussocks, that absolutely destroyed me whatever I tried I couldn’t keep any sort of pace and was being bounced all over the place. Other riders flew past me….on about the 4th run through I was contemplating the need for a dropper post…

Well indeed. I rode Xc on a FS at thetford and it just sucked my energy away. I’m about to ride a much smother circuit with interludes of 10ft long rocky transitions. I’m thinking of taking my FS with extra psi in the shock, with a view to blasting the rocks while the HT’s stutter. Both my bikes weight the same/same gearing so that’s my only advantage I feel*

*i am just testing my potential “race” setup rather than posing any kind of threat to the podium 8)

I’m not totally convinced of the real world application of the science there, adding 2/3 of pound = 1w additional power required?

By that logic switching to DH wheels (@6lbs heavier) would only require 10w additional power on the climbs?

Think of it differently, you wouldn’t notice if you had a full bottle or one with 200ml in when you’re racing. Further, you do not notice daily fluctuations in weight of yourself do you? These are usually a few hundred grams. Obviously rotating mass has different implications due to inertia, but I think these are often overstated, but hard to calculate due to variables.

But yeah, 6lbs more:
Rider 1 = 70kg, 340 watt FTP, bike = 10kg.
Total W/kg = 4.25

Rider 2 = 70kg, 340 FTP, bike = 12.7kg
total w/kg = 4.11

Now let’s rearrange it.
Rider without dropper = w/kg = 4.25, total weight = 80kg
4.25*80=340w
4.25*82.7=351.5w

So 11.5 more watts with a 6 pound heavier bike to operate at the same relative FTP. This is why most coaches say if you’re not fat, don’t try and lose weight, it’s far easier to increase power by 5 watts than to lose a kilo.

But yes the real world application of that is far more complicated and probably impossible to truly measure.

If we were looking at the difference of 300g of body weight on performance of two riders with equal thresholds, I don’t think we’d even have questioned it. 300g of non-rotating weight just doesn’t matter.

My racing the last few years have been limited because i haven’t been arsed, anyway from experience which doesn’t translate to short course. Cristalp is not technically hard but the repeated abuse your back takes means i feel better on a firm short travel full sus compared to a hardtail. But it does mean carrying more weight and being slower in theory, but as your less fatigued you may be faster.

He rides international MTB stage races…

So what? Has he done lab tests on it? Riders with wide bars have no aero advantage from tucking?

🙄

If you want to drive the weight through the pedals more effectively you are already standing up, so moving something that you don’t actually touch is going to have no effect at all.

If you want to drive the weight through the pedals more effectively then you have to put your body where an XC height seat doesn’t let you. I actually made a “duh?!!!” face when reading your post and nothing on STW thus far has achieved that which says a lot…

If you want to drive the weight through the pedals more effectively then you have to put your body where an XC height seat doesn’t let you.

No, you just don’t sit down; driving weight through the pedals requires you to press on….the pedals…. Not going to happen if you sit down, so the position of your seat is not important.

Riders with wide bars have no aero advantage from tucking?

Riders with wide bars are making themselves less aero; that’s the point. Tucking makes a difference, but you’re not tucked all the time.

No, you just don’t sit down; driving weight through the pedals requires you to press on….the pedals…. Not going to happen if you sit down, so the position of your seat is not important.

You can’t put your body in the correct position for optimum cornering with an XC height seat because there is a saddle and seatpost in the way. Look at any pro DH/4X/Enduro racer mid-corner and it’s obvious. They don’t just move like that because it looks ‘fashionable’…

So 11.5 more watts with a 6 pound heavier bike to operate at the same relative FTP.

I didn’t doubt the science, I said I doubted the real world application of it.

Al – perhaps descents was misleading, but a lot of the top guys attack in the singletrack – good place to get a gap when everyone’s marking each other on the climbs.

Crikey – you don’t need to be aero all the time, that’s the point.

Look at any pro DH/4X/Enduro racer mid-corner

Thread about XC racers; did you forget?

you don’t need to be aero all the time, that’s the point

.

But equally, you don’t need to be un-aero all the time either, that’s the point.

Crikey, give it up. Xc race speeds aren’t relevant to aero apart from descents.

Alternatively just keep saying the opposite to me.

Xc race speeds aren’t relevant to aero apart from descents.

Just like dropper posts then, which brings the whole thing back to the start?

No answer then?

No answer then?

No question to answer then?