Belt drive article from Thorn Blog

[in4]

Very interesting and informative article; best read before you get the hacksaw out!

https://thorncycles.co.uk/blog/carbon-gates-belt-drive

[martinf]

Belt drive from my persepective :

I tend to keep my bikes for quite a long time. The last new bike frame I bought was an old stock Raven Tour step-through frame in 2018. All the bikes I use myself are more than 10 years old, so not worth spending about £400 to try and convert to belt drive. Instead, most of them now have ChainGliders, which prolong transmission life and reduce maintenance, perhaps not to the extent that a belt does.

Two exceptions though :

1 - If I ever replace one of the family Bromptons I would be quite interested in a belt drive. Since retiring I don't use a Brompton on a daily basis, but in bad weather conditions the chain needs cleaning very often - my "record" is just 40 kms between cleaning after 3 short rides in the recent storms. The chain on a Brompton picks up much more road muck in bad conditions.

2 - If I ever get a purpose-built electric bike. But, when the time comes that I need assistance, at the moment my plan is to convert one of my existing bikes, or perhaps a second-hand mountain bike (available for about 50 euros), and use a chain, chainring and sprocket designed specifically for electric bikes together with a ChainGlider. These KMC transmission components cost significantly more than standard ones, but still a lot less than belt drive components.

[mickeg]

Five or six years ago there was another option for belt that did not involve a split frame, the Veer split belt drive.  On this forum do a search for Veer belt and you will find a few posts by someone that installed and used one.  I have no idea if that is still an option available to buy or not, I have not seen mention of it for some time now.  This was the last update on that person that installed one:
https://thorncyclesforum.co.uk/index.php?topic=15262

When I bought my Nomad Mk II 13 years ago, I considered that bike against another bike from a different manufacturer that had the belt drive option.  Thus, I considered belt drive.  But I decided that I wanted chain drive for one simple reason.  When touring where I am carrying heavy loads, I wanted lower gear range than when I am riding that bike near home when the bike would not carry much weight.  With the chain drive, I use a 36T chainring for touring, and a 44T chainring for unladen riding elsewhere.  This means I add or subtract four chain links when I make the switch.  I use a 16T sprocket.  Thus my chainring to sprocket ratios vary from 2.25 to 2.75.  It is possible that I would have been able with a split frame to buy the sprockets and belts to enable switching gear ranges, but I decided it would be simplest to just use a chain without researching it further.  I do not regret my decision at all.  Would I make the same decision today?  Probably.  I have several bikes, all have chains.  That said, I used to work as a bike mechanic, doing a bit of maintenance on a regular basis is something that I am happy to perform.  Those that want a maintenance free bike, I can understand that too, I know several people that want to do as little maintenance as possible.

[Andre Jute]

2 - If I ever get a purpose-built electric bike. But, when the time comes that I need assistance, at the moment my plan is to convert one of my existing bikes, or perhaps a second-hand mountain bike (available for about 50 euros), and use a chain, chainring and sprocket designed specifically for electric bikes together with a ChainGlider. These KMC transmission components cost significantly morer than standard ones, but still a lot less than belt drive components.

I agree with you, Martin. Having discovered the Chainglider and the KMC X8 chain, and steel chainrings, I have zero interest in the frame-weakening a belt drive brings with it. It may be that I'm biased by having been a motor racer as a young man, whose specialty was suspensions, which absolutely demand stiff frames. But I'm not convinced by the special electric bike components KMC are marketing.

I discovered steel chainrings serendipitously: I was ready to order a Utopia Kranich but hated the amorphous cranks that was their standard supply, and had been put off the aluminum chainrings that went with the ugly cranks when I used Nexus transmission from Shimano, which ate itself up pretty shortly; I never saw as much as thousand miles from a set. I thought about the Thorn default chainring which then as now had a pretty good reputation of longevity, until I discovered it wouldn't fit in Utopia's Country chain enclosure (same principle as the Hebie's Chainglider but much lighter build). Someone suggested I fit a temporary cheap steel crankset from India, Amar brand, until found a way to buy a set of the Japanese cranks I had my heart set on. It was many months before I found a way of actually having the cranks I wanted delivered to me, from Paris as it happened, and not too long after that a lot of things happened simultaneously: I moved up the steepest hill in town, the Country chain protector started falling apart, I discovered the Chainglider, I bought a not too outrageously expensive electric bike kit to educate myself, and I discovered that the only really satisfactory upmarket chainring inside a Chainglider is Surly's stainless steel model. After about 3500 miles the black paint on the Amar was still intact. When I went from a front-drive to a mid-drive electric motor the Surly chainring couldn't be made to fit, so I got a couple of sizes of 8Fun's standard steel chainrings, dished to fit over their motor to give the right tread width for the Rohloff, both in steel. The chainring that on test I found most suitable has since done 11000 miles inside a Chainglider without any sign of wear. It follows logically that I see zero reason to fit anything more expensive than steel on a utility or touring bike -- I presume a road bike someone intends to race would be built to a more weight-conscious decision pyramid.

