(whoosh)
- Welcome to the GCN Tech Clinic,
brought to you from the last day of our GCN event
over at Avoriaz.
That's Dan Lloyd over there, look.
- [Off Camera Man] (laughing)
- You see that? (laughs) Loddy!
(laughing)
Coming up this week, I answer your questions
on squealing disc brakes, tubeless emergencies,
single front ring setups and disc brake calibration.
First up, is a question from Larry Dice,
who's struggling with squealing discs on his Giant Defy.
Now, Larry, sorry you're having this trouble.
Squealing discs, it could be one of three things.
First off, it could be a contamination issue
on the pads or the rotor.
It could be vibration, and it also could be your setup.
And I recommend doing the same protocol for all three issues
and that would be completely strip the caliper
down from the bike.
So remove the pads, take the caliper off the bike,
the spacer that's on there as well,
and then remove the rotor
and then give everything a really good clean
and then using a little bit of copper paste
on the contact patches that don't move.
Reapply everything and make sure everything's
nice and square and torque everything right up
to the manufacturer's recommended torque settings
and that should help eliminate your issues.
Good luck!
And hopefully this will actually finally cure your problem.
Next up is Kelly S.
Who has written in with,
"What is the appropriate way to remove
the bearing retaining clips
from a BB30 bottom bracket shell?"
Wants to replace it with a one-piece unit.
Now, I'm imagining you've got something similar
to what's on the screen now which means you don't actually
have the bearing circlip in there,
which would take a circlip plier.
So in that case you're going to use
two flat bladed screwdrivers,
hold one blade up against the flat end of the circlip
and then with the other blade of the other screwdriver
under the wedged end,
try and pry that up and out of your frame.
Be really careful not to damage the inside of your frame
but with a little bit of practice and gentle wriggling
around in there you should remove with not
too much trouble at all.
Good luck and take your time.
Jojo Feliciano, big fan of Jon's by the looks of it,
writes in with a question about going to 1x up front.
Running an 11-34 in the rear,
rarely uses the big 50 tooth ring,
so why not just remove it?
And of course, why wouldn't you just remove it?
Your bike would be lighter,
look a little bit sleeker as well.
And if you weren't using it anyway,
you're not going to be missing out.
Start off by removing the big ring
and then check that your chaining bolts
are actually not too long.
They were, of course, designed to fit
two chain rings in there.
And you might find that you either need to run a washer
over the collar of the chaining bolt
or just replace them with shorter chaining bolts
that are designed for a 1x setup.
If you are then going to be moving
that front ring to the outside,
you might want to also consider
running a specific narrow wide ring.
These have been designed to retain the chain
on the chain ring,
prevent any drops that you don't really want to happen.
I also recommend, actually, leaving your front mech
on there as well,
that adds a little bit extra security.
You can use the screws to adjust it to the correct position
but definitely remove the cable
for making it look a little bit neater.
Barry Ensten's up next with a question about tubeless.
"Is it better to take a spare tire and CO2 to seat it,
rather than an inner tube?"
I recommend absolutely taking an inner tube.
It's actually quite hard to carry a big, bulky tire
out on the road with you.
And then you're going to need to carry
sealant as well and all those CO2 cartridges.
And you never know with tubeless,
sometimes you can have a particularly difficult setup,
so you might end up snapping tire levers
trying to get the tire on.
It's just a lot easier to stick with
what you've already got
and just throw an inner tube on there.
And when you get back home you can set up
a new tire, tire tubeless,
on the next time you're ready to go out.
(smacking lips)
The next question is from Josse McKenney,
who's interested in going bikepacking
on his new gravel bike.
The gearing is a 48-32 with an 11-34 at the rear,
Ultegra RX rear mech,
so you don't get all that chain slap,
because of the clutch mechanism.
The rear mech's capacity is listed as 39 teeth
and a max low sprocket of 34.
Could he add Wolf Tooth derailleur hanger extender
to get a larger cassette fitted?
Well yes, of course you can.
On their website, they've got all the recommendations
for what size and what size extender that you actually need.
So, some of them are actually really tiny,
can barely extend it at all,
but others are two to three times the length
and you can use those.
