Belt drive single speed
#1
Belt drive single speed
Hi everyone, this is my first post here !
I have a Trek District 1 single speed front 55, back 22 - Gates CDX system, so I have a 2.5 gear ratio. I will move in an area with more hills, so I would like to have an easier, 2.3 gear ratio. What is the cheapest way with less work/trouble to achieve this ? Can I replace only the front chain ring with a 52 and adjust the belt tension (if yes, how ?) ? Or do I have to also buy a new belt (and maybe other things) ? Thanks in advance !
I have a Trek District 1 single speed front 55, back 22 - Gates CDX system, so I have a 2.5 gear ratio. I will move in an area with more hills, so I would like to have an easier, 2.3 gear ratio. What is the cheapest way with less work/trouble to achieve this ? Can I replace only the front chain ring with a 52 and adjust the belt tension (if yes, how ?) ? Or do I have to also buy a new belt (and maybe other things) ? Thanks in advance !
#2
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First off, I don't own a belt drive bike but a quick look at the Gates website lists an owner's manual for their products. https://www.gatescarbondrive.com/~/m...rive.pdf?la=en As I suspected, the tension on the belt is critical to making it work. The picture below shows the tension adjustment points on your bike. It doesn't look like there is a lot of room to make the adjustment. While not cheap, one solution would be to have the wheel rebuilt with a 3 speed hub such as the Sturmey Archer hub and use the same drive train parts you already have. That would give you a wider range on both ends,
#3
Typically you should be able to change rear cog or front sprocket and adjust it if there is room for any net shift of the axle.
I don’t have specific experience with the Gates, but if they have two teeth per inch of belt, like a standard chain has two links per inch, then each tooth of net change in the sum of front and rear moves the axle about 1/8” or 3 mm.
Is there actually a 52 tooth option in front? On the Gates website it looks like there are 50 and 55 in at least some lines, but I didn’t see any 52.
However, 55/24 would be about 2.3 and they do have 24 tooth cogs. That would require about 1/4” or 6 mm of room to move the rear axle forward in the slot due to the same belt having to span the larger cog.
Note: the belt only sees the outer half of the front sprocket and rear cog, so each net tooth adds half of a belt tooth length or 1/4” and the shortening of the BB to axle length changes both top and bottom paths on the belt, so 1/8” net axle shift per net additional tooth.
Hope that helps.
Otto
I don’t have specific experience with the Gates, but if they have two teeth per inch of belt, like a standard chain has two links per inch, then each tooth of net change in the sum of front and rear moves the axle about 1/8” or 3 mm.
Is there actually a 52 tooth option in front? On the Gates website it looks like there are 50 and 55 in at least some lines, but I didn’t see any 52.
However, 55/24 would be about 2.3 and they do have 24 tooth cogs. That would require about 1/4” or 6 mm of room to move the rear axle forward in the slot due to the same belt having to span the larger cog.
Note: the belt only sees the outer half of the front sprocket and rear cog, so each net tooth adds half of a belt tooth length or 1/4” and the shortening of the BB to axle length changes both top and bottom paths on the belt, so 1/8” net axle shift per net additional tooth.
Hope that helps.
Otto
#4
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My only advice is to get rid of that belt drive and get a chain drive.
#5
Also, I might add, you might try it with the current gearing. If your bike has 700x25s and 55/22, that is about 66 gear inches, which is a very reasonable choice for SS with some hills, if they aren’t too big. YMMV, but it might be worth a try.
Otto
Otto
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#7
If you have, or have access to a bike with a variety of gears, perhaps use that to determine the ratio appropriate to your new home. Then you can ask the simpler question: How can I convert my SS to ratio. X?
#8
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If you live in hilly or rolling terrain, I'd recommend a multi-speed bike. Whether that's a belt drive on an IGH (internal gear hub) or a chain drive with a derailleur system, that's your choice.
For me, the issue with a single speed bikes are that if the gear ratio is appropriate for climbing a hill then it's very inappropriate for going down the other side of the hill and even inappropriate for cruising on level terrain.
For me, the issue with a single speed bikes are that if the gear ratio is appropriate for climbing a hill then it's very inappropriate for going down the other side of the hill and even inappropriate for cruising on level terrain.
#10
This is what I did ! So far, so good.
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