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My Gates Belt Drive Broke!

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My Gates Belt Drive Broke!

Old 06-22-17, 01:11 PM
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My Gates Belt Drive Broke!

My wife and I just got from a cycling trip in the Netherlands. It's a great place to ride! Very flat, but really beautiful and different than anywhere else that I've ever been. The cycling culture there has to be see to be believed.

Anyway, on our last day, with 1.6 miles to go to our hotel, I passed a bunch of cyclists in the big ring and then got stuck at a light and forgot to downshift. When I went to take off at the light, I stood to really crank on the pedals and get us going while in way too high a gear and the Gates timing belt snapped!

Early in the week I noticed that the belt had an abrasion on the outside. I think I banged it into a curb or cement step. It didn't look like any real damage, just a surface scuff, so I didn't think anything more about it.

However, for the several days prior to the break, the belt had been driving us crazy making a lot of noise. I tried pouring water on it and that helped for an hour or so. Another trick someone told me was to rub a dry soap bar along the belt, so I tried that and it quieted the belt for a few hours. Gates once told me you can spray the belt with silicone, but I didn't have any.

I didn't really think the noise and the scuff had anything to do with each other. But with the break, now I think the scuff led to the break, and there must have been some internal damage that was contributing to the noise. Although why the water and soap tricks worked even briefly if the damage was causing the noise does not make sense.

The belt had about 8,300 miles on it and this is our travel bike. It's been on about 15 flights during that time, meaning that many assembly and disassembly rotations.

Anyway, we're going to be carrying a spare when we go on trips now.

Anyone have any similar stories of Gates belt breaks?
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Old 06-22-17, 01:26 PM
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Some questions:
- CDX center track belt or older type?
- did the break happen where it was scuffed?
- when you travel, how do you pack the belt? Do you fold it?
- what sort of tension do you run on the belt?
- how old was the belt?

Last edited by reburns; 06-22-17 at 01:47 PM.
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Old 06-22-17, 01:36 PM
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When you put the belt on, how do you do it? Rolling the belt on the pulley the way you would a chain on a chain ring is a major no-no.

Twisting of the belt can break the internal carbon fibers. I learned that the hard way.
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Old 06-22-17, 07:40 PM
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  • It was a center track belt.
  • It was about 3 years old.
  • It did break at the scuff. Meant to say that in the original post.
  • I always loosen the eccentric to install or remove the belt.
  • My tandem has only one set of couplers and I travel with it in an Evoc case. The belt is velcro'ed to one of the rims on the side with the disc, and that side is always facing inward, toward the bike.
  • I use the Gates app on my iPhone to set the tension according to their spec.
I am sure that the scuff ultimately caused the break. I wasn't really questioning the why here, just wanted to hear if anyone else had a similar experience. And maybe what other failure modes people have had with the Gates drive.


Thanks
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Old 06-22-17, 08:54 PM
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For those of us trying to learn from your experience, the good news is that there appears to be a fairly clear cause, and also that the belt gave you some warning by making some noise. Thanks for the post.
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Old 06-22-17, 11:33 PM
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Never had a CDX belt fail.

On trips we have always pack a spare belt along with at least one spare tire, a few tubes, etc... common sense. For packing, I re-coil the belt in the same way that it is delivered new in 3(?) loops. The correct action for doing that is gentle enough and does not necessitate twisting the belt to any excessive degree.

However, just this last weekend a small twig flipped up into the belt and into the rear timing sprocket, derailing the belt half way on the rear sprocket. We stopped pedaling as soon as we realized what had happened and coasted to a stop. Seems like no harm, but we'll see as we continue to ride with it.

Last edited by twocicle; 06-24-17 at 11:53 AM.
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Old 06-23-17, 04:10 AM
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As interesting timing would have it, I had ordered a new belt to have as a spare just before we left on this trip. The new belt was waiting for me when I got back. Please note that the new belt is packed flat - it is not coiled into 3 loops as you suggest.

