twocicle

This inside vs outside timing debate is mostly not specific to belt drive.

I think this is a key point... you are comparing the feel of your previous Pakata to the Vr2 with a much beefier 1.5" tapered fork. I am doing the same... our previous Calfee with our new frame and 1.5" tapered fork. I would not be surprised if the diff you are feeling is not mostly due to the huge upgrade in the front end stiffness as Pakata mentioned in regards to the ENVE fork? I do believe this is a key diff btwn the 2 Calfee frames in our case.

Dean V

We have noticed no change in performance with right hand timing chain and I wouldn't expect to. There is no reason for there to be. I only did it so that I could use regular single bike cranks.
As for frame flex from the timing chain load, yes theoretically effect of the load will be less the closer it is to the frames centre line, but I do not think it is significant. Has anyone noticed a difference in the amount and way the frame flexes from when you push with the right pedal as opposed to the left? Because if the timing chain load was significant you should.

twocicle

Comparing apples to apples (ie: same frame, fork specs and components) but with left vs right side, would be the only relevant test. Otherwise claimed differences are likely coincidental. Based on all the previous comments in the forum, there appears to be no clean data on the topic.

DubT

Well said! And the teams doing the testing would need to be in the same physical condition for each test ride. Hopefully the young teams and some of the not so young teams will get stronger as they ride/train more. So what I am trying to say is that if you rode a particular course a year ago and then rode it this year your performance may not be the same.

waynesulak

I agree. Actually I have not seen clean data that would prove that some small amount of boom tube flex reduces speed for any given power output. It seems intuitively obvious that flex is bad and that leads to an assumption.

Good data is hard to come by. A lot of bike decisions are made subjectively and the marketers love it.

Turbotandem

Good discussion.

Interesting to note that reguardless of which leg the captain uses, the compression on the bottom tube will be on the same said as the timing belt. Both legs tension the belt, so the flex will be on that side, and will feel the same on either leg.

I agree it may be splitting hairs, since top end frames are so well built and stiff to pedal forces that noticing that on your ride is a fine science. We have all certainly noticed an old average frame flex when compared to a new high end frame. Given that dramatic improvement over the years, it just seems to reason that more efficiecy can only help to improve those gains a bit more, even as the gains becomes more and more subtle. I wouldn't choose to negate an improvement even as those improvements are more incremental. It's not, as implied above, that the V2 frame is so sloppy that the V2R is needed to improve it; the goal is to improve an already top end design just that little bit more. Riders seek nicer stiffer cranks, no-stretch carbon belts over chains, stiffer chain rings, tighter wheels, stiffer stems, etc. All incremental improvements that are worth applying. When it comes to a frame the same value is pursued.

Agreed, I did notice the fork and front end improvements. But frame stuiffness assign, which is another string, the frames here are equal and I am talking about belt configurations in this string. I'd say, in my own comparison between right and left belts on the same tandem design, the transfer of force standing on my pedal feels more direct to the rear tire on the road with the right belt. Feels like my single. With the inboard right side belt, that tension is traped or triangulated in a way between the BB axle on one side, and the rear chain tension on the other. The belt is physically in between those two "fixed" points. There is, it seems, no where for thet belt force to go but into the chain; no parts to flex; no spiders, axles, frame, etc. needed to transfer the power. All you have left is whatever flex is allowed in the bottom tube. I'm sharing that I do feel that differnce in about as precise a test as can be done. Unfortunately the configuration is so rare, I often find myself alone in sharing that experience. But there it is.

Turbotandem

I recently heard that Gates may be adding the shallow bolt recess around the bolt hole on one face of the CDX ring. They'd had it on the CDC ring. This will allow a little more tolerance for centering the installation should one not have exactly the right length nuts. Not a big deal if you have the right hardware, it will center, but one more safegiard will be nice. Thanks Dave for pushing this topic with your contacts. Let's hope they follow thru.

DubT

Absolutely true!

waynesulak

I am not convinced belts are more efficient. Much cleaner and that is appealing but I think they are not more efficient and possibly less so.

DubT

This is a quote from Gates "Repeated testing has found new belt drives equally efficient to new chain drives, including a third party test evaluating the Carbon Drive system on a bicycle".

Is it market buzz or the truth? I cannot tell any difference in performance between the belt and the chain. I really like the cleanliness of the belt and the fact that I do not have to lube it. It is really nice being able to put it in the back of the Odyssey and not getting chain oil on the carpet. It is also nice being able to put our luggage in the car and not being concerned with it getting oil on it.

So far there is no way we would go back to the chain.

twocicle

Meanwhile, go reference the tip I posted about flipping the chainring bolts around so that the nut/sleave holds the gates ring in place. Or, get a set of longer nuts/sleaves that will go through the spider arm and into the ring hole. This really does help hold the ring centered, plus it should prevent any potential bolt shear and/or ring slipage.

I wonder if Gates would retro-ream our rings with recesses, or provide a swap program... it does seem a slight deficiency in their current release.

