Fat Vs Plus Mountain Bike Tyres | GMBN Tech Geek Edition

Fat Vs Plus Mountain Bike Tyres | GMBN Tech Geek Edition


Right, so this is the geek
edition of Blake’s video, his fat versus plus bike video, where he took the two different bikes out, compared them, did some riding tests, did some really random
tests, as Blake does. But this is more techy. We’re going to take a look at the technology that
goes into these wheels, and if the tech stuff does
agree with what Blake thought. And I want to kick this
one off with saying that a 2.6 tire is not officially
a plus bike tire, Blake, so you got that one wrong. A plus tire is actually
normally associated with anything 2.8 inches
and 3.5 inches wide, fat is anything above 4 inches. However, I’ll let Blake off a little bit, because 2.6 inch tires
have recently come around from plus tires, because
people are realizing that there are some disadvantages
with too big a tire, so actually 2.6 is
getting much more common, I think that’s just come
around because of plus tires. So, what are we calling these? Minus plus, smaller plus? I don’t know, but I guess you
could call it a plus tire, even though it’s not officially. So, let’s have a look at
the wheels to begin with. So, the plus tires on
Blake’s Nukeproof Scout, are the 27.5 FSA grid wheels, so, alloy rims, they’ve
got 27 mm internal width. Now, that’s something we’re seeing a lot more of recently as well, a sort of trend is going
towards 30 mm internal width, so that you get that
nice profile of the tire. So, that’s wider than, maybe,
two or three years ago, and again, the tires are wider as well, so you just get a nicer
shape to that tire. And these weigh in at 18
35 grams for the pair. So, the plus size tires
are on Boost wheels, which means a 15 mm width front axle and a 110 mm width front hub. Now, on the rear it’s
a 12 mm axle on a 148, so wider than normal to
give you that bracing angle of the spokes therefore,
to give you a stiff wheel. Now, fat is a whole different
thing, so, these are massive. So, it’s a 150 mm wide front hub, again on a 155 mm through
axle, so super wide. On the back, they’re 197 mm
wide, again 12 mm through axle. So, a few more stats about the fat wheels, these are the DT Swiss BR2250s, and just look at the size of them, that’s 78 mm internal width on that rim. 4 inch tire on here, you can
see the big cut outs as well, so there’s a bit of rim tape inside there, but there’s a tube in here, it’s just much easier to
fit a tube on a fat tire and actually, the tubeless, you don’t get that much
of an advantage from, whereas the plus size tires,
they are set up as tubeless. And they actually weigh in at 2228 grams, so not that much heavier
than the smaller wheels. Yeah, just a few hundred grams. These are 26 inch, that’s
pretty common, to be fair, for fat bike tires, you don’t
really find 27 and a half, or 29 for these things,
but it’s a big old wheel. So, we’ve ridden fat
bikes a lot here at GMBN and talked about them quite a lot as well, so originally they were
designed for snow and sand, sort of the most extreme
weather conditions, but actually now you see
them much more commonly used on regular mountain bike trails. So, the advantages of these tires is basically that sort of flotation, so it makes it possible to ride over snow and
sand in the first place, but actually on normal trails, I wouldn’t say it gives you suspension, but it just takes away
some of that chatter of those smaller bumps. And you can also run these
at super low pressure, so anything from five PSI up to about 15. One of the problems for
people like Blake especially, who ride these things hard,
is you can start puncturing, but also moving the tire around loads. So, let’s take a look at just how hard Blake has got these tires, and I would imagine it’s
much higher than 15 PSI. It’s not, it’s nine
PSI, that’s surprising. 9 PSI is surprising, but it
feels much harder than that. You can’t actually push it in that much. Just such a huge volume tire, and this is only a four inch tire, so it’s pretty much the limit on the smaller side of fat bike tires, they can go up to five
inch tires, these things. So, now it’s the plus size tire, which is definitely more than nine PSI. I’m going to take a guess,
I’m going to say 22. 19, that’s not too bad. Still, fairly soft though, to
be fair, for Blake especially. He’s a big clumsy bike rider, So the theory goes that
the bigger the tire, the more comfort and more
grip you’re going to have, and Blake did find that to be fair. But the disadvantages of
that, so the bigger tire, is more sidewall flex which means the tire’s just going to
move around quite a lot. So, that’s why you do have to up the pressures to stop yourself from puncturing, or even
ripping that tire off the rim, and we have seen that in the
past with plus size tires. Trying to ride them really
aggressively on Enduro, they can be a little bit too lightweight, and that’s why actually
