- Hello everyone.
Here's a brief explainer on threads on a bike.
Why they go certain directions
and understanding why they might work loose.
(dramatic sound)
Before we get into the nitty gritty,
let's start with direction.
A right handed thread is your most common
and left handed, often called averse,
is used far less frequently and where it is used,
it's application dependent.
The term right hand or left hand is named
not so because you tighten it with your right hand
or because the thread goes to the right
and adding hand at the end made it feel all the more homely.
It's because if you had a right handed screw on the counter
and place your hand with your thumb
pointing in the same direction
as the plane that the screw is going into,
then your fingers point in the direction
the threads elitely wrap around the axis.
It's the same on the non-drive side pedal.
And speaking of pedals, why do they have threads
that run in different directions?
What if our pedal threads were both right handed?
Well, then the non-driver side could potentially work loose.
As the non-drive crank goes through its rotations,
the axle is fixed, but the platform needs to allow movement.
Those bearings on the axle are rolling.
And even if running well looped and in good shape
will still generate a small amount of friction.
This is especially true when we add flex to the system.
And it's that small amount of friction
that will help tighten the pedal instead of loosening it.
The theory also goes that as bearings begin to seize,
the units will begin to loosen.
This isn't something that's happened to me personally,
but it would make sense
if there was a large amount of friction.
Another note where the opposite thread is in the drive side
of our bottom bracket shelves.
As the crank comes full and over it will tighten the thread.
But hang on a minute, these directions are all wrong.
Surely, that left hand pedal which is constantly turning
to the right and that Right hand crank,
which is coming up and over the bottom bracket
in a clockwise direction are going to work
irrespective fixing's loose.
Surely, well, let's focus on our cranks here.
You have to remember that the inboard of the bearing
might in fact be going clockwise,
but the outboard of the bearing
will be doing the exact opposite.
Now, let me demonstrate with this humongous bearing.
As I roll along the counter, you can see the inboard
and the outboard work inversely to one another.
Its the direction of the outboard that's important.
As that will be the thing driving our hardware.
The last prominent averse thread found on a bike
is often in rehab assemblies.
How do you know if it's in reverse thread?
When it's already in?
Well, it's a tricky one.
Be sensible and don't try and remedy
it with heavy handedness.
Knowledge is your friend.
If you get the feeling that something just isn't coming,
try and find the tech document.
The best way to identify threads when the axis is visible,
is to look at them square.
If all the threads points towards the top right,
then it's right handed.
If they go to the top left, then it's left handed.
Most pedals and bottom brackets have some kind of indication
be it a line on the non-drive side or a simple L.
So let's look back at our pedals and bottom brackets
and be sure in our knowledge before moving on.
Is everyone square?
Now let's look at the size of our threads.
(bouncy music)
Threads are often broken down into two terms;
coarse and fine.
The term coarse is used when there is a greater distance
between each thread.
And a finer thread is the opposite,
when there are more wraps of thread at any given distance.
However, please make a note here
that neither term is a denotation of quality,
but rather a technical term.
The more coarse a thread is,
the less likely it is to cross thread.
It also means there can be a great differential
between the major and the minor thread diameters.
Think of the major thread as the mountain's peak
and the minor thread as the very bottom of the valley floor.
All of this subsequently correlates
into that whatever our boat is turning into,
is less likely to thread, and it's quicker to do up,
perfect, for something like fork axles.
The more fine a thread is, then the better
it is at minor adjustments.
So perfect for aligning ideas.
It also has a longer wrap of thread for the same size
of bolt when compared to something more coarse.
Let me show you this string.
The bolt hasn't changed, but we've been able to maximize
the amount of thread wrapped around the axis
by using a finer thread.
A finer thread is more efficient than a coarse one
at transmitting Talk.
This means that higher tension can be achieved
at lower Talks.
Now I think I've been talking enough.
(laughs) (banging table)
onto persona non grata (foreign language)
Friction.
(bouncy music)
When you're tightening something up,
you will at some point,
notice an increase in torque required to turn the ball.
In an ideal world, this feeling is derived
due to clamping force at the head of the bolt
and not friction in the thread.
This can depend on a number of factors such as how fine
or coarse that thread is,
and whether it is lubricated or not.
The last big factor is the material.
(bouncy music)
It's also worth noting that some materials
have a friction coefficient far greater than others,
and some screws are application dependent
to achieve desirable results.
I think sometimes, and it might just be me,
but I'm often skeptical about five newton meters
or other top specified ratings.
Because most of the time, in bicycle components at least,
they don't specify what we're treating the threads with.
