27.5″ Vs 29″ Mountain Bike Wheels | The Wheel Size Debate Continues


– The Scott Genius has
always been designed to be a very versatile bike. And this is the latest edition, it’s had a full frame re-design,
but one of the really cool features about this bike
is that you can swap out the two different wheel
sizes really easily. So in this video I’m going
to try the 27.5 wheels, swap them out for 29, and let you know how
it feels on the trail. How it actually changes the
ride characteristics of the bike How it stacks up against
the clock, and ultimately, try and decide which
ones I prefer the best, but also give you guys,
hopefully, a bit of an insight as to how it affects the
characteristics of this bike. But first, let’s get back to the workshop for the nitty gritty. – Right, let’s start off with some facts in the workshop about these wheels, The 27.5 wheel has a
two-point-six inch tyre, the 29er has a two-point-four. Let’s start with the weights,
so the 27.5 weighs in at 1.87kg and the 29er weighs in at 2.12, so a 25g difference. Don’t forget that’s just for one wheel so when we’ve got a pair of
29er wheels you’re actually going to be 50g heavier. Don’t forget, that’s
actually rotating mass so that does make more
of a difference than just static mass on a bike. So I’d expect I’m going to be
able to feel that on a trail, and I’d expect the 29er
to actually sort of plow through rough stuff
a little bit better and carry its speed a little bit better but be a bit harder and slower
to accelerate and decelerate. The two-point-six inch tyres
on the smaller wheels of course are wider than your
average mountain-bike tyre getting into those ‘plus’ sizes, but also they’re deeper and
that will make a big difference to how the bike feels. It’s about ten millimeters
deeper, so when we talk about the whole diameter of the wheel, it’s about a 20mm difference so it’s 20mm bigger on the 29er. That does mean that the angle of attack, when you’re rolling over
bumps, is going to be lowered on the bigger wheel so it
should roll over those bumps a little bit faster. Let’s talk about tyre pressure as well, on the plus-size tyres
you’d get away with running, I find, a couple of psi lower because of that extra volume of that tyre, you can get away with running
slightly higher pressures on the bigger wheel. So from those numbers,
I think on the trail I’d expect the 29er to feel
heavier, feel smoother, but harder to start and stop. The 27.5, I would expect a bit more grip because of that wide tyre, I’d expect the bike to feel
a little bit more lively and be able to change
direction a little bit easier and stop quicker. So how do the wheels actually affect the geometry of the bike? So let’s look at the head angle first, it’s slightly slacker on
the 29er, 65 dgerees vs 65.6 so not a huge amount. Bottom bracket is going to change slightly so it’s six millimeters higher on the 29er so it’s not going to corner quite so well, but you do have more clearance for peddling through the bumps. The big one here for me I think, is going to be the BB offset. So you’ve got a seven 7.5mm
more offset on the 29er so it feels like you’re
stood sort of more down and into the bike on the 29er. That definitely helps for
trying to get through the bumps, you’re going to drive that
bike a little bit better. Okay, enough of that chit
chat in the workshop. Let’s do the fun part. So, I’ve been riding this
bike with the 27.5 wheels for probably two or three months now. It feels great, it feels like you can get really rowdy on this bike,
really aggressive down the hills, it doesn’t feel like a true
sort of ‘plus’ bike to me so a ‘plus’ tyre could find
the biggest disadvantage really is in the mud, where they
float, they don’t really dig in. It doesn’t feel like that on this bike. The tyres are 2.6″ but the
treads are evenly spaced , they clear the mud, it
digs in, it feels like an aggressive little bike. So it’s time to try out the 29er wheels and I’ve not tried them in this bike yet, so I’m excited to stick
them on, see how it feels. I actually raced a lot
of Enduro on 29er wheels, so I think this bike,
could work really well 150mm travel, great for
British Enduros, not quite EWS you might want a little
bit more travel for that, but for my style of riding I think this could be a
rocket ship on 29er wheels but I’m looking forward
to trying them out. So I’ve got a set of 29er
wheels set up with tyres, both are tubeless by the way,
so it’s actually really simple to swap just the cassette and discs over. So realistically, you could
have two sets of wheels for the same bike and swap
them over as you please. Cassette is on, time for the rotors. One final thing to do
is just flip the chip. The chip has been
flipped, the wheels are on and don’t they look big. Actually I can see a lot of wheel sticking out in front of me,
the tyres are quite narrow, I’m back on 2.4’s now, so,
let’s go give them a ride. Right, I’ve put a time
in on the big wheels now and it felt good, it felt
like a really consistent run, felt like 29ers always have done for me when I’ve raced in Enduro. So on the stuff at the top where it’s quite a mellow gradient but it is a bit chattery with bumps, it felt like I was absolutely flying. It felt seconds faster
than the smaller wheels, but when it got a bit more technical, it feels like you have to be
a little bit more cautious. So, yes, they do Monster Truck over stuff, don’t drop into holes quite so much, but when I hit something big and I’m really trying to use
my body to soak something up I find that I stick my
bum into the back tyre and I did do it on that run. So, I’m 5’10”, pretty much average height which is a bit taller
than Martyn and Blake would have you believe, but
I do find that on 29″ wheels that sometimes I stick my
bum into that back tyre when I’m really trying to use
my legs to soak something up. I guess, if I just rode a
29er, I would get used to that but swapping between
them… it’s always been a tiny problem for me. So, I’d be interested to see the times, because that felt really fast actually. So that’s enough about the feel, let’s talk about results, and the time. Which one was the winner? So, it was the 29er, but
there was nothing in it. I did a 1:42 on the
29er, 1:43 on the 27.5, so there was only a second in it. But the interesting part for me comes when you look at the splits. The top section of that
track was fast, flowy, stuff where actually it
felt really fast on the 29er but I was three seconds slower up there, so not an inconsiderable amount, but it was four seconds faster
on that rough lower section. I think we can say that’s
down to that roll-over it’s where I’m hitting all those bumps and there were some big
breaker bumps on there. The 29er doesn’t dip in quite so much, so it’s less tiring to ride but also faster over those bumps. So actually for me, that’s
a really interesting test. And as a racer, I’m going to
go with the faster wheels. I’ve been riding that bike
an awful lot with the 27.5’s so I think it’s time to
leave the 29ers on there. Feels great fun to me, I
think the biggest disadvantage with the 29ers is stopping the bike. I’ve always felt that when
I’ve tried to race the bike and there wasn’t much of it on that test, so I could bear that in mind in future but for now, I’m sticking
the 29ers on there. It’s one of those great features I think of some of these modern bikes, that it’s really easy to swap out wheels. Realistically, you could
have two pairs of wheels for your bike at home, the
smaller and the bigger, and just swap them around
for different conditions, or you might find you
prefer one over the other and just sell the other wheels. So actually I think it makes
the bikes really versatile. If you have any questions
about this video, leave them down below because I’ll be doing a follow-up video
on the GMBN Tech Channel so I can get into the nerdy facts. If you want to see how a
tyre is made, click up there for a Continental factory tour and down there for the
Scott Genius First Ride. Give us a thumbs up if
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