Fast hubs ? possible ?
zak3737
Posts: 370
This is puzzling me, and altho I'm no Physicist, seems strange......
I ride on a 2013 Roubaix, with Mavic Ksyrium Elite wheels, which the first owner had fitted.
Now, I'm less than 'good' up hills, always hated climbing, just not built for it at 15stone, so I'm happy to trundle up, spin it out, and give the guys with me a rest at the top.
This is the puzzle though, - one of my buddies is at least as heavy as me, perhaps a smidge more, and is riding a brand new BMC Gran Fondo, lovely bit of kit, but come the downhills, and gravity takes over, even free-wheeling, I'm frequently quicker, the bike just seems to fly.
Could it be the hubs are just super slick and combined with Gravity, just quicker ?
I think its even puzzling them as I cruise by free-wheeling !!
Thoughts ?
I ride on a 2013 Roubaix, with Mavic Ksyrium Elite wheels, which the first owner had fitted.
Now, I'm less than 'good' up hills, always hated climbing, just not built for it at 15stone, so I'm happy to trundle up, spin it out, and give the guys with me a rest at the top.
This is the puzzle though, - one of my buddies is at least as heavy as me, perhaps a smidge more, and is riding a brand new BMC Gran Fondo, lovely bit of kit, but come the downhills, and gravity takes over, even free-wheeling, I'm frequently quicker, the bike just seems to fly.
Could it be the hubs are just super slick and combined with Gravity, just quicker ?
I think its even puzzling them as I cruise by free-wheeling !!
Thoughts ?
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Comments
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Many variables, you could have a more 'aero' profile/clothing, more confidence0
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'Aero' I'm not, all the aero properties of a Breeze Block :-)
Same kit really, nothing flappy worn, and pretty sure it aint just bigger b@lls going downhill.0 -
A science person will probably give you the exact answer, but from my point of view, it's just gravity. I used be three stone heavier than I am now, and would fly down hills a lot faster than others, and on crappy wheels. Now I'm three stone lighter, with better wheels, I'm not much faster. Its' down to weight.Cycling prints
Band of Climbers0 -
Do you remember that Galileo thing from school with the leaning tower of Pisa, a hammer and a bag of feathers?
A bigger weight will have a greater gravitational force on it, but will accelerate less for the same force and so it cancels out. eg. Things fall at the same rate (in a vacuum anyway, or to Galileo's standard).
It is about the ratio of force to resistance. The resistance in that circumstance will be just rolling resistance and aero resistance. Heavy wheels will slow down acceleration, because they need to be spun up to speed, but shouldn't effect top speed. If your max speed is higher you must be either more aero or have lower rolling resistance. Wind resistance isn't linearly related to speed and is far more important when you are going quickly. Is it that you accelerate at the top quicker or that your top speed is higher? That may give you some indication where the benefit is.0 -
Guys, you arent reading my post, - I understand that IF I was heavier, i'd be faster.
But as I said in the OP, at least 2 of the chaps I ride with are at least as heavy as me, one more so,
so the normal gravitational forces dont apply.
I'm running larger tyres too, 28's v 25's, & doubtful they are higher pressures, and I certainly arent any more streamlined, so all those 'possible' factors dont apply at all.
Its just that, when booling downhill, my bike & I seem to roll quicker. *puzzled still*0 -
Just put it down to awesomeness.Advocate of disc brakes.0
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Just put it down to awesomeness.
Of course, I hadnt considered .........
No, seriously, could Hubs be free-er/betterer/more awesome ? Or any damn factor ?0 -
If you were a pro on the edge of the limits riding down an alpine descent then maybe the 0.001% advantage a better bearing will give you over your fellow riders would be a factor.
As a self confessed parachute, maybe not.Advocate of disc brakes.0 -
When I changed my wheels from Fulcrum racing 5s to racing zeros I found that all of a sudden I was having to hang onto the brakes when freewheeling down hill in a group. The zeros have ceramic hubs are, lighter, stiffer and have marginally more aero spokes. I do think the hubs are responsible for most of the difference.0
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Absolute nonsense.
