[Closed] Power loss on full sus' bikes compared to hardtail's

Anecdotaly I reckon my rigid bike gets away with a 2t bigger chainring than my HT, and about 6t over the (32lb #enduro) FS.

So assuming the rigid bike is 100%, the HT is about 95% and the big FS about 80%. IME an efficient ~100mm FS would be quickest of the lot up any kind of long rough climb, the added traction and unstopable-ness adding more speed and energy saving in not having to constantly lose speed and re-accelerate over rocks/steps/ruts makes up for the pedaling losses.

120mm proabbaly doesn't climb much worse (less eficient, even more traction), probably past the peak but no worse than a hardtail, just different, but....

150mm+ bikes tend to be designed to be great at being shock absorbtion first, and just enough comprimise to allow them to pedal up to the top. Similarly some 120mm bikes are aimed at being technical 'XC 'bikes so are close tot heir 100mm cousins, and others as short travel 'enduro' so only pedal marginaly better than their 150mm+ siblings.

Hmm.. what I said about FS only applies if it's rough. If it's not, then the lower weight would be a benefit of HT.

Isn't that at odds with my argument you refuted about riding on the road? If you're losing negligle power (in your words) surely there's negligible difference? The shock gets hotter on a really rough climb, which again is completely at odds with your 'if the shock doesn't get hot you're not wasting power' argument.

Having spent years riding FS and gone back to hardtail, you can't argue that if you get out of the saddle for a sprint up a climb, irrespective of rough or smooth, a hardtail feels far more responsive. Not having a power meter on my bike I can't quantify efforts, but thinking >500w. If you don't ever climb like that (and plenty don't) then you're likely losing what is the single biggest area where a hardtail excels. I'd seriously consider going back to a 29er FS if I could get one without too much of a weight penalty, but to say that x or y is faster just isn't true.

Isn't that at odds with my argument you refuted about riding on the road?

Well no because in your scenario the weights were equal. In real life a FS will be heavier.

You are right about the sprinting of course. Feels much faster, but is it?

Also, there's FS and FS. My XC racer only has 63mm travel, you barely notice it. My results speak for themselves 😉

The shock gets hotter on a really rough climb,

Wow, that surprises me.. Still.. The question is, is the energy lost made up for by the other gains?

Thanks for the comments regarding my fatigue post chaps.

2 days in a row that I'm on the same page as you RP, should I be nervous 😉

It is indeed the 'link up' sections where I find the fatigue kicks in. Those rough road / landrover tracks type of thing. Unfortunately where I ride (often dictated to by time/opportunity) the fun singletrack is linked by either road sections or towpath or cross country tracks already mentioned.

I don't want to drag this in to a wheel size thing or a what bike for me thing but I do think I need to persist more with FS. I saw a lovely looking Epic for sale yesterday on clearance. The thing is I'm not excited by the prospect of owning a 100mm xc bike. I'm drawn to the glamour of the longer travel stuff I see being ridden on YouTube / Vimeo vids in midweek mini movies! After years working in marketing I should know better!

LOL .... whoever said "In short, hardtails are shite.

#science " obviously can't ride for toffee

Full sus riders who eschew hard tails are shite riders coz they don't have the proper riding skills to get the max out of the bike

We know who they are. Typically male, carrying a few too many pounds, more money than sense thinking that buying the most expensive kit makes them a better rider and they spend more time pimping their bikes in the car park than riding on the trails

.....recognise yourself?

@markrh, the trails at Cannock were specifically designed to suit hardtails hence the reason you find your faster. in fairness we don't like to talk about it too much for fear of impacting on local bike sales.

I'm drawn to the glamour of the longer travel stuff I see being ridden on YouTube / Vimeo vids in midweek mini movies!

I own an XC race FS and a 7" travel Patriot. After owning the latter for years it is now finally dialled in, and let me tell you - it's [b]not[/b] just marketing.

It's an absolute blast on my local trails. I can't get over how much fun it is. Ok so I'm not doing 30ft gaps, but I'm going way faster and getting more air than I have in my life. Brilliant.

