Henry Quinney: We know how to change the weight of our mountain bikes, how to add a burlier
setup, or indeed lighten it up. We know we can change pretty much any single piece of
componentry for a different purpose, but how do we change the geometry of our mountain
bikes? Well, today, with some slightly left of field thinking, I'm going to take my new
proof reactor into three distinct different geometry setups.
What is my goal? My goal, like I said, is to take this bike into three very different
setups. The first is an XE-inspired bike not totally dissimilar from the reactor ST. The
second is the bike as you see it before you, my middle ground, which is my go-to normal
riding setup. The third is a bike where-- Well, I'm going to try and increase the rear
travel, but I also wants to give it the same head angle as the reactor RS. Now, the RS
is the most aggressive bike in the reactor lineup and comes with a 10 mil longer fork
as stock. What tools do I have available to me to change
the geometry? Well, the first and most obvious is the flip chip on the seat stay. Now, this
means I can alter the geometry between two settings. There's trail and rail. Trail is
half a degree steeper, so it takes the seat tube and head tube to 75.5 degrees and 66
degrees respectively. It's not just the geometry that changes, but also the kinematics of the
suspension itself. Now, having it in trail mode basically increases
the value of anti-squat. This essentially means that it'll be more efficient under peddling,
but like everything with mountain bikes, it's a trade off. A higher value of anti-squat
tends to impede suspension performance when descending, but that's why Nukeproof give
you the flip chip so you can decide for yourself. That's my first means of adjustment. What's
my second? Well, my second is I'll be adjusting the stroke
length of the shock. What is stroke length? Stroke length is the length of suspension
that compresses. For instance, on 140 mil travel fork, the stroke length is 140 millimeters,
but our shocks have a lot less length. How does that work? Well, on a linkage system,
there will be a ratio, say 3:1. That means for every centimeter that the shock compresses,
the rear axle will move 3 centimeters. This particular shock on this particular bike
has a standard stroke length of 50 millimeters giving 130 millimeter travel, but I can decrease
it to 47.5 millimeters and increase it to 55 millimeters. That means I can take it down
to 125 mil travel whippets, or indeed increase it to a burly hundred and 40 mil travel bike.
That's not all. To accompany the different travels outback, I'll also be changing some
of the fork internals and things at the front of the bike to boot.
Now, when I thought about this video, I wanted to keep it relatively cheap as I wanted it
to be something that you could potentially think about doing yourselves. It's for that
reason I imposed a strict £100 budget cap upon this challenge, so needless to say, I
had to get a little bit inventive later on. This is my first setup, and it will count
as my midway point. It is 140 mil travel fork paired to a 50 mil stroke length, which gives
130 mil of rear wheel travel. I run it in the rail mode, so that gives a seat tube angle
of 75 degrees and a head tube angle of 65.5. Now, a modern trail bike like this can do
pretty much anything, and it covers me for all the eventualities I find out on my riding.
Now, a huge factor in this, and something that's very important when fettling with our
suspension is sag because sag is king when we're setting up our shocks. For that reason,
I'm going to keep it very consistent, always 30% on the rear and 20% on the fork irrespective
of stroke length. The importance of sag cannot be overstated, and that's for a couple of
reasons. The chief of which is that it is relative. That means that 30% of a 50 millimeter
stroke is obviously longer or more than 30% of a 47.5 millimeter stroke. This therefore
then consequently changes how the bike rides dynamically.
If you'll bear with me and take on a couple of assumptions regarding spring rate and progressivity,
if you have two of the same bike both running at 30% sag but with different stroke lengths,
and they hit the same bump, and we know that the speed and velocity, et cetera, is all
the same, they will use a different amount of the rear wheels travel. That's because
there is something that we can adjust in that spring rate via air pressure.
In that scenario, because I'm always going to set my bike at 30% sag, it means a shorter
stroke length when hitting the same bumps will use less of the bike's travel. That means
it sits higher in the travel, and consequently keeps the geometry steeper. This is really
good if we want a bike that's going to spend more time going uphill.
