I love Calfees, but that is totally lame. Imagine if you have ordered with a chain drive, they may have not discovered this. My front water bottle mounts are crooked. One day I will bring the frame back to fix it.... but still that kind of stuff should not happen.

Gates Tension and Alignment Challenges !
 

Hi Folks,
I'm new on the list, and have read a lot!
I'm trying to update our 2009 Cdale. Co-Motion has/had a sale to close out the Gates CDC system. I thought, "what the heck" and purchased. Now I am having some difficulties with install...of course I'm hoping someone will set me straight.
Equipment:
FSA Gossamar cranks
FSA MegaExo BB.
Cannondale dual-wedge ECC

First question: I am using the iPhone app for tension. I tested with the cranks in various positions to see what the range is and expect some differential in tension. I am getting a 15hz variation i.e 50hz in one position vs. 65 in another. That seems significant to me especially since the Gates App indicates a 5hz variation between "lightweight" and "big and powerful" for tandems.
I have repositioned the front pulley on the spider to see if it changed, it didn't have a noticeable impact.
What kind of hz ranges are others getting with this App?

Second question: Alignment. If I can rotate the cranks forward and backwards without the belt walking off, is that considered aligned? I believe I can hear the belt rubbing against the flange of the pulley but I currently have the system "aligned" such that the belt will not walk off while on the stand but have not ridden it.
I ask this question after investing a significant amount of time trying to attain alignment. I am using the ECC to attain aligment though I do have some option with shims. Once I get the alignment set I have to rotate (using a pin spanner) the ECC for tension, the ECC "walks" in the BB which throws off the alignment. If I'm lucky and get the tension acceptable (see above) and the alignment is still good, I have the challenge of tightening the ECC which again may cause the alignment to shift ever so slightly...and the belt will wander.
Am I the only one pulling my hair out? - technically not my 3rd question...
Any insight appreciated!

My experience over 4+ years on a CDC system is you can run it with much lower tension than specs recommend if the alignment is good. I no longer use the app or the kricket but just do it by feel. I can actually put it on be sliding it on from the inside without moving the eccentric. YRMV but I would try riding it a much lower tension and see if it walks. My experience if it stays on pedaling backwards on the stand it will ride just fine. We recently climbed many ascents in New Zealand with grades up to 17% without skipping at the low tension.

You are correct that ring positioning on the spider is key to obtaining a consistent tension. That said, it is doubtful you will get it perfect. At least the CDC rings have a crank bolt head recess which should help you with the ring positioning.

Our belt tension varies somewhat depending on the crank positions, but as it is neither binding nor terribly loose, it appears to otherwise run fine. I do not use the app. I gave our CDX ring positioning my "best effort" and then left it at that without fretting too much. With the CDX rings it is best to rely on the sleaves of the crank nuts to provide the best concentric position.

If your ECC insists on centering itself, then perhaps you should resort to using chain ring spacers (aka washers) instead. Likely you can use 1-2mm without any issue, but more may require longer chainring bolts/nuts (which can be surprisingly expensive, especially if you need 10 of them. Problem Solvers packets of 5 at ~$16/ea).

I chose to wait for the CDX system so that I would not have any of the issues that you are describing. I hope that you saved a lot of money. I would pack the whole thing up and send it back and spend the extra money for the redesigned system. Engineers redesign for a reason.

Wayne, retired engineer!

If you subscribe to the school of Dilbert, you would know it is marketing that drives product development ;)

I'm just glad this kit now costs less than half of what people originally paid (>$500) for the CDC setup.

Amen.:thumb: Just because they designed a new system that will stay on the pulleys doesn't mean they addressed alignment issues specific to the frame and cranks! That's the beauty of chain drive, its very tolerant!

I agree with those saying tension can vary. I'd set it to proper tension at the point the belt feels tightest, such that it is a bit less tension at certain points in the rotation. IMHO I would not slack it all the way down below spec.

I think you are trying too hard. In my experience, the belt will ride against or rub the inside flange of one of the CDC sprockets, and that's OK. It won't catch and run off. But that's why the CDC has a flange is so the belt can't walk off. If it means one sprocket is a couple mm outbord of the other that's OK too. That is, if when riding under load, which is the importnant metric, and the belt tends to walk off to the inside under the stoker, you can move the captains sprocket out a mm. In an ideal world the bottom tube, cranks, spiders, axles all have so little flex that aligmnet in the bike stand is the same as on the road. But short of that ideal, it takes a bit of nuance to set up alignment, especially on a retrofit tandem. Thus the release of the CDX to solve this problem.
I would also say that back pedaling may lead to differnt results; if it walks off while pedaling backwards, don't pedal backwards. I've seen belts walk over if you pedal backwards a whole bunch. But why would you? If you pedal backwards just to get the stokers cleats in and your own, a couple pedal strokes is not going to throw the belt.

