(clanking iron)
- So I'm back with another episode
of the GCN Tech clinic where we answer
your tech related problems and questions
and quarries that you may have.
First up though, last week I tackled a question
from Paraic Furlong who wanted to fit an 11 speed
cassette onto a 10 speed free hub,
on a Shimano RSAT wheels.
I did in fact give a couple of options
but Shimano have actually got back to me
with another option and it was the following
the CSHT 800 mountain bike cassette,
which is an 11 to 34 ratio.
Basically by using a 34 tooth sprocket
you reduce the chance of any interference
between the rear derailleur cage and the spokes.
So there you are; however, you're likely
or possibly anyway, gonna need a new
rear derailleur for that because a 34 tooth
cassette isn't necessarily compatible
with your current rear derailleur.
But hey, that's for you Paraic, for you to decide.
Right, let's get on with it then shall we?
So, a question from Russ Starke, who says,
"With most of the breaking power up front
"why bother with a rear disc?
"Why not have a disc upfront and a direct mount
"brake in the rear, especially for pros
"with in race rear wheel swaps."
It's a great question actually and I can't answer obviously
on behalf of the pros because I'm not one
but I don't even know.
Maybe it's been tried in the past.
What's important to remember though is that by using
a disc brake it's not actually for out and out
power, cause that's just gonna result in a skid
and loss of control.
It's actually for modulation and essentially
it really comes into it's own in wet weather
and poor conditions where using a rim brake
isn't necessarily the best option.
And I think most people have used disc brakes
can agree with that.
Now, I think the big stumbling point here
will actually be the feel of lever hoods.
So a rim brake and disc brake lever hood
are gonna feel different because there's a reservoir
inside the disc brake hood to obviously hold the oil
or fluid so that's gonna be the biggest challenging
point I imagine because you don't wanna have one
feeling different from the other.
But, it's certainly for one to ask the pros
when we meet them next if they would use that option.
So, I'll keep you posted.
Next up is a question from Osman Erdogan who asks,
"Hi guys I hope you're well."
I'm fit and healthy so I can't complain.
"I'm upgrading my bike at the moment from Tiagra 4700 set
"to an Ultegra 6700 set.
"Everything is bought apart from the shifters.
"The question is can they use 6700 Ultegra rear derailleur
"with a 6800 Ultegra shifters?"
Osman, nice bit of upgrading there.
The Ultegra group set is actually a fantastic bit of kit
and great value for money.
Now the internal ratchets of the 6800 shifters
are different from the 6700.
So there's a different amount of lever movement
which in turn changes the amount of cable
that's been pulled at the rear derailleur.
Unfortunately, you're not gonna get spot on gear shifting
there so you're gonna have to match the levers
with the mex in that case because really
you want to be going along with smooth gears
because you're gonna enjoy your bike riding more.
So, make sure it matches.
Next up is a question from Kev O'Meley who asks,
"Were the teams concerned with tubular tyres,
"that they would come off the rims in extreme heat
"at the Tour Down Under?"
Hi Kev, great question, I was actually at the
Tour Down Under this year and I had the sunburn
to actually prove that too.
I spent quite a bit of time actually there
with mechanics and none of them mentioned
any special procedures or really any concerns
that any tubulars would come off of the rims.
And in fact, it doesn't happen that often anymore.
Years ago we used to see it sometimes
in the mountains back in the 80's and 70's
you would see the old tubular tyre
would come dislodged from a rim probably
through a mixture of heavy braking and also the heat.
In recent times though, there's a couple for you.
2015 there was a stage of the Tour of Oman
I think it was, where they actually had to cancel a stage
because of extreme temperatures and there was
a photo going around of a tubular tyre
that actually come away from a rim
because of the glue melting.
I'm not sure if it was during use or if it was
because the wheel was left out in the sun.
Direct sun, obviously, on something that's not moving
along, yeah, it's not gonna take long really
for that to get up to temperature.
And in 2016, I think it was, Wilco Kelderman,
he actually had a crash during the Tour de France
and that was caused through melting tubular glue
apparently and I think it was George Bennett
who assisted him with his problem and actually burnt
his hand on that hot glue.
So there's one for you.
But no, I didn't actually hear anything about that.
Continental, they actually make a special glue
for carbon wheels so when you're braking on carbon rims
it generates quite a lot of heat which in turn
could possibly melt glue.
They've actually got a special compound of glue
which apparently is better at resistant
to the heat generated through heavy braking
on carbon rims.
So there we are.
So Sam wants to know, "Tape or glue for tubs?"