The Gates site FAQ says this about coiling:

For general storage, Gates does not recommend coiling. It is best to leave the belt in its original packaging until ready to use. However, if you want to carry a spare belt with you, proper coiling is an option. Care should be taken not to damage the belt, please watch this
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Old 06-23-17, 06:58 AM
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I've tried the Gates App with questionable results. The phone often has a difficult time picking up the vibration of the belt. Best I could determine was that our belt is at about 25 - 30 Hz (in one orientation). The recommended 60 - 65 Hz seems awfully tight to me. I doubt that a high tension has any effect on the belt breaking but I would think a higher tension would be less efficient than a lower tension.
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Old 06-23-17, 07:16 AM
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I don't actually bring a BB wrench with me when I travel, so the belt is only tightened to as tight as I can by hand, which is about 40-45hz. Like you say, lower than their recommended amount, but 60 is really tight.

Never really understood why they want it so tight as that would introduce additional friction and wear on the BBs.
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Old 06-23-17, 07:24 AM
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^ The original belts were prone to skipping under heavy load if not pretty tight. The center track belts in our experience are much less prone to skipping, and can be run at lower tension.

I think Gates may just not have revised their recommended tension with the new design.

And from their point of view, a little bearing wear and reduced efficiency has less risk to them than a failure from the belt skipping or derailing.
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Old 06-23-17, 08:41 AM
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Originally Posted by oldacura
I've tried the Gates App with questionable results. The phone often has a difficult time picking up the vibration of the belt. Best I could determine was that our belt is at about 25 - 30 Hz (in one orientation). The recommended 60 - 65 Hz seems awfully tight to me. I doubt that a high tension has any effect on the belt breaking but I would think a higher tension would be less efficient than a lower tension.
I also have trouble with the app but when it does "hear" the belt, it's right at 65.
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Old 06-23-17, 11:16 AM
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Originally Posted by twocicle
Never had a CDX belt fail.

On trips we have always pack a spare belt along with at least one spare tire, a few tubes, etc... common sense. For packing, I re-coil the belt in the same way that it is delivered new in 3 loops. The correct action for doing that is gentle enough and does not necessitate twisting the belt to any excessive degree.

However, just this last weekend a small twig flipped up into the belt and into the rear timing sprocket, derailing the belt half way on the rear sprocket. We stopped pedaling as soon as we realized what had happened and coasted to a stop. Seems like no harm, but we'll see as we continue to ride with it.
I had the exact thing happen a couple of years ago and called Gates to get their input. The tech that I talked to recommended that I change the belt, the failure mode is catastrophe and usually does not give any warning. Some of the internal fibers could have been damaged.

I immediately put on the spare belt an ordered another spare. I did not want a catastrophic failure!
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Old 06-23-17, 01:59 PM
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To me this is a classic example of carbon fiber. It is a great material but has drawbacks that users should consider and evaluate. Light and strong but some small danger of complete failure with only subtle warning signs. Danger that can be mitigated when the user keeps it them in mind and uses due care. Items need to be replaced if damaged or in doubt of damage. For those who want a product with a tolerance for user inattention or error it is not the best choice.
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Old 06-24-17, 12:00 PM
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Originally Posted by mikebian
As interesting timing would have it, I had ordered a new belt to have as a spare just before we left on this trip. The new belt was waiting for me when I got back. Please note that the new belt is packed flat - it is not coiled into 3 loops as you suggest.

The Gates site FAQ says this about coiling:

For general storage, Gates does not recommend coiling. It is best to leave the belt in its original packaging until ready to use. However, if you want to carry a spare belt with you, proper coiling is an option. Care should be taken not to damage the belt, please watch this video.
I seem to recall they did have some diagram showing the correct twist technique to recoil a belt. Funny to see that now Gates has reversed that (AFAIK) perhaps because they do not want to be on the hook for replacing belts (or liability) from people screwing up by attempting to follow a posted recommendation.

Look at 1:18 in the video you linked and observe how easy it can be to perform. Then just after that when she demonstrates bad handling. Big difference.

We have been riding with the CDX for a few years now and I have had many opportunities to pack and reinstall the Gates belt. Never a problem for us, but your mileage may vary depending on how you hand it.

