- A well-tuned and smooth drivetrain is mechanically
really efficient.
Which is good to know if you are turning yourself
inside out going up a climb.
But nevertheless, the amount of power
that you could potentially save from just this area
is really surprising.
And if you don't believe me,
well, a company based in Boulder called Friction Facts
has been actually lab-testing all sorts
of different drivetrain components, lubricants,
and even gear ratios to find out just how efficient
they really are.
So how do you make your drivetrain more efficient?
Well, coming up, we've got some tips based on
Friction Fact data.
And we're gonna start with one that's completely free.
Number one, clean your drivetrain.
It is common sense, isn't it?
But have you ever thought that actually having a dirty chain
could be costing you 3 watts at the 250 watt
testing benchmark?
Serious.
That is because dirt creates friction,
and friction is the enemy of efficiency.
So if you needed any, that is added incentive
as to why you should clean your bike.
We'll come back to other free adjustments later on.
But for now, once you've got a scrupulously clean chain,
let's talk lubricant.
Because you can actually save in excess of 4 watts
just by choosing the right lubricant.
Now, I'm not gonna delve into
Friction Facts' actual test results here
because that's their proprietary information,
and that's how they actually make their money.
But nevertheless, there are some interesting things
to be learned.
Firstly, dry lube, actually on the whole,
generates more friction than wet lubricant.
Although that is in the laboratory environment
and not after a long ride
where you might expect dry lube
to actually attract less dirt than a wet lubricant.
But then, amusingly perhaps,
one of the most efficient lubricants tested
was extra virgin olive oil.
Now no word on real world performance,
but it's probably worth remembering
next time you have a dry chain,
and you sat out having lunch somewhere.
While we're on the subject of chains,
how interesting is this?
You might expect that a worn-out chain is less efficient
than a new chain, and you'd be right.
It is by about two watts.
But, did you know that a brand new chain
is actually one watt less efficient
than a chain that has already been broken in
by riding 50 to 100 kilometres?
I know, I told you.
Interesting, isn't it?
Now, the lesson from that is you should always
replace your chain when it gets worn out,
but you should never race or do an important event
on a brand new chain.
Where else then, if we're actually spending money?
Well, there are small gains to be made on your pedals.
Not on your pedals.
And also your bottom bracket.
But perhaps some of the most significant savings
can be found in your choice of rear derailleur,
or more specifically, the jockey wheels.
It would seem that generally a more expensive
rear derailleur is more efficient than
a cheaper rear derailleur, and that is often
a result of having slightly larger jockey wheels.
And then if you really wanna upgrade,
you can get oversized jockey wheels,
and they can save you nearly 3 watts.
And that increase in efficiency is actually because
they stop the chain from turning too tightly.
And it is a point linked to this that actually leads us
to our last, and perhaps most intriguing,
free, energy-saving tip.
Gear selection.
That's right, one gear choice can be up to 3 watts
less efficient than another one.
Partly due to the alignment of the chain,
and then partly, like we just said, about how tightly
the chain needs to turn.
So effectively, the cog size.
First of all, for those of you that are appalled
by cross chaining, here is the data to back you up.
You do indeed lose drivetrain efficiency
from cross chaining.
Between 1 1/2 and 2 watts.
And so that is when you run either the small chainring
and the smallest cog,
or the big chainring and the biggest cog,
like I've done here.
Of the two, this one here, big and big,
is actually the least costly.
So, the more efficient of the two.
And that in part is because the chain line actually
isn't that bad, but then also because
of those cog sizes.
That's right.
Your big chainring is almost always more efficient
than your little chainring.
So, how cool is that?
Not only do you get to ride around looking good,
but you also get to know that it is
mechanically more efficient.
Now, at what point do you, though, change from
your big ring to your little ring.
Well, it's when you get to cog number eight at the back.
So that's four down from the top,
or eight up from the bottom.
And when you get to that point,
you shift into a little ring,
then knock it down two sprockets at the back.
And then use six to 11 with your little one.
Now theoretically, I'm afraid to say, that does mean
that compact chain sets are mechanically less efficient
than standard versions with large cassettes on the back.
And potentially, if you became really obsessed by it,
you may wanna consider running 55-42 tooth chainrings,
and they're like 12 to 30 cassette at the back.
Like world time trial champion, in fact,
Tony Martin, who may well already know something about this.
Does this change anything that I would do though?
Well, not really.
I think I'm already on record as saying that
39-11 is my least favourite gear ratio.
Although in fact, I think I hate 34-11 even more.
And then while I do really like riding in the big ring
and two and three down on the cassette,
I am prepared to sacrifice one watt
in order to keep doing that.
And actually, on SRAM-equipped bikes like this one
of Lasty's,
I'm actually still happy cross chaining.
Because I can.
And they say that I can.
Friction Facts, as I said near the beginning,
do all of these tests at 250 watts.
So, if you put out more power or less power
then your savings will be more or less correspondingly.
Although, the difference is linear and not exponential.
So do bear that in mind.
Or in fact actually, don't bear in mind.
It may be that
these efficiency savings are of absolutely no interest
to you whatsoever, and they have nothing to do with why
you like cycling.
And is that is absolutely fine.
But then, it is also fine to become slightly obsessional
about your equipment.
That's cool.
It's whatever floats your boat.
Whichever way you look at it,
if you add up all of these possible drivetrain
efficiency savings,
then you get to a number that's really quite significant.
If someone came to you and offered you a 5% improvement
at 250 watts from training,
you would definitely take it.
And while I do understand that you may not want spend
a load of money on expensive bearings
or oversized jockey wheels,
the fact that cleaning your chain and using your
gear selection intelligently are also part of those
drivetrain efficiencies.
There are some thing that all of us
can be doing for free.
All right, there we go then.
That is how to make your drivetrain more efficient.
For more videos like this,
make sure subscribe to GCN.
Because that way, you're always in the right place,
particularly on a Monday when we do these
maintenance videos.
And, if you want more content,
then how about knowing how to clean your chain scrupulously.
That video is just up there.
Or to see how to index your gears,
something that will also have a bearing
on your drivetrain efficiency,
click just over there.
Oh, and give a thumbs up for drivetrain efficiency savings.