Mountain Bike Fork Offset Explained | What Is Fork Offset and How Does It Make Your Bike Feel?

Mountain Bike Fork Offset Explained | What Is Fork Offset and How Does It Make Your Bike Feel?


(bouncy music) (horn sounding) – Fork offset is ever
more commonly talked about but what is it? And what effect does
it have on the overall feeling of our bikes? The onset of offset, what is it all about? So, what is offset? Well, most mountain bikers
are probably very familiar with talking about the head tube angle of their bikes,
so, we have our steering access coming down here, offset is how far the front axle is offset or in front of that steering axis
and changing the amount of offset on a fork is a way to affect how much of our weight sits on the front wheel of our bikes. To talk about offset,
I’m actually going to talk about our stems but hear me out. The reason I’m going to talk about stems, as its something you’ve most
likely experimented with, and I want you to call upon
that experience you have, whilst I’m talking about offset, to help quantify what I’m referring to. So, stems, the longer your stem is, the more stable your front end is because the more weight is being exercised upon the front wheel, conversely, the shorter your stem
is, the more rearward your weight is in relation
to the front wheel. So, with a short stem,
something like 40 or 50 mil, steering can be more responsive but it can go too far and
come across all twitchy and unstable, that’s
because, you guessed it, there is not enough weight
upon the front wheel. That means that there is only our weight driving our wheel into the
ground to deliver grip. But isn’t that auto
correcting sensation you get with a nice, long stem. Think of it like dipping your heels, as you ride through rough terrain, you’re not making yourself heavier but you are weighting the
bike in a certain way, to make it feel more stable,
to achieve grip and drive. This is what a long stem achieves, hence why professional road riders, who achieve warp speed, want that nice, long stem paired to a
relatively short top tube, to give them that much needed stability. Another good way to think about offset is to think of what we
know about chain stays. Now, the longer your chain stay is, the more it weights the front wheel and takes weight off the rear wheel. Now, this might sound slightly ridiculous but if we take that knowledge and apply it our forks,
if we had an offset of a thousand, it would actually be taking pretty much all
of the weight off the front and be putting it upon the real wheel. So, hopefully that’s
a good way to quantify where our weight sits in
relation to the bottom bracket. And our axis. So, weight on the front wheel
is good, viva la long stems. Stability, boy, oh boy, now we are talking but is it that simple? Well, maybe not, we’ve moved away from long stems for aggressive riding for a couple of reasons,
if we combine a short stem with a longer frame, we can get out weight to sit more centrally plus stubbier stems tend to play a lot nicer with
our nice slack head angles that are becoming ever more prevalent. That twitchy feeling that a short stem can cause is actually
quite nice for striking a balance of stability with
out super wide handle bars. So, the modern mountain
bike, perfection, right? Well, maybe not, there
is a term called trail which is often overlooked
but less so recently. But what does it mean? And how does it relate
to the rest of our bikes? Trail is the number derived by measuring the distance between your contact patch, so, directly below your front axle and the angle of your fork
axis as it dissects the ground. The larger the trail
number, the greater the self centering stability
will feel on the wheel, the lower the trail figure, then the more twitchy
your steering will be. Why don’t we try reducing that offset on the forks, a number we
landed on many a year ago, this will help us weight the front wheel, by increasing the trail number, giving lots of grip whilst letting us reap the collective benefits of all the other changes
in progressive geometry. Its going to mean we can generate a very stable bike that’s nice and roomy in the cockpit but also it enables us to weight
the front wheel a bit more by reducing that front center slightly. So, as you can imagine, as we
slacken out head tube angle, it has a drastic effect
on that trail number. Similarly, when we raise our front axles, it also has a really big effect. So, in the last couple of years, more people are riding big wheeled bikes and have slacker head angles than their dizziest day dreams of a few years ago. So, its no surprise that
we’ve landed on offset as a cause of conversation because its a very logical thing to
think about changing. Can this go too far? Well, absolutely, trail is a number and there is a sweet spot, we know, from our long stems, that that stability inducing feeling is absolutely
fantastic at high speed but it can cause the wheel to bite and be a cause of
instability at low speed. The theory being that high amounts of trail give stability, kind of, goes out the window when
