Viewing 35 posts - 1 through 35 (of 35 total)
  • Anyone used a powered meter on a steep hill to compare crank power with mgh?
  • thegeneralist
    Full Member

    / still ruminating about another offroad Everest attempt and trying to work out what the best power level is that I need to maintain to get it done in a semi reasonable time ( sub 30 hours. Ie two daylights and a night)

    Assuming I weigh 81.7kg, my bike weighs around 15 and clothes etc take that up to a round 100kg. Each metre altitude converts 1000 joules of energy ( mass x g x height.)
    Agreed?
    The only metric I have I have is that a ( metric) ~Munro is around 2 hours climbing time or thereabouts for me. I have to do 9 of them, which is 18 hours climbing in total.

    Back to the theoretical Munro, if the average gradient on the descent is 10% then my descending will be 10km. Assuming 30kmh that takes 20 minutes, thus leaving 6000 seconds for the ascent.

    100kg x 10 x 1000m = 1MJ
    Divided by 6000s = 167 Watts.

    So that’s my theoretical target average power for the first half of the attempt. Assuming it goes slightly to shit after that, and I’ll need at least 4hours to eat then that still keeps me in my “just over a day” target.

    But, getting to the point eventually, I have no idea how measured power translates into progress up a hill.
    I intend to use a 10% ish hill, so will be going very slowly so wind resistance will be negligible.
    Likewise tyre resistance shouldn’t be huge…
    Drivechain..

    Anyway has anyone got any data on a ( preferably steep) hill that they’ve cycled, know their average measured power on that hill, and the height of that hill. ( and how fat they and bike are, natch) 🙂

    Cheers

    molgrips
    Full Member

    Power meters are generally fairly accurate, so it will translate directly yes. Clean chains are like 98% efficient if you use a straight chainline, but on an MTB with 1×11 or 1×12 you won’t be, so probably 95% or maybe even less. And on an MTB you will lose power squirming those knobbles about and flexing the tyre carcass. And then, if you are off road, you’ll put some energy into moving the trail surface around i.e. mud or gravel. I’d guess your potential energy gain will be about 80% of the power you put in. At a guess.

    n0b0dy0ftheg0at
    Free Member

    Is this any help, my gentle paced ride up Road To Hell? Link is to steepest bit, but it’s a wildly varying gradient ~6.9 mile climb.

    https://www.strava.com/activities/7742432671/analysis/5299/5583

    I was ~81.6Kg; bike ~9Kg; ~1.5Kg fluid; ~1Kg kit; ~1Kg for tools and food… ~95Kg all in.

    25/32mm GP5000 tyres. In easiest gear up that steep bit and plenty of other bits that day, 34/34, the challenge was completing the climb rather than getting near my March time that day.

    jonnyboi
    Full Member

    sounds like you need best bike split

    https://road.cc/content/tech-news/225123-cycling-app-week-best-bike-split

    5lab
    Full Member

    I everested my local (road) hill so know it fairly well.

    On my touring bike I can get up it, flat out in just under 6 mins. On my trail bike the best I can do is 8. The bikes weigh the same.

    Power loss on a slow effort may be a smaller percent, but you will lose loads off-road with an off-road bike compared to a (probably fairly efficient) road attempt.

    thegeneralist
    Full Member

    Is this any help, my gentle paced ride up Road To Hell? 

    Problem is that is both up and down, with a few other hills added in. I really need a segment that is just up.
    N9 idea how to set up a segment.

    thegeneralist
    Full Member

    On my touring bike I can get up it, flat out in just under 6 mins. On my trail bike the best I can do is 8. 

    Bloody hell, that’s a 33% difference. Eek

    igm
    Full Member

    Singlespeed it in an appropriate gear for 10%.