So good that I am going to use it as my everyday FS and I'm changing the 5 for.. a fully rigid 29er 🙂

Everyone talks about pedal bob as a disadvantage on FS, but what about all the energy absorbed effortlessly by the shock when riding over rough ground. On a HT that's energy your legs are having to absorb which leads to fatigue too. So really depends on the ratio of rough v smooth trails as to which would be fastest. If you take somewhere "flat" like Thetford you might think a HT would be fastest, but for me at least I'm quicker on FS because of the endless rolling bumps.

I suspect for most average riders on an average trail a modern short travel FS would be fastest overall in most cases. Especially on a longer ride.

Thetford is a strange case. When I did a 100km there I took a longer travel fs and set it up with really slow rebound, so I could stay sitting down and pedalling through the bumps. The suspension compressed in the dips and extended nice and controlled on the ups so I didn't get chucked into the air. Worked nicely too.

2 days in a row that I'm on the same page as you RP, should I be nervous

You certainly should 🙂

I know you don't want a what bike thread and that we've already done it on the other thread, but I wonder if this is where the "nu-skool" 29ers will shine. Bigger wheels for efficiency over rough ground, geometry for the fun bits and just enough suspension to get by.

[*]The shock gets hotter on a really rough climb,[/*]

Wow, that surprises me.. Still.. The question is, is the energy lost made up for by the other gains?

Bumps don't generate energy. They just lie there looking all mean and moody. If you are climbing then the only source of energy is you. If some of that energy is being used to heat the shock then it isn't being used to propel you forwards. Of course, without the suspension it may have been "lost" somewhere else.

So what's the difference between a warm shock and the job a shock is meant to do in normal operation - i.e absorb energy?

I still don't get this shock getting hot thing.

What I meant was that a warm shock would indicate that a significant amount of energy is being lost, since that's what we are talking about. However, njee's shock gets warm so maybe it is!

But a hot shock does not mean that pedalling energy is being absorbed.

Indirectly it does - the heat in the shock is being subtracted from your kinetic energy, which in turn comes from pedalling.

So what's the difference between a warm shock and the job a shock is meant to do in normal operation - i.e absorb energy?

Nothing - it's absorbing energy that's come from your legs, and is turning it into waste heat.

I still see it as a complete red herring.
If you were riding along a completely flat road, and your shock got hot, then I would see the theory as having merit, but a shock functioning over rough ground isn't analogous. It could well be reducing the amount of energy needed to overcome obstacles.

If you were riding along a completely flat road, and your shock got hot, then I would see the theory as having merit,

What do you think my theory is?

I'm saying you DON'T lose much energy from suspension.

roverpig - Member

You certainly should

I know you don't want a what bike thread and that we've already done it on the other thread, but I wonder if this is where the "nu-skool" 29ers will shine. Bigger wheels for efficiency over rough ground, geometry for the fun bits and just enough suspension to get by

I've been compared to a lot worse so don't worry! Anyway you seem like a decent enough chap.

True enough. The chaps at my LBS recommended a Camber Evo to suit my needs. The only thing that put me off (other than the purchase of my Solaris just a few months ago) was the fact that the 26er FS I have and rarely 'go to' is indeed a Camber 😳

That's the joy of the internet. None of use are who we appear to be online 🙂

What is it that you don't like about your 26" Camber?

What do you think my theory is?

I'm saying you DON'T lose much energy from suspension.

I just think that shock temp is irrelevant when it comes to judging this.

But it probably had something to do with JCL agreeing with you - I like to take an opposing view to anything he says 😀

I'm saying you DON'T lose much energy from suspension.

Exactly. You lose some energy in unwanted pedal bob (not much of an issue these days anyway with efficient geometry, platform shocks, lockouts etc) and you gain some in not having to use your legs to absorb bumps in the trail. There's also a small weight penalty of course in like-for-like bikes.

Personally I'm quite happy to carry 6" of plush and reasonably efficient rear travel around most trails. Might not be the fastest solution on most UK trails, but easy on the old bones and still a lot of fun - especially on the downhills.

