Tandem Cycling - Thoughts on Gates belt drive

As the build of my new Calfee approaches I need to decide if should spend the extra money for the belt drive ($525 vs $50). As I understand it the advantages are lighter weight, less noise, no grease or lubing, longer life, less stretching and so fewer adjustments of the eccentric. If the price was half of what it is or if I had idle money I would not even think about it. But having spent close to $8K already I am getting wallet fatigue. I am thinking maybe I can just go with chains for now and maybe in a year I will feel better about spending the money, or the price will have gone down or Gates will stop making it. Any feedback would be appreciated.

I have not had any experience with them, but I can say that with a conventional timing chain I have found them to be quiet, require minimal lubing, and rarely need adjustment for tension. So all you are left with is the weight saving and the novelty/bling factor. It would be interesting to know how efficient they were. They can't be exactly the same as a chain. It would only have to be a tiny bit less efficient to cancel out the weight advantage. On the other hand if it were slightly more efficient then that would be another advantage in their favour.

I got one, only because of the weight weenie factor (and I like the idea of no grease). They probably are less efficient, and thus you'd be losing some watts.

What's more, the weight savings are overrated, as they are dependent on using a heavy chain and chainrings. If you select a relatively light chainring and chain the weight difference is as little as 112 grams (http://www.bikeforums.net/showthread.php?532680-Carbon-Timing-Belt-System&p=9028812&viewfull=1#post9028812). Weight savings that small are nothing to be losing watts over.

Dean,

I went through all of these gyrations a year ago and ended up going with the chain. Because I have couplers and do occasionaly take the bike apart for travel (as recently as last night) I am happy with my decision. One thing you should not worry about is how to spend any extra money you might have, I keep finding plenty of ways to do that.

I can see the novelty of using a carbon fiber reinforced belt drive to replace the chain on a single bike (which interestingly enough, you'd have to find a way to pass it through the rear triangle of a standard frame since you cannot break and reattach a belt...).

But for just the timing chain on a tandem since I wouldn't be going completely chainless (e.g. chain on drive side) $500 smackers would be too much for me personally to spend for the novelty of a belt drive at this point. Like you said, maybe if it went down in price significantly.

Come to think of it, even for a single bike, I'd probably rather try a Dynamic shaft drive/internally geared bike to go chainless before going to a belt drive system. There's also something in motorcycling about Harleys using belt drives that probably unfairly prejudices the issue somewhat for me too.

.

Have ridden a prototype tandem with Gates belt crossover a couple years ago (before Co-Motion or Calfee had it). Was not overly impressed.
A well lubed/adjusted cross-over chain is not noisy.
As for weight weenies, you can use smaller cross-over chainrings and . . . less chain too.
As for no chain tattoo/grease marks, we don't get that as we lubricate our chains via the hot wax method.
Maybe am a bit of retro grouch? We still use barcons (yes tried D/A STI) and we use toeclips/pedals (yes tried "clipless" . . . you still got to 'clip-in').
If you got the need for bling and the dough . . . why not?!
Just our input.
Pedal on TWOgether!
Rudy and Kay/zonatandem

Now I don't feel so bad about putting it off, maybe indefinitely.

Couple of thoughts. Our belt drive saga is documented in other threads, so I won't rehash.

The relative efficiency is open for debate, with at least some data that the belt is more efficient.

One thing I recently learned about the cost is that most of the cost of the system is in the rings. Gates sells the rings for $185 each, and the belt for $86.

Thus looking at long term costs, its hardly more than a high end chain to replace, and if the 4-10 times better wear claim is even close to true, over the very long haul you'll recoup a good portion of your investment.

One thing I recently learned about the cost is that most of the cost of the system is in the rings. Gates sells the rings for $185 each, and the belt for $86.

Thus looking at long term costs, its hardly more than a high end chain to replace, and if the 4-10 times better wear claim is even close to true, over the very long haul you'll recoup a good portion of your investment.

So if you buy the rings and belt separately it adds up to $456?
Can you buy directly from Gates?
I was never given a straight answer on the cost of a replacement belt.
I can't even find one online. I have heard numbers as low as $50.
Looking at using two KMC X10 chains at $32 each.
From my calculations I am getting 446g for chains plus chain rings vs 295g for belt drive.
That's a difference of 151g.

So if you buy the rings and belt separately it adds up to $456?
Can you buy directly from Gates?


That's what another forum member related to me. I haven't verified it.

I can see the novelty of using a carbon fiber reinforced belt drive to replace the chain on a single bike (which interestingly enough, you'd have to find a way to pass it through the rear triangle of a standard frame since you cannot break and reattach a belt...).

.............


Why does the belt have to pass through the rear triangle?



133191 (http://www.performancebike.com/bikes//Product_10052_10551_1073614_-1___)

GT Aerostream at Performance (http://www.performancebike.com/bikes//Product_10052_10551_1073614_-1___)

Why does the belt have to pass through the rear triangle?

