How Does A Chain Affect Suspension Performance | GMBN Tech Geek Edition

How Does A Chain Affect Suspension Performance | GMBN Tech Geek Edition


So this is the geek edition
of how does your chain effect your suspension. There are many different
factors when you’re talking about suspension kinematics. Things like brake jacking, anti-squat, but the one we’re talking
about today I pedal kick back. And how your chain tension
effects your suspension action. So, what is pedal kick back? Well, I did talk about it a
lot I the main feature, but basically it’s when your
rear suspension moves, your rear axle actually
moves away from that crank set and that stretches the chain. Of course, chains don’t stretch
so what actually happens is the crank tries to rotate
backwards but your weight is stopping it from doing that. So that chain tension actually
restricts your suspension movement. But that isn’t all negative,
because that does actually keep the bike firmer and
more stable when it comes to pedaling and it makes
that bike a better pedaler if you have a decent amount
of anti-squat on the bike, You’re talking about that
bike not being super supple. It’s all about being more
agile on a fast pedaling bike. And that does work well
for things like this. This is Nuke Proof Mega. It’s an enduro bike that needs
to be able to pedal well. It also keeps the bike
higher on its travels. So when you’re talking
about going through big compressions, things you
want to pump really hard, you don’t want to sink in so
far and lose all that effort. But, it doesn’t make your
suspension as supple. So if you’re talking about
pure suspension action, through the roughest terrain,
through rocks, roots, it’s not going to work as
well as a bike that doesn’t have a chain or any tension on it. That bike’s gonna move a
lot move if the chain’s not pulling. So I’ll try and give you
a quick example of what pedal kick back is so I’ve
taken the shock out so I can really move the
bike through its travel. I’ve butted the rear
wheel up against something so it can’t move. You see how the crank there
is pretty much horizontal. If I need push the
suspension down, it actually tips back. So imagine if your weight is
on that, it’s stopping that from rotating back so
therefore I tend to just go right through chain and it’s actually restricting
your rear suspension. Something we see most
mountain bikes rear mechs come with now is a clutch. Now that designed to put
tension into the bottom of the chain, so this part
here, um, see that’s with it off so the cage actually pushes forward. With it on, that now
it won’t push forward. So that means it’s much tighter. So your chain isn’t going to
bang itself like chain ring. So they have become much more
popular with enduro bikes, trail bikes, you know,
short trail bikes okay are ridden pretty hard, chains
come banks off them if you don’t have a clutch. So it helps that, however,
that again, something else adds more tension into that system. It does effect the sensitivity
of your rear suspension. We’ve seen a couple of incredible rides. Aarron Gwin, must have been
a couple of years ago now, at Leogang where he snapped
his chain out the start gate went on to win the race
with an absolutely amazing run. Of course Aarron is an unbelievable rider. So talented. But it did get everyone
thinking about how your chain effects your suspension. We’ve seen this same thing
happen just a couple of weeks ago with Rachel
Atherton at Fort William. Again, snapped a chain out
the start gate, ah, it’s a pretty physical track the
top isn’t quite so peddaly. But really it was on the
motorway section with loads of big jumps that she managed to clear and actually make time All the girls without a chain
was really really impressive. But just goes to show that
on full suspension bikes, that rear suspension really
does work well without that tension on the chain. So, of course you get rid of
the chain but that’s not very practical for most mountain bikers. So what were looking at
here is trying to devise a system that really gives
you almost a neutral gear so your chain can rotate around
the cassette, not be in one of those teeth and actually
restrict that suspension. Now, I’m not claiming
to invent this, at all. It’s actually Chris Porter
who’s a guy from Mojo Suspension in the UK, who’s
done this with bikes in the past. He’s experimented with loads of things. Things like putting weights,
so lead wights, on the frame of the bike on the rougher
tracks to try and play through the bumps. And I’ve seen him do this
with spacers so basically your chain runs down, sits on that plastic spacer so it just rolls around. It won’t really wear your
chain out ’cause it’s just plastic. I’ve only ridden this morning,
probably done eight runs on it, and I’ve actually
worn two sort of ruts in into this plastic spacer already
so it’s not going to last forever. But I have found it’s
been really effective. My suspension been working
really really really will today. And actually it’s not completely
stopped me from pedaling, because I can put it on to
the spacer when I do get to a slower section I can
bang it up through the gears and eventually the chain will
pull itself back up onto the cassette. I’m not saying it does it
very nicely and I don’t think the chain would last very
long if I kept doing it. Definitely could risk
