UPDATE: It turns out our problems had nothing to do with the braking surface at all. The rim was splitting in two right down the middle. I didn't see this until I removed the rim tape. Click here for a continuation of the story.
Roughly one hundred days ago, my rear rim, a Velocity Cliffhanger failed while we were climbing Julierpass in Switzerland. When we arrived at our campsite we discovered that Tara's rear rim was failing in exactly the same way. After contacting Velocity we were amazed when they immediately offered to replace both our rear wheels and our front wheels for free. Rather than sending us the same rim, Velocity opted to use their newly revived Chukker model, a "deep V" (refers to the shape) mountain biking rim.
Two countries and nearly 3,000 kilometers later, Tara's new rear rim is failing. Like last time, there is an odd-looking crack in the middle of the braking surface and the rim is bowed out around it, making the use of her rear brakes impossible.
When we contacted Velocity with this new problem they were immediately willing to help. Within days they'd built and mailed two new rear wheels, this time using their widest, thickest rim, the Psycho. I can't say enough about how great Velocity's customer service has been.
I'm a little bummed that when we leave the Kerkennah Islands we'll be riding away on our third set of rear wheels in 9,000 kilometers. Before we left I did loads of research about what rims we should use, specifically hoping to avoid this very situation. I chose Velocity because of their high standing in the cycling community, and their Cliffhanger rims because they were the most heavy-duty offering at the time. When they failed in Switzerland all signs pointed to a manufacturing defect. This new problem seems to be the same defect again but since we've had a similar failure, now I'm scrutinizing our bikes.
It is a simple fact that when you use rim brakes you are slowly grinding away the rim's surface. We're running Koolstop Salmon brake pads specifically to mitigate some of this effect. They are well known in the touring community for their rim-friendly material and impressive wet weather stopping. Since our first failure I have been obsessive about ensuring that our brakes are properly aligned and the brake pads clean. I can't see that in less than 3,000 kilometers Tara has worn down her rear wheel to the point of failure; especially given that 90% of our braking occurs on our front rims.
We are carrying very heavy loads by any touring standards. Both of our bikes weigh in excess of 100 pounds and when last I checked, mine was well over that! I've never been too concerned about this; both Tara and I are lightweight riders, coming in around 130 and 140lbs. We know of cycle tourists who weigh more than either of us with our bike combined, so surely our heavy loads can't be causing the failures? I'm just not sure.
One thought put forth in a thread over at Bike Forums was that tire overinflation could cause this sort of problem. That can't be it because we run 60-65PSI religously, a very low pressure. Another suggested that our rims, just one inch wide, were too narrow for our two inch wheels. This seems like a reasonable hypothesis; I can see how a heavy load would exert a lot of outward force on the sidewall of a rim half the width of its tire. I had raised this concern with Velocity back in Switzerland but they assured me it was fine. Even so, it seems like a reasonable suspect for the cause. In any case, our replacements on the way are the widest offering Velocity makes, coming in over a quarter inch thicker than our Chukkers.
There is one sure way to prevent all of this supposed sidewall wear: disc brakes. I briefly considered this out of frustration when I realized we'd need new rims yet again. Ultimately though, it isn't an option. Our Long Haul Truckers don't have the braze-ons required to use them. There are exotic mounting solutions out there but I'm not willing to try them, especially given that our frames weren't designed for it. Apart from wheel issues, my motto of "simple, simple simple" for our bicycles has proven effective. We've had no other major bike-related problems after eight months on the road. Millions of miles have been logged touring with rim brakes and ours will join them, failures or no.
The final hypothesis for all of this rim distress (har har) is simultaneously comforting and disconcerting. Maybe we've somehow managed to wind up with three dud rims. My rear rim seems fine and I am carrying the heavier load; why didn't it fail first? Though Velocity replaced our entire wheelsets in Switzerland, our front rims, which see the bulk of our braking, never had any issues. We even sold them to a bike shop before we left! It would be nice to know that we haven't done anything wrong but it would be even nicer to know that any time you purchase a rim from Velocity you're going to get a defect-free product.
All of this considered, I'm still glad we have Velocity equipment. I don't know for sure what is causing the problem but I hope I can report a year from now that we've finally found a winning combination of tires and rims for our journey. Waiting around for wheels instead of riding isn't the most fun in the world, but thankfully my business is still booming. I have more work than I know what to do with to fill the time productively. Tara has been hard at work too, writing our journals and preparing some fun Christmas stuff which we'll post soon.
No matter what happens, I know Velocity will keep us rolling, even if we're on a desert island in the middle of nowhere.