Why use a chain rather than a Gates belt drive
- Thread starter Alaskan
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J.R.
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A final drive belt does rob some of the power. That's the only reason I can think of.
I've owned motorcycles, using Gates final drive belts for near 30 years and testing shows the belts rob horsepower far more than chain drive does. It's not really a problem on MC's; I expect a low power eMTB is a different story.
Scarecrow
Member
I have read a lot on these since 2012. Not an expert, however. Here's my take...
Belts are lighter, cleaner, and last forever. Chains are less expensive and fit far more frames. The frame on a bike has to be engineered to work with the belt, and requires a stiffer frame to handle the increased torque. In some configurations, the gear-shifting with a belt and internal gears would present a proble -- you've read hoew the earlier iterations required a slight hesitation to allow those gear changes to take place, I'm sure. So I would put that up as "Chains are usually more-responsive, or quicker to respond." Which might be far more critical on mountain bikes. It's just a guess.
I think the designers figure "Why change something that is working so well?" -- especially if it entails a full frame redesign. And once redesigned, it's possibly ONLY usable with the Belt Drive.
I love Belt Drives. I love everything about them -- but, most especially, the low-maintenance feature. What surprises me is few designs include a cover for that belt. Maybe because those designs are typically heavier, already. It's a way to cut some fat. But in my estimation, "In for a penny. In for a pound!" I'd rather have that cover - especially if it was hinged in some way to make it easily removable.
Belts are lighter, cleaner, and last forever. Chains are less expensive and fit far more frames. The frame on a bike has to be engineered to work with the belt, and requires a stiffer frame to handle the increased torque. In some configurations, the gear-shifting with a belt and internal gears would present a proble -- you've read hoew the earlier iterations required a slight hesitation to allow those gear changes to take place, I'm sure. So I would put that up as "Chains are usually more-responsive, or quicker to respond." Which might be far more critical on mountain bikes. It's just a guess.
I think the designers figure "Why change something that is working so well?" -- especially if it entails a full frame redesign. And once redesigned, it's possibly ONLY usable with the Belt Drive.
I love Belt Drives. I love everything about them -- but, most especially, the low-maintenance feature. What surprises me is few designs include a cover for that belt. Maybe because those designs are typically heavier, already. It's a way to cut some fat. But in my estimation, "In for a penny. In for a pound!" I'd rather have that cover - especially if it was hinged in some way to make it easily removable.
Alaskan
Well-Known Member
My wife and I have two Riese & Muller Homage Rohloff bikes, one a 2018 with a chain and tensioner/idler, the other a 2019 with a Gate carbon belt and tensioner/idler. The swing arm with tentioner on the belt drive version avoids any break in the chainstay/swing arm assembly.
I notice no difference between the two bikes in terms of power or efficiency. It is true that the Rohloff speed hub requires a slight hesitation while shifting. It is not even a pause but rather a momentary easing up on the pedals when they are at 12 & 6 o'clock. It takes a day or two to learn this. Once done it presents no issues, even when climbing a very steep hill and having to downshift. The combination makes for an incredibly durable, low maintenance drive train with a very wide gear range.
Given that I ride over 500 miles a month, having a chain that needs cleaning, lubrication and replacement every couple of months is not to be preferred for any reason other than lower initial cost. I could still be missing an important point.
As to a cover on the belt, having gotten a pants cuff mangled and almost tossing me off the bike in the process, I would prefer to have a belt guard in place for safety sake. Now I am diligent in putting on a velcro strap around my ankle when wearing long pants.
I notice no difference between the two bikes in terms of power or efficiency. It is true that the Rohloff speed hub requires a slight hesitation while shifting. It is not even a pause but rather a momentary easing up on the pedals when they are at 12 & 6 o'clock. It takes a day or two to learn this. Once done it presents no issues, even when climbing a very steep hill and having to downshift. The combination makes for an incredibly durable, low maintenance drive train with a very wide gear range.
Given that I ride over 500 miles a month, having a chain that needs cleaning, lubrication and replacement every couple of months is not to be preferred for any reason other than lower initial cost. I could still be missing an important point.
As to a cover on the belt, having gotten a pants cuff mangled and almost tossing me off the bike in the process, I would prefer to have a belt guard in place for safety sake. Now I am diligent in putting on a velcro strap around my ankle when wearing long pants.
smorgasbord
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The Delite is a full-suspension bike, which means the distance from the crank to the rear axle varies. That's fine for a chain with a spring-loaded derailleur, but not for a belt, which needs a minimum tension to not fall off. R&M uniquely uses a belt tensioner to maintain the proper belt tension. My speculation would be that under heavy off road conditions, the tensioner may not maintain the proper belt tension at all times. I don't know of a full suspension bike other than the R&Ms that has a belt drive.
Another aspect is that going with a belt means using an internally geared hub (IGH), which has its own set of advantages and disadvantages. On the down side are cost and weight and, for the Rohloff at least, ability to shift with a load on the pedals. The Delite with e-Rohloff and belt I test rode did this pause thing whenever I shifted. That was fine on downhills, OK on flats, but a killer on steep uphills if you didn't chose the right gear to begin with, or the hill gets steeper around the bend, etc. I can see where people touring would live with that trade-off, but mountain bikers might not. BTW, this "slight hesitation" is for all Rohloffs, especially the new electronic shifting Rohloff, which is typically setup to enforce that pause. I don't know the NuVinci's behavior, but that hub is less efficient and less high torque compatible, aspects which may make it non-optimal for mountain biking. In other words, belt may be better than chain, but external gearing still has some advantages over IGHs.
ilanarama
Member
My ebike (city/utility) has the Gates belt and the NuVinci CVT, my acoustic mtb has a chain and 1x11. I can believe your argument here, that chains are used on the emtbs because of the external gearing, because thinking about the kind of terrain I mtb on, with sharp steep changes in grade, I think using the NuVinci would be harder. It doesn't pause that I notice, but the twist-to-shift feels less responsive than the positive click of the discrete shifter.
