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

Look at the results of the XCO World Champs. Only one hardtail in the top 10.

Wasn't a full sus in the top 3 of the olympics xc race? Might have been 650b too.

Wasn't a full sus in the top 3 of the olympics xc race? Might have been 650b too.

Kulhavy won it on a Specialized Epic 29er full sus.

But the xc bikes will have a lockout so they aren't losing any power, just carrying more weight.

The answer is it depends.

fat blokes lose power on full sus.
dont think there is a full susser really suitable for fat blokes.

Any power you would lose would have to end up as heat in the shock. Does your shock get warm when you ride XC? No.

I don't think you would lose speed anyway. If you ride rigid the rough stuff slows you down more than any theoretical energy loss. On a FS some of your forward momentum ends up in the shock; on a HT some of your forward momentum gets converted into up and down momentum instead.

What Molgrips said plus the extra climbing traction, cornering traction and lower fatigue.

In short, hardtails are shite.

Useless to compare an xco bike to a normal susser. They are using things like electronic lockouts now which is why full suss has become an option again. When climbing you can see there's no bob at all.

On a normal bike I can't see how the saddle bobbing up and down as you peddle can be anything but bad.

Do you suppose in a another 20 years, someone will pose the wheel size question?

In short, hardtails are shite.

I'd say full suss bikes (unless they lock out) feel slower up most hills than a hardtail. Much less direct when you stand and pump. Similar when you sit and spin. They're also generally heavier, which doesn't help. Most people would probably make any time lost back up on the downs. I think Ton is right in that the weight of the rider is also a factor.

Useless to compare an xco bike to a normal susser. They are using things like electronic lockouts now which is why full suss has become an option again. When climbing you can see there's no bob at all.

They've been pretty viable for about 10 years now. Some riders use them religiously (Kulhavy) some do so rarely if the course necessitates (Schurter, Absalon), some never do (Emily Batty). Personal preference. One isn't better than the other.

Molgrips I'm intrigued you don't think there's [i]any[/i] power loss? So if you outfitted a V10 with some 23c slicks, and hung some weights on a road bike they'd climb Alpe d'Huez the same? Can guarantee the shock won't be getting warm!

I don't think there's no power loss, I think it's negligible.

Re the v10, I think riding position, wheels and tyres are most of the slowness.

Hence you fit some 23c slicks in my hypothetical test. It's a climb, so negligible aero gains, position needn't be an issue. Frankly plenty of modern road bikes are just as upright anyway!

I think like the wheel size thing you can answer the question for a rider on a course

But as the relative amounts of climobing and different surfaces change you get a different answer

I'm also unconvinced that comparing bike swith the same tyres is fair. It might be that the Fs lets you run a thinner tyre or a higher pressure for the same level of comfort or traction

If I was dumping 10W into my shock is that negligible? What it cause a noticeable heating effect?

Over a shorter course I don't think there is much in it.

But after 3 or 4 hours of riding the full suspension is quicker because the rider isn't so battered about.

And yet marathons (up to and including 24 solos) are won on hardtails.

There is no 'better' or 'quicker', it's not that straight forward!

I am so much faster on my hardtail - and it can't be all down to weight. Although it is a good 9 lb lighter than my full suss, as a percentage of rider + bike weight the difference is bugger all.

On my local trails I always go for the easiest and smoothest ascents and the techy DH. So I don't loose any traction on the climbs. If I have to ascent rocky climbs then the difference is much less maybe even quicker on the full suss.

So yes - depends what your riding.

Use to be that you'd see the FS bikes ridden to please a sponsor and the shock would just be pumped up and locked out so that it was pretty much a HT. Think they are more prevalent now that the shocks are getting better, lockouts easier to use, and everything is getting lighter. Aren't the WC XC courses getting more technical too (maybe why bars seem to be getting wider too.)

Also tend to see more of the men on FS bikes than the women. Maybe any efficiency loss is more significant for the women as a percentage of overall power, or maybe a weight thing or speed down the rocky stuff?

Are you lot talking about pedalling bob, or thekinetic energy lost to the damper?

It's a climb, so negligible aero gains, position needn't be an issue

I think position has a lot more to do with it than aerodynamics.

i think the terrain makes the biggest difference. From my own experience on my local climbs, there's definately a correlation between roughness/ technicality and amount of suspension.