Right, well for those of you that don't know there are two
methods of attaching a tubular tyre to a rim.
First up, let's talk about tubular tape.
So essentially it's really strong double sided tape
that is applied first of all to the rim
and you apply it with loads up pressure.
And a little tip here, I actually once I've applied
that tape on, I put the tubular on, inflate it
to it's maximum pressure, that in turn forces
the tape even more onto the rim and then basically
I go through the whole process of fitting
the tubular tyre to the rim.
We have actually got a video in the description
down below so you can check out how to do that.
Tubular glue, well the name gives it away.
It is a glue and it is specific as well for tyres and rims.
Essentially, there are different methods.
Some people don't like to apply too many layers
of glue onto the rim whereas others like to apply
lots and lots.
Take for instance cycle o cross riders, they will
put on quite a lot of glue because they don't want
that tyre to dislodge from the rim.
The reasons being, they're using a lot less pressure
in the tyres so there's less pressure
being forced onto the rim from the tyres based tape.
So when they go around a corner,
they don't want it to fall off.
With tape, it could possibly happen.
Now, I've used both of them and I've never
actually had a tub come off of the rim.
For cycle o cross though, I've never used tape.
There will be people I'm sure, who have used tape
and with great success and I'm sure they'll
let me know in the comments down below.
But ultimately, it's up to you.
If you're short of time then go for tape.
If you wanna do a really good job, make that tyre
extra secure, then go for glue.
Next up is another tyre question,
feeling all rubbery today.
This one's from Felix Baquedano who says, "Could you
"do a tutorial on how to fit a tube
"into a tubeless tyre in case of emergency."
Well, this one is actually pretty simple.
It's exactly the same as fitting an inner tube
to a normal tyre.
The only thing is that quite often tubeless tyres
are a little bit tougher to actually put over
the edge of the rim and put in place.
Reason being because obviously they're a lot more
air tight for their intended use
of being a tubeless tyre.
One thing to also consider is once you've put it in
and inflated it, the tyre may not sit exactly right.
So if that is the case, just give it a little bit
of a flex backwards and forwards to actually try
and get it to pop into position.
And yeah, inflate it to your desired pressure.
Personally, I'd probably try and head home
because it's quite unlikely a lot of the time
without a CO2 canister, for instance,
that you're gonna get that tyre back
into it's original place cause tubeless tyres
can be sometimes a little bit of a pain to fit.
Next up is from Tom Govelitz who asks, "Hi GCN
"I just got a set of Mavic Cosmic Pro SL tubeless wheels
"and my question is if you get a flat, which they did
"on the first ride after hitting a huge pot hole,
" and the sealant does it's job, should I replace
"the $80 tyre, or did the sealant make a permanent fix?"
Hi Tom, well that's a pity isn't it, on your first ride
you had that happen.
I once hit a pot hole so hard and deep,
I thought I was gonna need a ladder to get out of it.
And do you know what?
It wrecked the rim, it dented it
and I got puncture so it wasn't good.
The good news is though your sealant did it's job.
But have a good look as well to make sure
the tyre isn't damaged from the pot hole
and also the rim itself because you may have
hit it hard and it might have dented it.
Fingers crossed tough for you Tom,
you haven't had that happen.
But just give it a good inspection,
and the good news is you didn't get a puncture.
TriRussell and this is a very regular commenter
and also Tweeter for GCN Tech.
They ask, "Can non-tubeless ready rims be run
"with a conversion kit and a tubeless tyre safely?"
Basically, in my opinion, it's a tough one.
It is really, really tough because you have got
that conversion kit and it is a tubeless tyre
but basically I wouldn't use it, I don't think,
from my own piece of mind.
I've never tried it.
There will be people who have and I'm sure
they'll let you know TriRussell
in the comments down below.
But I'm afraid I can't answer from firsthand
experience if it is safe or not.
But, if it's not designed for that purpose,
personally I wouldn't go for it.
Next up is a question from Can Vural who asks,
"Should the inner bearings of a BB90 bottom bracket
"come out really easily?
"They removed the crank and part of the bottom
"bracket was stuck to it.
"They put it back in place but it's easy to move.
"Is it supposed to be like that?"
Okay, right, so just to clarify things
for everyone at home.
The BB90 bottom bracket is a press fit one.
So ideally, you're actually gonna need something
like this to remove the bearing.
So you go from one side of the bottom bracket
through and then hit it out with a hammer.
Requires quite a bit of force so it doesn't sound
ideal really that your BB90 bearing was able
to be removed like that.