J.R.
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I can't say I would notice the power difference, but it's there.
"But is it more efficient than a conventional chain drive? According to Jason Smith at Friction Facts, the answer is no. By his measurements, a conventional chain drive consumes 2.92 watts on average, while the belt eats up 3.93 watts. Although the difference is just 1 watt – not enough for most people to care – this works out as a substantial 34.6 percent."
https://www.bikeradar.com/news/chain-or-belt-drive-which-is-faster/
Ravi Kempaiah
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Belts are preferred for high-mileage usage but there are a number of advantages for chains.
- Chain-derailleur setup is lot more forgiving of shifting under load. The derailleur setup is lighter than any IGH. With new systems like SRAM EX, cassettes can be made to last longer.
- It is not possible to find a durable and yet lightweight IGH for E-bike usage. What is the point of having carbon wheels and then increasing the unsprung weight in the hub by using a Enviolo or Rohloff?
Unsprung weight is certainly noticeable when one starts highly technical riding in the mountains.
- Belt tension needs to be accurate for IGH+ Belt setup to work.
Rohloff has had some increasing hub failures because of incorrect tension and misfiring of the E-14 system, especially using the Gates system.
- Complexity in frame design and cost favors the tried -true chain-derailleur setup.
[PS: owner of Delite GX Rohloff HS with chain and Wattwagon Ultimate Commuter with belt.]
I have a custom hardtail mtb with splits on the seatstays with an IGH. In assembling, I got a deal on a XTR crankset, but with a bolt pattern that isn't compatible with Gates. OEM is different, but the mtb crowd had to really customize to do belt not too long ago. Not to mention the first generation of Gates were not reliable and were very sensitive to tension.
Offroad, I can remove a chain or split links easily and quickly. With a belt, you have to carry a spare and in a certain shape at that.
Any hesitation off-road is difficult to deal with. Loss of momentum sucks on a climb.
I suspect there are geometry reasons too. Pushing the stays higher to avoid having to split them affects COG.
Offroad, I can remove a chain or split links easily and quickly. With a belt, you have to carry a spare and in a certain shape at that.
Any hesitation off-road is difficult to deal with. Loss of momentum sucks on a climb.
I suspect there are geometry reasons too. Pushing the stays higher to avoid having to split them affects COG.
Some of the disadvantages only apply to a mid drive motor. Under load, front hub configuration doesn't stress the drive train. I don't even think a rear hub motor would. Belt tension I don't think is an issue with either configuration ...just the mid drives. I love my Tern Verge Si8 conversion...front hub drive, gates belt drive etc. I would never buy a derailleur e-bike when the belt option is available to so many models out there. That old, tired and true technology that is probably great for the racers but not old guys like me. Sometimes, I wonder how people could pay $5- 8K for an e-bike that has a derailleur system.
Mr. Coffee
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I think it comes down to two things:
- Maintaining belt tension usually requires that you have an oddly-shaped dropout.
- You either need a bike with a raised chain stay or a break in the frame to get the belt in and out.
smorgasbord
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One watt is just one watt, and no math can convince me that 1 watt is "substantial." The NuVinci, for instance, has loses of 22 watts compared to the Rohloff, which is close to a good external gear setup (see https://www.cyclingabout.com/speed-difference-testing-gearbox-systems/ for the data). Losing 22 watts to gain 1 isn't a win. There clearly are other reasons.
Except the OP was asking why some bikes with the same frame (R&M Delite) are not offered in belt drive, but others are.
Feliz
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Why would designers hate an elevated chain stay? Just curious.
Feliz
Well-Known Member
You don't need a Rohloff to use a Gates belt, I have a belt and Alfine 8 IGH that works like a charm and if I recall the setup was under $500. Belts are the future, I see them on a lot of EMTBs now when I'm out and about. Using them with a rear suspension doesn't work too well but someone will figure that out.
Mr. Coffee
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The claim is that it isn't as strong for a given weight. That sound plausible. I've also heard the argument that it forces a lower bottom bracket and thus less clearance. That doesn't sound so plausible to me.
I have a suspicion it is all about fashion and what the other guys are doing. In the early 1990s elevated chain stays were all the thing on hardtail mountain bikes, and they seem to be making a comeback today for mountain bikes because you can get quite a bit of tire clearance for a given short chain stay length.
Feliz
Well-Known Member
Makes sense, thanks Mr Coffee. I've noticed I'm seeing a lot more now.
tomjasz
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Hard at my age to bother waiting, I’m for my rewards today. I’m thinking about the lithium graphite battery thread as I write this. Lots of promise but no beef. Jeez we’re old, that where’s the beef ad is likely unknown to many here....
. We’ve been watching belts for nearly a decade? Longer? Bicycles are funny, there have been ground breaking changes in tech and materials, and yet the same basic mechanical principles seem consistently static.
I’d like to ride a belt drive but I doubt there are flat foot frames.
tomjasz
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But a what a combination! Like switching from $10L of blended whiskey to a 20 year old Speyside, maybe? <insert a childish grin>
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