ECVT/MGU: The Great Belt vs. Chain Debate

[slickrock]

Starting a separate thread on the chain vs. belt debate, as the topic has been cropping up a lot on other threads now.

Now that ECVT's have have been the talk of the town and we are clearly starting to envision a future without derailleurs, a significant Y in the trail is to embrace the new ebikes with either belt drivetrains or chain drivetrains. Before MGUs and ECVTs the choice was like the Ford Motor company slogan "you can choose any color you want so long as it's black"; no choice - it has to be a chain.

This choice between belt vs. chain has always existed, but stake were a limited market in which this choice has up till recently been quite small or has simply not applied to our EMTB space: bikes with IGH hubs (e.g. city bikes), downhill gearbox MTBs, esoteric bikes (e.g. Cavalerie), and those few Pinion MGU converts happily riding their new breed of EMTBs.

But now we must chose as the derailleur-less EMTB market will soon explode . We must influence the product managers as to what system we prefer or think what we prefer. Let the debate begin.

Edit: Areas of discussion:

• Aesthetics
• Exclusivity
• Reliability
• Maintenance
• Efficiency
• Noise
• Weight
• Performance
• Implications for bike rear suspension design
• Chain tensioner consequences
• Cost
• Choice driven by Locales/Weather/Terrain

 

[DylanJM]

Chain all the way for me. With a chain driven ECVT you will still save a decent amount of maintenance over a conventional drive train. Cleaning and re lubing essentially a single speed chain drive will be very little hassle.

 

[slickrock]

Chain all the way for me. With a chain driven ECVT you will still save a decent amount of maintenance over a conventional drive train. Cleaning and re lubing essentially a single speed chain drive will be very little hassle.

In a way, chains have been getting a bad rap because of what they have evolved into: thin, finicky, and fragile versions of their prior selves. Namely, because the industry has pushed rear cassettes to 12 cogs to take on what a front chainring used to do - provide the extra gear steps and range for MTB riders. Already this is overkill for EMTB. A good, old-fashion, single-speed chain, is really all that is needed for MGU/ECVT will be more durable and reliable like the Schwinn chains of yesteryear, except with a tensioner.

 

[Onetime]

I’ll take the belt. Reese Wilson and several others have proven them to be durable enough on the World Cup DH series for the last few years.

 

[irie]

But now we must chose as the derailleur-less EMTB market will soon explode .

Loving opinion stated as fact.

 

[Brawwp]

I’m on the mgu train, but for sure gonna wait for the issues to show when they first drop and the hype dies a little. I think time will just tell which is better. I’m not one to freak out if my bike breaks and I can’t ride a week or two.

So imo I’ll just go with whatever bike is attached that I think is better (hopefully crestline). I also trust troydon would make the right call on what is best on his frame. We know belts have had failures and so have chains. Unless we find belts to be failing at a much greater rate when they drop then I’m fine with it.

 

[slickrock]

Loving opinion stated as fact.

To be facts, they must have already occurred. Rather, this is prediction with high precision (based on my Bayesian model, which of course could be wrong). Also, what I meant by "explode" is reference to where it is now, at probably less than 0.2% of all EMTBs out there.

I’m on the mgu train, but for sure gonna wait for the issues to show when they first drop and the hype dies a little. I think time will just tell which is better. I’m not one to freak out if my bike breaks and I can’t ride a week or two.

So imo I’ll just go with whatever bike is attached that I think is better (hopefully crestline). I also trust troydon would make the right call on what is best on his frame. We know belts have had failures and so have chains. Unless we find belts to be failing at a much greater rate when they drop then I’m fine with it.

Agreed, that the bike design has a much bigger influence on chain vs. belt debate. It's doubtful that a bike brand would offer an option to choose belt or chain for a particular model of bike, like in an Orbea bike configurator. Either the bike design will force this decision or the other way around. Bike companies and their designers will probably take sides on this debate, and that could factor into the choice more than anything.

 

[irie]

To be facts, they must have already occurred. Rather, this is prediction with high precision (based on my Bayesian model, which of course could be wrong). Also, what I meant by "explode" is reference to where it is now, at probably less than 0.2% of all EMTBs out there.

Agreed, that the bike design has a much bigger influence on chain vs. belt debate. It's doubtful that a bike brand would offer an option to choose belt or chain for a particular model of bike, like in an Orbea bike configurator. Either the bike design will force this decision or the other way around. Bike companies and their designers will probably take sides on this debat, and that could factor into the choice more than anything.

Impressive prescience.

 

[Astro66]

This is what a do not like. The bottom of the tensioner is below the line of the motor bash guard. The whole point of the MGU for me is to remove exposed bits where there is sometimes contact with obstacles. Just have that a bit higher, and the arm slightly longer if needed.

A belt, tensioner and snubber like below. I would try. Because I just don't see the belt getting damaged in that configuration on the terrain I mostly ride. Also it would be very straight forward to replace all the belt cogs with chain sprockets, and remove the snubber, if I was experiencing issues with the belt, and I could replace with a chain.

 

[Astro66]

I’ll take the belt. Reese Wilson and several others have proven them to be durable enough on the World Cup DH series for the last few years.

The only thing with those guys, is how often are they checking and changing the belt ? Any nicks in the belt, would be picked up by the mechanic, and they would change them. So the chances of a nick becoming a broken belt, would be slim. Same with any stripped teeth not being picked up.

My gates belt drive E-motorcycle belt had stripped teeth. I did notice the slightly odd sound before belt failure. So replaced it before getting stranded.

Chain failures are far less an issue, if you carry a spare link, which I do. Hence my reluctance to run a belt on an EMTB.

