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Gates Carbon Belt Sizing

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Gates Carbon Belt Sizing

Old 06-22-20, 07:14 PM
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telebianchi
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Gates Carbon Belt Sizing

Short version: Will a two tooth difference in belt length be a problem? Current set-up is 46/28 with 122T belt on the older center port CDX system. Eccentric bottom bracket is about 3/4 of the way forward in the BB shell. I've located a newer center track system with same ring and sprocket size, but the belt is 120T.

Longer Version:
I have a 2012 Raleigh XXIX with the older (non Center Track) Gates Carbon belt drive. I recently wanted to upgrade my wheels (wider rim, tubeless, lighter). When removing the Gates sprocket from my original hub I noticed that the tabs which line up with the splines on the hub have gotten beat up over eight years of use. Because of that I can't slip the sprocket onto the new hub. In fact, it would probably take a rubber mallet or similar to get it back onto the original hub. I've looked for replacement sprockets but they have been out of production for a number of years and I can't locate one new or used.
But I did find a used complete CDX Center Track system. It has the same size ring and sprocket (46/28) as my older system, but comes with a 120T belt.

And this is where I end up with questions: Gates has a belt length calculator on their website where you input the ring size, sprocket size, and chain stay length to determine the belt length needed. I am not certain of the chain stay length on my Raleigh. A rough measurement with an inch-scaled tape measure comes to a little over 18 inches, or about 460 mm. I cannot find a geometry chart for my XXIX frame, but some contemporary reviews list 440, 455 or 466 - seriously, three different reviews each with a different chain stay length in their article. I have emailed Raleigh for this info but have not heard back yet.

So back to the Gates belt length calculator each of the three chain stay lengths listed above result in a different belt length. 440 mm = 118T, 455 mm = 120T, and 466 mm = 122T. And the final non-conforming piece of information I have is from the Raleigh 2012 catalog that lists a 118T belt.

Does anyone know how much of a difference two teeth make on a Gates belt? As mentioned at the top, I do have room to move my eccentric BB backwards but it's difficult to measure that without taking things apart.

Thanks in advance. Feel free to ask questions if what I wrote above doesn't make sense.
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Old 06-24-20, 08:16 AM
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aggiegrads
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If the gates belts use the same tooth pitch, then two teeth should be exactly 1/2 inch in chainstay length.

Don’t rely on geometry charts; measure your chainstays. Even with a tape measure, it should be easy to measure from center of BB shell to center of axle.
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