What Are Drivetrains On Road Bikes?

Cycling Weekly

Road bike drivetrain technology is under the constant scrutiny of the entire cycling industry.  There are some very promising options out there so Cycling Weekly's Sam Gupta  runs through what he believes could be the tech of future for road bike drivetrains.

Transcript

00:00The drivetrain as we know it, with two derailleurs and a chain, has been the favoured method of

00:05converting spinning legs into speed for nearly 100 years. As we all know, over this time we have

00:12seen countless improvements to the system, which has landed us with where we're at today,

00:18which by all accounts is a pretty refined and efficient system. However, as we reach what may

00:25be a plateau of innovation in this space, suggesting we may actually have the best version

00:29of the system, it's only natural to wonder what the next generation of drivetrains will be.

00:35While the current system serves the masses really well, for some, there are some potentially huge

00:41gains to be had in other technologies. CeramicSpeed debuted its wacky looking system back in 2018,

00:53much to the intrigue of anybody who set eyes on it. It works by using sculpted plates rather than

01:00chain rings and sprockets with an electronically controlled driveshaft which can shift between

01:05different diameters of the plate to engage a different gear. As yet, it's still very much

01:12in the testing and development phase. However, CeramicSpeed claims that it was able to achieve

01:16a speed of 45 kilometers per hour on the track, on a single speed prototype during part of its low

01:24testing phase. If this drivetrain ever does hit the market, in the first instance, it will undoubtedly be

01:32incredibly expensive. But of course, that's the same for any brand new and truly revolutionary tech.

01:39It always takes a bit of time for it to trickle down to those lower echelons.

01:43If CeramicSpeed really are successful in creating a drivetrain that is 99% efficient,

01:50it will of course attract the attention of those chasing every single want.

01:55Drivetrains like this could find a home on top-end TT and triathlon bikes, maybe even aero bikes

02:02optimised for flat races that will end in a sprint. The drivetrain efficiency is one thing,

02:08but the other benefits that come along with a setup like this is that there's no chain to come off.

02:14The system is more compact and therefore more aero. CeramicSpeed are claiming that they have

02:20recorded an advantage in specialised wind tunnel. But finally, since there are no delicate components

02:26hanging off of the frame, if a rider is to have a crash, they should just be able to jump on the bike

02:31and carry on. Snapped mech hangers will become a thing of the past, although SRAM's direct mount

02:37rear derailleur also seems to be doing a pretty good job of this.

02:45From one direct drive system to another, but one is actually in existence and is available to purchase,

02:52is the driveshaft tech from Honda. They have done away with convention and constructed a pretty sturdy

02:58and utilitarian version of a similar concept. In Honbike's case, they have also made the housing

03:05for the driveshaft integral to the frame and it doubles as the chainstay which holds the rear wheel

03:11in place. Honbike has offered the system within their e-bike range and given the system weight,

03:17it's unlikely something similar would make it over to the world of road bikes. However, it's not

03:23impossible. There are a lot of engineers in the world, all of whom are much smarter than me,

03:28so perhaps there could be a middle ground between what Honbike has created and what CeramicSpeed are

03:33working on and perhaps that's where we'll see more of an affordable direct drive system emerge from.

03:44One of my favourite drivetrains and one which I feel is often overlooked is the Humboldt Belt Drive.

03:51Commonly found on urban and commuter bikes, the Belt Drive is just that. A belt very similar to the one

03:57that you might find in your car but also has humps or teeth that engage with a similarly shaped front

04:04chainring and rear sprocket. Unsurprisingly, the belt itself can't be shifted so to work around that

04:10limitation, belt drive bikes are often ones that instead incorporate a hub gear.

04:16For riders who demand bomb-proof simplicity, I don't think you can get much better than this. There's no oily

04:22chain to make your legs or clothes dirty, it doesn't need lubing and it cannot rust. The hub gear is

04:29completely sealed from the elements and often only ever need servicing once every few thousand miles and

04:36even then it's just a case of topping up any oil that might have escaped. Hub shifting is notoriously smooth,

04:43it's very much a fit and forget type of system. Perhaps it's down to a lack of awareness or education,

04:51but I think that this tech on a flat bar hybrid is quite possibly the best option out there. There are

04:58minimal downsides for the intended user but there is so much to be gained.

05:07E-Bikes have actually played host to quite a few innovations years before they've made their way onto

05:13road bikes. Let's not forget that Shimano Di2 was first found on an e-bike nearly five years before

05:19it showed up as an option for road bikes. So I think it's prudent to keep a keen eye on the latest

05:26innovations that pop up in that sphere as one day it would not be a surprise to see it become the new

05:31normal for road bikes. One innovation that has come from the behemoth that is Shimano is their automatic

05:38stepless shifting. You may be thinking what does it do? Well quite what it says on the tin. You start

05:47pedalling and when you do you'll be in a nice easy gear to get you going. Then as you build up speed and

05:53work up to a faster cadence the auto box will move up the gears to allow you to increase your speed while

05:59keeping you at a comfortable cadence. But the really remarkable part about this is the ease at which it

06:06changes gear. You barely feel a change, it's more of an audible click quickly followed by a change of

06:13cadence. Perhaps this could be a great option for those who just want to focus on riding and let the

06:19bike take care of the rest. Lastly, and potentially most importantly, Classified seems to be leading the

06:29charge in terms of the next best alternative to the conventional drivetrain. Perhaps this is because

06:36it's not too far removed from what we already have. As the brand seeks to ditch the front derailleur and

06:42replace it with a wireless two-speed hub gear we're still left with a conventional chain and rear derailleur

06:48setup. But the new tech does mean that front shifts can be conducted under extreme load without the risk of

06:55misshifting or dropping a chain. And chain lines can be optimised for an even more efficient setup.

07:02The last hurdle that the brand has to overcome is the integration with the shifters themselves.

07:09At the moment the hub is operated by a wireless button that mounts to your handlebars but hopefully

07:16one day in the future the tech can be integrated into the OEM shifters without voiding any warranties.

07:23My hope is that SRAM decide to acquire Classified and then build it into their entire ecosystem.

07:31Imagine this, a pair of zip wheels with a classified hub that also makes use of the brand's ownership of

07:38PowerTap to create a zip classified PowerTap set of wheels and then perfectly integrates with SRAM's

07:46already wireless group sets. What a dream that would be. One for the future I'm sure and perhaps

07:53I'm being a little optimistic that such a thing could ever exist but it's not outside the realms of

07:59possibility. Let me know, what do you think the future is for the Humble drivetrain? Do you think

08:06it will ever develop beyond the conventional two derailleur system we already have? Do you think

08:11Classified or CeramicSpeed have the answer? If you enjoyed the video then please do drop it a like,

08:17subscribe to the channel for more content and I will see you again very soon.

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