(whooshing noise)
- Welcome to this weeks' Tech Clinic
where we aim to answer your tech questions
and queries about your
bikes and equipment.
Now, if you're wondering where John is,
well, he's at the world
championships in Harrogate
on the hunt for hot tech,
though I hear it's currently
raining there at the moment.
Now if you'd like to
submit your questions,
you can do easily in the
comments section down below,
just use the hashtag ASKGCNTECH.
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when we upload our next Tech Clinic,
which might even have an
answer to your question.
So without further ado let's get going.
The first question is from Oneris Rico,
he says that he's just got a new TT bike,
and he got a great deal on it.
Good, love TT bikes.
But he says that it has
shorter cranks on it
than his road bike,
and he said that he's
temporarily had to try
some longer cranks on his TT bike,
and it had a big negative
impact on his performance,
and he says he knows that
there's a difference in torque
between different crank lengths,
so if you use longer cranks,
they generate more torque.
And he's wondering if he should switch
to shorter cranks on
his road bike as well,
and will that be a
benefit that he'll notice.
Well, shorter cranks
are really interesting.
I've experimented with
it myself on TT bikes,
changing my crank length.
I didn't put shorter ones on,
I put longer ones on,
and the idea with short cranks
is that they allow you to open
your hip angle more when pedaling.
Now the torque you produce
from a shorter crank is less,
meaning longer cranks have
kind of bigger effective gears.
But this shouldn't really matter too much,
you can compensate for that
by just being in a gear lower,
so don't worry too much about that,
that's not a reason not to do it.
But by using shorter cranks,
you can open your hip angle more.
Now, this can really help
with getting the power out
in an aerodynamic,
aggressive, TT position.
A closed hip angle means that your legs
are brought up closer,
tighter in to your chest,
and this can be less efficient.
It can be harder to recruit
some of the most powerful
muscle groups in the body,
so, like your glutes and your hamstrings,
and so with shorter cranks,
you're able to recruit them
in a greater range of motion.
Personally, I'd love to try
shorter cranks on a TT bike.
I've got a TT bike challenge coming up,
and I'm actually thinking about
trying shorter cranks for
it, something like 165's.
In the past, I've used 172.5's
and gone up to 175's,
and I found that that two and
a half millimeter difference,
to me, I too noticed a big drop off.
I found it really difficult.
On the road, if you
ride in a more upright,
less aggressive position, as
people often do on road bikes,
then the hip angle is likely
to be more open anyway,
meaning that you might not
necessarily need shorter cranks.
It might not make much of a difference.
But, if you like it on your TT bike,
it's worth trying on your road bike.
And if you can replicate
your TT bike position
to be more like your road
bike position, or vice versa,
then you'll get a greater training effect
for your TT bike when you're
out on your road bike.
Give it a go.
Our next question is from Richard Clayton,
he says, Hi, I'm taking a trip abroad
with some decent climbing,
and I'm wondering, could I use
a Shimano Tiagra 4600 chainset,
compact, 5034, with an
Ultegra 8050 groupset,
which is 11 speed,
which currently has
5236 chainset on there.
So he wants an easier gear.
The problem you've got is that
the Shimano Tiagra chainset is 10 speed,
Ultegra 8050 is 11 speed.
So it may work to some degree,
but I wouldn't recommend it.
The spacing between the chainrings
is different from 11 speed to 10 speed,
and the chain is a slightly
different thickness, different gauge.
Now, one of the great things
about the Ultegra chains
that you have though,
on Ultegra 8000 is the bolt
spacing for the chainrings
is universal on those cranks.
That means that now,
you couldn't do this with older Ultegra,
but now it's all 110 bolt spacing.
What that means, is,
that you can put compact
chianrings on there,
mid-compact, like you have,
or even you can go up to 55 chainrings
if you really want to.
The great thing about that means
you could just buy some compact chainrings
for your Ultegra chainset
and put those on if you wanted,
and that way that will work fine.
If you want to spend a bit less money,
you could get the 11 speed 105 chainrings
and they'll fit on fine.
They might just have a
slight difference color,
but it'll still fit fine.
And that way you can get a 34 on.
Just make sure if you do that,
that you lower your front
derailleur slightly,
if you change compact rings.
Another option if you don't
want to change your chainrings
is to get a different cassette on the back
if you haven't done already.
So you could get a 30 or a 32 cassette.
If your Ultegra has a long cage rear mech,
then it will take up to a 34 cassette.
If it's just a normal one,
then it's officially
rated to a 32 cassette.
But, it will take a 32.
I know because I've done it.
You just wind in the B-limit screw.
I did that for my Everesting and it works.
Have a question from the THEoldgreydude.
Now, who says he loves the show,
and he has a question
just out of interest.
Not many things on bikes are standard,
there's so many different sizes
and types of headset,
and bottom brackets, and hubs,
and all the rest of it,
but pedals, the threads on them,
seem to be all the same.
Was there ever a time when there were
several different sizes of pedals?
Well, if you are THEoldgreydude,
you can't be that old,
because, well, even in the 80's,
there were still
different pedal standards.
But it's a good question.
Thankfully, we only really have one
pedal standard these days,
but imagine if it were
like bottom brackets
(makes shivering noise).
That would be horrendous,
I mean, it's a good fact actually,
the first bikes, people's left-hand pedals
kept on unscrewing, so this is back
in like Victorian times, 1800's,
and they had to work out that they needed
to put a left-hand thread
on the left-hand pedal
to stop it unwinding as
people rode it. Crazy.
Anyhow, most pedals have a 9x16 inch
by 20 thread per inch threads.