    Freewheel down

    Lighter and more efficient.

    slowoldman
    Full Member

    The ClimbbyBike Calculator might give you some idea.

    markgraylish
    Free Member

    Anyway has anyone got any data on a ( preferably steep) hill that they’ve cycled, know their average measured power on that hill, and the height of that hill. ( and how fat they and bike are, natch) 🙂

    What are you expecting to gain from this?
    I’ve got a couple of rides on Strava up a ski hill with a power meter if you want to look them up (just short of 1000 meters of constant climbing in ~12km)
    No idea how they’d help you though as you have no idea how hard I was pushing!

    n0b0dy0ftheg0at
    Free Member

    @thegeneralist You can change the size of the “analysis” area very easily on pc with a mouse, holding down left button when on edge of grey area on the route profile, having clicked any segment bar under the route profile. Just under the profile, it tells you the distance, average gradient and elevation gain of the highlighted area. So for my link earlier, 0.3 miles; 285 feet; 15.1%.

    convert
    Full Member

    The ClimbbyBike Calculator might give you some idea.

    That’s a good starting point. I’ve used better ones than that in the past when I cared more about these things. The power it says you’d need to put out to do a 25mile time trail in an hour is very high so suspect it set up for a very sit up and beg position. Rolling resistance is substantially higher off road though.

    It’ll certainly be quite a challenge. Biggest issue will be choice of hill – avoiding any hill with steeper sections taking you beyond comfortable but crucially as smooth and tech free as possible all the way up – both those will be the killer features. You’ll also want to be able to sit in a gear that gives you a sustainable efficient cadence with a nice clean chainline. I think I might be looking for a hill with an average gradient of less than 10% – I suppose the perfect location would be a loop with a 7% up and a rapid 10+% down.

    markgraylish
    Free Member

    I suppose the perfect location would be a loop with a 7% up and a rapid 10+% down.

    I thought the Everesting rules did not permit loops…

    convert
    Full Member

    I thought the Everesting rules did not permit loops…

    Got to confess I didn’t realise it was a ‘thing’ with rules – just thought it was a vague concept.

    Again, ignorant of the rules – is it from sea level or from Everest base camp equivalent.

    5lab
    Full Member

    Again, ignorant of the rules – is it from sea level or from Everest base camp equivalent.

    sea level – aka 8848 meters. unless you’re going for 10k or the double 😉

    if you’re not racing up I don’t think chain line makes much of a difference. not needing to shift gears or travel excess distance are probably bigger priorities – a 7% hill would mean an extra 40km of riding uphill vs a 10% hill

    thegeneralist
    Full Member

    I thought the Everesting rules did not permit loops…

    True, unless you are forced to by one way roads/ trails.

    TBH though I’m not arsed about the everesting rules which were clearly devised for road Es.

    My aim is to find a downhill that ” needs” a mtb for the descents, with an off road ascent nearby.

    I don’t think there exists a trail that needs an mtb to descend * but that is cycleable up **

    Last time I attempted Minton Batch but even that was way too hard up without constantly going into the red. And also there’s loads of it which is far too shallow gradient to gain substantial height. We did 20 laps of it but then binned it ar about 3am as I realised it was going to take at least 34 hours. ( we had to buy a new tyre as well and my BB fell apart too!)

    Whinlatter final descent looked excellent, with a great fireroad uphill right next to it. But unfortunately the descent was so smooth and easy that it would be fine on a gravel bike.

    I’m going to have a look at Whinlatter south, as I seem to recall it is rougher.

    * multiple times at a speed commensurate with covering 180km

    ** multiple times after having already cycled up to 180km!

    continuity
    Full Member

    @thegeneralist

    I think you might be underestimating the impact of having to ride a technical downhill for 8000m on top of the climbing.

    I don’t think there exists a trail that needs an mtb to descend * but that is cycleable up **

    Plenty of those around – usually natural, loose but wide, like Pin Dale; a bit too much for grovel bikes but ideal on an xc bike.

    thisisnotaspoon
    Full Member

    Bloody hell, that’s a 33% difference. Eek

    Off-road it’d be even worse, My rules of thumb for route planning are

    16mph on a road bike
    13mph on a gravel bike
    10mph on an mtb

    Based on non-technical terrain.

