- This is Ask GMBN Tech, our weekly Q&A show.
You ask the questions, we give you the answers.
If you wanna ask a question, get involved,
the email is address is at the bottom of the screen,
hellotech@gmbn.com, and if you wanna ask the questions
in the comments, use that #AskGMBNTech,
and get involved in the conversation below.
We love hearing from you.
So first up this week, is from Karolis Borkertas,
"I've got some Hope Tech 3 V4s that uses dot fluid.
"I wonder, can I replace the fluid with mineral oil?
"Would there be any benefit?"
No. In other words, they're completely different oils,
dot fluid and mineral fluid, they're not interchangeable
in any way.
Now, the reason for this is dot fluid essentially
can be corrosive to seals and O-rings,
and all the other internal components,
even including the hoses, on some brakes,
and mineral fluid's completely different.
So dot stands for Department of Transportation.
Now, it's a regulated fluid,
there's different categories in there,
and it's designed to withstand certain boiling temperatures,
obviously this is certified for motion vehicles,
like motorbikes, cars, lorries, that sort of things.
And they have to adhere to that, in order for safety.
Now a lot of bicycle brakes use dot fluid in them,
for good reason.
But also, a lot of brakes, let's say Shimano,
as opposed to your hose brake, use mineral fluid.
Now that's an unregulated fluid,
but a good thing about that is it can be designed
to spec for the exact brakes.
So Magura brakes, for example, make and manufacture
their own specific mineral fluids
to be compatible with their brakes, to their exact spec.
And the same with Shimano.
Now you can interchange some mineral fluids, but not all.
They are slightly different, and the manufacturers
do stipulate that, even though we have made it work
with many different brakes before.
The best bet is just use the recommended oil for your brace,
and you'll not run into any problems.
Okay next up, it's a shifting related question
from Leo Molloy.
Ask GMBN Tech, "Can you please ask for Neil's opinion
"on the Grip Shift Eagle on his Kangin Lux,
"I'm considering buying it for myself."
Before we get involved in that,
a Grip Shift, in case you don't know,
compared to regular, under-the-bar trigger style shifters,
is literally a section of the grip you can twist
to change gear.
Now they were really popular in the 90s,
although the ones back in the 90s were actually terrible.
They had a huge throw on them in order to change gear,
and you'd see riders as they're racing
literally grabbing big arms full of throws
in order to shift a couple of gears,
which is a terrible idea when you consider
your grip is your control area.
Now the latest version of the Grip Shift,
they're probably the lightest shifters available,
because there's barely any moving parts,
so you do the moving, as opposed to mechanical components
on the inside.
They're very reliable, because of this,
and of course, you move your hand position
in order to change gear, it's entirely up to you.
Now they're super popular on the XC world cup scene,
because they're so light, and because of the way
you use them.
But I know that Neil's not that much of a fan.
So Neil said, "It didn't suit the way I ride
"with my right hand on the end of the bar."
Yeah, so quite an important thing.
A lot of downhill style riders and Enduro riders
like to have their hands almost hanging off
the end of the grip.
Now I know that Neil has the end of the grip
imprints nearly on the sort of middle of his heel
of his hand here.
So of course, to use a Grip Shift,
he would need to cut his grips right down,
in which case he'd be almost on the Grip Shift itself,
so not good for him.
He had to move it a lot to shift,
but he did like the way he could bang through the gears
really fast and it shifted really well.
I've actually just made a super easy to switch
to an Eagle NX Shifter.
So he's using the regular under-the-bar shifter,
but he does praise the fact that you can just go
and do a whole load of gears.
And the same for you if you're in a really high gear
coming into a climbing situation,
you can just load up a whole bunch of low gears
in one go, where as under-the-bar style levers,
you can obviously change the placement
of the shifter itself, it doesn't always work out for you
if you wanna just dump a load of gears,
you can only do a certain amount,
depending on the shifter.
I think they're really cool,
I haven't actually used Grip Shift for some time,
but I'd definitely be keen to, in the future,
it's a lot of money to spend, so if you can,
try out a bike first, just to see
if it suits the way you ride,
but they're great.
There's nothing wrong with them, they're just different.
Alright next from Gareth MacDoyle.
"Doddy, I'm just wondering what your opinion is
"on Angle store headsets that Cane Creek,
"Works Components and Slackerizer make.
"I was thinking of making one my next mod
"on my 2010 Kona Cadabra.
"Are Z's and EC headsets
"interchangeable? Thanks Doddy, love this show,
"it's helped me out many times with numerous bike repairs."
Awesome, thank you!
