(gentle music)
- If you're buying a gravel wire
one choice you're likely to be faced with
is whether or not you go, for a double chain ring
or a single chain ring option.
Either two by or one by.
Now given that Shimano have just launched
their first ever one by drop bar specific option
as part of their new GRX range,
we thought, it was high time to try and clarify
just what the relative advantages of each system are
and then, try and work out which one might
be better suited for the type of riding
that you want to do.
(gentle music)
First up a quick explainer.
Just in case you need the whole on by
or two by thing clarified.
Now very simply a one bar two bar refers
to the number of chain rings that you
have on your bike either on or two.
Now it sounds simple and it is, but there are
one or two things that you need to know.
In order to run a single chain ring set up
you are going to need a special chain ring.
One that's designed to stop the chain from coming off
which would otherwise be a problem
if you were to just remove your front derailleur.
Now the way manufacturers achieve this
does vary but very generally this type of chain ring
is called a narrow wide chain ring.
And that refers to the alternating width
of the teeth on the ring and then
they correspondingly fit much more precisely
between the narrow and wide links on the chain.
And it's really really effective so much so
that although this bike does have a chain catcher
I would not bother with one
and also you could only ever run this type
of chain ring one bite because you wouldn't
be able to shift off it.
In addition to that specific chain ring,
you're also going to want a rear derailleur
with a clutch type mechanism on there.
Now these clever little gizmos effectively
and resistance the derailleur arm
in a forward moving direction.
So that basically stops the chain from bouncing around
and potentially bouncing off.
A byproduct of this, is that it also makes the bike
so much quieter on bumpy terrain because the chain
is much less likely to be slapping around
against the frame.
And so effective is it that it's also on
the two by group set option as well.
Now, a two by set up, I think for a lot of us
might sound simpler.
But then I think that's probably because it's
what we used to.
Front derailleur have been on road bikes now
for 70 years but natural facts,
it is going to be more complicated
in that you have a front derailleur,
you have an additional shifter
you also have an extra cable to connect the two
plus you have, an extra chain ring of course.
Now,once you know how a front derailleur
is super easy to set up and work perfectly
but a lot of people do seem willing to put up
with poorly adjusted ones that means
that they might not shift as well as they should
or, you just get a bit of derailleur rub on your chain,
making it a little bit noisy.
(soft music)
Let's not dwell on that though
because as I said, when a front derailleur is set up
somewhere close to correct, it worked perfectly.
So what are the advantages then of a two by set up?
Well predominantly, it comes down to gear ratios
you have double the number of gears
on a two by set up compared to a one by set up of course.
Although, interestingly or perhaps not I'll let you decide
you actually don't get double the number of gear ratios
and that's because there's a little bit of overlap
between the two chain rings.
You have a wide range of gear ratios
in fact wider than ever on this GRX 810 chain set
because of other first-time Shimano,
have created a 17 tooth gap between the ring.
So this is 48-31.
Perhaps most importantly though
you get smaller jumps between the gears
on buy by set up generally,
and that's because you can run
a closer ratio cassette back.
So in this case, we've got an 11 to 34
and it's good because faster speeds so perhaps tarmac
or smoother gravel, you can be more comfortable
and potentially even more efficient
cause you're more likely to find a gear
that suits your optimal cadence for that particular moment.
But then you don't need to worry
about being stuck without small gears
cause of course you have that tiny little chain ring
on the front, in this case a 31
which is going to be well suited
for the much slower speeds
associated with riding off-road.
Ultimately, you can safely say
that given this tech has been refined
over the last 70 years, it's pretty tried and tested.
Two by setup works, and it works really well.
(gentle music)
Whats' about one by then, what are its advantages,
why get rid of half of your gears?
Well that is a good question
because for a lot of us, it may well be
a slightly counterintuitive.
I'm going to start with a personal one
but I really like the aesthetics.
And that's really important actually
I think if we all admit to ourselves, deep down
at least part of the reason we've chosen
the bikes that we have in the past
is because we like the look of them.
And so don't underestimate the importance of that.
And I'm not just referring to
the view of the bike in profile either
when I'm taking a bike vault photo.
What I actually mean is when riding it
and you look down at your legs pedaling
and it just looks so clean, I love it
then you might love it too.
But then you might not, it's an entirely personal choice.