Conversely, when you have the side point deeper into the rear shock stroke, that means it
will slacken out the angles more. That's because the more rear travel you use, the slacker
the angles become. Keep an eye on this inclinometer which I'm going to attach to the fork. I'm
going to cycle it through the rear wheel travel and you're going to see how much that can
change. With a shorter length stroke, even at bottom out, the bike won't be going to
such an extreme place. Now, that's going to affect everything, head
angle, trail, bottom bracket height, you name it, it's in there. That is why it is so vitally
important that you set up sag correctly in the first place. It's worth noting here that
as the fork compresses, it steepens up the angles so they can largely cancel one another
out. It's also worth thinking about pedal efficiency here because it is relative to
both sag and stroke length. That's one of the things that makes it such an interesting
thing to explore. A shorter travel bike, anti-squat notwithstanding,
will pedal more efficiently than a longer travel bike. That's because it's relative
to sag. Changing stroke length and changing the flip-chip do quite different things. That's
because one changes where the bike pivots around, and the other changes the amount of
rear wheel travel. Now, most people tend to run their bikes in the low settings with their
flip chips but, funnily enough in a weird twist of fate, this is the only setting today
that I'll be having with the rail mode. Now, it is time for the first change. I want
to change it into XE mode. That means I want to change the stroke length front and back,
I want to steepen up the angles and increase the level of anti-squat. Let's get into it.
The first thing I've done is reduce the travel of the fork by fitting a new air spring. I've
taken it down from 140 millimeters to 130 millimeters. Now, this deepens up the head
tube and the seat tube angle by around half a degree. The head tube is now 66.5 and the
seat tube angle is 76 degrees. This was the first thing that ate into my budget. The air
spring cost me around £35. Speaking of steepness, not only did I reduce the travel in the fork
but I've switched it into trail mode. This means my riding position in terms of head
tube and seat tube angle is a whole degree steeper than normal. Not only that. Having
it in trail increases the value of anti-squat so it'll be more efficient on the pedals.
Now, people often ask us, is it easy to detect half a degree change here or a small incremental
change there? Well, it depends on rider to rider. I don't believe it's necessarily anything
to do with wider skill, but more consistency. If you're very consistent in your inputs when
you're riding than when the output is different, you can get an idea of what's changed and
what's you. Like I said, I don't think it's got anything necessarily to do with skill
or speed. It's just about being consistent and quite methodical in your riding.
I also took out that 5 millimeter spacer from the shock and replaced it with a 7.5 millimeter
spacer. This reduces the travel to 125 millimeters at the rear axle. Now, 2.5 millimeters, it
doesn't sound like very much, but you've got to remember that it's relative to sag. We're
going to be running the same 30% sag, which means it's going to be running higher in its
travel, which means the angles will be steeper as we ride, which really lends itself towards
climbing. Now, could we have just pumped up the shock a bit harder? Potentially, but where's
the fun in that. Now, I think the bike rides very definitely
in this set up. It's like a bit of a rocket ship, especially on the descents.That's because,
well, around here in Barth[unintelligible 00:09:51], a lot of our descents aren't that
technical. They're not that rough, and so as you're pumping the bike, it's that bit
sharper, that bit more responsive. That's because the travel is reduced. Pedal efficiency
is one way that the rider's weight and mass effects suspension, but also when we maneuver
in turns and pump lumps and bumps on the trail. It does wide very differently, and it turns
this trail hooligan into something of a rocket ship.
As I mentioned earlier, I'm trying to do all of these changes for £100, but you could
put on some lighter tires. I think this isn't something I would do week in/week out this
sort of change, but if I had one bike such as this and I wanted to go for a 100-kilometer
cross-country epic, would I do this change? Absolutely. Especially in the fork. That's
a really, really big one. Like I said, you could just pump up the shock a little bit
harder, but the fork, there's no substitute for that.
[music] Now, it is time for the main event, how to
make a versatile trail bike vversatilier. Well, what that I want, I want to give it
the same head angle as the reactor RS and increase the travel to 140 mil at the back.
You might recall that earlier when we mentioned the travel spaces. This is the stock 5 millimeter
one. This is the 7.5 millimeter one I put in to limit the travel in XE mode. Now they
are both out the bike to give it 140 mil travel at the back.
