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Need guidance on selecting proper Gates belt drive components for my belt-ready frame

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Need guidance on selecting proper Gates belt drive components for my belt-ready frame

Old 10-03-19, 06:17 PM
  #1  
Morimorimori
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Need guidance on selecting proper Gates belt drive components for my belt-ready frame

I have a very cheap, locally made bike with a belt drive installed on it (the frame is belt-ready). One more thing to note is that the bike is equipped with SG-3C41 IGH from Shimano.

The problem is it's cheap for a reason - all stock belt drive components are some kind of Chinese cheap copies, and they perform quite bad (belt itself tends to fall-off often, and local bike workshops weren't able to solve this for me).

I would like to swap both sprockets and the belt itself for a brand new Gates belt drive set - while not changing anything else on this bike, if possible. But I'm getting completely lost when I try to figure out myself which components I need to order, and what size of the belt I need. So far I only figured that I need CDX line of components, and that SG-3C41 should be supported by some of them. I'm totally lost when it comes to details, and afraid I'll buy something that won't fit, as it's quite expensive.

Unfortunately, I'm living in a backward Eastern Europe country, and bike movement isn't very developed here. When I asked for help in a few local bike workshops, they said they don't have enough experience with belt drive either, and certainly are not able to help me acquiring them, as nobody imports those in here. They can only help with installing them, if I'll somehow buy them myself.

I'm ready to provide any exact measurements or additional details, if anybody is willing to help.
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Old 10-04-19, 04:02 AM
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JoeKahno
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Belt Drive?

I sympathize. I'm in the Philippines with a Bridgestone Albelt. These were never produced for the export market and arrived here as surplus. It uses a standard 14mm wide 8mm pitch synchronous belt. Continental was rolling out a version of this for the European market when they shut it down and recalled whatever was already out. While this size works well enough for Asians, if anyone heavier than the average European twelve year old gets on the pedals hard the belt may snap with a very real possibility of serious injury.

So, the first thing you want to do is determine if your frame really is, "belt drive ready", or just has a stay break to let you get a belt on/off of it. If the frame is not rigid enough it will not hold the proper belt alignment under load. If you can't get the belt it came with to stay on the cogs I suspect it isn't truly "belt drive ready" even if it was sold with one installed.

What are the dimensions of the current drive belt? (width, tooth pitch, number of teeth) What are the present cogs tooth count? Are you trying to keep the current gearing or looking to modify it as part of the change?
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Old 10-04-19, 06:48 AM
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Originally Posted by Morimorimori View Post
I would like to swap both sprockets and the belt itself for a brand new Gates belt drive set - while not changing anything else on this bike, if possible. But I'm getting completely lost when I try to figure out myself which components I need to order, and what size of the belt I need. So far I only figured that I need CDX line of components, and that SG-3C41 should be supported by some of them. I'm totally lost when it comes to details, and afraid I'll buy something that won't fit, as it's quite expensive.
CDX is the good stuff. It looks like you need a three-lobe CDX sprocket for the rear.

What is your front crankset like? How many arms does it have? And do you know the bolt-circle-diameter (BCD)?

Gates has a calculator (not intuitive to use) here to help you sort out the correct length belt: https://www.gatescarbondrive.com/App...tor/index.html

Last edited by JonathanGennick; 10-04-19 at 06:51 AM.
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Old 10-04-19, 10:33 AM
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Originally Posted by Morimorimori View Post
I have a very cheap, locally made bike with a belt drive installed on it (the frame is belt-ready). One more thing to note is that the bike is equipped with SG-3C41 IGH from Shimano.

The problem is it's cheap for a reason - all stock belt drive components are some kind of Chinese cheap copies, and they perform quite bad (belt itself tends to fall-off often, and local bike workshops weren't able to solve this for me).