If a two five Newton meter torque reading with a loot box
is drastically different to the same talk reading
if the thread is dry.
I'm sure we've all turned break bolts
where they have so much compound on them,
they're hard to get in or out.
Well, take that experience and apply
it to the bigger picture.
Is it tension at the head or friction in the bolt,
they were measuring, friction coefficience,
quite a complicated matter.
The lower the number is, then the less their gripping
against each other.
There is a static and sliding measurement.
Static can take a great feel of forced to overcome
and then the force required lessens,
to continue to overcome the sliding friction.
This of course is being similar to pulling a car.
It can take a huge amount of effort to get it moving,
but once it begins to move, it requires less effort
to keep it rolling.
So, do we want high static friction in our bolts?
Well, it is me my opinion, we want at the head of the bolt
and not in the thread.
It's for that reason,
that sometimes we conversely put grease onto things
when we want them to stay put.
Its so the friction required to achieve that static load
at the head of the bolt is reduced.
So, how to retain our bolts.
Apart from having Talked them correctly Of course.
Well, you can use a washer
between the bolt head,
and the thing that is clumping towards.
This enables the head to spread its load evenly
upon the surface it's being driven against.
Ever wondered what that wire does,
that comes in shimano break adapters?
It's there to run through the small holes
in the head of the bolt and wire them into place
that stops them unwinding over time.
Threadlock appears in all kinds of places of our bikes.
They could be separated into two different groups,
anaerobic and aerobic.
Anaerobic is the kind that comes in a liquid form.
You apply it to the threads and once assembled,
it will slowly cure independent of the bar.
In its liquid form, it can even reduce the friction
on the threads to aid assembly.
Aerobic, which is often referred to as dry,
this comes applied straight from manufacturer
and is primarily used to fill out threads.
It can whittle away over time,
so if you ever installing and reinstalling a lot,
don't be afraid to top it up
with some anaerobic thread locker.
Retaining compounds are more like a party.
They often aid in keeping things
that pressed or riveted in place.
It's a pretty common when on road bottom bracket shells,
the bearings are pressed straight into the frame.
And if the tolerance is even slightly out,
you sound like you're being chased
down the road by John Bonham.
Now retaining compounds and thread lockers
come in a huge variety of strengths.
The weak ones are made so you can still service the parts.
Be careful where you use the strong ones
and even on what material.
I've seen soft alloy bolts
loose their whole thread before,
because they become chemically bonded
due to either excessively strong
or excessive amounts of thread locker.
Sometimes well, things can just go awry.
Now cross reading is something that is easy to do,
especially with finer threats.
A good way to avoid it is to turn it backwards
in the opposite direction that the thread runs.
While you're pressing it in lightly.
You'll eventually feel a small click
as the units find their starting threads.
Then you can dial in from there.
And what to do,
if you've completely removed all of the threading there.
Well, when damaged to a lesser extent,
sometimes they can be just cleaned out with the tap.
Often though, you won't be so lucky.
Losing all the thread or damaging them beyond repair
is a common problem with crank sets.
I, in my experience, find running a pedal
with washers helps prevent this.
If however, you're already up a certain kind of Creek,
without a certain kind of paddle,
you might be reaching something to rectify the damage.
A heli coil.
A heli coil is a simple device
where you drill out the original hole to increase its size
slightly and tap it with a thread.
You then fit a coil, you in some cases insert a tube
that has thread on both the outside and the inside.
You then fit this coil using an external thread
directly into the crank.
Then apply a good dollop of thread lock
to leave it to the set overnight,
like a prize winning blancmange
before re-installing your pedals.
Once that pedal is installed, here are some notes.
In my experience, it's a good way to salvage a crank,
but it is a repaired unit
that I don't think is as strong as the original.
It won't like super hard compressions for instance.
And letting that thread locker cure is absolutely vital.
And you must must must must must
connect with a pedal washer.
The same theory applies to other heli coils and inserts.
Sometimes you hear people heli coiling
stems or their foreclose.
The problem lies when you having to remove material,
potentially weakening the parts, to install the heli coil.
Or as you increase the diameter, the original thread,
it's weakening it.
So just be wary, as it can often be a can of worms.
(air whooshing)
And so there it is, my thread explainer.
Certainly a mouthful some of that.
Now if you want to stick with the channel,
click down here to see a tour of the Gore Factory
with Daddy, which is highly recommended.
And click down here for a real time service,
of an air shaft on a RockShox Fog.
As always, don't forget to like and subscribe
and we'll see you next time.
Cheers.