00:00This is the bike that I've been riding for the last few weeks. It's the new Cervelo S5 and it
00:05is very good. It's more aero than the last one, it's more comfortable than the last one, and it's
00:12lighter than the last one. There is just one thing about it though which I'm not too sure about.
00:18You see, you can choose the new S5 with either a Dura-Ace groupset, an Ultegra groupset,
00:24a SRAM Red groupset, a SRAM Force groupset, or this, a gravel groupset.
00:32Now this might seem like a little bit of an odd choice. This is about as race bike as race bikes
00:38get and yet it has a cassette that is quite literally bigger than the one on my gravel bike.
00:45It's a 1046 in fact. Now Cervelo aren't the only people offering this either. 3T are offering
00:52something similar and if you project one a Trek, you can also spec this groupset onto the latest
00:57Madone. But should you? Is 1x13 the future of groupsets? Does it offer any meaningful advantages
01:05over a 2x system or indeed a 1x12 speed groupset? And should more road bikes start offering it?
01:13Well, this is Cycling Weekly and I've been finding out.
01:16I've been wanting to test this groupset out on the road for a little while now,
01:25ever since Lidl Trek used this groupset at the Spring Classics. More on that later.
01:30Why? Well, I'm a self-confessed fan of 1x. I think that it adds simplicity,
01:36I like not having to switch between front rings mid-climb and I also like the clean looks.
01:42In fact, I like 1x so much that I now not only run it on my gravel bike, but also on one of my road
01:49bikes. I've found it great for the criterion racing that I do and the rolling terrain around where I
01:54live, but this isn't all about me. I think that it has benefits for lots of other riders too. Riders
02:00just getting into the sport, for example. Riders who can't help but cross-chain. And anyone who wants to
02:07get rid of the seven or so gears that are literally overlapping. Let me explain. But before I do,
02:13make sure you're subscribed to the channel because it really does help us out.
02:17So, this bike here. Right, it's got a 50 tooth ring at the front. Now, that is fairly big by 1x
02:24standards, but fairly small by usual road race bike standards. And these are the gear proportions
02:30that you get when it's paired with that 1046 tooth cassette. You can see that there are 13
02:38unique gear combinations. 13 gear combinations that give me the following speeds when ridden
02:44at 100 rpm. So, the easiest gear down here gives me a speed of 14 kilometers an hour when peddled at
02:51100 rpm. Obviously, I can comfortably pedal a fair bit slower than that if I need to, but 100 rpm
02:58does make the maths a fair bit easier. In the hardest gear, so using the 10 tooth cog up here,
03:03I can get to a speed of 64.3 kilometers per hour, again, when peddling at 100 rpm. In a sprint finish,
03:11I might be able to pedal a bit faster than that. And so, this can be stretched depending on what
03:16cadence you find comfortable. So now, let's compare that to a more conventional setup. As you can see,
03:24there is a lot more gears going on here. Now, I rather like the look of this Cervelo S5 with the
03:30Dura-Ace groupset. And that has quite a generous 11 34 tooth cassette at the back. And then at the
03:37front, it's got a 54 tooth big ring and a 40 tooth little ring. Now, type in those numbers and we can see
03:45that in the big ring at the front and the smallest cog at the back, I can now travel at 63.1 kilometers per
03:52hour, again, in the hardest gear at 100 rpm. Now, that is about 1.2 kilometers per hour slower than on
04:01the 1x13 system. So, maybe I get an easier gear as a result. Well, actually, no. When peddled at 100 rpm,
04:11little ring at the front, in the 34 at the back, you can see it gives me a speed of 15.1 kilometers per
04:17hour, 1.1 kilometers per hour faster than on the 1x setup. What this means then is that without a
04:26doubt, the 1x setup offers me more range than the 2x setup that I would go for. And there's more. So,
04:35if you look at these gear ratios, you can see there's loads of overlap. In fact, 9 out of the 24 gears
04:42are overlapped. And what that means is that you're lugging around some gear combinations that you will
04:48quite literally never use. This one, for example. That would be a horrendous cross chain. I'm never
04:55going to use that. All of these, Shimano won't even let me use these ones because my chain will be too
05:02baggy. What this comes down to is the fact that if we'd been using 1x since the dawn of time, I don't
05:08think that anyone would come along and invent such an overcomplicated and, frankly, inefficient system
05:17as 2x and manage to convince anyone that it's the way to go. So, why is it still so popular in 2025?
05:25Well, the way I see it for three reasons. Number one, it's not actually any heavier than the 1x setup.