The two local 15 min fire road climbs im significantly quicker on my CX bike than either hardtail or full sus, the singletrack slightly rocky more technical route out of the village, my top few times are all on the full sus, i dont think i could clean it on the cx.

down or along, my anecdotal experience is that im quicker on the full sus, i stay off the brakes more and can keep the power down pedaling easier in the rough stuff on a full sus. once again, flat fireroad non rocky trails, the cx is quickest

got it logged on strava? do a raceshape to see where you are losing time.

http://blog.strava.com/whats-your-best-effort-see-how-it-compares-8480/

It's probably been covered already, round Cannock that might be the case, but up here in Cumbria my hardtail was (with the exception of tarmac) slower and had poorer traction, up, along and down, than my 6" AM full susser. Same rider, same trails, different bike.

I won't be buying another hardtail.

the terrain makes the biggest difference

njee20 - Member

Hence you fit some 23c slicks in my hypothetical test. It's a climb, so negligible aero gains, position needn't be an issue. Frankly plenty of modern road bikes are just as upright anyway!

I've done recent rides on 3 various bikes. All road based all on my 'TT' circuit which is 29km with some climbs/flats

My times are for a Carrera TDF(road rubber), Charge Cooker(commuting rubber), MetaAM29 (Ralphs)

There's 3 mins difference between the 3 bikes overall. Interestingly I make up any gains on the flat section of the TDF, uphill I'm less than 2s difference between the 3 bikes. Downhill I'm quickest on the Cooker (confidence thing).

That's for me....

Any power you would lose would have to end up as heat in the shock. Does your shock get warm when you ride XC?

My mate's squeeks and squeels like a stuck pig - that energy harnessed would make him awsumz

Are you lot talking about pedalling bob, or thekinetic energy lost to the damper?

I think course designers in XC are under pressure to keep courses rough enough to prevent bikes from being too much like flat-barred CX bikes.
A higher UCI weight limit would mean more suspension too, if that's what the marketeers decided was important.

Is their a comparative approximate industry figure of power loss?

Yep, a full suss loses roughly 5-10 Glimbarts in comparison with a hardtail.

I don't think pedalling bob is an issue on XC FS bikes tbh.

down or along, my anecdotal experience is that im quicker on the full sus, i stay off the brakes more and can keep the power down pedaling easier in the rough stuff on a full sus.

This.

Also, on the more difficult climbs you have to be moving around on the bike more to keep the bike moving. This costs energy.

All and any power that doesn't get transferred to forward motion I guess.

This also includes energy absorbed by the shock over bumps. The question is if this energy is preserved if you are on a ht.

This also includes energy absorbed by the shock over bumps. The question is if this energy is preserved if you are on a ht.

Except when there's pedal bob (or honking bob). Then the shock absorber is working directly against you.

The shock does absorb forward motion, of course it does. If you coast along the flat on a bumpy trail, the shock moves and does work against the damper fluid - where's that energy come from?

The swingarm might be moving vertically but only due to the forward motion of the bike and the leverage of the wheels against bumps.

I've logged various rides on a number of hardtail (FF29 and Solaris) and full-suss bikes (Five, Trance and Gyro) over the past few years, including lots of attempts at the same segments different bikes. I've made a few attempts at trying to analyze these to see which bike is faster in various segments and I'd have to say that it is really hard to come up with any definitive conclusions. It does look as though the HT has an edge on smooth climbs (and roads) and the full-suss has an edge on rougher climbs, but the differences are much smaller than the day to day variation in my fitness/enthusiasm etc. So, I can find examples of smooth climbs where my fastest time was set on a full-suss (or rough ones where a HT wins), simply because I was feeling good that day.

Make of that what you will, but personally I'd say that, if you sit and spin up climbs (as I do), there is not much in it. The HT should win (if only because it is slightly lighter) up a road or smooth trail. The full-suss probably wins if it gets technical.

Racers do tend to stand on the climbs though.

I used to ride with a really quick bloke. Couldn't keep up with him with both of us on rigid. I stood more chance with bounce. This was racing on really rough tracks.
So you may lose power but it's quicker.

