thoughts on Shimano's tubeless road wheelset...

I try to keep the blog light, but this time I’m going to get a little technical with talk about wheels – bike wheels, specifically. For the last two years of racing cyclocross, I rode on a traditional clincher wheelset. Rough courses were made rougher by the high pressures I was forced to run (50+ psi) and on more than one occasion I had to drop out of a race due to flats (usually goathead induced). On the plus side, I could quickly and easily swap tires for nearly any condition (I have a stack of “barely-used” clinchers on my porch).

Before this season started I decided to make the switch to the Shimano Dura-Ace WH-7850 SL tubeless wheelset. Only two tires were offered, Hutchinson’s Piranha and Bulldog, but I’d spent all of last year running the Piranha with great success so I wasn’t concerned. I was a late adopter to tubeless in the mountain biking world, but once I changed over I became a convert. The potential benefits of tubeless in cyclocross were intriguing – resistance to thorns/goatheads and pinch flats and the ability to run lower pressures.

So far, I’ve run the Shimano WH-7850 SL wheelset in four races and I’m disappointed. Setup was easy enough: add a scoop of Stan’s sealant and pump the tire up until the bead “pops” into place. From there, you can adjust your tire pressure as you desire. In my initial tests with the tubeless setup I started with tire pressures in the mid-30 psi range. Now, I’m no lightweight svelte racer – I weigh in at about 175 pounds – but I’m not really a heavyweight either. After starting my first cyclocross race with those mid-30 psi tire pressures I nearly finished the race on a flat rear tire. At several locations on course I “burped” the tire and lost tire pressure. At subsequent races I tried gradually increasing the pressures until burping stopped. At my weight, I found that tire pressures around 50 psi yielded good results, namely no burping. Unfortunately, with a tire pressure that high, it negates one of the primary reasons to run tubeless in the first place: I couldn’t run lower pressures!

At one race, on the hardscrabble dirt roads and paths in Watkins, Colorado, I did find that the tubeless setup provided one advantage over the clincher setups – resistance to goatheads. After my warmup laps I pulled five goatheads out of the front tire and the Stan’s expertly closed up the punctures with no noticeable pressure loss.

This past weekend, I planned on running the tubeless setup on the Frisco cyclocross courses. Unfortunately, on the way to the starting line at Saturday’s I felt my rear tire intermittently rubbing on the brake pads and discovered the wheel WAY out of true. I swapped over to my backup wheel setup (clincher) and ran the race on those, but after the race I closely inspected the Dura-Ace wheel. It turns out that the end of one spoke close to the hub broke, apparently during my easy warm-up laps. Word from the bike shop is that Shimano is out of spokes for this wheel, so I’m off of this wheel for at least one week.

As I mentioned above, I’m pretty disappointed in this tubeless option for cyclocross. Yes, I gain the advantage of thorn protection, but I’m still forced to run the same pressures I ran with clinchers. And now, it seems that the durability of the wheel is in question.

While the wheel is getting repaired, I’m setting up the Stan’s tubeless system on my Easton Circuit wheelset. I’ll document how that goes and how it performs.