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 few 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.

Self fulfilling. Tak

Molegrips, yep, your assumption is right

This is as retarded as a wheelsize debate.

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 😀

More like;

Do you own a map holder?
Do you have a beard?
Do you think Enduro is only marketing but you’ve never raced one?
Have you ever owned a pair of Ron Hill Tracksters?
Do you still use tubes?
Is your stem longer than 50mm?

If so you probably ride a hardtail and you suck.

Same ride, Tarmac commute, 10 miles

Allez 29 minutes
Spesh Globe hybrid, 31 minutes
Inbred 40 mins
Enduro 45 mins

I put it mainly down to suspension.

If so you probably ride a hardtail and you suck.

Every time you post I’m a little more saddened by how pathetic and juvenile you are.

JCL, other than the map board, thats me 😯
Impressive rider stereotyping skills…

Every time you post I’m a little more saddened by how pathetic and juvenile you are.

Every time? Come on!

Cheer up. Don’t let that hardtail get you down.

Same ride, Tarmac commute, 10 miles

Allez 29 minutes
Spesh Globe hybrid, 31 minutes
Inbred 40 mins
Enduro 45 mins

I put it mainly down to suspension.Might help if you mention which have suspension. I suspect tyres will play quite a big part.

Why do all debates on St regress to pissing competitions?

Surely not all hardtails are equal, not all fsers are equal, not all terrain is equal and not all people are equal thus there is no clear cut ‘better’ , just what you like.

I only ride full suss and can do it quick and for a long time, from my vantage point. I have friends who do the same on hardtails.

Arguing physics doesn’t really progress anything really as there are probably too many factors to take into account.

Hardtail riders should be force to drive cars without rear suspension to help them understand the dificencies.

you guys

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

what utter trot
The heat comes from air compression
If the Fox is hotter then its absorbing more bump energy
PV = nRT

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

I thought the argument was that the FS bikes were more efficient the lighter the rider, or did something happein inthe intervening pages.

Hardtail riders should be force to drive cars without rear suspension to help them understand the dificencies.

Based on your comments in the chainstay thread, you should ride a hardtail to understand your own.

what utter trot
The heat comes from air compression
If the Fox is hotter then its absorbing more bump energy
PV = nRT

[gameshow host voice]

YOU SAY THE IDEAL GAS EQUATION. OUR SCIENCE SAYS…………….

EEEHHHHHHEERRRRRRRRRRR, ohh dear

[/gameshow host voice]

The equation you were looking for needs gamma (y) = Cp/Cv. for air this is about 1.4 as it’s mostly nitrogen.

PV=nRT will still be kinda true (air’s mostly diatomic, so isn’t actualy very ideal), but you could simply halve the volume and double the pressure, what actualy happens is you halve the volume, and both the pressure and temperature increace, Cp/Cv tells you how far from ideal you go.

T2/T1 = (P2/P1)^(1-(1/y))

Although that still doesn’t tell the whole story as if the temperature goes up you can’t actualy know the new pressure becuase it’s not just dependant on the new volume.

thisisnotaspoon

🙄 Not you again
That equation is more then adequate to demonstrate where heat build up in a shock comes from – i.e. not from the seals that are designed to be as friction free as possible.

So shut your science book, take you’re ideal gasses and get back in your box.

That equation is more then adequate to demonstrate where heat build up in a shock comes from – i.e. not from the seals that are designed to be as friction free as possible.

No it’s not, in an isenthalpic system T could (and for an ideal gas would) be be a constant, it’s the non ideality that leads to the gain in heat under compression. T and V are opposite sides of the equation, if you reduce the volume by a half if you wanted to compensate for that with the temperature the system would have to halve in temperature, not increace.

Once compressed some of this this heat is then conducted through the walls of the shock as the system is not isenthalpic. The shock then de-compresses, the gas cools by the same process it heated up, but as it’s lost some heat while compressed the gas actualy ends up cooler than it started.

The heat in the shock comes from the damper doing work, and a small ammount of seal friction. None of it comes from the gas being compressed repeatedly.

ok – so now that we all agree that the shock heat is a red herring (even if molgrips still doesn’t understand why*)… 🙂

Surely someone’s done a test? A basic test would be someone with power meter cranks riding the same course on different bikes. You’d end up with time taken and power used.

