Received the CenterTrack parts from PrecisionTandem (Mark). I did err on the free shipping, cost was $230 + shipping.
69T rings. 86gm/ea (x2)
The matching components off our tandem (SRAM 9spd chain + 1 half-link, 2 - 2012 Ultegra timing rings) weighed 492gms. Interesting observation: the gates rings weigh exactly twice as much as the Ultegra timing rings.
Gates weight savings over our previous components: 212gms (7.48oz)
Ask me in 2.5 months how I think it works (new frame eta). For now, these are Christmas tree ornaments :)
Our scales must be pretty close as the 280 grams is the exact same weight that I recorded.
We got our Gates CenterTrack last week. I've installed it on the right-hand side of our tandem using the outer ring position on a pair of triple cranksets and had a couple of test rides riding the bike solo. We're using single bike cranks so that we can have 165mm cranks, and we have no need for a large chainring - our 26 - 42 ring combination plus 11-34 10-speed cassette gives us enough range for loaded touring plus unloaded, but relaxed road riding (including lots of riding in the mountains). I've discussed more details of this in this thread. Note that we're using Shimano 105 5603 cranks; I know that the non-center track belt rings do not work on the current-generation 5703 cranks because there is not as much clearance behind the crank arm, I'm not sure whether the center track rings would avoid this problem or not.
I'd tried this with the non-CenterTrack version of the belt drive, but there was not quite enough room behind the crank for it (despite flipping the ring and shaving off 0.5 to 1 mm of the ring that was behind the crank). With the CenterTrack version, it works quite nicely. I had to play around with several variations of ring spacers. In the end, the combination that worked best was about 3.5 mm between the crank and the belt-ring, the middle ring spaced 0.5mm closer to the frame, and the inner ring also spaced out 0.5 mm. The right-hand cup of the bottom bracket is also spaced out about 2.5 mm, but this is only to make the MTB front derailleur (a Shimano Deore model) swing in far enough to downshift easily, with a road FD this may not be necessary.
I'm using some extra-long chainring bolts on the rear, and the front crank is the same, except regular-length bolts can be used because there's no middle ring. Because the belt ring is not sitting on the mounting tabs, it was a bit tough to get it centered and so have the belt tension be consistent, but I got it in the end. We also have an N-Gear Jump-Stop to prevent derailments off the inside ring.
2. What about sixtiescycles admonishment to have the sync drive as close to the frame center line as possible, so to avoid the boom tube flex that the leverage from offset purportedly induces?
EDIT: The belt-line was about 57 mm. I've now removed one of the BB spacers to make this 56 mm (and changed the FD to a road version to allow it to move far enough inboard to downshift easily). The official chainline for the FSA Gossamer and SL-K tandem cranksets on the timing-chain side is 53 mm, so I don't think our setup is going to be noticeably different than that. I also added two pedal washers behind each pedal on the non drive-side to make the pedals a similar distance from the frame's centerline.
Re: Inner ring mounting
On the 2013 Tetra, I was able to install the rear CDX ring on the inside of our Ultegra R603 timing side spider, leaving approx 2mm clearance from the belt to the chainstay.
The front Ultegra R601 spacing is a bit narrower than the rear (as verified by Q-factor diffs), I guess Shimano didn't think perfect timing ring alignment was needed - at least for typical chain setups. So, I mounted that CDX ring on the outside of the spider and then shifted the EBB by 2mm to the driveside. The timing ring alignment is still out by approx 1-1.5mm, but with the CDX setup this appears to be tollerable.
Besides the purported benefit of having the timing load moved as close to the centerline as possible, another more trivial benefit is that the crank magnet for the Garmin sensor now has plenty of clearance between it and the belt.
Here is a shot of the rear ring/belt clearance achieved:
* note the little piece of frame saver tape on the chainstay. It's there as a wear indicator just in case any rub occurs... like when riding in wet, mucky conditions when grime buildup can occur. I may remove this once we gain more confidence there will not be any rubs on the frame.
I've not been paying too much attention to this thread, so maybe someone can fill me in.