Now, in terms of the performance advantages.
First up, you will get rid of a little bit
of weight of course, cause you're removing
your front derailleur and one of the chain rings.
It's not a massive amount to get excited about
perhaps 250 grams if you factor in the cable
that you can get rid of as well.
One of the most significant advantages
and one not shared with road bikes actually,
is that if you remove the front derailleur
you can fit wider tires.
Even with GRX where the front derailleur and the chains
that have actually been spaced out slightly
there is still an official restriction
of 42 millimeters on the width of your tires.
When you remove that, frame manufacturer
can then fit much wider tires in there.
Now at this point, a lot of you
have mentioned already
that if your change days are long enough,
you can still fit in really wide tires
and a front derailleur as well.
But here's the thing, sure to change that bike
does tend to feel a lot livelier
and more responsive even with wider tires.
And so that's why it's quite an important consideration.
Removing front derailleur has completely liberated
mountain bike designers
and the same is kind of true with gravel as well
even if it's not quite so significant.
Finally you can use your left shifter now
to do other things, like activate a dropper post
(gentle music)
Seriously, yes, I mean I do actually
have a dropper post on my mountain right now
and I think it's great.
But personally I can't see the need
for one on a drop bar bike.
But then that's what I said about mountain bikes
and now I wouldn't be with that one
so yeah so yeah come back to me in four years time
and I'll probably have one.
You might not be quite so slow on the uptake as me though.
(soft music)
Okay, let's talk gear ratios.
Again how does it work if you remove half of your gears?
Well in the first instance you'll want
a much larger ratio cassette at the back.
So in this case I've got an 11
to 42 mountain bike set on there
with GRX you'll need a specific rear derailleur
in order to accommodate such a wide cassette on there.
For cyclo-cross, it wouldn't be quite so important
but for gravel you definitely want
those easy easy gears, just in case the terrain demands it
because getting off and running with your bike
isn't really that much fun outside of a cross race.
And actually if we're honest, it's not
that much fun in a cross racer either.
And 11 to 42 cassette like this one
with a 42 chain ring will mean that you'd run out of gears
at about 60 K an hour as opposed
to 70 kilometers an hour with a 48 tooth big ring.
Now that actually doesn't sound too important to me
I said it before but I do tend to stop pedaling these days
at about 60 K an hour.
However I do know that a lot of people worry about that.
At the other end of the spectrum, a 31-34 combo
would allow you to stay on the bike
at about three to five kilometers an hour
as opposed to five to seven kilometers an hour
for a 42-42.
In terms of the jumps between the gear ratios,
on-road, they can feel quite significant
particularly if you're riding a group
and your left or not dictating the pace.
But worth remembering the point
that we've touched on earlier
which is that, with a 22 speed two by set up
you actually only have apparently,
around 14 distinct gear ratios.
So with an 11 speed one by set up, you're only missing three
even if it might sometimes
feel like it's more than that.
When riding off-road though and speeds are generally lower,
you'll find that those larger jumps between the gears
are actually something to be welcomed,
it's a positive thing because otherwise
you do spend your life changing gear.
And that's something that I found out when I was 16.
And I spent ages saving up for a close ratio cassette.
My mountain bike cause I thought it's going
to make me faster, when in reality all I did
was spend every race changing gear constantly
because I could never find the right one.
It's a true story that, not a good one
but it is true.
So if those are the advantages of each,
how do you know which one to choose?
Well, if you want a responsive lively gravel bike
with really wide tires,
you're going to need one by on there anyway.
So the choice might be taken away from you.
Then if you like the idea of the simplicity,
slight reduction in weight, and then
potentially also a little bit of extra robustness,
one by definitely has the edge over two by.
Then of course, there's the important question of aesthetics
which is entirely personal, but two by ain't dead yet,
far from it in fact.
It's tried its tested it's more refined than ever
and as long as your tire choice and frame choice
doesn't preclude it, it is a fantastic option.
I think a lot of people will still be swayed
by those smaller jumps between the gears
but still getting that wider spread of ratios overall.
Do make sure you let us know what you think,
which is your choice or which would be your choice,
and let us know why, in the comment section down below.
Also give this video a big thumbs up
and if you'd like to watch another one
about how to choose at your gravel bike,
then you can click switch to that on screen now.