we’ve seen them rise, these 2.6 inch tires. They are tougher, stronger tires to deal with that, basically. But when it does come to suspension, I think it really works for
taking out those smaller bumps, those tiny little stones
and roots in the trail. I think that showed on some of the tests we’ve done previously, so
on “Are Fat Bikes Fast?” That video, I rode the
bike on quite a, sort of, bumpy, choppy trail, and
it felt like I was riding a magic carpet, I could just keep pedaling over those little bumps, and it did actually seem super fast, and it showed on the clock as well. So, all that stuff is nice in theory, but let’s try and put
some science behind this. I’ve got us some perspex here, and I’m actually going to try and see how big a tire foot print there is. So, going from plus to fat bike, can I actually measure the difference of how much tire is touching
the floor at any time? No, more like that. Six knobs. So, check it out, we’ve just put a decent amount of pressure
through this perspex, onto the tire, you can see the fat tire, that’s probably not quite
as big as I’d expect. Like Blake said, most of the
time, if you’re riding upright, you’re not actually using the
sides of the tire that much, you’re still kind of sat in the middle, but I reckon that’s about a third more contact on the ground. But one of the big
differences on the plus tire, you’ve actually got nine
knobs touching the floor, pretty much, at any point, and they are deeper, so
nine aggressive knobs. You know what an aggressive knob is, well it’s going to give
you grip on a tire for one. But with a fat tire, you’ve
only got six of those knobs touching the floor at any point. So, that sort of stands up to
what I think about it as well, a little bit. I found that fat tires, when
you’re talking about riding in anything where it’s loamy or mud, you do feel float and you
don’t dig in very well, and, because you’ve got three less knobs touching the ground
probably, at any one point, you’re just not going to dig
into that dirt quite as well. Plus, you’ve got that
higher surface area as well, which does mean a bit more float. When it come to actual weights, by the time you’ve got a
rotor, a tire, and a tube, the fat bike wheels are
600 grams each heavier. So, 1.2 kilograms, and of course, we’re talking about a rotating mass there, so that does make a big
difference how the bike feels, but also that gyroscopic effect, so once I’ve got this thing going, to actually, whoa, okay, to actually get that thing moving around takes quite a lot of effort. Give us a spin. Whereas actually now, the
2.6 feels much easier. So, I’ve done a bounce test,
it’s not very scientific, but I dropped a wheel to see
how high it would bounce. So, starting from the same point, and actually that does
show that the fat bike tire bounces marginally less, so that’s the opposite of what Blake said, where it feels like it’s
a more bouncy wheel. But I think actually the reason
it bounces less in my test, is that there’s more volume of
the tire, so in that impact, that could be absorbed
by that bigger tire, much wider, much deeper sidewalls. But there’s no arguing the fact that when you ride these bikes, you do feel like you’re
sitting on that tractor seat, they do bounce around quite a lot. I think that, again, is down
to the size of that sidewall, you know, that’s probably
three or four inches deep, as well as wide, and
it’s not damped at all, like I’ve talked about before. So, as soon as you hit a
bump you start bouncing, and you keep bouncing for
quite a while, to be honest, with a fat bike tire. Something that’s very difficult to measure is rolling resistance, especially when you’re sat in a workshop, so let’s get out and
let’s do it on the bikes. So this is going to be a very simple rolling resistance test, so no pedaling whatsoever, I’ll lean off against the wall, press start and when I
hit that brick down there, I’ll stop my stopwatch. Ready, set, go. 11.79 seconds. 11.46, point two, point
two five of second faster on a fat bike. So there were three
tests, rolling resistance, and the plus bike was slower every time. Between 0.25 and 0.75 of a second slower, going from a really short
one to a 20 second roll. So, it’s not actually
as fast as a fat bike, which is contrary to what Blake said. I think a lot of that is
actually down to tire tread being deeper and slower rolling. So we tried to put some
science behind what Blake felt on a fat bike and it’s fair to say that our tests have not
always agreed with Blake, but Blake still loves fat bikes, that won’t change that. If you want to see that original video, click over there for that one, and if you want to see
our “Fat Bikes Fast” really fun video, click
over there for that one. So, it’s time to ride back to the office, which one am I going to take? I reckon, I’m going to take the plus bike. I commuted to work on the
fat bike this morning, you get some funny looks
riding around town on it, so Tom, you’ll have to ride that one back. Give us a thumbs up if you like GMBN tech.