05:31Despite adding a front mech and a chainring, the rear mech is much, much smaller and lighter,
05:37and this 13 speed cassette is not that light. I mean, it is light for how big it is, but it's not
05:44that light. In fact, it's about 100 grams heavier than the one you might see on SRAM's 2x setup.
05:50Number two, efficiency. Now, I don't have any figures, but I will be trying to get some,
05:56but we do know that big cogs are more efficient than little ones and that a nice straight chain line
06:01is more efficient than a cross chain. That's why, in time trials, we see such massive chain rings.
06:08Whichever way you look at it, I just don't think that a 1x system is advantageous from a purely
06:14efficiency point of view. Feel free to disagree with me in the comments, though. And finally,
06:20and this is the kicker, the jumps in between the gears are much bigger on the 1x system than they are
06:25on the 2x group set. So, what's that like to ride with? Well, I've been using this bike for just over
06:32a month now on a range of rides, ranging from slow bimbals to races and fast group rides and chain gangs,
06:40like the bike's intended for. Towards the lower end of the gears, and it feels fairly normal, and there
06:46shouldn't be much surprise by that, because if you look, a lot of the gear combinations are actually
06:49very similar. 10 versus 11, 11 versus 12, 12, 13, 13, 14, 15, 15, 17, 17, 19, 19, even 21, 21, 24, 24.
07:00It's this bit where things get slightly more weird. When you're on this bit, you're normally
07:06travelling at speeds of, let's say, 30 kilometres an hour and less. The jumps, well, they just feel like
07:14they're a bit too much. Out on rides, I've found myself staying in gears longer, sometimes churning
07:20a big one, and other times spinning a smaller one than I ordinarily would. And that is not an efficient
07:26way of riding. And on rides where you're on your limit, the last thing that I want to be thinking
07:31about is my cadence. The truth is, I never normally think about my cadence, and yet on this bike,
07:40I've been forced to. And no, that's not just because I was making a video on it. It is in fact
07:47the reason I'm making the video on it, because I thought that 13 speed was going to be the answer
07:52to all my prayers, and was then, frankly, slightly surprised. The other thing I've noticed when out
07:59riding is the dragginess in the easiest gear, and I can show you what I mean now. So if I spin this
08:06and put it up to the biggest gear, you can almost hear it. You can hear how much drag is on that gear.
08:16And if I put it down here, it's much quieter, and the cranks spin freer. Now, like I said before,
08:23I really, really want some data to back this up, and I will be trying very hard to get some.
08:28But if I can feel the difference in the cranks with my hands, then I think that this is in
08:36magnitudes of full watts rather than points of watts. Now, I said earlier that Little Trek had
08:41been using this groupset during the classic season in 2025, including at races such as Paris-Roubaix.
08:48They were extremely complimentary about it, and even went so far as to say that they'd never go back
08:53to two by for those races. Now, whilst the likes of Mads Pedersen did use a 1046-tooth cassette like
09:00this for some of the races, they too clearly wanted some closer ranges and less jumps in between gears
09:06when it came to races that are a bit flatter, such as Paris-Roubaix. And on those races, they modified
09:12their mechs, and they used a more conventional 1033-tooth cassette. Now, I am all for tailoring your
09:20gearing to the terrain that you're riding, but I just don't think that switching out cassettes
09:26is as necessary on a two by setup. And let's face it, cassettes really aren't cheap.
09:33As I said before, I am a big fan of one by group sets, and I really do think that they have a place
09:39on the road. This 13 speed explore groupset though, it's exactly what it says it is, a gravel groupset.
09:46And although I've loved trying it, I would personally buy a bike like the Cervelo S5,
09:51with one of Shimano or SRAM's two by options. Fair play to Cervelo though, for giving the consumer
09:57the choice, and speccing the two by version with rings that suits the bike's purpose. Going fast.
10:04Circling back to one by, and the crux of it is that to get all this lovely gear range,
10:08I simply think that for me, the jumps in between the gears are too big for performance road use.
10:15I hope that we continue to see more endurance road bikes and all road bikes with one by on them,
10:20and for select rides, I will still be very happy on my one by setup. For me though,
10:25the maximum size cassette that I want to be running on the road is about a 1036, not a 1046.
10:32Anything above a 1036 and I find that the changes in cadence are just too big of a sacrifice to make.
10:39Let me know if your next road bike will be one by or two by down in the comments below,
10:43that will be controversial I'm sure. Do you wish that more bike brands offered both?
10:48The full review of this bike will be live on Cycling Weekly shortly, and before you go,
10:53make sure you like, comment and subscribe. We'll see you next time.
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