MTB Wheel Size Experiment | 29er Front & 27.5+ Rear Geek Edition

MTB Wheel Size Experiment | 29er Front & 27.5+ Rear Geek Edition


– This is the tech
follow-up of the GMB video where I actually tried a
bigger wheel in my Scott Genius where I ran a 29 up front
and 27.5 plus in the rear. If you’ve not seen that video already, I would check that out
before you watch this. But also, I’ve done a video in the past and we try and add 29s
on both front and rear and 27.5s so lots of
different variations here. Today, I’m talking about running
the 29 up front, 27.5 rear and I’m going to get in some
of those stats about the bike. (jazz electronic remix) So the Scott Genius is designed
to run either size wheel and all we need to do is
flip the chip between the two to try and keep the angles about the same. I’m lucky enough to have two
pairs of wheels for this bike and they’re both identical,
the DT Swiss with an M1825 rim. Both of them are 30 mill
wide so that shouldn’t affect the tire profile too much
between the different sizes. Of course, on the plus, I’ve
actually got a 2.6 inch tire. On the 29, it’s just a 2.4. So, it’s narrower up front and also not as deep as the rear tire. It is really easy to swap the wheels the one’s that’ve got center lock rotor. So all you need to is whip
that off, change it over, and then change its set. I’ve got tires on so it’s
quite an easy thing to do. Is it practical to do all the time? I guess it is. It’s gonna be expensive if
you want two pairs of wheels. (jazz remix) So the thing you do
need to do on the Genius when you’re moving between wheel sizes is actually flip that chip
on that shock linkage. Super easy to do. All we do is undo the bolt
and then turn ’em around and put them back in. And what it does is it keeps
the geometry really similar between the wheel sizes. So it’s 65 degree head
angle on the 29 wheels and it’s 65.6 on 27.5. So when I messed around and put
a smaller wheel in the back, it actually went down to a 64.2
head angle, so pretty slack. That’s getting towards
downhill bike, that is. And the BB went to 332 millimeters. So for me, that is the biggest compromise on that setting within the low. It just felt like it was too low, I’m gonna start clipping my pedals on more technical terrain. So I flipped it over and then I rode it and it did feel much more balanced so actually the head
angle went back to a 64.8, so almost 65. The BB angle, BB height went up to 336. So it actually only
changed four millimeters but that did make enough difference for me to make the bike feel like
that’s how I’d want to ride it if I was gonna do this setup. (jazz remix) So the first geometry values I gave you are all from the Scott website
so they’re official numbers. When it comes to messing
around with the wheels, I’m finding the other numbers. I’ve actually used a tape measure and I’ve borrowed Dot E’s
Wixey digital angle gauge. I don’t have one of these because you need a nerd
certificate to get one of these and I’m afraid I don’t have one. So that does mean the numbers
are a little bit approximate but that is how it feels to me. The bike does feel a little bit
slacker, a little bit lower. Also, the ride difference does feel… Basically, you’ve got more
volume in that rear tire so that does make a difference
as I talk about in the video. It’s those little bumps. So when you’re riding over little stones and edges and things like that, that bigger volume means
it’s a bit more compliant so through my feet, I felt less bumps. And then, it’s the same thing really with the bigger wheel on the front. I’ve got thinner tires so less volume but the bigger wheel has more rollover. Like I talked about in
the last tech video, I got the two different tapes out, show them rolling over that tool. The bigger tape will actually
roll over a little bit easier. So, that does mean it makes
it a little bit easier on my wrists up front. What I’m really doing is mixing up the advantages and
disadvantages of both wheels. So, let’s talk about advantages first. Front wheel, greater rollover. Real wheel, I’ve got more compliance and I’ve got a bit more
grip in certain situations and it’s a lighter wheel
than the bigger tire. Disadvantages, heavier wheel on the front. And also, when we talk about
the actual tread of that tire, one thing I find on plus tires, I talk about this quite a lot, is in the wet, they
can float a little bit. They don’t dig in quite as
well as a thinner tire does and on really hard-packed dirt, you can find that you have
to run quite high pressures otherwise you’ll be rolling
that tire around quite a lot. So all in all, is it a
good idea to mix them up? Um, for me, jury is still out. Today the test was really wet. While it was still quite grippy, it was so wet, the mud was so thin. But I think I need to try it out again and actually, I think I need
to put some times to it. But on the trail, how much
difference did I actually feel? Surprisingly, not a huge
amount, to be honest. In the past for racing in
(mumbles) on a bike like this, I’ve actually run a heavier
weight tire on the rear or an insert like a Schwalbe ProCore, because I find that I more often than not get punctures on the rear and also I give that rear
wheel a lot of punishment so I can ding the rim. So it did feel a little bit like that. I’ve got more air volume there so it just feels like that
rear wheel is more protected. I’m not getting as much
feedback through my feet. It feels slightly heavier
even though it’s not. That rear tire and rear wheel setup is actually lighter than a 29er. So, I don’t know. It’s a hard one to tell, really. I think I need to test
it more, like I said, but is it actually worth it? I don’t know. Is it the future of mountain bikes? Probably not. The big problem here is the UCI. So when it comes to racing bikes, you’ve got to have the same
size wheels front and rear. Obviously, this isn’t a downhill bike, it doesn’t count for that. You’re not gonna race cross-country on it. And Duro isn’t UCI regulated
so we could see it, I’m just not sure if
the bike manufacturers are gonna get on board with it. So it’s been nice to test this out. Will I keep riding a
mountain bike like this? Probably not, to be honest. I like this bike on 29 inch wheels, so I’ll be chucking that back on. I also think it’s a bit
of a practicality issue of having spares, so
why are you gonna carry two spare tires everywhere? Tubes, not so much of an issue. I’ll let you into a little secret here. 26-inch tubes will fit anything. They’ll pump up and fill it
so that’s not a massive issue but I think I’m just gonna
go back to riding 29. Leave us your questions, if
you’ve got any down below. I’m sure you’ve got some good ones so what I’ll do is I’ll
try and answer those in the dirt shed next week. Also, if you’ve not
seen the original video of me riding this bike like
this, click up there flat one. Give us a thumbs up if
like it and star the video, and like I say, keep
leaving those comments.