Efficiency increase

SimonAH

Was looking around for suggestions for a bike for Mrs AH and on the ThisIsMoney website (under the heading of best commuter bikes for under £500) found this rather odd statement;


If you're extremely fit, used to riding bikes and live in town, fixed-gear bikes are the latest urban trend. Because the chain doesn't have to go round a derailleur, they transfer power more efficiently (90-95% as opposed to about 70%). And they look pretty good, too.

Read more: http://www.thisismoney.co.uk/bargains-a ... z11J7juUZL

Now, I could envision a little more efficiency as less energy is being wasted bending the chain and from friction in the mech -but a 20 to 25% improvement???? I smell manure.

Stevo_666

I have nothing to prove it but instinctively that sounds like bollox. 20-25% transmission loss from going round a rear derailleur??

davis

I did some analysis of that article:

          ^     /
Amount    |    /
of        |   /  
Cobblers  |  /
          | / 
          |/      
          +-------------->
             Amount of words
              written

The first clue was the insinuation that hybrids will last longer than "flimsy racing bikes".

Stevo_666

davis wrote:

The first clue was the insinuation that hybrids will last longer than "flimsy racing bikes".

So it wasn't all bollox then

davis

Stevo 666 wrote:

davis wrote:

The first clue was the insinuation that hybrids will last longer than "flimsy racing bikes".

So it wasn't all bollox then

Curse you! now I've got apoplexy all over my keyboard!

dondare

"Novice riders should consider a 'hybrid' bike. They have bigger, slower tyres but offer more comfort and grip. And for those who don't mind looking like a 'nodder' - the cycling-snob term for casual cyclists - they often have racks on the front and back for your bags. They also last longer than racing bikes because they're less flimsy."

Nodder?

stuaff

dondare wrote:

"Novice riders should consider a 'hybrid' bike. They have bigger, slower tyres but offer more comfort and grip. And for those who don't mind looking like a 'nodder' - the cycling-snob term for casual cyclists - they often have racks on the front and back for your bags. They also last longer than racing bikes because they're less flimsy."

Nodder?

Nodder= inexperienced cyclists using too high a gear (or just being woefully unfit) and whose heads almost invariably bob up and down with the effort, even when they're doing 5 mph on the flat. Hence 'nodder'.

EKE_38BPM

Never heard the term?

It refers to their heads (and bodies) nodding up and down with each pedal stroke because they use their body weight to turn the pedals rather than the power in their legs. Its usually used to refer to fixie riders though.

dondare

So the article is not accurate in this repect.

deptfordmarmoset

If you can't get up a hill because your SS ratios make it impossible, how efficient is your drive as you push your bike up the hill? I'm not an engineer but I'd guess that the ''efficiency'' is pretty much 0%.

And if you're on a fixie going down a steep hill, you might find that this ''efficiency'' really isn't working in your favour - unless you're trying to slow down, of course.

In fact, I've no idea what kind of efficiency they're referring to.

UndercoverElephant

Sounds quite reasonable, as long as you're comparing a well-maintained SS to a derailleur which has been sat in a ditch for a few years. Even hub gears aren't that rubbish.

Blue Meanie

Epicyclic gearboxes (hub gears) have lots of friction in certain gears (7th for Rohlof, 1st&3rd for Sturmey...) and can lose 20%
The main problems with mech-geared bikes is when the chain runs diagonal (big on the front, big on the back), which we never do, right?
If you use your (french) gears correctly you shouldn't ever lose more than 10%.

Ooh, and lube your chain!

rjeffroy

I'm sure the physiological advantage of being able to stay near your most efficient cadence over a wider range of speeds with a geared bike far outweighs any frictional loses through the drivechain when compared to a singlespeed.

Butterd2

Well as the owner of both a FG and a "Flimsy" road bike I can confidently say this is complete bollox.

wgwarburton

rjeffroy wrote:

I'm sure the physiological advantage of being able to stay near your most efficient cadence over a wider range of speeds with a geared bike far outweighs any frictional loses through the drivechain when compared to a singlespeed.

No, I don't think it's that clear cut... though I think the article in question sounds poorly researched. My recollection is "efficiency" (how do you measure that, anyway?) of near 100% for single-speed/fixed, close to that for well-maintained derailleurs and not far behind (90% or do) for hub-gears. Hub gears gain an edge when derailleurs are suffering neglect.

While a geared bike is physiologically "better" the difference isn't enormous. A fixie can (well, should!) be lighter and the lack of gears forces you to push yourself hard uphill to keep cadence & momentum up and to spin downhill (you can't coast, so you have to pedal... that tends to mean applying some drive, so you go quicker).

I'm usefully quicker on my commute when riding fixed than I am riding geared, though i daresay that won't apply to everyone.

Cheers,
W.

rjeffroy

I'm usefully quicker on my commute when riding fixed than I am riding geared

I found the opposite, hence my comment. No doubt depends on the individual as you say.

Radioactiveman

I appreciate this is the commuting section but I think the best use of the hub design is on an MTB. WIth a derailleur once it is covered in mud,filth and bracken the jockey wheels get massively obstructed and efficiency falls- plenty of experience of that tbh.

However a hub gear will remain relaitvely constant, the dogs conkers would obviously be a belt drive. A chain drive hub drive will get a bit of mud and cack on it but will self clean unlike the jockeys on a derailleur set up.

Unfortunately I have no experience of a hub gear covered in mud and filth,only ridden one in the dry. But i reckon that is a good best guess.

asprilla

rjeffroy wrote:

I'm usefully quicker on my commute when riding fixed than I am riding geared

I found the opposite, hence my comment. No doubt depends on the individual as you say.

Makes little difference to me, journey times are about the same. Geared is generally easier and accelleration is quicker, but my top end is higher on the fixed and maintaining high speed is easier too.

If it's windy, gears are preferable.

snailracer

WGWarburton wrote:

...the lack of gears forces you to push yourself hard uphill to keep cadence & momentum up ...

This line of reasoning reminds me of when I asked a roadie friend of mine why he always rode fast - his reply was that his saddle was so atrociously uncomfortable, he had to get to his destination as soon as possible so he could get off it.