we begin to lean the bike. Like everything, its a compromise. Think of it like standing up, as we widen our stance, it can actually give us a huge amount of stability. But only in one direction, ala trail. But if we start leaning forward and back, it can actually be a cause
and generate instability. This is the conundrum. Like everything on our
bikes, its a balancing act, literally in this case, namaste. Forks are available in
many different offsets now, be it Fox, RockShox,
Suntour, Formula, whatever. You just have to choose your flavor. Today, we’re using this
system from Mojo Rising, as opposed to anyone else’s forks just because the adjustment
is all in the same fork and it saves us trying
three individual set ups. We can just change the
offset and ride back to back different settings in this comparison. Now a small caveat, is offset important? Absolutely but it is just one piece in the larger puzzle of our bikes. Its just as important as
something like stem length, as if people still talk about that, when it is so 2013, what I’m tryna say is, there are no golden tickets in bike design and everything we change
has a ramification within the larger picture of our bike. So, what fiendish plan
have we come up with to try out this system? Well, its undoubtedly very cunning and highly sophisticated, for weeks, I have been scouring roots and rain with various algorithms and formulas to find out my perfect candidate and I am very confident I have done so. We’ve got our very own Top Gear Stig, an anonymous racer to push this fork to its absolute limits,
to hopefully give some feedback about how the
different settings feel. And, of course, I’m not going to tell him what offset he’s running. So, who is our mystery rider? Well, they’ve won national
downhill and endurer racer, they’ve top 10’d at world cups and if you feed him a few stiff shandies, they’ll tell you all about the time they won rear of the year in 2007. Who is this mystery rider, well– – All right, Henry? – Its, Neil, its mean to be anonymous. Can we pixellate his face? I’m sorry mate, I told you to wear a full face and tints. – Yeah, I missed that man, I’m sorry. – Can you just put this on, so we can disguise your appearance? – What is that? – Its a bloody, its a
highly sophisticated– That’s straight from MI5, that. That’s what they use in the field. – Should have had a shave. – So, its (bleep) first
run, he hasn’t ridden these forks at all yet,
he’s in the 46 mil offset but he doesn’t know that and away we go. Be really interesting
to hear his thoughts. (intense electronic music) So, we’ve changed the fork settings a bit to reduce his offset but don’t tell him. Lets see how this anonymous rider goes on for a second run. (casual bouncy music) So, we’ve had two tests,
now, I’m not going to tell you which one was which but one of them was slightly longer than the stock set up on the strive, one was slightly shorter and now we have this which
is obviously very different. – Oh, its much shorter, I mean, it looks crazy, doesn’t it? From the side, from up
here, birds eye view, it looks all right. – I had a little wander around the carpark ’cause what we’ve done, if
its not immediately obvious, is swapped round the crowns, now, this isn’t advisable to do at home but its going to make an
interesting experiment. So, we’ve swapped around the crowns and put that flip chip in
its most extreme position. So, I think it gives an
offset of almost, like, zero. Its really, really, if you drew a line through the head tube to the axle. – It doesn’t feel as crazy as it looks, just riding along on the flat, it feels like you are putting
a lot of input into the bike, the whole time it feels
like you’re turning a lot, sort of just keep to
keep your balance, so. – It felt to me like, when
we just rode around there, if I closed my eyes, it
felt like I was riding a road bike with a really short stop tube and a really long stem. – Yeah, true. – Just that, kind of, oh my god. – Yeah. – The way it arced but
anyway, we’re going to go for a bit of a potter, well, you are. I always potter, yeah,
we’re going to see how we go and we’ll end the day in the pub, I guess. – All right, lets do it. (slow electronic music) I don’t feel bad but that’s
went, for me, like wheel base. Like, that feels like
the biggest difference but if you’re going straight
through rough stuff, wheel base, to me, doesn’t
make that much difference. Whereas if you change the head angle, I would really notice it, this doesn’t feel like a huge difference. Its only when you add
it all together, for me, I’ve always been really sensitive about front wheel weight and
being able to drift a bike. Rather than just slide on the front and that’s been everything together. Stackers under you stem,
bar rise, head angle. – [Henry] But do you feel that– You know, offset is obviously
something we can change with a system like that and that’s great but you can’t view any one part of a bike in isolation. No fork set, where it sits in the travel, that effects head angle,
which then effects this– – Exactly, how aggressive your fork is, actually dynamically
effects where your weight is not just, like, when I
was riding around on this, you can really feel the
difference, I think, in when you’re going slow and you want to just turn along the far