I would like to swap both sprockets and the belt itself for a brand new Gates belt drive set - while not changing anything else on this bike, if possible. But I'm getting completely lost when I try to figure out myself which components I need to order, and what size of the belt I need. So far I only figured that I need CDX line of components, and that SG-3C41 should be supported by some of them. I'm totally lost when it comes to details, and afraid I'll buy something that won't fit, as it's quite expensive.

Unfortunately, I'm living in a backward Eastern Europe country, and bike movement isn't very developed here. When I asked for help in a few local bike workshops, they said they don't have enough experience with belt drive either, and certainly are not able to help me acquiring them, as nobody imports those in here. They can only help with installing them, if I'll somehow buy them myself.

I'm ready to provide any exact measurements or additional details, if anybody is willing to help.
Sounds like a forty dollar saddle on a ten dollar horse.

Maybe convert to chain drive -- cheap, available, easy.
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Old 10-05-19, 07:17 PM
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Sorry for the delayed answers, guys. I had to retrieve the bike from workshop I left it at, and then I finally broke that stock flimsy belt drive train it has, the rear sprocket got deformed and developed a huge play around the axle, so I guess it's made of some very cheap material.

I'm now adamant on buying Gates drive train. I just need to solve a problem of selecting belt of a proper length, and also ensuring chainline will be straight. Not sure how to approach both problems yet.
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Old 10-05-19, 07:27 PM
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Originally Posted by JoeKahno View Post
While this size works well enough for Asians, if anyone heavier than the average European twelve year old gets on the pedals hard the belt may snap with a very real possibility of serious injury.
Yea, as I mentioned above, I was able to destroy the rear sprocket on my 2nd ride - and I'm not even close to being a professional sportsman. Just a few quick sprints while standing on pedals - and it's got deformed.

Originally Posted by JoeKahno View Post
So, the first thing you want to do is determine if your frame really is, "belt drive ready", or just has a stay break to let you get a belt on/off of it. If the frame is not rigid enough it will not hold the proper belt alignment under load. If you can't get the belt it came with to stay on the cogs I suspect it isn't truly "belt drive ready" even if it was sold with one installed.
Well, after the guys at workshop did some magic on it, it stopped to fall off, for some time - until it finally just failed, bending in several places. So I take it should be rigid enough. After all, it's aluminium frame, and seems like quite a simple one, with thick tubes and all.

Originally Posted by JoeKahno View Post
What are the dimensions of the current drive belt? (width, tooth pitch, number of teeth) What are the present cogs tooth count? Are you trying to keep the current gearing or looking to modify it as part of the change?
I'm not trying to keep the current gearing, as it's awful. The front cog has 80 tooth, and the rear one is around 28-30 mb. It's so bad that I never used 3rd speed in both my rides, and only a few times used 2nd speed. It's also hard to go up the hills, even a moderate ones. I'm aiming for standard ratio for shimano hubs, something around 2 - 2.2 should be fine.

As for the belts parameters, I'm not sure how to measure it properly. But there are some marking on it: "1344-8M-12" - whatever this means.

Last edited by Morimorimori; 10-05-19 at 08:04 PM.
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Old 10-05-19, 07:29 PM
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Originally Posted by JonathanGennick View Post
What is your front crankset like? How many arms does it have? And do you know the bolt-circle-diameter (BCD)?
It's 4 arms, 104mm BCD
Originally Posted by JonathanGennick View Post
Gates has a calculator (not intuitive to use) here to help you sort out the correct length belt: https://www.gatescarbondrive.com/App...tor/index.html
Thanks a lot for the tip, I'll check it out.
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Old 10-05-19, 07:32 PM
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Originally Posted by AnkleWork View Post
Sounds like a forty dollar saddle on a ten dollar horse.