I just think that shock temp is irrelevant when it comes to judging this.

Think you are getting hung up on this point for no reason. All he said was that your shock doesn't get hot simply from pedal bob, hence 'probably' not a lot of wasted power. But yes, it is irrelevant as even a loss of say 10 or 20 watts might be significant on a long ride. But then of course there are benefits of FS too.

@ RP.
I couldn't say I don't like it as such. I just preferred the 29er HT's to ride. Firstly a Carve Expert and more recently the Solaris.

That pushes it towards a wheel size thing but can't help but feel that is only part of the equation. I like the propedal, for example, for smoother sections but then find it isn't active enough when hitting a rutted / jarring section.

It does have a lever for 'on the fly' adjustment but sometimes you just want to ride, others the terrain might change frequently (ie parts of a towpath) plus I find with gloves on I once moved the rebound dial at the same time which was my fault but annoying nonetheless.

On the plus side, the mods I've made 50mm stem instead of stock 90mm and slightly wider bars have been great. The stock tyre set up is excellent too.

Given that "work" is being done within the shock then it is likely to heat up but since the shock has a small volume relative to its surface area then this heat will dissipate quite quickly.

I think you'd need to look at a bike through a thermal imaging camera shortly after it's been ridden down something like a World Cup DH course to see anything significant change.

I don't know what people are talking about regarding XC racers locking out rear suspension. Sure they usually run a remote lock-out but Niño wasn't using it much in those last two World Cups he won. You could clearly see the suspension was active on the climbs.

If those guys can win on FS on those limited tech courses then the argument for a hardtail is over. Unless you ride around on bridal ways but that's hardly mountain biking is it.

Hardtails, halfway to cyclocross. Shite.

Has anyone thrown in the use of SPDs and proper pedalling technique to remove pedal bob? 😉 (obviously not as much help when out of the saddle).

My 29 FS feels less fast/responsive than my 29 fully rigid, or my 26 HT I had before, but I can ride further without acheing and hit technical stuff much faster. I feel a nice flexy (steel) 29 HT would be the ideal inbetween, but I'm liking the comfort of the FS right now.

I'm sure there's no one corect answer here though, each to their own and all that.

molgrips - Member

Any power you would lose would have to end up as heat in the shock.

Eh, no, it mostly gets lost in vertical movement.

Eh, no, it mostly gets lost in vertical movement.

good point. If you had no damping at all, then the vertical movement would be increased and yet the spring wouldn't heat up as a result. So yes it's really a red herring. In practice a shock is not going to get hot from just pedalling a bike up a hill.

Yes. Wheel goes up, gas gets compressed, wheel goes down, gas expands. In theory the energy spent pushing the wheel up comes back when the wheel comes back down again. Except for two things:

1) when the gas is compressed it gets hot. Whilst it does cool back down again some of the heat is lost because that energy is conducted to the atmosphere.

2) The damper oil slows the piston down, taking some energy away and turning it into heat.

Njee's shock probably gets warm due to 1 I think.

In practice a shock is not going to get hot from just pedalling a bike up a hill.

THAT WAS MY ORIGINAL POINT!

@NN

I know what you mean about the simplicity of the HT. It's probably what I like best about the Solaris. I just get on it and ride. I've even set it up 1x10 and the fork is always left open, so there is very little to think about. Unfortunately that just means that I have more time to think about how sore my poor old back is getting 🙁

Maybe what you need to look for is a full suss that you don't have to fiddle with. It may just be marketing guff but I notice that Transition talk about their Gidy Up suspension being designed for people who just want to get on and ride and don't want to mess about with flicking switches. So there you go. Get yourself a Smuggler and let us know how you get on 🙂

😀 sounds like a plan RP!

I love my Solaris BTW, also 1x10. Although I'm currently over thinking saddles 😉

You don't have to fiddle with suspension once it's set up. It's never been a big issue for me. Set sag, ride. However if you want to fiddle with it you'll get more out of it.