    That would suggest that the efficiency is nearer 50% off-road (so 33% is lost in the bike and the remainder is to the ground), so 167W is really >300W.

    You’d be better off doing a test yourself with the right bike/ground conditions and see how much you can do in ~3 hours.

    And compare that to whatever Zwift tells you you can currently achieve. I presume the ultimate point of this question as you don’t have a power meter is “what power do I need to average on Alpe du’Zwift/Mt Ventoux in training”?

    I don’t think there exists a trail that needs an mtb to descend * but that is cycleable up **

    Don’t underestimate it. The local hillclimb champion/nutter tried an Everest and bailed because he’d chosen a sensibly steep hill around 10% that suited him, but descending was giving him blisters from braking, and that’s on the road!

    thegeneralist
    Full Member

    What are you expecting to gain from this?
    ….
    No idea how they’d help you though as you have no idea how hard I was pushing!

    I want to know the average power that your power meter read over that segment. And compare that with the theoretical power output ( height gained x g x mass)/ time

    The bit you may have missed is the request fif someone with a power meter. I’m not interested in the strave calculated power estimate, just in the measured power at the cranks.

    Did you have a power meter on this segment? If so them then I do know how hard you were pushing.

    thegeneralist
    Full Member

    Plenty of those around – usually natural, loose but wide, like Pin Dale; a bit too much for grovel bikes but ideal on an xc bike.

    I disagree. There’s no way I could ride up pindale more than half a dozen times max. Doing a single dabfree ascent of it puts me well into the red.

    Hell, I seem to recall you didn’t even clean it once at the weekend there 😉
    After 20 ascents you’d be walking almost all of it. 🙂

    convert
    Full Member

    The bit you may have missed is the request fif someone with a power meter. I’m not interested in the strave calculated power estimate, just in the measured power at the cranks.

    I know it’s a mountain bike forum so maybe it’s obvious, but the bit that’s missing from your request is that its by someone on a mtb on an off road section. And then a report on the ground conditions of that off road section. A steep hill on a road bike with a power meter will be pretty useless to you.

    ampthill
    Full Member

    This guy does what you are describing and might therefore might be a useful source

    “Everesting – the act of climbing the total elevation of Mount Everest, 8,848m, in one ride on a bicycle. At the Forest of Dean; this equates to 82 laps, a fireroad climb rises 108m followed by a technical off road descent back to basecamp. Henry, a man with the drive and fortitude (and some might say insanity) to take on this epic ride from the early hours to the late night, rose to the occasion.
    Sit back and grab a drink – this one’s a good one!”

    slowoldman
    Full Member

    Rolling resistance is substantially higher off road though.

    Ah, I hadn’t spotted it was offroad.

    thegeneralist
    Full Member

    the bit that’s missing from your request is that its by someone on a mtb on an off road section. And then a report on the ground conditions of that off road section. A steep hill on a road bike with a power meter will be pretty useless to you.

    I agree that it’s not perfect by any means, but I don’t think it will be that different for the following reasons:
    I plan on finding a pretty smooth forestroad to do it on. They vary hugely in surface and I totally agree that a bumpy one ( like Pindale, though its not in a forest 🙂 ) would be totally different from a road.
    I will be going ridiculously slowly, ~4mph, so I reckon that the gravity fight will be by far the biggest factor. And that won’t change much between an mtb and a road bike

    Will have a watch of that video

    convert
    Full Member

    I think it would be enough different to render the data pretty useless through a combination of different bike, tyres and terrain – though as you say you can mitigate that a bit by making the off road as close to onroad as possible. There is however a reason why people above are quoting the different times/speeds for their touring/gravel and mtbs. If you are a zwifter with a smart trainer you’ll have an idea of this already, but in the real world with a power meter 20 watts average is like a full season of training difference so the difference between terrains will be similarly fundamental.

    prontomonto
    Full Member

    This is an interesting one.