Turbotandem

Not just the 15 g difference on the belt , but the sprockets are also heavier. Dave just weighed one of each; CDC 73 g, CDX 86 g. He also weighed a couple belts while at it; CDC 95 g and CDX 109 g. Overall, for two sprockets+belt you're talking approximately 40 g difference. Not much, but still...

twocicle

Check your numbers again. It has been reported in this forum many times that the CDC system was 295g. When I first received that system it weighed the same, so AFAIK it is valid.
Gates sync belt ring. 95 grams X 2 = 190 grams
Gates carbon drive belt 105 grams
Total weight of the Gates system = 295 grams

A few of us have weighed the CDX system at 280g, here for example,
"The new belt weighs 108 grams and the new chainrings each weigh 86 grams for a total of 280 grams."

and here:
69T rings. 86gm/ea (x2)
belt: 108gm
---------
Total: 280gm

Based on thiis info, the CDX system is 15g lighter.

Turbotandem

Agreed we all have matching weights for the new CDX at 280g.

The question is whether the CDC sprockets are 73g or 95g. So I checked, and the 69t sprockets Dave has are not from the very latest runs, somewhere earlier in the distribution and are INDEED 73g. The CDC ring I have on my rear is 73g not 95g. Go figure. If you out there have confirmed your CDC rings are 95g maybe those are newer "beefier" runs of that sprocket? Can't say. If true, interesting that the CDC rings vary from 73 to 95g. So for my tandem, changing to the new belt and one new CDX sprocket, I picked up some 27g. I'm OK with that given the more reliable tracking of the CDX.

mtn.cyclist

Since it is still very winter like here in the mountains I visited a tandem specialty shop over the weekend to satisfy my cycling jones. While discussing a Gates upgrade to my 2005 Cannondale RT I was told, "the belt won't be able to fit your bike", and "you have to have FSA cranks to use the Gates system". Anyone care to weigh in on this?

Bent In El Paso

I updated our CoMo from the CDC to the CDX system this weekend. The only issue was with that the Garmin crank magnet interfered with the belt. The CDX belt is positioned more outboard than the CDC belt. I tried mounting the sprockets on the inside of our FSA SL/K spiders. It worked but the clearance to the chain stay was too close for comfort (at least my comfort). I chose to keep the sprockets on the outside.

I like to be able to monitor cadence so losing the magnet was not acceptable. After doing some research, I purchased some 1/2" X 1/4" X 1/8" ring-shaped rare earth magnets. These magnets fit nicely into the recess on the back of the crank where the pedal bolt is located. If you don't have steel pedals, then other methods of adhering the magnet in place were discussed in various forums. It was recommended to use the ring-shaped magnets instead of a disc because the discs are almost impossible to remove once they are in the pedal recess. With the ring, you have a center hole in the magnet to help pry it off without damaging the crank.

Feedback in the forums indicate these work nicely with the Garmin speed/cadence sensor.

I should receive the magnets by the end of the week. I believe this will nicely solve the clearance problem and eliminates the fairly large Garmin magnet and the zip tie that held it onto the crank.

I had to order 10 magnets which is probably 9 more than I will ever need. If anyone else is interested in some of these send me a PM and we will see what we can do.

Here is the link to the magnets from Amazon.com....

Neodymium Magnets 1/2 x 1/4 x 1/8 inch Ring

The new system worked flawlessly on our first couple of rides. It was quiet, quiet, quiet! I set the belt with less tension than I ran with the CDC system. My un-calibrated opinion is that the cranks rotated more freely than before. So far we are pleased.

twocicle

Find a shop that doesn't have their head up their wazoo.
As far as the Gates timing ring compatibility with cranks, any 130BCD 5-arm crank/spider should work. That said, I'm sure you can find enough material posted in this forum about the other setup requirements for the Gates system.

twocicle

Another simple solution that can resolve this issue is to modify the plastic magnet mount that comes with the Garmin. You can gain a couple millimeters by simply peeling off the thick rubber backing and grinding down the plastic (mostly behind the magnet itself). Then, when you reinstall the magnet on the crank use a thin piece of tape (frame saver, black electricians tape, whatever).

If you can mount the ring on the inside of the rear spider and have at least a 2mm gap left over between the belt and the chainstay, that should be ok for road riding. If someone where to use the belt offroad (mtn tandem) or otherwise really mucky conditions, then I'd say 5mm or more clearance.

mtn.cyclist

I have determined that I can make it work and I truly wonder why I got that kind of info from a tandem shop. I just wanted to throw it out and hear the responses. Thanks!

Bent In El Paso

Good point!

The magnets are on the way. It is really an elegant/simple solution to mounting the magnet. No zip ties, no tape, no adhesive, etc.. as long as you have steel pedal spindles. I found many posts in other forums where folks are changing over to these magnets just because they like the aesthetics of not having a visible magnet mounted to the inside of the crank arm with the associated mounting hardware.

According to reports in other forums, another benefit of these magnets, is that they do not need to be as close to the sensor as the OEM magnets. I can't speak to that until I have tried it out. I haven't really had any setup issues with the Garmin speed/cadence sensor and associated magnets but if this magnet allows for a greater distance, that just makes the system more robust to adjustment variation.

Carbonfiberboy 

What they're probably thinking is that for sure with the old Gates system the pulleys had to be in exact alignment. You usually have to have a shim-able BB to get them to line up, which the FSAs are. Many others are not. I swapped out our Race Face BBs for FSA for that reason. I expect perfect alignment is best with the CDX also.