Although most likely a rhetorical question given your example of one of several different ways of routing the belt from the cranks to rear hub, I would allow there are several innovative ways that folks have come up with to design frames that accommodate a belt. However, I believe Stray8 was correct and clear by noting that a belt would have to... 'pass [] through the rear triangle of a standard frame' , standard frame being the operative phrasing.

Why does the belt have to pass through the rear triangle?

Yes, for a standard single bike frame. Newer frames may have a special provision like a split frame that permits access through the rear triangle.


http://www.bikeforums.net/attachment.php?attachmentid=133197&d=1263582974

http://www.carbondrivesystems.com/overview.php?lang=us

http://www.carbondrivesystems.com/installation.php?lang=us



How do I retro-fit a Carbon Drive System onto my current frame?
In order to retrofit a Carbon Drive System to a frame, you may need to modify the rear triangle. The belt cannot be broken and reattached, so for a standard rear triangle, you’ll need a way to get the belt through the frame. Belts also need adjustment for installation and tensioning. Several ways of doing this are: horizontal dropouts (track forks), eccentric bottom brackets, or eccentric hubs.


http://www.carbondrivesystems.com/support.php?lang=us

Why does the belt have to pass through the rear triangle?
for a normal left-side timing/synch installation for a tandem, it doesn't have to. Single bike, yes.

I would say that if there was any performance advantage for a belt we would of seen them on track bikes by now.

I would say that if there was any performance advantage for a belt we would of seen them on track bikes by now.

And then the UCI would immediately create a new rule to ban them.

That's what another forum member related to me. I haven't verified it.

I'm the source of the cost info. Here are the details:

It's been discussed on other threads here that the stock Gates belt and rings that were originally sold, although designed for the Co-Motion BB distance, yielded an extremely tight fit even on a stock Co-Motion (ours is a Speedster Co-pilot). With the eccentric bottom bracket in the most rearward position, the belt is supposed to slide on quite easily, and can then be tensioned by adjusting the eccentric. In fact, the belt is very tight even with the eccentric in the most rearward position, and is difficult to install even then. If any further tension is added by moving the eccentric bottom bracket after installing it, the belt exhibits signs of having too much tension.

merlinextralight made a thread about his snapped belt that was likely caused by damage made by installing the belt by rolling it onto the rings rather than sliding it over them, then tensioning. Unfortunately, we have to always do a little bit of rolling on because it is too tight to do it any other way. We haven't noticed any damage to the belt yet, but I contacted Gates because I heard they might be offering some slightly smaller chainrings to solve this problem, the original rings have 71 teeth (but are similar in diameter to 42-tooth chainrings). This was their response:

"You are correct that a Co-Motion tandem with 71t sprockets is a very tight fit, even with the EBB adjusted to the shortest distance. This was the original size of sprockets offered to Co-Motion and after initial production, we now offer a 69T size which puts the tension adjustment in the middle of the EBB adjustment."

In a subsequent email I was informed of the prices:
250T, 8mm pitch belt cost; $86.00
69T, 8mm pitch sprocket; $185 ea.

So yes, this would make the whole setup $456, but only if bought direct from Gates, and you may not be allowed to do so unless you were only looking for replacement parts. I had the same reaction as merlin, because I had thought that the belt would be the expensive part, and not the rings. I've therefore given up on the idea of switching our 71 tooth rings for the 69 tooth version. We've had about 2,500 miles and about 10 removals and re-installs of the belt without any problems so far, and without the belt stretching noticeably to make installation any easier, or any other problems. I'm therefore going with the proverb "If it aint broke then don't try to fix it", and will have to continue to install the belt in the non-recommended way.

If anyone has a tandem with a slightly shorter distance between the BBs than a stock Co-Motion, and wants to buy a pair of used 71-tooth belt rings for $250 then I'd be interested in selling them. You could then get a brand new belt for $86 and we could buy a pair of 69-tooth rings for $370 and keep using our current belt.

I'm not sure which size rings are now being offered on new Co-Motions or by after-market sources, but if you have a stock Co-Motion then I would insist that anything you buy should be the 69 tooth version. WebCyclery (http://www.webcyclery.com/product.php?productid=18445&cat=0&page=1) still list the rings as 71 tooth.

PS. I also discovered that a company called Spot Bikes (http://www.spotbikes.com/clothing) may soon be selling Gates belts and rings.

PPS. Dimensions of a stock Co-Motion: "If you have a Co-Motion tandem manufactured in 2000 or later, chances are good that the Gates Carbon Drive will work on your bike. Most of our tandems made within this time frame have a 28.5" boom tube length- measured from the center of the rear bottom bracket, to the center of the front bottom bracket, disregarding the placement of the eccentric unit." Other requirements: 130mm BCD timing cranks, the timing cranks must be in perfect alignment with each other, and the alignment of the rear cranks must be far enough out to allow clearance between the chainstay and belt ring.