You do need to be careful, though,
and they even say this on their website
that, actually, it's never going to be quite as smooth
as the shifting would have been
had you used the manufacturer's original one.
So you have to really question
do you need that extra gearing?
If you think you can get away
with the gearing you've already got,
using the standard mech with no extender,
I actually recommend doing that.
If you do decide to go down the extender route
and you put a bigger cassette on,
you might also need to consider
putting a new, longer chain on there, because, of course,
you're going to have about six extra teeth
to get the chain around.
And that could well be the difference
between a snapped rear mech or a nice, enjoyable ride.
Enjoy the bikepacking! Sounds like lots of fun.
Another question about disc brakes!
Now this one is from Paul Bertram
who has Shimano 105 hydraulic discs.
"Size for size, could I easily upgrade the discs
to Ultegra or Dura Ace without any other changes?"
And absolutely, you can.
You will probably have to realign your caliper
just to make sure that everything is, indeed,
running nice and true.
Which is a sensible thing to do.
And if you are putting new rotors on,
then you should also consider putting new pads on,
just so they bed in together.
You got a nice brand new setup working there.
But, it's a great way to try and save a little bit of weight
or just change the look of your bike
because all the rotors do look slightly different, enjoy!
Right, my favorite question of the week,
this one goes to Roger Furness, I'm sorry,
you don't actually win a prize,
it's just my favorite question, 'cause I'm a complete nerd
when it comes to this topic.
Roger has power meters on his bike
which he calibrates before riding.
When stopping for coffee the power meters sleep
and the Garmin Edge 1000 stays on.
Should he recalibrate the power meters
when they wake up again?
Now, I've written a really in-depth answer
so I'm going to refer to the screen every now and again
to make sure you get all the information
that I've put on the screen.
Because I am a nerd and I really enjoy this sort of subject.
So, over the years, the topic you've brought up
has been a great discussion on all sorts of forums.
And 15 years ago when power meters were quite new,
you had to really stay on top of those calibrations
because there was a lot of drift.
Except we're not actually talking about calibration,
we're talking about zero offset.
I don't know why it doesn't say
on the screen's computer head unit,
but it's like using the tare function on your kitchen scale.
Imagine you put a weight on your kitchen scale,
so a bag of flour or something,
then you press tare, it goes back to zero.
This is exactly what's happening
when you're doing the zero offset on your power meter.
Or at least as close as.
A calibration is when you hang
a set of known weights from your crank,
measure the zero offset and then input that data
into an online calculator.
You can do the calculations at home,
but I can't remember the exact protocol for that,
so I just looked it up on the internet
on cyclingpowerlab.com/powermetercalibration.aspx
And Dan and I are having a little discussion about this,
Dan Lloyd and I, the other day.
He used to love doing this as well.
He had a set of known weights that he had weighed
at his local delivery office, something like that.
Where you'd get a stamp of the weight on there,
'cause it's really important to have the exact number
to, I think, four decimal places, it was quite far.
So then you'd start off
by putting your cranks dead level
and you take three measurements weighted
and three measurements unweighted from each crank arm.
So both in the three o'clock position,
as it's on the bike,
and then you'd input this into the online calculator.
And you'll come back with what is known
as the slope of your power meter.
And this is a great way of checking,
is your power meter still functioning correctly?
If it's not, after you've done this,
you can then send it off to a service center
and make sure everything's back in check.
Going back to your zero offset question,
I thoroughly recommend doing it on every ride
because it gives you this little glimpse
into the health of your power meter.
If you were to see massive fluctuations from day-to-day,
despite not traveling anywhere,
then you would know that something
was going wrong with your power meter.
Generally these days,
they are much more stable than they used to be,
and you should have no worries whatsoever.
Let me know if you do go through this really nerdy route
of trying to calibrate it yourself,
'cause I'd be quite curious to see how you found it.
Right, that's it for this week's tech clinic.
If you do have a question you'd like answered,
drop it in the comments below
using the hashtag #AskGCNTech
and you can do that over on Twitter as well.
If you want another video to watch right now,
click on the screen there.