Maybe convert to chain drive -- cheap, available, easy.
Yea, I can see how it may sound like this sure But belt drive was my long-standing fetish, and as I'm already started working towards it, I just can't calm down until I'll get what I want. Also, as I'm planning to use it as a winter bike, I hoped for some low-maintenance solution so I won't need to care about dirty and rusty chains and sprockets, and about oiling and cleaning it all constantly.
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Old 10-05-19, 07:58 PM
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According to this calculator provided by @JonathanGennick , these are the parameters of drive train I need: front sprocket - 50 teeth; rear sprocket - 24 teeths (2,08 ratio); belt length - 120 teeth. That should fit chainstay of 456.80mm (mine is 455mm, and I can slide the rear hub in dropouts for a few more mm easily).

Currently, I'm puzzled with which of the next rear sprockets I need:
https://www.bike-components.de/en/Ga...tooth-o300034/
https://www.bike-components.de/en/Ga...tooth-o300034/

What is the difference? What does "45.5 mm Belt Line" marking on the 2nd one mean?
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Old 10-05-19, 10:35 PM
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Yeah, that's the standard 8mm pitch industrial synchronous drive belt. 1344mm long, (168 teeth), 12mm wide, I thought mine was under sized at 14mm.

I have a Shimano SG-3R45 hub which has some advantages with cog mounting but has the same gear ranges as yours. Standard practice for the manufacturers was to set the thing up with second as your main gear. That usually worked out with second gear being a little low for level ground, third being useless without a down grade or tailwind and first being useless on anything steeper than a mild hill. That was with a belt drive that works out to a 55 x 25 on 27x1 3/8 wheels.

Right now I'm waiting for a 36 x 20 chain set that should give me the gear ranges I need. Once I've ridden it long enough to verify that I'm happy and don't need to adjust that up or down I'll order the Gates components that match. There is just no way I can lay out that kind of money on what amounts to an educated guess. I have to *know* I've got the right ratio before I buy the expensive parts. See if you can find a used chain ring and cog. It doesn't matter if they're nearly worn out as long as you get them cheap enough. All you're using them for is to prove you have the right ratio before you spend the heavy money. It's a lot cheaper in the long run than buying precision parts that are different from what you really want precisely enough to be really irritating.
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Old 10-06-19, 06:29 PM
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Morimorimori
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Originally Posted by JoeKahno View Post
Right now I'm waiting for a 36 x 20 chain set that should give me the gear ranges I need. Once I've ridden it long enough to verify that I'm happy and don't need to adjust that up or down I'll order the Gates components that match. There is just no way I can lay out that kind of money on what amounts to an educated guess. I have to *know* I've got the right ratio before I buy the expensive parts. See if you can find a used chain ring and cog. It doesn't matter if they're nearly worn out as long as you get them cheap enough. All you're using them for is to prove you have the right ratio before you spend the heavy money. It's a lot cheaper in the long run than buying precision parts that are different from what you really want precisely enough to be really irritating.
Good point. I'm kind of person that often gets too impatient with things I want, and end up with bad deals, in the end. Though in my case, I have another bike with Alfine 8 speed IGH, which I've been riding for the whole year already, and I know how different kinds of landscape present in my city map to gears of this IGH pretty well. So I guess I could just figure out something that would work, solely on paper.

But I also have some rear sprockets lying around already, and I've managed to salvage 2 front sprockets of fitting size too. I guess I'll postpone the project for a week or two, and test my theories in real world then

Thanks, guys, that was really constructive. Hopefully, I'll manage to find the ratio and belt size I need now.
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Old 10-10-19, 06:49 AM
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Originally Posted by Morimorimori View Post
Currently, I'm puzzled with which of the next rear sprockets I need:
https://www.bike-components.de/en/Ga...tooth-o300034/
https://www.bike-components.de/en/Ga...tooth-o300034/

What is the difference? What does "45.5 mm Belt Line" marking on the 2nd one mean?
I believe belt line is analogous to chain line. I believe it's the distance from center of the frame to center of the belt.

Belts are less forgiving of misalignment than are chains. You had mentioned in your first post that your current belt falls off often. Is that due to it not being aligned?
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