My feeling is that weight being equal, the FS is more efficient.
But as we’re still not at the UCI minimum limit, weight is still a critical factor.
Also – that psychologically, the direct, instant feel of a hardtail is important.

* my point isn’t that it’s negligible, it’s that it’s irrelevant. A shock at 1000-degrees still wouldn’t show that pedalling energy was being lost. Nor does the point of ‘any power loss would reveal itself in heat in the shock’ hold water. Power loss could be in the form of up/down movement – that up/down movement doesn’t have to result in a shock getting warm depending on the frequency. It could even be downward movement (with a high pivot position and chain growth) which could be useful, or not, but it still energy transfer that wouldn’t heat a shock.

ok – so now that we all agree that the shock heat is a red herring (even if molgrips still doesn’t understand why*)

Molrips does understand it, I’ve been understanding it all along!

A shock at 1000-degrees still wouldn’t show that pedalling energy was being lost.

It would – because where else woudl that heat come from? The only input to the system is your pedallin energy.

Power loss could be in the form of up/down movement

Yes. And where does the up/down movement come from? From forward momentum. And where does that come from? Pedalling.

A basic test would be someone with power meter cranks riding the same course on different bikes. You’d end up with time taken and power used.

Yep, but that’ll depend on various factors. If you mash a big gear, out of the saddle, with a squishy shock, the results will be very different to if you’ve put 500 psi in your shock and you spin along at 100w. This is why it’s not a case of ‘x% better’.

It would – because where else woudl that heat come from? The only input to the system is your pedallin energy.

What about if you’re coasting over rough terrain?

ok – so now that we all agree that the shock heat is a red herring (even if molgrips still doesn’t understand why*)…

Well it does get, hot but it’s the damper doing it, not the air, the air gets hot because it’s arround the damper. The dampers whole purpouse is to absorb energy and dissipate it as heat.

My 2p on it would be that pro-pedal and the like are increacing the force and decreacing the distance the shock/suspension moves, so possibly the shock is absorbing just as much energy with the PP on or off? What makes efficient suspension is the chain growth and rearwrd axle path working against the riders weight shift to effectively reduce the distance the suspension compresses to zero, the force is stil the same, but like leaning agaisnt a brick wall, no energy is actualy transfered as there’s no movement. If the suspension bobs then energy is being wasted in the shock.

I think molgrips is right, the bike loses some kinetic energy over the bumps which gets disipated through the shock. But this is probably offset against what would have been lost by the bike just jumping up and down if you allowed a hardtail to just slam into the obstacles, and the fact the suspension allows the rider to pedal at a relatively constant power all the way up makes the rider more efficeint.

What about if you’re coasting over rough terrain?

To coast, you have to be moving to begin with. How did you get moving? You pedalled…

TINAS yes that is basically exactly what I am saying. The HT in theory would lose some forward momentum and convert it to upward momentum, which then ends up downward.. but that energy ends up being bashed into the floor so is still lost.

To coast, you have to be moving to begin with. How did you get moving? You pedalled..

If we’re being picky then not necessarily, plenty of trails where gravity does the large majority of the work, and there the suspension is most definitely working on absorbing and dissipating the energy from hitting bumps, not from pedalling*.

*yes, unless you started at the top of the hill and just rolled in you pedalled at some point to get going, but we’re talking about a situation where you coast into or through a bumpy section, and that’s exactly where this becomes relevant.

If you input speed (from pedalling) is the same for the hardtail and the full sus, and you add no more pedal strokes the chances are that the suspended bike will have a greater exit speed, all other things being equal, if you factor in some extra input from the sus bike due to being able to pedal better in the rough stuff then even more so.

Obviously this is idealised and the skill of one rider could overcome the suspended advantage of a lesser rider.

If on the other hand we’re talking a less bumpy course in general but with rough sections, then your losses on a hardtail on the bumpy bits would likely be outweighed by gains on the smoother and sprintier bits, but not always that clear cut.

I’m very much in the ‘horses for courses’ camp, it depends on many factors, not least of which are the terrain and the rider. There is no ‘best’ just ‘better in situation X for rider Y’

I race XC either fully rigid, hardtail, or full sus depending on the race (and often my mood!).

I race Enduro on full sus, but have been tempted to enter in the HT category as well from a fun POV and to have a different challenge, I dont doubt that ill be slower if I do, but I bet I’ll have a giggle doing it.