Thanks Turbo,
That is what I needed to hear.
On a couple occasions I did manage to get it aligned perfectly such that it was not rubbing on either flange at which time it was very quiet and smooth! Alas, the alignment was not quite right and it would walk off the stokers pulley. On this CDale there is only about 2mm clearance between the stoker pulley and the chain stay so it really cannot walk off but is can rub if misaligned. My back pedaling comment was driven off of what i read on the Co-Motion FAQ's page and another comment I read which indicated a perfect alignment would allow both forward and back rotation but maybe that is pie in the sky...
As an additional comment on the tension challenge, I find it amazing the either the belt or the pulleys cannot be manufactured (economically?) to a higher tolerance such that the variation is minimized.
I will get things aligned and tensioned and give a report back.
Thanks again.

For those of you that are finding the tension on the Gates Belt changes as you rotate the cranks you might try the following. After setting the initial tension on the belt, back off the chainring bolts holding the Gates sprockets on both timing side spyders so they are still snug but not tight. Now rotate the captain's crankset through several full rotations then re-torque the chain ring bolts. If the sprockets were not concentric with the bottom bracket axle initially, causing variable tension as the cranks are rotated, this may improve the concentricity.

After initially installing the Gates CDX system on our bike equipped with a DaVinci crankset I found quite a bit of variation in tension as the cranks went through one full rotation. After I had carried out the above procedure I couldn't detect that difference any longer. This should apply to bikes equipped with the CDC system as well. Regarding the tensioning of the CDX belt, I found quite a bit or rotational resistance when the belt was tensioned near the recommended level. When I backed this tension off there seemed to be a lot less resistance, as a result I now run the belt with relatively low tension.

Curtis

The CDX system is supposed to be able to absorb some misalignment.

I use the iPhone app and ours only varies a few hz as I rotate the cranks.


BTW Dilbert is not always right.

I just looked at the co-motion website and they are selling the CDC system for $195. I paid $245 for the CDX system directly from Gates.

Just saying!

You are not alone, my front bottle mounts are crooked too, the bottle is the angled slightly clockwise. I tried adjusting it using the slop in cage mounting holes but it didn't help much.
Also they put the mounts too high up on the downtube, had to go to a side loader cage to get the bottle in and out.
Guess I can't complain since the bike rides like a dream and for the most the construction is as good as it gets.

I managed to get the belt alignment pretty darn close. Back pedaling a bit will still cause the belt to wander off of the stoker pulley to the point it will rub on the chainstay. The ECC protrudes from the BB on the drive side about 1-2mm. I may get a spacer and make it right but its working for now. I was able to attain a reasonably consistent tension but still quite a bit of variability in my opinion!

Yesterday we managed a 25 mile ride with a lot of stop and go as well as a solid hill. All I can say is that it worked flawlessly and is amazingly quiet!

We had a tape dot on the chain stay right at that point where the belt might rub when we back pedaled. With CDX no longer needed.
As metioned above in the string, a dry film silicone spray from an auto parts shop is used for belts in cars. Great for the cardon drive belt. For the CDC especially it was nice to spray it from above the teeth and a little from side such that it coated the side face of the belt that rides against the flange of the CDC, as well as on the teeth. Spray liberally, a couple rotations of the belt. Don't skimp on it, it wears off in a month or so from abrasion and/or rain. That removed any residual squeek.

As others adopt the new Gates Center Track belt drive I am sure some will run into the issue of the Garmin cadence magnet interfering with belt. The center track belt is positioned in a more outboard position then the older CDC belt drive system. I have found a nice solution to this problem. I apologize for the poor photo quality. The batteries for the camera were dead, so I took these with my phone.

I ordered 1/2" X 1/4" X 1/8" rare earth magnets. I had to order 10 but they were less than $10 for the bunch.

http://bikeforums.net/attachment.php...hmentid=316278

Here is the image of a single magnet...

http://bikeforums.net/attachment.php...hmentid=316279

The magnet was then placed on the inside of the stokers left crank on the end of the pedal spindle...

http://bikeforums.net/attachment.php...hmentid=316280

As you can see here, there is good clearance between the belt and the magnet...

http://bikeforums.net/attachment.php...hmentid=316281

It is recommended to go with the ring-shaped magnet vs. a disc-shaped magnet. These babies are really strong and the ring allows you to use a small screwdriver to remove it from the spindle. The disc could lead to damage of the cranks while trying to get a tool behind the magnet for removal.

The magnet is strong enough that the Garmin cadence sensor picks it up easily even though there is considerably more clearance than with the original magnet.

I hope this is helpful for others who may run into this same problem in the future.