road, it feels different but when you’re riding hard down this, you’re only changing one thing and I don’t that huge
amount of difference. – So, there is our day wrapped up of trying out different
offsets, back to back. – Yeah, fun day. – Yeah, now I’ve, kind of,
experimented with this, actually, just last week, wanted to, kind of, get my head around it and really understand the
nuanced world of this– – I mean, something that I don’t– ‘Cause, in the past, its something that, you know, you couldn’t
really change your offset, you had what you were
given and that was it, so, for me, I was more dial then on, head angles, bar height, all these, sort of, different things, whereas, this offset is a new one to me. – Yeah. – And its a difficult one
to get your head around. – Yes, could you tell, what do you feel you were trying, you
know, for the first one, second one set ups, could
you tell the difference? – I mean, yeah, visually, for me, you can see, when I get on a bike, I look down, you can sort of a gauge from the head angle and
all these sorts of things like reach, just by sitting on your bike, so, it did feel like it was
coming further towards me. – Yeah. – Obviously, the last
one, it was very obvious, it was right back. – Yeah, yeah. – And, again, its, sort
of, only when I’m riding around a carpark where I can
really notice the difference. Like you say, a bit more
agile, bit more twitchy. When I’m bombing down a
straight bit of track, I really, it starts going down
into the minute differences, where its not a big
enough difference for me, it has to work with other things together, for it to really make a difference. Yeah, I found, for me, I really noticed shorter offsets when, if you’re kind of, you know, we should always
brake in a straight line with our bike, you know,
perpendicular to the ground. – [Neil] It doesn’t happen. – It doesn’t happen, and
ever I was dragging my brake, it felt the grip was more, maybe, binary. – Yeah. – Do you know what I mean? I felt like, as a mountain biker, I’ve conditioned myself to realize where the locking point and
modulations on the front wheel. And it was, kind of,
flying in the face of that. I think, for short offset forks, whether they have their place or not, well, they obviously
do but I think, for me, I would have to commit to riding them. – Yeah. – And it would have to
be the system I used ’cause I think it is quite a difference. – Yeah, for me, I’ve always been really sensitive to get in the weight balance of front to back wheel. And now there’s just an extra
thing to try and dial in to get that right, so. Yeah, I think for a lot of people it can get confusing tryna
find all these things to make their bike ride
how they would like. Its funny, when we had Martin’s tandem, that’s one thing, when I
re-noticed the offset on that, with it flopping side to side but then changing it and
making it feel more direct and feeling like you’re
not just going to go thwak and, sort of, just flop
over and lose your balance. – Because, originally, on Martin’s bike, although he’s currently running the set up that we are
today, he actually just has swapped around– Reversed his low end, sorry. – He did try that, yeah, yeah. – Yeah and that was a thing that opened up that big conversation and then, for me, well, I think actually there are some really important things
to take away from this. The offset will be more effective when you’ve got a really
slack head tube angle. – [Neil] Yep. – If, Doug’s in on it as well,
if you’ve got a steeple on, then actually it moves
it on that plane, almost, so, I think in terms of the effect in the amount of trail,
I think we should do a second video but we do
it with a downhill bike. – With a slacker angle? – With a slack angle. – Yeah. – I mean, the Strive’s
such a fun bike to ride but I don’t think, its not, you know, some bikes have 63 degree angles on them, its a few degrees off that. And I think, yeah, I think it’d be really interesting to try. But thank you for your time. – Its been good. – Thank you for, you
know, riding the bikes, you poor sod, having to
spend all day, you know, mountain biking, the final
say, does offset matter? Yes or no. – To me, not much. – Cool, well, there we have
it, its personal choice, part of a big equation and, like I said, there are no golden
tickets in mountain biking. And, well, that’s it, I
want to make a joke about fork offset except with these bad boys. I really am racking my brain and I just can’t get it done. – You’re starting to bore me now, Henry, with your fork offset. (crickets cheeping) – Fine, well, lets end it there. Now, actually, the last time I came to the Forest of Dean, was when
I decided to do the laps– Enough laps for a lifetime. – Yep. – And I Everest’d this very hill. So, I’m going to throw to that video. – You pedaled up that hill twice today, that must have been easy. – I can’t get my head around it, I was in a really weird mental space but 82 didn’t seem like that much but hey, ho. – Its a lot. And if you want to JMBN throw
their hats in the tech ring, two pot versus four pot, check
my new video, over there. – Don’t forget to like and subscribe and we’ll see you next time. – See ya.