To coast, you have to be moving to begin with. How did you get moving? You pedalled…

Hang on… so are you now saying that if you pedal, then freewheel through a rock garden and your shock gets warm that it’s doing so because you pedalled previously?

I think the whole thing is a massive red herring, but I’m even more confused by what you’re trying to say!

If we’re being picky then not necessarily, plenty of trails where gravity does the large majority of the work, and there the suspension is most definitely working on absorbing and dissipating the energy from hitting bumps, not from pedalling*.

You still had to pedal to the top of the hill, or get in a van and burn some diesel.

Both pedaling and inputs from the ground end up in energy being disipated from the shock as heat. As i saw it the argument was that:

A hardtail 1 would be 100% efficient in terms of pedaling
2 lose lots of energy being thrown up and down over bumps

A FS bike 1 would not be 100% efficient in terms of pedaling
2 would dissipate some up/down movement as heat, but this would be less than the hardtail was wasting,a nd largely offset the pedaling losses, its sacrificing some energy to save a lot.
3 would go faster simply because the rider could put down more power more of the time

Poits 1 and 2 are why the FS bike is quicker over a rough downhill course with no pedaling, if there’s no pedaling then theres no pedaling losses, so the FS bike converts more of the gravitational potential energy into speed. But on a smooth climb or trail the HT would be faster as there’s no up/down movement from the ground. 3 isn’t about efficiencty but is about speed.

So a FS bike is faster if pedling losses < the extra pedaling thats possible + energy saved over bumps

A HT is faster if pedlaing efficiency gains > losses form lack of ability to pedal + losses from bumps

Just think, if you all spent as much time and effort actually riding as you do pontificating on here how much better a rider you might be! ?
It’s as much about the rider as it is the bike … now log off and go for a ride!!!

Just think, if you all spent as much time and effort actually riding as you do pontificating on here how much better a rider you might be!

nah, I’m perfect already and besides I can’t ride while at work on lunch break, better to argue on the internet 😉

It’s as much about the rider as it is the bike … now log off and go for a ride!!!

I think that we were all pretty much in agreement about that anyway, but the discussion was around how much and what effect the bike has.

And just because we don’t/can’t know for sure, doesn’t mean it isn’t worth talking about.

Now go for your ride and think about it, or don’t, just enjoy your ride 🙂

Got a bit lost in all the technicalities of kinetic shock heating physicsy type stuff.

My two penn’orth is that on the standard “trail centre” red run my 26″ 120mm hardtail is faster than my 140mm 650b FS. This is partially due to weight, but I also feel that the steeper geometry of the hardtail is a factor, as is the fact that unlike the FS it is less likely to wallow a bit in dips, the lack of suspension means that it pushes through a bit more. There is nothing scientific behind this, just lots of runs on the same tracks with the two bikes.

In truth factors such as weight, geometry, ground conditions will all play their part. For sure my FS is faster on crazy steep, rubbly descents in the Lakes. And there’s a negligible difference in climbing times on those runs as the bikes on my back for most of them anyway 🙂

It’s as much about the rider as it is the bike … now log off and go for a ride!!!

I suspect most of us are at work, hence precluding that!

“ So a FS bike is faster if pedling losses < the extra pedaling thats possible + energy saved over bumps

A HT is faster if pedlaing efficiency gains > losses form lack of ability to pedal + losses from bumps “

which is what i said three pages ago pretty much and also explains why a cx bike (which is after all a super efficient hardtail)is fastest on a smooth offroad climb

I find my hardtail puts the fear back into MTBing, whereas the Full susser allows me to ride Gnarlier stuff without killing myself. Hardtail slower on technical climbs and descents but faster if more smoother terrain, both bikes weigh the same at 30lb.

Hang on… so are you now saying that if you pedal, then freewheel through a rock garden and your shock gets warm that it’s doing so because you pedalled previously?

Yes. Of course – where else would the energy be coming from? The sun?

However yes I agree it’s a red herring in practice, but we are now talking about physics. Physics which don’t matter in the real world 🙂

Yes. Of course – where else would the energy be coming from? The sun?

The wheel moving up and down and compressing the shock. 😕

I fail to see how rider in put can have a delayed impact. What if you remove your chain, catch a chairlift to the top of the hill, then ride it down. Is it the pedalling around you did several hours hence!?

Why do pumps get hot incidentally? Is that the same thing, or friction from the seals?