    I did a comparison: offroad climb (Strava). Mix of firm grass + rocks, not doable on a gravel bike. 7% gradient, XC bike with XC-ish tyres. mgh calculation gives 152 W for 103 m elevation difference (82kg rider+bike+gear). Power meter says 216 W.

    For comparison, a road climb showed 5% difference between power meter and calculation.

    thegeneralist
    Full Member

    Bloody hell prontomonto thats exactly the type of thing I’m after. 🙂

    So you’ve got a power meter on your mtb. Cool.

    So 33% difference on the mtb.

    prontomonto
    Full Member

    I looked at a few more climbs. Even on mtb, tarmac climbs generally agree within 5%, power meter vs calculation.

    Off-road, I see about 10% extra power needed on smooth fireroad, up to 50% extra needed on a technical climb like the previous comment – it obviously is very much terrain dependent.

    prontomonto
    Full Member

    Also I think on a steep hill your speed is low enough to ignore wind resistance, but this does not apply if there’s a strong head or tailwind. That could make a big difference.

    DanW
    Free Member

    You are looking at this backwards. Your target power will be whatever Z2 is for you. Increasing that dramatically will take many months or longer. Gearing and hill should be chosen to allow you to stay in Z2. Time will be what it will be and I guess that is the part you want to estimate to see if an attempt is on.

    I ride with a power meter and as others have said MTB tyres are pretty inefficient and terrain makes a massive difference.

    As a ballpark I have a 1.1km, constant 10% gradient road (ie not taking in to account rough, loose or sapping muddy surfaces) near me. It is the perfect constant hill for equipment/ fitness testing.

    With fastish MTB tyres like Bontrager XR1’s/ Ray + Ralph/ Thunderburts/ etc, set up with normal MTB pressures, I need to put out around 240W just to keep moving up the road. I am mostly around 70kg with a ~9kg bike. Dawdling at that power takes 8:30 for the 1.1km road hill. Power up to 250-260W and it takes around 7:50. 290W gets me to about 7:00. 350W takes the time down under 5:30. Those numbers are a bit all over the place but I’ve ridden this hill more than 150 times so have a fair amount of data on a 10% gradient road of decent length.

    If you add in a rougher surface then another 10% pretty constant gradient 5 minute hill I have nearly required 270-280W just to keep moving. That is a massive chunk extra. I am easily over 300W to feel like making any progress and it takes too much out of me to do anywhere close to an Everest amount!

    More “all around” tyres like Bontrager XR4’s add about 20W to the power needed to hit those same times. That is really hard to overcome in fitness gains so don’t underestimate going for the fastest tyres possible. Conti Race Kings maybe?

    I am also lighter with a lighter bike so add some more effort on top.

    It will probably be a little bit of a hard ride 🙂 Very few people have done an off road Everest, especially climbing anything other than smooth fireroad

    thegeneralist
    Full Member

    You are looking at this backwards. Your target power will be whatever Z2 is for you. Increasing that dramatically will take many months or longer.

    Yep. I keep meaning to work out what my zone 2 is

    Gearing and hill should be chosen to allow you to stay in Z2.

    I’m sort of planning to adjust speed to stay in zone 2

    Time will be what it will be and I guess that is the part you want to estimate to see if an attempt is on.

    Yep. Totally agree. That’s what I’m doing, trying to get a ballpark figure. On attempt 1 I was pretty surprised and disheartened to find I was [ effectively not ] on course for 33+ hours. I’m now significantly less fit and so want to get some idea of what I’m looking at without a 2 hour diversion to a bike shop and with a much more optimised hill.

     I need to put out around 240W just to keep moving up the road. I am mostly around 70kg with a ~9kg bike. Dawdling at that power takes 8:30 for the 1.1km road hill.

    Which equates to about 173 theoretical Watts. Interesting that it’s actually taking you 39% more than that

    don’t underestimate going for the fastest tyres possible. Conti Race Kings maybe?