Well first up, the Z's and EC I'm actually not sure
if they are compatible, but an easy way to check,
this is a proper good cheat system.
Just gonna throw you on screen right now,
here's a Crane Creek headset finder.
It's a really cool system.
It has most bike frames you could possibly imagine in there,
or at least you're gonna be able to find one
that's got the same configuration as yours,
and it would tell you exactly what style
upper and lower units are compatible in your bike,
including Z's, ZS's, all that stuff,
so that's super helpful.
But as far as actual angled headset cups go,
I think they are fantastic,
and you can really, really tune the way your bike feels.
Now the different types, I'm not too familiar
with the Slackerizer, but I've got a Works Component,
and I've got several Crane Creek angled sets laying around.
Now the angled set really is the king,
because of the fact it's adjustable.
So it's a simple system,
you have two different sets of cups, top and bottom,
then you have kind of like a gimbal effectively,
it sits inside that, and enables it to move
to the angle that the cup allows,
and then you lock it all down as you would
with a conventional headset.
Now this set up is really, really good,
because of the fact that you can adjust it
.5 degrees at a time, normally up to 1.5 degrees,
but sometimes up to 2 degrees,
depending on the configuration of your particular frame.
Now this is fantastic, because if you buy it,
and you say you wanna take a degree and a half off,
and it's too much, you can put a half degree back on,
and settle on that 1 degree, which is fine.
However, you do get some issues,
especially with longer travel forks,
and on some configurations, they can creak
if not installed absolutely, pin-pointedly perfect,
because a gimbal system can move.
We're talking like a microscopic amount,
but that's enough to lead to creaking.
It can drive you crazy.
Now they are absolutely fine,
as long as they are installed completely perfectly,
but this can be hard to get it that precise,
so for that reason, I do prefer going for something
like the Works Components, which is a fixed cup,
but in order to do that, you do need to know
the angle you wanna go for,
otherwise it starts getting expensive,
having to buy a .5, a 1, a 1.5, etc.
So work out really what you wanna do,
and weigh up on the cost.
Obviously the Works Components will be slightly cheaper
as well, and once it's fitted, it's fit and forget.
It's just gonna do the job,
exactly as you want it to.
Now if your bike say had a 66 degree head angle,
I'd be fine taking off a degree,
because you can adjust for a degree,
but taking off a degree and a half
is gonna change quite a lot on your bike.
It will lower the front end very slightly,
it will steepen your seat angle very slightly,
all minute things, but that head angle
will have a dramatic effect on handling your bike.
Now I've had friends, who have gone the whole hog,
the one and a half degrees before,
and actually not liked it.
They found it's gone too far for them.
So sometimes, half a degree or a degree
is all you need.
So if possible, try something out with a similar head angle
to what you're trying to get to first.
But it's not always gonna be that simple,
they do vary.
So if you're a fatler, maybe the angled set
is the best way to go.
But if you're not quite sure,
and you don't wanna mess around with that stuff,
pick a number, half a degree or degree,
commit to it.
If you don't like it, sell it,
and buy the one that you do like.
Okay so this is actually a really cool question.
This is from Alfonso Lizarazo.
"Great video thanks. I still don't understand
"how rear shocks are measured.
"For example, I have a 120mm travel fork at the front,
"and it's actually 120mm. I can measure that on some rides
"to determine the percentage I'm using,
"so that I can adjust it.
"But on the rear, I have a 120mm travel.
"But how do you measure it?
"The shock obviously isn't 120mm.
"Can you please enlighten me on that?"
Okay Alfonso.
So the first thing to think about is,
the fork is telescopic.
So what you see is what you get.
You measure the 120mm, that is what you're getting.
At the rear shock, you've got anything
up to about 65mm of movement on the shock itself,
and it will translate to more travel at the wheel axil.
The amount the wheel axil moves is 120mm in your case.
Now obviously, the shock moves a little bit,
the wheel is further away, so that's what it equates to.
It's kind of like looking at a seesaw.
So if I was just to say this Alan Key was your pivot point,
and then for example, on this end of this screwdriver
is your shock, and that end is your wheel.
It's something like this.
So, your rear shock moves a tiny bit,
and the wheel moves a lot.
So it's called the leverage ratio.
So this can obviously change,
depending on how much travel the shock has,
and the configuration of the suspension on a bike.
So if your bike was to have a 2:1 ratio,
for every 10mm that the shock moves,
the rear wheel will move 20mm.
It's that simple.
Now there's loads of different suspension designs
on bikes out there,
and they all have different leverage ratios,
different length shocks.