snapping a chain doing it. But, it works. So I’ve actually really enjoyed
riding the bike like this. You get, you know, some good
cranks out at the start. Make sure you’re still in
your proper gear if you’re still pedaling and then
whack it into the neutral, give it a quick check to
make sure you’re there, then it’s all about your riding craft. Really trying to rail the
corners, get some nice wide lines, relax fast as you can, pump
as hard as you can and the suspension really does
feel completely different. It works really well. I’ve really found in some
of the steeper rough corners where I’m braking hard,
it feels much smoother and much faster. But it’ not without its flaws,
my chain has bounced off these spacers and wedged
itself into the frame. Luckily, it’s an aluminum
back end on my Mega so it’ not doing too much
damage although it doesn’t look that pretty. And once it’s wedged in
there, I’m really not benefiting at all. Also, I can’t peddle and
then it’s adding more tension into the system, so it’s
stopping my suspension working, as well. Again, once it’s gone and
I’m finding it’s actually starts to drop off the
chain ring, as well. So it’s all game over once
your chain has come off. I’m sure I could tweak it a
bit more, put a difference spacer on there to try and
stop it from doing that. It’s actually a pretty
simple system that I’ve done here and I’ll just show you
exactly how I’ve done it. So it’s really simple to try this mod. What I’ve done is got three
bomb bracket space, that they are, Doddy found
these in his tool box, and then just taking off my
11 and my 13 two sprockets. So this is a Shimano XT set ’cause they do come apart super easily. You can’t do this with
something like a Sram Eagle, that’s just a one-piece cassette. And then replace those two
sprockets with three of these spacers, and stick
my lock ring back on. That gives me a good amount of space. The chain sit there. I definitely think this could be improved. You could do with maybe
a sort of wider spacer behind the lock ring
so the chain can’t drop off the bottom of these
spacers and then get wedged in your frame. Of course, I’m doing
this on an enduro bike with 11 spade. I think this is gonna be
probably more applicable to the style of bikes where you have those smaller cassettes, those
seven speed nowadays. You’d have more space to
play around with fitting some of these plastic spacers. I think it could really work
for those down hill racers. I’ve been inspired by
Aarron Gwin, Rachel Atherton amongst others, and Chris
Porter to try this. But some manufacturers
have actually tried to find a solution to this problem. And one that springs to
mind is Canyon with their Sender disc connect. Basically, a system that
actually tries to disconnect the set from the free wheel
in the rear hub so that at any point on the track,
you could push a shifter, completely disconnects it
so your suspension works really well, could push
shifter back to normal and then pedal away. They said it’s really
just a concept bike at the moment. They’ve been testing it. It’s kinda dangerous as
this system is, you know, you could really mess this up
if you’re in neutral and try and peddle, you could really go flying. Same with the Canyon center
disconnect, but they are saying that they would
love to make this automatic so when you run to peddle then
reconnect it away it goes. So, watch this space. We do still see quite a few
variations of rear suspension design. One really interesting design
is the Commencal Supreme 29 and that’s been ridden for
the last two world cup downhill victories by the Frenchman Amaury Pierron. And it’s got that high pivot
on the back of the bike so basically gives you
a really good axle path That rear wheel goes up
and back so when you’re obstacles it’s really easy
for that rear suspension to work and be super active. However, that design does
give you loads of pedal kick back so to fix that
you’ve got that really high chain like this, so the chain
goes up over the swing arm and then down so that
chain rinse will fix that. However, what happens, the
rear of that bike actually the virtual chain stay length
of that bike changes all the time as the rear
wheel moves back and up. So it can be quite an unusual
characteristic for the rider to get used to. One final thing on suspension
design, uh, Doddy, the expert has informed me that
actually Santa Cruz with their VPP system actually rely
on some of that anti-squat and that chain tension to
actually keep the suspension in that mid part of that
travel so when the bike sags in, the chain actually
keeps it there to make that suspension work as they see fit. So it definitely does
play a big part in how your suspension works. I do wonder if there’s
a better solution to this but to be honest I really enjoyed riding it. I might even leave it on my
bike for a little bit longer. But let us know if you’ve
got a better idea, maybe a 3D printed spacer you can do at home. See if you’ve got me
wondering about BMX freecoasters if that would work. I don’t know if the hub
would fit but the idea of it being able to roll
backwards, I don’t know. That we know. Love to see your comments down below. If you want to see the original video, click up there for the feature. Give thumbs up if your a geek, as well. And hit that sub button GMBN tech.