Curious how your new belt was actually packaged if not coiled at all. Was it somehow wrapped and delivered as one big loop? Everybody I know has always received their belts coiled, plus we had 2 delivered this way as well. So yes, I suggest that ours were delivered that way.

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Old 06-24-17, 06:51 PM
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It is the same method as coiling a bandsaw blade.
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Old 06-26-17, 09:28 AM
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Originally Posted by DubT
I had the exact thing happen a couple of years ago and called Gates to get their input. The tech that I talked to recommended that I change the belt, the failure mode is catastrophe and usually does not give any warning. Some of the internal fibers could have been damaged.

I immediately put on the spare belt an ordered another spare. I did not want a catastrophic failure!
Our incident had a very small twig and only a 1/2 derailment which did not appear to involve a significant potential for damage. After a few more rides with this belt, there are no signs (visual or audible) of any further issue. Will keep on riding it as a test case.
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Old 06-26-17, 11:14 AM
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Originally Posted by twocicle
Our incident had a very small twig and only a 1/2 derailment which did not appear to involve a significant potential for damage. After a few more rides with this belt, there are no signs (visual or audible) of any further issue. Will keep on riding it as a test case.
The belt was no doubt stretched. I would hate to see that belt break while you are hammering our of the saddle. That might be painful! A catastrophe failure mode was enough incentive for me to change belts.
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Old 06-27-17, 09:27 AM
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Originally Posted by waynesulak
To me this is a classic example of carbon fiber. It is a great material but has drawbacks that users should consider and evaluate. Light and strong but some small danger of complete failure with only subtle warning signs. Danger that can be mitigated when the user keeps it them in mind and uses due care. Items need to be replaced if damaged or in doubt of damage. For those who want a product with a tolerance for user inattention or error it is not the best choice.


Chains break as well. So far we've managed to break one timing belt and one timing chain.


One fortunate thing is that when they do break, its usually under very high torque load, which typically corresponds with low speed.
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Old 06-27-17, 06:29 PM
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Yup chains break as well . . .
Broke drivechain in TWO places simultaneously a month ago! Fortunately we were quarter mile home!
Some stokers (Kay is only 82 years old) can be tough on chains!!!
Pedal onl TWOgether!
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Old 08-28-18, 09:39 PM
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Reviving this old thread just in case anyone has had new failures of their Gates CDX belt.

I just purchased a bike with Gates center track carbon drive.

I'd like to hear your experiences about when / if your belt broke. Were you standing up while pedaling? Were you riding at high speed? Were there any warning signs?

How many miles or days/months had you been using the belt?

Thanks!
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Old 08-29-18, 07:23 PM
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We've been using the CDX belt for about 3 years without any issues. We have a spare belt but it's still un-used. We prefer the belt to chain because it's quieter and cleaner. .
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Old 09-03-18, 05:01 PM
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We also have a CDX belt. We never tighten it to the Gates spec. If we do that, our BBs have more drag than we like. We normally run it with ~1" of total up/down movement. Never had a problem with it or slipped a cog. OTOH, we're not the strongest team that ever rode a tandem.
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Old 02-12-24, 12:40 AM
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Belts can fail suddenly. I got over 15,000 miles on my CDX belt. The time from minor fraying to a few missing teeth to falling apart was only a few weeks. I replaced it before it snapped. It's wise to carry a spare belt if getting a replacement would be a big problem.
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Old 02-12-24, 07:41 AM
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Weíve got 55,000 miles on our original belts, now almost 8 years old on our coupled tandem and havenít had any issues. We do a lot of overseas traveling and have packed it at least 30 or more times into the cases (including test runs of packing). We bought spare belts (still unused) when we got the tandem and have kept them coiled since then - apparently not a good idea based on what Iíve now read on the Gates FAQ site. We always take the spares on our tours. We donít run the belts super tight - I havenít had much success with the Gates app - and now just use my judgement on belt tension. Weíve had some squeaking occasionally, but the silicone spray cures that quickly (or some water from our bottles when on tour has been effective). Weíve also had a small twig caught in the belt a couple of years ago, but apparently it didnít damage anything.
Iíll cross my fingers and knock on wood now.
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