    Was planning Ikon and Rekon both well worn. But 2.6″ ☺

    DanW
    Free Member

    Do your theoretical Watts include MTB tyres at MTB pressures? I wouldn’t be surprised at all if that accounts for the large difference, even on a road.

    The zones thing can be debated but I’m sure you ride more than the rest of us to know what kind of hill and gearing keeps you in a “all day” effort level.

    The problem with trying to adjust your speed to stay in the all day effort “zone” is the situation may dictate that you physically can’t without coming to a stop. The tyres/ ground conditions/ chosen hill/ wind/ etc may mean that it just isn’t possible to stay in Z2 (for arguments sake). The interesting thing about riding MTB with a power meter is you quickly realise why it feels so damn hard most of the time- it is hard! 🙂

    I missed out time as well. To save you getting the calculator out the speed range is ~8km/h at ~240W to ~12km/h at ~330-350W.

    Like I said, add in a loose surface, some mud and more normal MTB tyres and those power number quickly jump up.

    I think your tyres could be changed to save you a heck of a lot of effort. Maxxis never seem to test fast in the various lab tests (debatable how well that translates but at least all are tested the same as some kind of baseline) and the 2.6 size is going to be sapping energy. Conti Race Kings pumped up as hard as you can get away with and still have the climbing grip you need will be a whole load of free Watts.

    thegeneralist
    Full Member

    The zones thing can be debated but I’m sure you ride more than the rest of us to know what kind of hill and gearing keeps you in a “all day” effort level.

    The irony of it all is that I have never really kept my effort restricted to a sensible “All day ” effort. When I did my triple century I did about 40 minutes of it desperately trying to hold the wheel of some random bloke i met. Then in the evening it ebbed and flowed with me going well into the orange.

    Likewise, similarly to what Dan said, when I did Lord of the Loops I was damned if I was pushing up hills if I could ride them instead, so I went well into the red at various points.

    Ditto Minton Batch, the first few times I tried to clean the climb and so got gubbed.

    The sad thing is that my body is no longer capable of that sort of riding style. Even on a relatively short ride last weekend I was completely gubbed at the end because I had overcooked it trying to clean Cut Gate.

    So if I am to have any chance of this, as you say, I need to work out what my zone 2 is and stay in it. Which is something I have never done.

    Just done a quick Google, and based on a highest seen heart rate of 171, and age 50, it reckons::
    Zone Feel Heart Rate
    1 Easy 116 – 126
    2 Steady 127 – 138
    3 Moderately Hard 139 – 149
    4 Hard 150 – 160
    5 Very Hard 161 – 171

    Yesterday I did two 20 minute sessions trying to keep power constant. 165 Watts had me at 115bpm.
    Then on the second session I was around 225W I think at around 135.
    Before looking up the table above I had assumed that Z2 would be sub 120 bpm for me. Quite surprised that it suggests 130ies. So is the theory that I should be able to push Z2 almost indefinitely? It certainly didn’t feel like it. 🙂

    Will try again later in the week

    Thanks for all the awesome input all.

    n0b0dy0ftheg0at
    Free Member

    Just remembered this old climbing calculator and it has options for mtb and bar ends.
    http://bikecalculator.com/

    As regards heart rate zones, I’m struggling to remember when I signed up at https://intervals.icu/ (donate-ware site by fastfitnesstips I think) earlier this year, whether it automatically looked at my recent data history to put my LTHR estimate at 170 or if I manually set it to that.

    BadlyWiredDog
    Full Member

    Which hill are you thinking of using? Just wondering.

    I also think you’re maybe overthinking the zone thing a little. Essentially you need to start more gently than you think and take it from there – think easy conversational pace.

    And in terms of timing, go and do a trial run or five up the thing at that pace and extrapolate from there woudl be my take. You also need to put some thought into fuelling and logistics, road Everesting means you can leave a car or van somewhere handy and fuel from there, off road it may be more complicated depending on where you do it.

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