There's a lot of configurations.
So the way to do this is, you set up your shock
with a percentage of the sag on that.
So you don't have to worry about the 120mm.
If your shock has got 60mm of stroke,
you could work out a percentage from that.
Now on some shocks, you'll even have markings
on the actual shock shaft itself,
to help you work out, like this one on the screen,
whether you've got 20%, 30% or 40% sag,
so you can set up to your desired amount.
Just use a percentage of the available travel,
which on any rear shock, it will compress
the whole amount of that shaft,
so that is where you measure your sag.
Okay, so last question's from Dwight Jackson.
"Really like your videos.
"I just bought my mountain bike,
"which is a used 2013 Santa Cruz Tallboy C.
"I live in Jamaica, where there isn't a lot
"of trail riding, but it is very possible
"given the makeup of the country.
"The bike has dual shock absorbers,
"with 100mm of travel, which from watching your videos
"I think will be fine with what I'm doing.
"However I wanna know if it's possible
"to safely change out the sock absorbers
"to 110m rear and 120-130mm on the front,
"or can I get the existing 100mm absorbers
"to perform like 120mm by adding those things
"I've totally forgot the name of?"
Well firstly, Dwight.
Awesome to hear from someone in Jamaica.
I know there's not a massive riding scene over there,
but I have heard of a bike park over there.
I've got a feeling it's a private park,
but either way it's a country
I'd absolutely love to visit at some point.
I'm stoked to hear from someone over there.
Alright, so firstly, your bike is absolutely fine
for most things you're ever gonna throw at it.
So the Tallboy 29" wheels is gonna eat up
what you throw at it, no problem.
It's got really stout frame,
with 100mm of travel, front and rear.
Now outback, you can't extend that travel unfortunately.
Even if you could fit a longer shock
into that frame design,
it's gonna change your angles too much
and gonna mess up the handling of the bike.
But chances are, you won't even be able to fit one in there,
because of the way the backend won't be able
to extend enough to cater
for the addition length needed on the shock.
But, your shock is absolutely fine on there.
Now depending on what model of shock you have,
whether you have a Fox or a Rockshox unit on there,
there were different options available,
so if you leave a comment underneath this video,
in response to this answer,
I'll see if I can give you some more specifics.
Now you should in theory be able to fit
air volume spaces,
which I think is what you're talking about,
into that shock.
Now you don't always need these on a bike.
Now the Santa Cruz Tallboy's got a nice feeling
backend on there.
It can feel a little linear,
but that does make it feel like
it's got slightly more travel.
If you put air volume spaces in,
it will feel a lot more progressive,
and a little bit more supple
at the beginning of the stroke,
but that can actually make it feel like
the backend has slightly less travel.
So I would just get used to riding the bike,
as it is, to be honest.
I think it's absolutely fine,
and rest assured, you will cope with almost anything
you throw at it.
Now upfront, you definitely could extend the fork
to cater for a little bit more travel.
Now I wouldn't go more than 120mm,
so adding 20mm to the 100mm you've already got on there,
cause you will just make the bike
a little bit too relaxed,
and the handling gets a bit wishy-washy.
So a 120mm, with a 100mm out back.
It'll feel like a really good bike.
Now again, it depends on what model of fork you have,
I'm assuming it's probably got a Fox or a Rockshox on there.
Now some forks around that era,
you could effectively internally adjust them
to give more or less travel,
but more commonly these days,
on both Fox and Rockshox forks,
if you wanna increase the travel on a fork,
you will need a new air tube inside.
Now this is a relatively inexpensive part,
and it's fairly easy to fit,
if you're into your home mechanics.
All you really need to be able to do
is a lower legs service, essentially,
and then take out that air leg unit on the inside.
If you wanna know how to do a lower leg service,
I'm throwing a link to that
in the description below this video.
Now if you feel comfortable with something like that,
then I'm pretty confident you'll be able
change that air tube.
Now you can get these from £20-£50,
depending on the model that you need,
for your particular fork,
and you'll be able to extend that,
no problems whatsoever.
And if you want a little bit more help with that,
if you just let me know the specific models
of the shock and the fork that's on your bike,
I'll see if I can make some exact recommendations
for you, cause I just think it's super cool
to have a Jamaican mountain bike rider,
watching my channel, so thanks for tuning in.
And that's all for now folks.
So for a couple more great videos,
click down here for a fork, lower leg service,
and click down here if you wanna see how to bleed
a SRAM bleeding edge brake.
As always, don't forget to get your comments
in this section below.
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and don't forget to click subscribe!