Monday, February 27, 2012

Tightening the belt a couple of notches

Rear pulley showing signs of distress after 4000km of lovin'

While the durability of the Gates carbon drive system is touted to be ‘off the scale, astronomically good’, there is precious little real information out there about just how long it lasts. Here is my take on the system, and whether it lives up to the hype.

As a rider I can chew through a regular mountainbike chain in a couple of months (approximately 2000km). If I replace it, I can prevent the dreaded cog wear that can destroy chainrings and cassette, leaving you skipping, chain sucking and poor.

With this durability as a benchmark, and in a constant quest for more, I was an early adopter of the Gates system, first setting it up on my El Commandante singlespeed. While I’ll usually ride this bike at least once a week, it was difficult to ascertain the real durability, with the constant switching of belt lengths and cogs to suit varying rides and events. I find it amusing that while singlespeeders tout that 'one gear is all you need', the cumulative time spent tinkering with ratios is in the order of days, while for geared riders it is only the second required to execute a shift. 
Typically I’d run a 52” gear for the hills of Christchurch, dropping it as low 44” for hill savagery such as the infamously ball breaking 2010 Queenstown nationals.  At the other end of the spectrum I’d go as high as 76” for the ludicrously competitive McLeans Island World Champs which invariably came down to a leg searing sprint where the highest gear would win.

It wasn’t until I sourced a belt pulley for the Rohloff internal hub that I use on longer touring rides and ultra-races that the system got a true test. The wait for this one item was ridiculous, with some 2 years elapsing between when the cog was first announced and when I finally took delivery of the prized pulley. The reason for the delay was clouded in mystique, with a reason cited being the reluctance of Rohloff to approve the belt system for use with their hub. Despite laboratory testing form Ventana to prove the frame was sufficiently stiff, and efforts from Pure Sports in NZ to grease the wheels, the cogs were proving harder to source than prehistoric hens teeth.
That was until I got onto Cycle monkey, who as a trusted distributor of both Rohloff and Gates, could provide the pulley and adapter needed so that I could finally realise the awesome potential of this ultimately durable mountainbike drivetrain.

I built up a sparkling blue new El Commandante in August last year, and after a month of casual rides dialling the tension of the belt, I took it on a proper outing in the 2011 edition of Le Petite Brevet where it performed well under admittedly benign conditions.
It took some tinkering to get the tension just right. Not a pickle to adjust with the Ventana’s sliding dropouts, but too low and it would skip under harsh acceleration, too high and the system lost some efficiency.

Shiny new Centretrack cogs ready for some miles of their own

Since then I’ve logged some serious miles on the system, including a big summer in Nelson riding all of the technical trails on offer. I made a conscious effort to ride in the wet, slathering the system with gritty mud that I was sure would be the systems downfall. But it kept on trucking, and by the time the Great Southern Brevet rolled around I’d clocked up 2900 km. While most of the conditions around the Central Otago course were dry, there were a few sloppy sections notably through the Nevis and over the Old Man Range which started the wear in earnest.
I didn’t lube the system as fellow chain riding Breveteeers did for there chains, but in its worn state the belt needed the odd squirt with a drink bottle to clean grit and quieten an irritating squeak. I’ll admit that this was a shade annoying, especially with the temperature was pushing 30 degrees and through the Dunstan trail where I was forced to squirt precious thirst quenching water at my dirty belt.

On completion of the Brevet, I took some time to investigate the wear on the system. It was clear that the hard anodising had been stripped on the loaded face of the rear pulley, with a small gap visible on the back side of the belt teeth. Just to see if there was still life in the old cogs, I installed a new belt and was stoked to see this gap disappear, and this told me that the relatively inexpensive belt wore before the expensive and difficult to install cogs.
While my observations of belt wearing before cogs were at odds with the manufacturer’s advice, it was heartening as it meant I could extend the systems life just by swapping in a new belt, a relatively lightweight and easy to source part. I rode this for another 1050km in the Kiwi Brevet with no dramas, and it is safe to say there is plenty of life on the ol’girl left.

Stainless adds durability while the central flange simplifies setup
So with 4000km already from the system, how could it get better? Mindful of the issues with setup some people had been having, the folks at Gates went back to the drawing board and produced a new design called Centretrack, which shifted the pulley flanges from the outside of the cog to the centre. The system was more tolerant of misalignment, featured much better mud clearance, and used rear pulleys made form durable (and slightly heavier) stainless steel rather than the anodised aluminium of the earlier design.

Safe to say with these changes, the system will be even better, and while I won’t get a chance to clock up 4000km on it before the Tour Divide in June, I’m confident that the system will be suited to the epic ride that is in store in the USA. I’ll be sure to carry a spare belt, and should trail conditions prove too harsh, I can always install the spare to get me to Antelope Wells.

While there are risks being an early adopter, I’ve been thoroughly impressed with the durability of the belt system. It really makes for the most worry free transmission imaginable which is just the ticket when you have almost a month of endless days in the saddle ahead!


Stephen said...

The belt will survive the divide just fine.

Peoples Bicycle said...

Hey Ollie, I watched your progress on the Tour Divide and I was impressed by your choice of drivetrain. I'm curious to hear your impressions, post race win. Thanks for the writeup.