ECVT/MGU: The Great Belt vs. Chain Debate

[ArmyOfEvilRobots]

There you go, it has to be changed on a interval unlike a timing chain, so the life span is lower, so there is more maintenance on a cog belt.
Without a tensioner, sprocket needs to be a certain diameters to maintain tension.
I have been around cogged belt drives for decades. Warm weather, clod weather etc.
What degrades a cog type belt is shock loading and harsh cycling loads. They work yes, just talking from experience not a opinion.
I would chose a chain over a belt drive on any application.
Now in a mtn bicycle application 30km from the truck, hard no for me with the riding I do, a chain is alot easier/quicker to repair/replace then a cog belt. Lol I have seen what a stick can do to the spokes and a rim.
A commuter bike around town and in the city? Sure

To be pedantic, I personally would (and have) chosen belt drives for a LOT of applications (I design mechatronics). My 3D printers, automation systems large and small, pen-plotters, etc. all use belts exclusively. They're awesome for precise, repeatable motion.

Here's the violent agreement part: You'll note that none of those applications are bicycles. That's for good reason. I just don't trust belt systems in harsh environments. Yes; chains are heavier, but they're cheap, easy to replace, ludicrously durable, and less prone to damage. The only reason they seem so fragile now is because the bike industry has pared weight and width down to the point where they are barely adequate for purpose. Those paper-thin side-plates would be cute if they weren't so easy to twist, and yet they STILL work correctly most of the time.

If we can ditch the complexity of the derailleur/cassette combo, we can make our chains substantially stronger and more durable (although I don't have much hope the industry will go that way in any hurry). We definitely shouldn't be looking only as far as linkglide either. Imagine if we had Shimano style surface treatments and precision, but on a 1/8" wide chain with thicker side-plates that could handle 2x the tension and spread the wear over a wider roller for longer life. I don't remember ever breaking my BMX chains, despite the abuse I put them through, and those were _cheap_ (mind you, I was 60lbs lighter too ).

 

[RustyIron]

To be pedantic, I personally would (and have) chosen belt drives for a LOT of applications (I design mechatronics).

I work on big machinery, old machinery, and well-worn machinery. Back in the olden days, we used a lot of big chains (tiny chains, too). They'd run forever covered in dirt and grime, until the metal just ground away. But to be fair, I"ve worked on a lot of belted systems, too. They last for a long, long time, until sometimes the threads are just flying off the belts. One of the challenges with belts is slippage, which will have your belt's smokin' in no time. As you know, the solution is cogged belts. In a slow-speed system like our bikes, maybe cogged belts could work out. The thing I don't know is how a wide belt would react to accumulated mud and debris. Roller chains and sprockets like ours tend to shed debris. How would a belt perform when it starts winding up grass and mud? Really, the discussion is somewhat moot until the big manufacturers start putting gearbox/belt bikes on the showroom floor.

 

[irie]

I would chose a chain over a belt drive on any application.

So would I.

 

[slickrock]

OK, so here is my current weigh-in on the debate and here's where I currently stand (though I'm open to be swayed). I will use the criteria in the OP to weigh my take on this, but I must admit this take is based on a decade of belt-drive use on my full suspension MTB:

Criteria	Weight	Choice	Comments
Aesthetics	HIgh	Belt	I find belt drives aesthetically more pleasing. They look cool. They draw more attention on trails because they are rare. I get people always asking me how to get one on their bike. I tell them it's complicated (at least before MGUs/ECVTS). More importantly for me, chains require chain tensioners and those tensioners look too much like derailleurs themselves - the very aesthetic I want to get away from.
Exclusivity	Mid/High	Belt	Because with MGU/ECVT, "you can". With derailleur systems, "you can't". The mere presence of a belt announces that you have internalized transmission, either at the hub or mid-drive. EMTBs that will sport belts will feel like a separate class (for better or worse) on the trail.
Reliability	High	Neutral	I've been using the same belt for like 10 years. No issues with CDX. But I feel as a category, that a BMX style chain would be pretty much bullet proof.
Maintenance	High	Belt	No question here. Set and forget. Wash bike. Done. Belt life has exceeded chain life/cog life in my case.
Efficiency	Low	Neutral	Chains are more efficient at low speeds, belts more efficient at higher speeds. Chain efficiency really drops with muck; with ebikes efficiency is less of an issue.
Noise	High	Belt	Belts are so quiet, and you get used to it fast, so going back to a chain can be unnerving.
Weight	Mid/High	Belt	Belts are much lighter and have an important consequence on performance (see below)
Performance	High	Belt	Really improves pedal kickback effects when coasting. I feel chain whipping effects is a big reason most bikes use Ochains more than trying to ameliorate actual pedal kickback. So you won't really need an Ochain or Sidekick with a belt. MGUs/ECVT elevate rear suspension performance and belts push it further.
Implications for bike rear suspension design	Mid/Hi	Chain	In general you will have more freedom with chains for rear suspension design. This implies the existing rear suspension IP from the various makers (especially those with lots of chain growth) will likely be able to get their designs to work more readily with chains. Belts require elevated chains stays or Horst Links route the belt. Belt tensioners tend to take up less slack than chain tensioners. Belts require strict belt lines and no noodly rear ends.
Chain tensioner consequences	Mid/Hi	Belt	As mentioned above, I'm not a fan of chain tensioners. Not only do they look too much like derailleurs, but they are noisier. They often have two pulleys (e.g. Rotwild) compared to belts with only one. Why this is is up for debate, but it may have to do that a lot of bike designers already have large chain-growth rear suspensions, and only a two-pulley chain tensioner can take up enough slack. In general I despise tensioners and advocate rear suspension designs that don't require them (like on my dual suspension MTB), but this will be hard to accomplish with all the current MGU/ECVT models announced.
Choice driven by Locales/Weather/Terrain	Mid/Hi	Neutral	My Bay Area locale is quite welcoming for belts based on my own MTB riding with belts. Mostly fair weather, tacky to dry terrain. Not quite the PNW and North Vancouver gnar that some contend with, but still have had broken derailleurs.
Cost	Mid	Chain	No need to have costly fragile 12-speed derailleur chains. Belts will likely remain more expensive than chains
Availability	Mid/Low	Chain	Chain are ubiquitous.
Repair	Mid	Chain	A powerlock link is pretty much all you need to get by on the trail. But how often you break a chain has much more do with broken derailleurs and bad shifting than anything else. My sense is chain or belt damage on trails will be rare on MGU/EVCT EMTBs.

 

[sethimus]

Sethimus: 'learn to ride dumbass...'. Cue 6-year-old crying while picking up new bike.

me online is not the same persona i can play when i get paid. you get the real deal though

 

[Mikerb]

I read with interest the views of those with experience of using belts and chains in various applications. Clearly both have pros and cons.
For me assuming both are essentially functional on an emtb with a mgu the choice would come down to convenience, most especially at the end of a ride. Here in the UK for most months of the year trail conditions are wet and muddy and that means a chain needs degreasing, washing and lubing every ride. Even in hot dry conditions like we are currently experiencing., whilst the rest of the bike merely needs brushing off, the chain still needs the full maintenance treatment because that fine dust also gets into the chain.
So would a bigger/ stronger chain fitted to a mgu still need such tedious maintenance? Would such a chain be heavy? Would such a chain cause wear on the chainwheel and rear sprocket? What price comparison is there between a mgu chain or belt. Would a mgu chain still have a quick link? Does a belt have any type of connector? I would happily change either at 1000 miles if that process was fairly easy and neither had required full maintenance after every ride.

 

[Ndanger]

Dear God please tell me you don't work in customer service in that shop.

Lmao, brutal but true! Though if he's holding down the fort at a big city shop right now, he's definitely fighting for his life, standard customer service burnout right there! Honestly though, if he’s working a Swiss shop in the summer, I totally get why his brain is cooked. The alpine riding season is peaking, the service bays are backed up for weeks, and city floor space is so tight it’s wild. You can't even get past the front door without booking a Termin (appointment) ahead of time, It's a total culture shock how slammed they get in that part of the world.

 

[Janc]

I'm at >2000m

I read with interest the views of those with experience of using belts and chains in various applications. Clearly both have pros and cons.
For me assuming both are essentially functional on an emtb with a mgu the choice would come down to convenience, most especially at the end of a ride. Here in the UK for most months of the year trail conditions are wet and muddy and that means a chain needs degreasing, washing and lubing every ride. Even in hot dry conditions like we are currently experiencing., whilst the rest of the bike merely needs brushing off, the chain still needs the full maintenance treatment because that fine dust also gets into the chain.
So would a bigger/ stronger chain fitted to a mgu still need such tedious maintenance? Would such a chain be heavy? Would such a chain cause wear on the chainwheel and rear sprocket? What price comparison is there between a mgu chain or belt. Would a mgu chain still have a quick link? Does a belt have any type of connector? I would happily change either at 1000 miles if that process was fairly easy and neither had required full maintenance after every ride.