In practice a shock is not going to get hot from just pedalling a bike up a hill.

THAT WAS MY ORIGINAL POINT!

My issue was that you're using this as proof that FS doesn't waste energy. You then backtracked and said you only meant rough ground, where the shock would be working harder and thus more likely to get hot. I see now how you get into so many stupid circular arguments.

Gah.

First, I said that energy loss was negligible. A possible indication of significant energy loss would be a warm shock. I'd never experienced this, but njee has so I may be wrong.

However given the other things pointed out on here about energy wastage fs might still be more efficient on rough stuff for more indirect reasons.

I'm not after a big hit-athon, relax!

People timing themselves and showing themselves faster on a HT. There may be some element of self for-fulling prophecy here. You expect to quicker on a climb, so the extra effort you think you need to 'thrutch' over a rock or whatever propels you faster up the hill anyway.

There are really very places places a FS has a definite advantage, really long extended flat is rocky sections, where you really can't pedal on a HT, is one that springs to mind.

People timing themselves and showing themselves faster on a HT. There may be some element of self for-fulling prophecy here. You expect

Self fulfilling.

Perhaps. My comments are based on a year of hardtail riding following 3 years of Strava data on FS. Including race courses and casual riding. Not as in going out on a brand new bike and sprinting everything and saying "see, its faster". It's far from impartial, but it really isn't as clear as FS = better. We can all post scenarios where one bike excels over t'other. That doesn't change anything. Different riders will go faster on different bikes on the same bit of trail.

This is as retarded as a wheelsize debate.

I agree with him.

Especially as this was done to death 10 years ago.

There are really very places places a FS has a definite advantage, really long extended flat is rocky sections, where you really can't pedal on a HT, is one that springs to mind.

I assume you mean there are very [b]few[/b] places an FS has an advantage.

I'd say that depends where you are. In some places most of the trails are pretty rocky 🙂

Anecdotally I always feel that I would be faster around the Chase on my 100mm 29er HT than my 26 160mm AM bike.

I race a FS 29er in xc races as I find it quicker for me, it's the traction available when sprinting up climbs that i feel a gain. It's not losing or gaining watts it's getting the watts on the ground that matters.. It's a fairly light FS though, 14lbs lighter than my play bike !

I'd say that depends where you are. In some places most of the trails are pretty

Indeed, and if one was fitter and could just plough through said flat rocky section out of the saddle what's not to say the hardtail isn't still faster there anyway?

Schurter/Kulhavy epitomises it very well. Kulhavy always on FS, Schurter overwhelmingly on hardtail. Plenty of victories each way.

[i]Self fulfilling.[/i] Tak

Molegrips, yep, your assumption is right

[i]This is as retarded as a wheelsize debate.[/i]

Aren't most 'discussion' on here... 😆

Indeed, and if one was fitter and could just plough through said flat rocky section out of the saddle what's not to say the hardtail isn't still faster there anyway?

However fit you are would it not be less fatiguing to be sat down?

But anywy you agree with me - there's nothing in it really.

However fit you are would it not be less fatiguing to be sat down?

This was about power loss, not fatigue. If you can skip over stuff then the power lost bumping through stuff on FS is potentially noteworthy.

Oh and the weight of the rider point is crap too. Pendrel won Worlds in an FS and she weighs 50kg.

The shock heat issue is bunk too. A Float gets way warmer than a Monarch because the seals have way more friction. Smaller negative spring etc.

This was about power loss, not fatigue

In terms of just power loss there should be none. The force on the pedal during one stroke is still transferred to the rear wheel by the drivetrain using the same materials. It's the bobbing, or effect of longer strokes due to the compression of the suspension that causes fatigue.

So, if 'power' is measured on one pedal stoke, there will be none lost at the rear wheel. However if you took an example like a sprint, the 'longer' pedal strokes on the full sis will cause some fatigue due to a possible longer time to complete each pedal stroke.

So, horse's for courses+what ever suits your skill set+ how deep is your pocket= is the most efficient?
Well, i'm glad we sorted that out 😀