(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.