Like a Chinese philosofer said, faith moves mountains.
Many many things can make a (small) difference, but hubs won't.
90% is air resistance
9,9999 is rolling resistance
0,0001% (or similar) is mechanical resistance in hub bearings.
If you draft, chain resistance (largest mechanical resistance) is not present.
No human being (and most measuring equipment) can distinguish 0,0001 % difference0 -
Keezx: That may be so, and I agree, but the fact remains, that even though I'm no heavier, def no more 'aerodynamic', not drafting, not pedalling, I'm still rolling quicker downhill than the others I ride with !
Not bothering me, but I'm genuinely curious why !!0 -
Keezx: That may be so, and I agree, but the fact remains, that even though I'm no heavier, def no more 'aerodynamic', not drafting, not pedalling, I'm still rolling quicker downhill than the others I ride with !
Not bothering me, but I'm genuinely curious why !!
That part is most likely where you are wrong.
By far the dominant factor is your body and position, no 2 body's /positions are equal.
100% sure the hubs have nothing to do with it.0 -
It's an odd one. Amongst our small group of friends I am heavier than some, lighter than others. I've had different bikes, different tyres. Yet there is one constant. Whatever I am on and whomever I am up against I always roll more quickly. It's become the group's little joke. I even outrolled my heavier mate on a CX with CX tyres on when he was on a Scott with Conti Road tyres.
So, anecdotally but, possibly scientifically, given that I am the constant, it appears that I am awesome.My blog: http://www.roubaixcycling.cc (kit reviews and other musings)
https://twitter.com/roubaixcc
Facebook? No. Just say no.0 -
Whatever it is, it's not the hubs.0
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It's probably charisma to be honest.My blog: http://www.roubaixcycling.cc (kit reviews and other musings)
https://twitter.com/roubaixcc
Facebook? No. Just say no.0 -
'Awesomeness' and 'Charisma' aside, which I of course have in abundence, (dont we all) - I also have the aero qualities of a brick, I mean, how aero can 95kg be ?!?!
Added to that, the Higher front end of my Roubaix should be in theory less aero, and I aint ever down on the drops either.
There's definitely summat at the root of this .......0 -
You wouldn't be tightening the other rider's brakes at the cafe stop, would you?
Old gag that one.The above may be fact, or fiction, I may be serious, I may be jesting.
I am not sure. You have no chance.Veronese68 wrote:PB is the most sensible person on here.0 -
It's a funny thing... and many cyclists will have noticed this relative-speed discrepancy when climbing and descending with friends or family.
However... On normal roads in normal conditions, has anyone ever been 'left behind'?
I find that a very rare occurrence. There is a 'safe margin' when descending on roads open to other traffic. It varies, but it tends to be bigger than the margin we leave when climbing or when on the flat.
But people do not get left behind.
Scenario 1: We are both (all) descending at 35-45 mph. I feel I am slipping back. I might tuck lower or (if possible) slam on some superfast foot-spinny pedal motion. I might then start to roll closer.
Scenario 2: We are both (all) descending at 35-45 mph and I find I am rolling away at the front and the other party (parties) do not look like catching up. I sit up or raise my head or stop pedalling and they roll up to me.
At any speed over 45mph, I do think it is bottle and experience. Many of us will say we didn't brake, but we are unconsciously (or subconsciously) feathering our rear brake every now and again. This takes a good bit of speed off a descent.
But up to 45 mph, I think that bearings have the square root of sod all to do with it, and above that speed rather less.
Funnily enough, brakes (rim and disc) can have something to do with it. It is astounding how many people ride with off-centre brakes that lightly scuff the rim. Tyre pressures are also a factor. Bearing are not, unles one set are dry and grinding or done up so tightly that the wheel just stops. If they are loose and wobbly, you will be thrown off and you'll never know what the speed difference was...