I'm at >2000m on my Pinion MGU with belt with only using water to clean it of grime. I call that pretty much zero maintenance. I recently bought a spare belt when I had the bike serviced as I didn't want the hassle of waiting should I suddenly need one. Having ridden chained bikes for 50+ years I wouldn't go back. As for the other benefits like suspension kinematics, silence etc overwhelmingly positive.

 

[Diby2000]

There you go, it has to be changed on a interval unlike a timing chain, so the life span is lower, so there is more maintenance on a cog belt.
Without a tensioner, sprocket needs to be a certain diameters to maintain tension.
I have been around cogged belt drives for decades. Warm weather, clod weather etc.
What degrades a cog type belt is shock loading and harsh cycling loads. They work yes, just talking from experience not a opinion.
I would chose a chain over a belt drive on any application.
Now in a mtn bicycle application 30km from the truck, hard no for me with the riding I do, a chain is alot easier/quicker to repair/replace then a cog belt. Lol I have seen what a stick can do to the spokes and a rim.
A commuter bike around town and in the city? Sure

Yes a belt will require changing at some point, as will a chain. I disagree that this translated to "so there is more maintenance on a cog belt."
Again these are dramatically different designs. how many single row timing chains have you seen? do you want a double (or even triple) row chain on your bike? How will the weight/efficency of that compare? These are also typically (not always) running in an enclosed, sealed area and in an engine oil bath. This is why you don't have to "maintain" them. Don't think I'll see one of them on a bike any time soon?
As others have noted, a single, larger chain will probably be the better solution for the chain option. But this will still probably require ongoing attention. I would rather change a belt every couple of years and forget about the rest.

This is a good discussion. I don't want to get bogged down into semantics but if we are trying to make comparisons, lets at least try to compare like for like.

 

[Red Peekay]

I guess at the end of the day it will be out of our hands. Each bike manufacturer will probably make a decision based on geo, ride and testing on what they will run, chain or belt. Can't see them being interchangeable and can't see the manufacturers offering multiple choices.... so will probably come down to a choice of manufacturer and what their offerings are!

 

[slickrock]

I guess at the end of the day it will be out of our hands. Each bike manufacturer will probably make a decision based on geo, ride and testing on what they will run, chain or belt. Can't see them being interchangeable and can't see the manufacturers offering multiple choices.... so will probably come down to a choice of manufacturer and what their offerings are!

I'm fairly certain this will be the case. Whether the preference for a particular bike ends up choosing the drivetrain (belt or chain) or the preference for a particular drivetrain ends up choosing the bike remains to seen.

 

[andreaverona]

Today, we can't compare the belt of an MGU system with the chain of a traditional 12-speed system.
A chain on an MGU system will always work in alignment, without twisting or moving up and down... it will have a much easier life than a 12-speed.

 

[Diby2000]

Today, we can't compare the belt of an MGU system with the chain of a traditional 12-speed system.
A chain on an MGU system will always work in alignment, without twisting or moving up and down... it will have a much easier life than a 12-speed.

This is true. We can compare a belt driven MGU system (even if only considering one gear) and a single speed though. This is probably the closest comparison we can make at this stage. But we would have to imagine that gear always being the right one.
I would think the majority of single speed bikes out there receive little to no chain maintenance and survive. How good they are to ride with this maintenance is probably questionable.
It's been a long time since I rode a single speed (bmx) but I definitely did at least semi-regular maintenance on it.

 

[andreaverona]

The ease of repairing a chain and its availability combined with the low maintenance of a constantly aligned system like an MGU are the best solution for me. I don't intend to carry a spare strap in my backpack.

 

[TimC7]

Today, we can't compare the belt of an MGU system with the chain of a traditional 12-speed system.
A chain on an MGU system will always work in alignment, without twisting or moving up and down... it will have a much easier life than a 12-speed.

That chain and the two sprockets are going to fairly sh@gged pretty quickly despite the lack of shifting if they continue using standard bike parts!