Although, pedals for one-piece
cranks back in the day
did have a half inch by
20 thread per inch thread,
if we're getting really nerdy
and geeky about this.
And then older french
bicycles used to have
14x1.25 millimeter threads,
but these are pretty rare.
Thankfully you don't see many of those.
But there you go, anyhow.
You asked so I answered.
Next up we have a question from Dapster,
who says he loves the show.
My question is from the
advent of thru axles,
how come rim brake bikes
don't come with them?
Since road bikes use 100
millimeter forks with a thru axle,
I'm sure they could do
the same for the rear.
135 millimeter rear thru axle
would be brilliant on a rim brake bike.
The answer is that they're heavier,
and they're designed to deal
with heavier loads on the axle.
Now, on a road bike with rim brakes,
this isn't required a lot of the time.
It might be beneficial
to some really powerful
sprinters, perhaps,
but disc brakes require them because
of the larger asymmetrical
torsional strain
that's developed from having the brake
low down next to the axle on one side.
And so under braking,
it's creating a twisting force
in the bottom of the fork,
so you need that greater strength
and rigidity of the thru
axle holding it all together.
So that's your answer.
Next up we have a question
from Solid Velocity who says,
what do you do when the disc
rotor is not rolling straight?
He says his road bike loses a lot of speed
when the disc is rubbing
against the brake.
Yeah, unfortunately this is quite common.
Disc rub can be really annoying
when you're riding along,
and you got that (makes rubbing noise).
You can use a tool to
bend it back into place,
if the disc is warped or bent.
But before you do that,
check that the caliber
is aligned properly.
If the caliber has been knocked,
then it might be rubbing on the disc.
Now, we have video where it teaches you
how to recenter the caliber,
so you can make sure that the
disc is right in the middle.
Now, if you've tried that
and you can see that it
is the disc that's bent,
it's easy to check,
you can look and you
can just spin the wheel
and see as it moves around,
if it's, like, got a wonky disc,
you'll see it moving.
If it is warped,
then you can try
and bend it back with a tool.
But generally the best thing is to do, is,
unfortunately to replace them.
Because once they get hot again,
then can often then bend again,
and it's very hard if a
disc is badly warped or bent
to ever get it back perfect.
It's tricky to do.
It's one of the unfortunate
downsides to disc brakes.
A question from Rhys Morgan here,
who says he's got a
Canyon Aeroad CF SLX Disc.
Good bike, that.
And he's currently running
Shimano Ultegra 6800 Mechanical,
so he's on Canyon's mechanical frame set.
He's going to upgrade to eTap,
which means that he's
no longer going to need
all the little holes for wires
and stuff there in his frame,
and he's wondering if
there's any hacks he can use
for grommets or bungs to cover the holes
and protect the frame.
Are there any hacks or
bodges that you can do?
Well, a short-term fix is
a bit of electrical tape.
That'll, you know, worth doing,
especially around the head tube,
'cause it will stop water getting in there
and potentially affecting
or washing the grease out
of the bearings that are in your headset.
Other brands may have frame grommets.
You say that Canyon doesn't
offer the frame grommets
for that particular issue.
Other brands will have frame grommets
that will probably fit
or that you could slightly
modify to make them fit.
I would investigate that.
Failing that, I would love
to hear from you guys.
If anyone watching has any suggestions
of hacks that Rhys can do.
I mean, if you really
wanted to go to town,
you could go to carbon bike
repair frame specialist,
which is carbon bike repair
who we visited before,
and then they can completely
cover it up the holes with carbon
and glue color matched with
the rest of your frame.
But that would probably cost more
than you're wanting to spend, I'd imagine.
So let us know in the comments
if anyone has any suggestions for that.
A question now from mm3burnett,
who says, I am upgrading my cassette
and crank sprockets soon
and was wondering, has anyone
ever powder coated them?
I'd like my bike to stand out,
but I'm unsure how it
would affect shifting.
I don't think a powder coat
would last on most components
unless it was some fancy-pants
tungsten carbide coating
with really high hardness on it.
But, I mean, it would probably come off
as the chain runs through it,
and end up clogging up the chain somewhat
with a bit of residue.
And I would also imagine
that a powder coating
adds quite a bit of thickness,
enough, I would imagine, to interfere
with the tolerances of the ramps
that are really, actually,
quite precise on the cassette
which could well affect your shifting.
There are loads of other
things that you can do, though.
So Wend Wax is a colored
wax that you can get
in various different colors,
you put that on your chain
if you really wanted to,
or you could get a gold chain,
I mean, we all love gold chains,
and KMC, they also do different
colored chains as well,
so you'd get a colored
chain, perhaps, as well.
But unfortunately powder
coating your chainrings, yeah,
wouldn't suggest doing that.
Lastly this week we've got a
question from Yeahbutnobut,
who says, can we all just
agree that front derailleurs
are more trouble than they're worth,
and can we move on now, please,
I'm a mechanic and they're
the bane of my life.
Uh, no, no we can't.
Well, one by systems do have
some advantages, admittedly.
They're lighter, they're more simplistic,
there's less to go wrong,
and they can be more aerodynamic too,
and they can look nice as well.
You have fewer gears,
you have bigger jumps between those gears,
and, well, narrow wide front chainrings
are less efficient in terms of friction
and drive train efficiency
than two by setups.
So, no, I quite like to
have the option of both,
and I'd like front derailleurs
to stay exactly where they are
for the foreseeable future.
Anyhow, I hope you found
this video interesting and informative,
and if you have,
then please give it a thumbs up.
Don't forget to submit
your questions down below
using the comment section
and the hashtag ASKGCNTECH.
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