My problem with the Gates belt (like boutique wheels) is availability. I do a couple of week long rides each year that are supported by a LBS mechanic. A chain can be replaced but a drive belt can't.

Since we broke the belt, I take the timing rings,and chain that they replaced with me if we're doing a multi day ride out of town.

Admittedly, you can't fix it on the road, (unless you want to carry some heavy parts that defeat the original purpose.)

To me, its kind of like wheels.
Low spoke count wheels/ carbon belts aren't really user serviceable during a ride. Break a spoke, or a belt, and you're looking for the sag wagon.

So if being able to fix whatever may happen during a ride is important, you're better off with conventionally spoked wheels and a timing chain.

That said, we are supossedly the only team that has broken one on a Co-Motion, and that was likely due to the installation.

The seeming paradox about the Gates belt is that the Carbon Drive™ Technology is touted to offer high linear tensile strength and yet in most carbon fiber applications, the strength of the carbon fiber weave lies in a fixed epoxied form.

For the carbon cords in a flexible belt to retain their intended strength yet be so fragile as to be affected by such lateral movement as rolling on or twisting the belt makes one leery of spending the high early adopter's premium for it.

The seeming paradox about the Gates belt is that the Carbon Drive™ Technology is touted to offer high linear tensile strength and yet in most carbon fiber applications, the strength of the carbon fiber weave lies in a fixed epoxied form.


I think the strength has always been in the tensile strength not in any fixed form. Strength in any fixed form is due to the design taking into account the tensile strength.

From Wikipedia:

"The properties of carbon fiber such as high tensile strength, low weight, and low thermal expansion make it very popular in aerospace .."

If anyone has a tandem with a slightly shorter distance between the BBs than a stock Co-Motion, and wants to buy a pair of used 71-tooth belt rings for $250 then I'd be interested in selling them. You could then get a brand new belt for $86 and we could buy a pair of 69-tooth rings for $370 and keep using our current belt.


Chris, I am interested, please PM me.

Joel

I think the strength has always been in the tensile strength not in any fixed form. Strength in any fixed form is due to the design taking into account the tensile strength.

From Wikipedia:

"The properties of carbon fiber such as high tensile strength, low weight, and low thermal expansion make it very popular in aerospace .."

Yes, but it's use is better established for high strength lightweight fixed composites, not so much for flexible transmission belt and cable applications. The carbon chains can fracture easily on high stress applications so it wouldn't have seemed to be as ideally suited for belt use as say Dyneema or Kevlar.


.

FYI, the only hard price I could get on a replacement belt is $145 from CoMotion and Webcyclery.
It seems like the price keeps going up, I thought I heard $80 at one point.
It became clear to me that Gates does not sell direct to consumers.

Maybe so on paper, but the properties of Kevlar, both 49 and 29 type, plus Dyneema is one of high elongation.

In the late 80's early 90's when my model race car lifestyle prevailed, I tested many belt materials for my handbuilt belt drives. A Kevlar corded belt with a urethane matrix worked very well and was proven to be most efficient in these electric cars. The cars would see more speed, longer run times from the batteries and slightly better acceleration. The drawback to a kevlar/urethane belt was failure. These belts were very life limited and would not tolerate high power motors. The belts would stretch under hard acceleration or loads like a collision or hit from the rear instantly stopping the tires from rotating. With high output motors the pulley would skip over the teeth and basically time was lost. After this occurred failure was within minutes. On the opposite end were fiber reinforced belts with higher tensile strengths, while slower they did survive for longer times and were not as prone to slipping.

Not condemning or praising the belt drive. However consider that we are now seeing performance automotive tires with carbon fibre reinforcements as opposed to the previous aramids (kevlar).

PK

Yes, it will be interesting as the carbon fiber belt technology matures. The trade off between durability and stretch is a vexing one. In archery, the Spectra based Fast Flite bowstring material is renown for resisting stretch. Fast Flight S4 is made from a combination of Spectra and Vectran.

Material science is a fascinating field that develops many ordinary things with strength and characteristics we often take for granted (e.g. belted radial tires...).

Maybe so on paper, but the properties of Kevlar, both 49 and 29 type, plus Dyneema is one of high elongation.

Not condemning or praising the belt drive. However consider that we are now seeing performance automotive tires with carbon fibre reinforcements as opposed to the previous aramids (kevlar).

PK

I can invision a carbon fiber bicycle tire coming out in the near future with a selling price of $200 or more.

Dyneema & Spectra, neat stuff with humble realitives...basically thermoplastic milk jug fibers, polyethylene or other another common thermoplastic, polypropylene like they make warm underlayers from.

As for the tire with a carbon construction, it will if it is not already done be there for cyclists. Myself, I would be curious to see if they could build a tire with non-continuous fibres, to minimize slice damage from FOD.

PK