 

[slickrock]

... Also it would be very straight forward to replace all the belt cogs with chain sprockets, and remove the snubber, if I was experiencing issues with the belt, and I could replace with a chain.
...

My sense is the moving to a chain from an EMTB delivered with a belt will be much easier than the reverse. There are additional constraints with a belt that chains can easily negotiate:

1. Chains can handle longer chain growth suspensions by using double pulleys (ugly yes, but is a hack designers can fall back on, such as Rotwild). This basically puts constraints on belted bike designs as to how much chain growth they can accommodate (which actually may be a good thing IMO)
2. Easier to route chains through VPP and DW4 unified rear triangles.
3. Belts have fixed sizes whereas chains have link-length adjustability. A specified chain-based loop size for the bike model may not have the corresponding length in belt size, where as you could easily create a chain loop to match a belt size.
4. HP idlers can be smaller and tighter with chains, so may be difficult to swap with belt equivalent

In short, if you buy chained MGU/ECVT, don't expect it can run on a belt.

 

[Astro66]

My sense is the moving to a chain from an EMTB delivered with a belt will be much easier than the reverse. There are additional constraints with a belt that chains can easily negotiate:

1. Chains can handle longer chain growth suspensions by using double pulleys (ugly yes, but is a hack designers can fall back on, such as Rotwild). This basically puts constraints on belted bike designs as to how much chain growth they can accommodate (which actually may be a good thing IMO)
2. Easier to route chains through VPP and DW4 unified rear triangles.
3. Belts have fixed sizes whereas chains have link-length adjustability. A specified chain-based loop size for the bike model may not have the corresponding length in belt size, where as you could easily create a chain loop to match a belt size.
4. HP idlers can be smaller and tighter with chains, so may be difficult to swap with belt equivalent

In short, if you buy chained MGU/ECVT, don't expect it can run on a belt.

Agreed. As someone who has played with belt drives and fitting motors to them. That configuration on the Radiate with the belt drive looks simple enough and protected enough, to not cause issues, and retro-fit a chain, if you do hate it.

So it will come down to frame and transmission design, whether I consider getting a belt.

Can I add. The most important point you missed with converting from a chain to a belt, is the chainline must be exactly lined up for a belt. Unlike a chain. A belt will not tolerate any misalignment of front and rear sprocket, or the idler either in a HP.

 

[Astro66]

Can I add. Because of the alignment between the front and rear sprockets, must remain perfectly aligned with a belt. The rear triangle on my belt drive is much stiffer. So this will also adds to the issues you may have if converting from chain to belt. The flex in your rear triangle, could cause the belt to drop when cornering.

Also. This may be a reason to stick with a chain, as you may want some flex. And also. The belt is not going to tolerate any sideways movement of your pivot joints. So you will need to keep them in perfect order. That said. You should anyway.

 

[slickrock]

Can I add. Because of the alignment between the front and rear sprockets, must remain perfectly aligned with a belt. The rear triangle on my belt drive is much stiffer. So this will also adds to the issues you may have if converting from chain to belt. The flex in your rear triangle, could cause the belt to drop when cornering.

Also. This may be a reason to stick with a chain, as you may want some flex. And also. The belt is not going to tolerate any sideways movement of your pivot joints. So you will need to keep them in perfect order. That said. You should anyway.

Gates belts aren't that sensitive, after all that's why Gates invented CDX centertrack. I've used my belt drive dual-suspension MTB with alloy frame for a decade without issue, albeit only 120mm travel.

 

[Astro66]

Gates belts aren't that sensitive, after all that's why Gates invented CDX centertrack. I've used my belt drive dual-suspension MTB with alloy frame for a decade without issue, albeit only 120mm travel.

I disagree. I had an alignment issue with my E-Motorcycle, and it wore the belt teeth out quickly. I fitted the new belt myself and got the alignment perfect. The new belt now has twice the km of the old one, and still in great shape.

The belt is not designed to be rubbing continuously to centre itself. It will eat teeth and the belt. There is significantly more tension required for the belt. So any rubbing is bad. And the belt will drop off the rear sprocket if not aligned properly or the rear triangle twists.

And the stiffer the frame. The less tension you need on the belt. Lower tension helps in so many ways, both wear and efficiency.

Gates Carbon Belt Drive: Everything You Ever Need to Know - CYCLINGABOUT.com

Belt drive systems are valued for their low maintenance requirements and typically offer 3-4× the service life of a traditional chain.

www.cyclingabout.com

 

[slickrock]

I disagree. I had an alignment issue with my E-Motorcycle, and it wore the belt teeth out quickly. I fitted the new belt myself and got the alignment perfect. The new belt now has twice the km of the old one, and still in great shape.

The belt is not designed to be rubbing continuously to centre itself. It will eat teeth and the belt. There is significantly more tension required for the belt. So any rubbing is bad. And the belt will drop off the rear sprocket if not aligned properly or the rear triangle twists.

And the stiffer the frame. The less tension you need on the belt. Lower tension helps in so many ways, both wear and efficiency.

View attachment 188569

Gates Carbon Belt Drive: Everything You Ever Need to Know - CYCLINGABOUT.com

Belt drive systems are valued for their low maintenance requirements and typically offer 3-4× the service life of a traditional chain.

www.cyclingabout.com

Is it CDX belt? Does it have a centerline notch? Tolerances, construction, size, pitch, and width for Gates Poly Chain GT Carbon or Gates Moto X9 are quite different.

Agree in general that belt line is more critical than chain line. I also agree that belts require more tension than chains, so bike designers do need to keep that in the back of their minds, but nowadays most frames, especially these enduro style EMTBS are not noodly enough to exceed belt tolerances and affect performance. I would be more concerned with the bikes if they were that noodly.