I already have a CDC 69 tooth, and it works fine for us. Is there any reason to 'upgrade' to a CDX?
Weight doesn't appear to be a reason. The CDX pulleys each weigh 6 grams less, but the +15 grams CDX belt more than makes up for them.
Is CDX any more efficient? Will we eke out another watt?
1. The CDX will absorb a little bit of misalignment.
2. My perception is that the CDX sprockets will last longer, the interface between the belt and the sprocket has been totally redesigned and incorporates extremely good contact.
3. It also appears that the CDX sprockets will self clean better if you ride in dirty conditions.
Add to the list...
4. Less belt tension required.
5. Addendum to #1... Belt will not walk off the CDX rings as it can with CDC.
6. Newer bling. Not that old school, out dated gear that everyone will laugh at.
In terms of watts, I doubt any change. It is supposed here on the forum the tension could be reduced on the CDX since the belt can't walk off. I contend the belt tension should still be nearly as high for the teeth to ride / engage correctly with the sproket. The wedge shaped teeth could watermelon seed up on the sproket, ride high and wear more quickly at too low a tension. One might argue slightly less belt tension results in slightly less pressure on bearings and give you another watt. But I suspect the tension induced by the captain, which is far more than the tension in the belt, over rides that model.
You might also have the freedom to run the belt off center, with the front or rear closer to the frame that the other. Mine for instance is 29mm in back and just over 30mm in front. The belt remains on, while minimizing the bottom tube bending. I would not do the belt much out of aling for concern about the angle wearing funny. But a little is fine.
The new Gates Center track belt drive came today. It took less than an hour to install it and tension the belt using the iPhone app.
The Wipperman 8 speed chain weighed 426 grams and the Shimano chainrings each weighed 43 grams for a total of 512 grams. The new belt weighs 108 grams and the new chainrings each weigh 86 grams for a total of 280 grams.
Andy said, "The belt is the exact same belt with a groove cut in to it. It would be less weight if anything. Gates is not going to remake their very expensive mold for the belt for any reason. Someone with both belts handy might weight them for us on this forum."
It is not the same belt, look at the chart that Ritterview posted, the original is 10mm wide and the new one is 12 mm wide
My first two homemade tandems from 50+ years ago were single speeds but utilized RH drive so I guess I am a very early Adopter. LOL! I only see RH drive on modern tandems as a marketing gimmick. There may be a small weight saving but really is there any noticeable gain in performance? For now we will stay with our LH drive, our triple and our 12-27 SRAM fairly close ratio cassette.
And BTW our CDX belt is 12mm wide.
Oh, there is clearly a difference RH drive. I've owned both versions of the Paketa and it's not a gimmick, our times reflect it, and you feel it right away standing on a climb. As do our friends who test do the same test even one ride at a time rather than year over year as we have.
But how much of that stiffness is from the direct load path of the right side drive to the rear wheel, and how much of that is from the tight belt line spacing I can't say. That's why I ask twocycle if he notices his 8mm / 20% change on the same bike, same side, same riders, etc. If I guessed I'd say that would be 1 millimeter or two less defelection on the bottom tube, a small number I suspect. And if he feels that or not is the question. It'd be an interesting experience to hear if that feels any differnt.
At this point, I'm just going on the reasons posted by Paketa and elsewhere that moving the timing side further inboard is technically preferable to outboard, as may help reduce twisting forces on the BB and frame. In case with the Ultegra cranks, the optimal ring alignment is 50/50 anyway (inboard or outboard there is a little compromise either way. Inboard-rear, outboard-front actually worked out better as it required the least amount of shifting the EBB and spacers).
The direct load path of the right hand drive could be an important factor since it would limit the effect of bottom bracket flex. I think that the actual BB shell can flex in addition to any crank axle flex. In addition there should be less friction in the system if that is a factor.
Andy do you have actual data that proves the RH drive has improved your performance. I mean objective not subjective data. Ride the old bike on the same course, same exact conditions and then turn around and ride the new bike under the exact same conditions. This type of data is extremely hard to get and often becomes subjective because of various factors. Wind, temperature, team condition etc.