After a nasty downhill crash at the Davis Double Century many years ago …
After our tire blew off at the Davis Double, I headed back to my Burley office in Eugene, Oregon to start a somewhat long process of trying to determine what happened. Part of our research at the time (some 15 years ago) included checking in with the rim manufacturer (Sun). We did learn a couple of important lessons from that incident.
Interestingly enough, Lon Haldeman (who used the same rims at the time for various cycling endeavors) had found issues with a rim’s diameter at end of a run-life cycle (becoming ‘smaller’). I imagine in the past decade that quality control issues have improved but all of us have read plenty of wheel QC issues the past few years with various companies.
I’m pretty sure that in our case the downhill scenario (and brake-rim heat) contributed to the failure … good tandem disc brakes were just starting to hit the drawing board, and we were using standard side-pulls. But we did find that the ‘sloppy’ (loose) tire/rim fit was probably the biggest cause of the tire being able to blow off. Over the years, I found the same thing with my single bike – I had a couple of situations where the tire blew off the rim for no good reason (no pinched tube, defective tire, etc.), and could trace it to a bad tire/rim combo. I’ve never had an issue with a tight fitting tire/rim combo blowing off – remember that the next time you’re cussing while trying to get a tire onto the rim. I’m pretty picky about making sure that I haven’t pinched the tube when re-inserting – even double checking everything – but about once every 5 years I miss it, and sure enough … Boom! If you’re lucky, you’ll get a ‘thump-thump’ feel in the tire before it blows – giving you a precious few seconds to slow down and check it out.
Some of you may remember when Specialized promoted their easier-fitting tires about 10 or 15 years ago because so many cyclists were having problems with getting their tires on the rim. The product/program didn’t last very long.
The other thing we learned from the crash is that ‘coke can shims’ aren’t a good idea … especially on a tandem. Scott had wanted a different stoker stem installed the night before the ride, but all he had for spares required a coke can shim to secure (wrong diameter). When we were crashing, Scott was holding on tightly to the stoker cow-horn bars (as you might imagine), and the bars moved to the side so that Scott’s shoulder took the brunt of the pavement hit (not the handlebars).
By the way, Scott Marin (my tandem partner for the Davis D.C.) and I are still good friends, and wrote a funny piece about the crash in Bicycling Magazine (see our website article archive section). He rode our Maui Triple Challenge a few years back (and wrote about the challenge for Road Bike Rider).