The shock does absorb forward motion, of course it does. If you coast along the flat on a bumpy trail, the shock moves and does work against the damper fluid - where's that energy come from?

The swingarm might be moving vertically but only due to the forward motion of the bike and the leverage of the wheels against bumps.

For me gains of a full suss on the rough stuff far outweigh any gains that might be had on a hard tail for the smooth bits. If I just ride canal towpaths I might come to a different conclusion.

Not for Winching and plummeting

If you ride smooth climbs, technical descents and no flat (which most people do where I live because of the geography) then the time you gain on the climbs far outweighs the time you loose on the descents simply because you you spend about 4/5 of your time going upwards.

The descents are no more or less fun on the HT, slower certainly but more challenging. I don't prefer one over the other - its nice to have a change - but I can definitely get more in on the hard tail.

What Molgrips said plus the extra climbing traction, cornering traction and lower fatigue.

Makes sense to me. I think in almost all cases a well set up and applicable FS will do a better job of covering the ground than a HT, especially loose or nadgery climbs when you want that rear wheel on the dirt not bouncing about..

In short, hardtails are shite.

False. Hardtails are great fun and I find I can't be bothered with the maintenance overheads and endless technology churn of FS.

Covering ground as fast as possible isn't the aim of MTB for me.

HTs for me.

This thread has inspired me to take out my hardtail (which hasn't been offroad since it was rebuilt in June) and ride back to back with my full suss. I feel a Strava coming on...

I don't think pedalling bob is an issue on XC FS bikes tbh.

Then why aren't they used by everyone in a competitive situation?

I'm quicker just about everywhere on my 29er hardtail than on my 26" FS of the same weight.

What about maintaining speed through less fatigue?

I'd be interested to hear what part people feel that has to play. Purely for selfish reasons I guess.

I find my HT is my go to bike (as was my previous HT) but my body carries a fair few injuries so although my fitness is ok I find the jarring, especially over repeated rutted ground for eg gets fatigue kicking in. Both the HT I mention are 29ers for reference.

I have a FS (120mm 26er) but have a love / hate relationship with it and the only time it was ever my go to bike was when it was new. But that was due 1) new bike love and 2) it was lighter than the 26er HT I had at the time but then that wasn't hard as it weighed over 33lb.

I'm quicker just about everywhere on my 29er hardtail than on my 26" FS of the same weight.

Could be wheel size.

I think in almost all cases a well set up and applicable FS will do a better job of covering the ground than a HT,

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.

Pedal bob/power loss is IMO quite minimal these days. The speed differential between my two bikes on a typical xc ride (some ascending/descending) is fairly minimal between my Covert and Bfe and IMO entirely due to weight differential as Covert is set up quite heavy.

@Normal - definitely get bashed around more on the HT which is actually deliberate as it's more fun on my typical trails. On an all day ride with lots of descending I would definitely be quicker on the FS due to less fatigue as well as more outright speed downhill.

What about maintaining speed through less fatigue?

I'd be interested to hear what part people feel that has to play

I did a couple of 5 hour rides on my Five earlier this year; just stringing together landrover tracks over shooting estates with logging roads, windfarm access roads etc. So, nothing really technical, just a few rough tracks with loose rocks etc.

I ended both rides feeling tired but happy. In both cases I then went back a week later with my Solaris. The logic being that there was nothing too technical, but lots of climbing and even a few road sections. So, it should be easier and more fun on the hardtail. In fact, in both cases, I got so fed up with the jarring on the landrover tracks that I cut the rides short after around 3 hours. I was marginally faster over those 3 hours, but mainly because I wasn't enjoying the ride and just wanted to get it over with.

Not sure that really answers your question, but for a ride of more than a few hours (even if it's just bimbling along on simple tracks) I tend to go for the full-suss these days.

When a rigid bike hits a bump some of your forward energy is used to lift the bike and rider up not forward. With suspension its only the unsprung weight that that gets lifted up. Same reason why tubless tyres with lower pressure that can deform over rough surfaces roll quicker.
A previous poster noticed his fast mate was quicker than him on a F/R but not as much with suspension. A skillfull rider will absorb a lot of bumps with his body, rather than loose the the forward motion energy.