What's worth remembering though is that there is
actually a V2 bearing available.
What's that?
It's not .1 millimetres bigger in diameter
than the first edition of the bearing.
So pop along to your local shop, get them
to have a look inside your bottom bracket
to see if there is any other reason
why that bearing has come out so easily.
If not, sounds like the V2 bearing could be
the answer to your problem.
Now, Samuel Ljungvist asks that, "I'm thinking about
"buying a power metre, specifically a stages.
"Can you for example, use an Ultegra crank arm
"on a 105 group set or vice versa?
"So if they upgrade components later
"it would be nice to be able to use the same power metre."
Great question Sam and actually
that's a really good option to use
because traditionally power metres used to be
on the real high end scale of pricing.
Yeah, providing if you're using the same style
of fitting, then it's not a problem at all.
So you're probably talking about Shimon
Holotech 2 so it uses the same fitting type.
As far as I'm aware, it doesn't actually change
the cue factor so that's the distance
from if you take a vertical plane
through the bottom bracket shell and the distance
on both sides to the centre of the pedal,
it doesn't actually change it
as far as I'm aware.
So importantly, keeping you even and being able
to let the power out that you can measure.
Daniel Brace, "Hello guys, I have stripped the threads
"on the drive side crank arm, is there a way
"of it being salvaged or is it time
"for a replacement?"
Daniel, a stripped thread.
That is an absolute nightmare in nearly all cases.
I think, now you haven't said if it's your pedal thread
or if it's one that you would use an old school
crank puller like this, so that would be
in the centre of the crank.
You'd screw that in and then wind this handle in
to force the crank off the bottom bracket.
But let's assume it's your pedal thread.
The good news is Daniel, you can salvage that crank.
Essentially what you do is actually remove
that thread with a special tool and then you insert
a bush or a heli coil in there and that's held
in place with glue or really strong lock tight.
I can't remember, I've never actually done it myself.
I have seen it done.
It's kind of a last resort really.
So if it's a very old crank that you can't find
a replacement for then that's certainly an option.
Personally I'd be tempted to have a look around
for a second hand replacement.
So you can just have a matching pair and you're not
gonna be using a glued in petal thread.
Okay, next up, Ben Moore who asks, they have one
gear which they can't use moving from the easiest
gear to the next easiest.
They have to change gear twice and it jumps a gear.
Is it an indexing issue or something else?
All changes are smooth.
Right, first thing I would do is have a look
at where you're inner cable goes into the outer cable
so then by the derailleur most likely,
and check to make sure that the cable there
is not kinked at all because if there is
that could be adding a little bit of extra
resistance to pull that cable in to the outer cable.
Another thing to check is that your cables
are working nice and smooth so that they're
nicely lubricated.
Also, check that the cable is clamped
in the correct position on the derailleur.
I have seen people do it wrong before,
leading to mis-shifts.
This one is gonna sound a little bit daft
but have a look at your cassette and where the
gears are not working right, make sure
that the sprocket is actually fitted
in the right direction so the profiling
or shifting ramps actually match
the other sprockets there.
That, well, is probably quite enough
to be getting on with but finally
check the rear derailleur hanger.
So make sure that it is nice and straight
because quite often that can actually plague people
with bad gear shifting.
Let me know how you get on.
Ali Yazdi wants to know, "Can car gear lube
"be used as a chain lube?"
They've seen motorcyclists use it on their chain.
Well Ali, you could but car lube
is pretty thick generally so it's not
gonna be ideal for the job where as a bike specific
lubricant is nice and thin so when you apply it
very carefully I must say as well, it can actually
get into those rollers and pins and work better.
A disadvantage really of that car gear lube
is it's gonna be thick and so thick
that it's just gonna attract dirt
and not work its way into the rollers.
Yet, people have used it in the past
but personally I wouldn't recommend it.
I'm quite meticulous about lubing chains
and I reckon our viewers are too
and they will let you know why not to use it
or maybe why to use it in the comments down below.
Final question this week is from Yura Tolstik
who says, "Can I use Shimano fishing hooks
"to pin a race number?"
Of those of you that don't know,
Shimano do actually make fishing equipment too.
I guess you could but you may get
reeled in quicker if you try a salt breakaway.
There we are, made me laugh anyway.
Now do remember as well to let me know
your tech questions down there
in the comments below and I'll try
and answer them here on the CGN Tech Clinic.
Remember as well to like and share this video
with your mates, always helps and also check out
the GCN shop, loads of goodies.
Now, for a video on essential tools
for your home workshop, click just down here.