A lot of these questions of technological advantage are addressed by the phenomenon of motorists driving with early ABS-fitted cars. Within a month or so of ownership, many swore they had survived a situation that would undoubtedly have killed or injured them had they not has ABS. Odd, then, that there were not billions of skiddy-brakey-swervy-slalom-stoppy car accidents prior to the arrival of ABS that just stopped after its introduction.
There are many tiny-margin gains to be made (or perceived) and the bike industry likes to vaunt them - as do the cycling press whose living is linked with our uncaesing thirst for new-better-costlier-faster-dearer stuff.
It's just a bicycle. You were faster because your brakes weren't rubbing. But you can believe it was the bearings if that makes you happy.0 -
I'm not saying 'I leave all behind' in my wake, so the advantage is slight, and I certainly arent talking about stupidly quick or long descents, or anything like 35-45mph, where we'd all be covering the damn brakes !
I'm also certain that none of us are stupid enough to be riding with rubbing brake pads.....
As for 'believing its the hubs if it makes me happy'........as the only moving part when freewheeling downhill, still seems to me the most likely explanation......somehow !
or perhaps my wheels have stretched ?0 -
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As for 'believing its the hubs if it makes me happy'........as the only moving part when freewheeling downhill, still seems to me the most likely explanation......somehow !?
Again. Wind resistance is much more important than free-er spinning hubs especially at higher speeds. and this is the most likely explanation. Look at all of the money bike manufacturers throw at aero frames/wheels/jerseys/shoes/helmets etc. You might not think your more 'aero' than your mates, but you descending quicker points to it.0 -
I'm not saying 'I leave all behind' in my wake, so the advantage is slight, and I certainly arent talking about stupidly quick or long descents, or anything like 35-45mph, where we'd all be covering the damn brakes !
I'm also certain that none of us are stupid enough to be riding with rubbing brake pads.....
As for 'believing its the hubs if it makes me happy'........as the only moving part when freewheeling downhill, still seems to me the most likely explanation......somehow !
or perhaps my wheels have stretched ?
Oh... I have misunderstood. I was under the impression that you were thinking in terms of 35-45mph descents. That is a fairly standard speed range on a decent incline and much below the lower end of that is not really an area for descent-speed comparison. So I may be involving myself in the wrong thread.
Also... I thnk I know what you mean, but covering the brakes is just that... covering them. I'm talking about the subtle little tweaks and squeezes on the levers that some (I) do to keep my heart in my chest at higher velocities. Not 35-45... like.... higher.
As to nobody being dumb enough to ride on rubbing brakes.... I've done it loads of times over the decades and will do it again. It's dumb (sometimes) not noticing it on a long ride. But many (more than will admit it) have done it and will do it again.
And on your final point, the drinks trolley is one of the few moving parts when an aircraft with engine failure is diving into the ocean... but that doesn't mean I'd look to its wheel bearings to explain the speed.
Honestly... and nobody is deliberately trolling on this thread.... wind resistance, tyre pressures and speed at the top of the descent are the key factors determining descent speed when not pedalling.
Also... do flip your bike (and his) and spin the wheels. This is (empirically) a very poor measure, but it does show up silly errors that we've all made, like overtight bearings or rubbing (chafing) brakes. In my highly mechanically illiterate way, spinning the wheels is my final check that new bearings are done up just right. Crazy how often they are not....0 -
Absolute nonsense.
Like a Chinese philosofer said, faith moves mountains.
Many many things can make a (small) difference, but hubs won't.
90% is air resistance
9,9999 is rolling resistance
0,0001% (or similar) is mechanical resistance in hub bearings.
If you draft, chain resistance (largest mechanical resistance) is not present.
No human being (and most measuring equipment) can distinguish 0,0001 % difference
So what is making me roll faster with a change of wheels, is it the minor change to the spokes, the wheel stiffness or am I just imagining I'm having to brake? In the words of a modern day thinker, "hold your beliefs lightly".0 -
Interesting read - https://fairwheelbikes.com/c/reviews-and-testing/hub-review/
Perhaps my old bearings were full of crud!0 -
Absolute nonsense.
