By: “c_g”, Grannygear, and Guitar Ted

Welcome to our report on the Gates Carbon Belt Drive System: Twenty Nine Inches has been intensively testing and researching the Gates Carbon Belt Drive System over much of the last half of 2010. In this final report we offer an analysis on the belt versus traditional chain driven bicycles, especially single speed mountain bikes. We also detail out our thoughts on how the belt drive affects the bicycle and its other components.

The previous two parts to this report can be seen here and here.

To recap briefly from the last report, we found that the Gates Carbon Belt Drive was a system that could work well out in the field, but while it is workable, it isn’t infallible. There were “hiccups” and reported failures from some riders, and even some issues that arose from our own testing. Okay, so nothing is perfect, but there is more. We left off last time by saying this:“While it is one thing to get positive performance experiences with the belt drives, it has to be asked, “At what costs?””

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Design Compromises: While it is true that the Gates Carbon Belt Drive System will work on a mountain bike single speed application, there are several things that have to be compromised, in our view, to fit the system on a mountain bike. Let’s use the tested Raleigh XXIX as an example. In our view, this most dramatically shows what the compromises in the system are, since the XXIX existed as a chain driven bike before the 2011 model year.

Previously, the XXIX sported a reasonably short chain stay for a 29″er especially. At 17.25″, and with clearances for up to a 2.4″ tire on a 28mm wide rim, the XXIX was well regarded by enthusiasts as a great climbing single speed. However; with the special offset of Gates cogs, their inherent width, and Gates requirement to run a bigger diameter cog up front to help combat ratcheting, the XXIX had to undergo some radical changes to accommodate the belt. The 2011 model saw the severe crimping of the chain stay to allow for the severe inboard set of the front cog. This forced the designers to push the rear tire backwards, and give up some tire clearance in the exchange as well. Now the older shorter chain stay had grown to over 18″!

Obviously, mass production requirements had something to do with what belt length Raleigh could get to make a certain number of XXIX’s, and perhaps a shorter chain stay length may have been possible, but the point we are making is that any lengthening of the chain stay, and any loss of tire clearance is a step backward in terms of design and performance on this model. Yes: The belt worked really well on this bike, but the cost to have it on there! It really negatively affected performance.

AC_fin_2Our European contributor, “c_g” also reported that the Mi-Tech 29″er he tested, (report here), that was designed from the onset to accept the belt system, was extremely stiff riding. This is another result of parameters Gates is placing on frame designers to accommodate a belt drive system. Gates specs call for a minimal torsional and lateral flex in the chain stay. To achieve such required numbers, frame designers are beefing up the chain stays to the point that flex is nearly wiped out. Good for the belt-bad for the ride quality. Supporters of Gates have said that designers can overcome this, but again, at what cost to riders? One has to also wonder if, as “c_g” alludes to in his reports, any current frame is a bad choice for a conversion to a belt driven mountain bike. Special frames for a limited amount of benefit and a loss of ride feel? That and a possible increase in costs to recoup research and development costs on an already expensive system?

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Following are comments from all three of the Twenty Nine Inches staff on their experiences and thoughts on the Gates Carbon Belt Drive System.

The first one up is Grannygear: Would I buy a serious single speed mountain bike with a Gates Carbon Drive belt drive on it? That is really the question in the proverbial nutshell. The answer is “not yet”. This is why not and also why I am keeping my options open. I do not think that, at this time, the requirements of a healthy belt system, that being a frame that is stout to the point of possibly detracting from the ride and handling qualities of a good bicycle, the work-around needed for the bigger ‘chain rings’, the finicky nature of the beast alignment wise, the tension issue and the way it binds on spinning parts, the oddness that complicates easy gear ratio changes, wear on the pulleys at the free hub (the rear pulley on the XXIX really should be replaced now, and that was only a couple of months of riding), parts replacement, and having to carry a spare belt to really feel good about big rides….it all combines to overwhelm the positives I think are there. The high required tension is one of my least favorite things about it.