Are there any associated problems with increasing the rear travel? Well, absolutely. Clarence
is the main one. As the wheel comes up, it might even be touching that c-tube. I'm going
to be running it in the bikes trail mode to give it a bit more clearance. Now, this is
one of the reasons I stayed away from the offset bushes. It's because that would actually
essentially decrease the [unintelligible 00:11:53] away of the shock bringing that rear wheel
ever closer. Now, another thing that is worth bearing in
mind here is, well, I wanted to make the bike more aggressive, so counter-intuitively I'm
happy to run it in the trail mode, which steepens the angles. By putting it in trail mode, I
am a whole degree off my target of 65 degrees. What can be done? Well, let's go back to my
£100 budget cap. I spent £35 of those on my 130-mil travel air spring of across country
mode. I spent £5 of those and admittedly called in a big favor with fin at full factory
suspension to make that spacer, that 7.5 mil spacer, for the rear shock.
What have I got left? I've got £60. What can I do? Well, I chose to spend that £60
on an angled headset. Now, these forks here, the maximum travel they can go to is 140 mil,
which is what they're already at, so it was my best bang for buck without buying a whole
new fork. These headsets can take off a different number of degrees. This one here is a -1 degree
headset. You can get them in -1.5, -2, and even theoretically, I suppose, you could run
them the other way around to steepen up your head angle, should that be what you wanted.
I think bang for buck, £60 to be able to, if you so wanted, drastically change your
head angle, that's a pretty good deal. Also, something I'm really keen on, is because
it's not raising the front end, it doesn't affect the seat tube angle, so it should theoretically
still have that really, really planted seated position that you get with the trail mode.
You've also got to consider things like handle bar flop, trail, front center, the list goes
on. Angled headsets are indeed very useful for people with specific needs such as downhill
racers who want to go absolutely warp speed. They can also certainly be of use to people
that want to [unintelligible 00:13:55] fly their geometry into the modern age, but I
would suggest doing your homework. Now, something that's quite interesting here
is the offset difference between the two flip chip modes is about 6 millimeters, so that
should be more than enough to cover for the 5 mil of adjustment I made in the stroke length.
By having it in the trail mode, I hope to avoid any clearance issues. Now, theoretically
in the initial part of the stroke, it might be more like the trail mode, and as it goes
deep into the stroke, it should become more like the rail mode, or at least that's the
theory. Now, a small but important caveat here. Nukeproof
didn't just close their eyes and pin the tail on the donkey without too much thought. I
imagine each one of these pivots was absolutely agonized over in terms of placement. What
I'm trying to say is, quality of travel and feel of the bike is far more important than
an arbitrarily bigger number that might not actually give you the desired suspension feel
that you require. People often write in to us to ask about increasing
travel by adjusting the stroke length. Now, this is something that if you were to do it,
you need large amounts of clearance behind the seat tube because your bike is going to
flex quite a lot under higher amounts of load. Just be careful with that. If you did want
to start experimenting with your own bike on how to make it slacker, a good place to
start could be some offset bushes and angle spacer which sits just below the head tube.
It can take about half a degree off the head tube angle.
The final question, is it worth it? Well, I think the XE mode is really worth exploring,
especially with the shorter travel fork. That's because you can pump up your shock harder
and largely cheat the system there. One thing you can't do is steepen the head tube angle
by pumping up your fork. That is really worth visiting. If I was going to the Alps or something
like that, would I fit an angle set? You know what? I'd probably put the money towards some
big old tires, or some rims I didn't care about.
As fantastic as they are, and how effective as they are, a bike like this doesn't need
it. Like I said, maybe your bike doesn't have such aggresive geometry and you want to get
the numbers to be more modernized or out there. Now I have to say, a bit of an egg-on-face
moment because all of this changing, and all of this fettling, Nukeproof were ahead of
me from the off because the biggest difference I could make was changing that, changing the
fork, the fork airspring, which is something they offer with the ST.
It was a good time anyway, and that's that. Now guys, if you like the channel, don't forget
to like and subscribe. Get in the comments below, let me know what you think. Was I radical
enough, or should I have pushed it harder? We didn't even get into anything like weight
or anything like that. Yes, lots of options. Thank you for watching. Don't forget to like
and subscribe. We'll see you next time. Cheers, guys.
[00:16:54] [END OF AUDIO]