Like a Chinese philosofer said, faith moves mountains.
Many many things can make a (small) difference, but hubs won't.
90% is air resistance
9,9999 is rolling resistance
0,0001% (or similar) is mechanical resistance in hub bearings.
If you draft, chain resistance (largest mechanical resistance) is not present.
No human being (and most measuring equipment) can distinguish 0,0001 % difference
So what is making me roll faster with a change of wheels, is it the minor change to the spokes, the wheel stiffness or am I just imagining I'm having to brake? In the words of a modern day thinker, "hold your beliefs lightly".
Who knows? Perhaps the bearings on your old wheels were knackered, perhaps the bearings were badly adjusted. Are you using the same tyres? Maybe your brakes were badly adjusted without you realising. Maybe the placebo effect of having shiney new wheels has made you subconsciously tuck-in more on decents or increased your confidence.
One thing is sure, if both wheel's bearings were working as intended, then the difference in rolling resistance will be minicule and not enough to explain your findings.
But hey, believe what you like if it makes you happy and justifies your purchase. Maybe we are all wrong (we're not
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Fast hubs are not a myth... when you spin your wheel at zero load, they all have negligible drag, but once you load them with 70-80 Kg, then this is not necessarily the case any more. Some hubs roll better than others under load. I find my Novatec 541/542 exceedingly fast downhill and I have always managed to better my top downhill speed like for like (same tyres and same bike) by a couple of mph
At a guess, bearing size and hub/axle machining tolerances are the discriminant factors... bigger bearings roll better under load.
As a rule of thumb, angular contact bearings, like Shimano have, roll better, as they are designed to carry loadleft the forum March 20230 -
Sorry, I don't agree.
Neither an anecdotical story nor the technical explanation makes sense.
Certainly bigger balls are better under load but the higher resistance of small bearings never gets a magnitude of being noticable.
Beyond human capabilities.0 -
Sorry, I don't agree.
Neither an anecdotical story nor the technical explanation makes sense.
Certainly bigger balls are better under load but the higher resistance of small bearings never gets a magnitude of being noticable.
Beyond human capabilities.
The problem of reducing the all issue to aerodymanics and tyres rolling resistance is that it doesn't account for empirical evidence of some wheels being quicker than others downhill given same tyres and maybe worse aerodynamics, which is a fact of life... so you have to "drag in bearings/freehub drag" to try to make sense of the evidenceleft the forum March 20230 -
Rounder, larger, harder balls (hubs not rider).
Shorter, narrower nipples (wheels not rider).
lighter pawls in the freehub.
Butted versus plain-gauge spokes.
correctly lubricated and adjusted bearings.
TYRES.
Also, if you are go over the top 2 seconds before the others at the same speed, say 10mph, and both go to 40mph the time gap will be the same but the distance will be four times as much.0 -
I'm not sorry ...Sorry, I don't agree.
May be not to you ... but it does.Neither an anecdotical story nor the technical explanation makes sense.
It's amazing that these vastly more expensive wheels are no better than the cheapo's that are sold with the bottom end bikes ... it makes you wonder why we bother at all - being that it makes no difference ....Certainly bigger balls are better under load but the higher resistance of small bearings never gets a magnitude of being noticable.
perhaps yours ...Beyond human capabilities.
For the OP - I don't believe it's mostly your bearings that's making the difference, although it may help - as has been said, the vast majority of resistance is wind resistance - it's not just about being lower on the bars - it's about air flow - so the whole body shape comes into account. Your mate may be the same weight as you, but how is it distributed? Is he wider than you?
Also - you say you "cruise by freewheeling" - which suggests that you've sat behind him, taking advantage of the tow, allowing yourself to build up speed - then pass - momentum will allow you to do that - and perhaps your mate isn't quite so quick to get onto your wheel as you go by ... ?0
