Editor’s Note: Lennard Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn.
This week’s column is all about wheels — building them, repairing them, and keeping tires on them. On a related note, we’re happy to announce that the 520-page fourth edition of Lennard’s Zinn & the Art of Road Bike Maintenance book is out now and available at bookstores, bike shops, and online.
More spoke holes than I know what to do with
While my initial reaction is, “No way!” I then ask why, and the question gets deeper…
Could I use a Chris King 32-hole hub with a 24-spoke rim?
If I do the math, I see some common denominators that make me question my initial conclusion…
I used to do this many years ago on lots of team wheels I built in the mid- to late 1980s for the Zinn-Alfalfa’s women’s team I used to sponsor, using Mavic 24-hole rims and either Shimano or Mavic 32-hole hubs. It always worked fine. Even in those days before deep-section rims, with a women’s team, 32-hole wheels were generally overkill for all but a few of the larger riders.
Losing my touch?
I’m an experienced wheelbuilder (over 150 builds) who worked his way through college as a mechanic. However, since graduating five years ago, I haven’t built a wheel until this past week. I also have never used tubeless tires until this week. I built my new mountain wheels (26-inch), got them all tensioned up, and mounted the tires. After mounting and airing up the tubeless tires, I had a noticeable difference in spoke tension (they loosened up!) and I had to go back and re-tension my wheels.
What gives? Is this normal with tubeless or has the five years off really diminished my wheelbuilding skills that badly? I used quality components (King hubs, DT spokes, nips, and rim, with a DT tubeless conversion kit and Maxxis LUST tires), so that shouldn’t be the issue. I’m just wondering if I screwed up my new wheelset. Both front and rear needed about a quarter-turn more tension per spoke to get the tension right.
Yes, that’s normal. Every wheel’s spoke tension decreases with increasing tire pressure.
In fact, Easton sells its rear wheels out of dish for this reason. Easton says, “Our spec is designed to put the wheel towards the non-drive side for dish because when the tire is inflated on a rear wheel it will decrease the tension on the wheel causing it to pull toward the drive side. That is not the case on a front wheel as the tension is equal.”
I recently bought a used set of carbon tubulars, with tires mounted. To be sure of the glue job underneath the tire, I am removing the tires and re-gluing them. The tires lifted off the rims fairly easily, but it looks like they took a layer of the rims off in a few spots; there’s some carbon stuck to the base tape of the tire. The biggest spot is about 2 inches long and the width of the base tape, with a few other smaller spots around the base tape. I assume that I will need to glue new tires on, but is this a problem for the rim?
Pulling off of some fibers in the top layer of carbon on the rim bed happens sometimes upon tire removal, and it’s impossible to judge at this distance how much your rim is compromised. I have often gone ahead and glued another tire on over some small patches where fibers had torn out of the rim bed, and I’ve never had a carbon tubular rim failure. However, yours is a bigger patch than I’ve ever seen.
Consult the rim manufacturer.
A riding buddy has had two Hutchinson Fusion Kevlar bead tires blow off rims on the same steep downhill — one on a Ksyrium rim, and one on a Neuvation. This downhill is a real brake burner, so he’s wondering if he could have heated the tire to the point where it would blow off, or is this more likely just a mounting error, a tire not seated perfectly. His concern is with the rims, but since they expand with heat, I would expect that would help, not hurt.
Well, the most common reason a tire blows off is because there is some inner tube sticking out under the bead. Avoid this by always starting and finishing at the valve stem when dismounting and mounting tires.
It could also have been a tolerance run-out issue — too big on the tire bead, or right on the big end of spec, and too small on the rims, or right on the small end of spec.