And that is too bad as I really liked pedaling it. It was quiet (although I never really got it too wet or muddy), smooth, and never skipped on me. It survived three young and strong guys who wailed on it with only one ‘pop’ and that was when the bottom bracket had shifted over a bit and the belt had crept off-line. Even then, we finished the ride, corrected the alignment, and then entered it in a team 12 hour race. It did not break, it did not whine. It just worked, and it did it despite all the baggage, but I cannot ignore that load of luggage that comes with it. And, frankly, I am not sure how many of those things can be improved upon. The “not yet” part? Well, I did not hate it, and I hope that the refinement continues, and at some point in the future, it will be a premium system for a single speed mountain bike.

Until then, I will take a chain.: Grannygear

Next we have our European Contributor, “c_g”, and his thoughts:

OK it´s about time to put down some more experiences with the GATES Carbon belt drive. In most all aspects I agree with Guitar Ted and Grannygear on their experiences on the system.

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• The prime issues are the high belt tension, that is required to have the belt engage securely. Bike parts are not designed for this and premature wear or failure can be the result. In my testing I have not had any problems with premature wear issues but then again I have split riding time between single speed and internally geared.

• In my testing in single speed mode I have only run gearing ratio (46/24) which had been really tough in places. Had I wanted to modify – the current choices of ratios are limited and costly as they involve new cogs and belts. For single speed use I find its primary advantage the absolute freedom of maintenance once set up properly – but honestly; how difficult is it to keep a single speed drive train running smoothly, not that much.

For me it is a different story though when running a belt in junction with internal gears. Here the benefits of a mostly maintenance free system for epic multi day adventures IS a huge benefit in my eyes. Here the need for changing gear ratios is non existent and so the only drawback over standard chains is the initial purchase price of belt components. After the initial mounting, which involves the same level of getting the chain line perfect, it turns pretty much into a set and forget system.

With this said, I have set aside a rig with exactly that configuration and will be running it for a good portion of the year both in mountain bike application and in utility use. I will report back about my findings periodically – should there be any.

Ride On,
c_g

Now here are Guitar Ted’s thoughts on the Gates Carbon Belt Drive System:

Going into this test, I was rather skeptical of many of the claimed benefits of the Gates Belt Drive. For a bit of back round, I should say that I have been a single speeder, primarily, since hopping on board with 29″ers in 2003. I have run single speed drive trains through the worst of mud, sand, salt, snow, rain, ice, and dirt with no failures. Certainly, I have replaced parts at times, but this was simple, and more importantly, cheap to do. In my mind, the belt had a high bar to clear. A very high bar.

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First of all, the belt drive works…..technically. However; I see the bicycle, and in this case, the single speed off road bike, as a system. Taken as such, the belt drive didn’t fare as well. In fact, I would say it was a poor alternative to the over all system we have as a single speed off road bicycle now. Why? Because, (as Granny Gear covered), the belt drive requires too many design compromises, has limited hard ware choices, (as “c_g” also mentions), and it is just too darn expensive. Compare cog and belt prices. Keep in mind that for just one alternative gear range choice, you will need a minimum of a rear cog and a new belt, if the bicycle you are using will even allow for that change. The overall price for both parts alone can be around the $200.00 range. You can buy a lot of cogs and chains for that much money. Not to mention the costs involved in getting a belt specific frame, which are not all that common, and are necessary for optimal belt drive performance. Contrast this with the fact that almost any mountain bike can be successfully converted to a single speed.

So, what of the advantages of a belt? Belt drive fans will tell you of several “advantages” over chains, but only two things they say really matter. (The rest are not really advantages over chains in single speed applications.) One: Belt drive set ups are lighter than chain drive. Two: Belts and cogs will outlast chains and chain rings in terms of lifespan. This is somewhat offset by the fact that the looming early wear issues on the bearings are still out there, the belt cogs wear prematurely, the efficiency of the entire drive train suffers, and obviously, in terms of costs.

Conclusions: The short and simple is this: Belts are not better than chain drive systems. Not in terms of single speed mountain biking. Belt drive has some advantages, but costs, unknown bearing wear issues, problems with cog wear, design constraints in terms of frames, and the limited availability of cogs and belts in all gearing ranges is holding belt drive back. For now a chain drive single speed just makes far more sense. In the light of “c_g”‘s thoughts on internal rear hub driven bikes with belt drive, we agree that this solution for low maintenance mountain biking makes far more sense now, and likely will be the best application of a belt drive for mountain biking into the future.