[Andyb1]

It is slightly ironic that Thorn do not make their bikes more compatible for chaingliders.   Certainly they were not enthusiastic about them when I bought one for my Raven……the problem being that the seat stays can touch the rear part of the chainglider and push it into the hub.  I started a thread here about fitting a Chainglider recently in the Rohloff section.

It may be that their later frames designed for a belt which is wider than a chain are more compatible with a chainglider?

In the article by Thorn I was surprised that they say that belts are more efficient than chains?

Currently in Sri Lanka where my chain feels fine in it’s chainglider after 500 miles of gritty roads, I keep thinking I should oil it….

[mickeg]

The guy that put together this video has done a LOT of videos on bike touring and related equipment.  I trust his opinions highly.  And for touring, he likes belt drive.  He also mentions some efficiency stats.  This video is a few years old. 
https://www.youtube.com/watch?v=PhXTl7gApVA

He often runs his belt looser than the manufacturer recommendation.

Regarding chain drive efficiency on Rohloff bikes, I think that the Thorn bikes with an eccentric bottom bracket are more efficient than the bikes that use a spring loaded chain tightener with a jockey wheel.  And of course once you start talking about chain efficiency, then different lubes become a factor.

He is sponsored by Koga, but he does not specifically push them, unless you watch the review of his bike.

[Andre Jute]

In the article by Thorn I was surprised that they say that belts are more efficient than chains?

Maybe on aggregate if you're talking about a bare, dirty chain being ground into dust against a belt. My opinion is that anyone who's still running a bare chain on a hub gearbox might as well go back to the days of constant running replacement expense and maintenance work and filthy derailleur. I'm not impressed with test numbers taken on spotlessly clean components in a humidity- and dust-controlled laboratory.

In any event, for many of us who've given the connection between cleanliness and component longevity some thought, the real world is a Rohloff hub gearbox without derailleurs and jockey wheels (definitely the devil's invention), with the chain covered by a Chainglider. In this particular case, the chain is always run in near-optimal conditions and likely to leave an open belt for dead as the belt cannot be effectively covered, and its efficiency degrades as it gets dirtier. The Chainglider is the nearest thing possible to the mythical 'oil bath' of which gear heads' dreams are made.

A good quality Chainglider-covered chain basically operates on peak efficiency throughout its lifespan. That applies even if the chain inside the Chainglider receives zero maintenance. I've proven that by running my chains for their entire service life on the factory lube. (KMC has an especially effective and long-lasting factory lube. That is one reason I recommend their X8 chains so warmly.) That simple procedure, and the modest cost of about 50-60 Euro including delivery for a Chainglider increased my mileage per chain by a 160 percent.

Currently in Sri Lanka where my chain feels fine in it’s chainglider after 500 miles of gritty roads, I keep thinking I should oil it….

Jobst Brandt, an engineer who worked for Porsche, who don't hire idiots, where he designed the Grand Prix brakes, was an enthusiastic cyclist who condensed the engineering of the bicycle wheel into his book, The Bicycle Wheel, and devised the first bike computer, and brought slick tyres and many other revolutionary components to bicycles. I drove Porsche from the 356 series forward, so I was inclined to believe his obiter dicta, one of which was, 'The chief ingredients of grinding paste are dust and oil.' It's why I don't put any additional (to the factory lube) oil or grease on my bike's chain inside the Chainglider.

[martinf]

My opinion is that anyone who's still running a bare chain on a hub gearbox might as well go back to the days of constant running replacement expense and maintenance work and filthy derailleur.

My own opinion, based on my (at first sceptical) test of a ChainGlider is that :

- A hub gear system with ChainGlider keeps the transmission much cleaner and requires significantly less maintenance than a hub gear system with a bare chain.

- A hub gear system with a bare chain requires significantly less maintenance than a derailleur system. And when it does need maintenance, it is much easier to clean 1 chainring and 1 sprocket than multiple chainrings/sprockets and the rear derailleur (front doesn't need much cleaning).

On condition, of course, that the hub gear is reliable. I have had one or two unreliable hub gears, notably the first version of the Sturmey-Archer Sprinter 5-speed, which was a real pain.