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Technical Q&A with Lennard Zinn: Recall, flipped Wippermann and more tubeless talk

By Lennard Zinn

Replace those face-plate bolts
Dear Lennard,
I have heard that 3TTT has recalled their Zepp stems. I have an XL version of this stem – how can I find out if it is on the recall list? Can you tell me more about the problems associated with the stems? Should I pull this puppy off the bike?
William

Dear William,
Yes, there has been a recall of those stems. You do not necessarily need to remove it from the bike, but you must replace the face-plate bolts with longer ones.
Lennard

Wippermann chain with Dura-Ace?
Dear Lennard,
I’ve got a Shimano 7800 drivetrain on my Seven Elium. In your most recent VeloNews column you write that you use a Wippermann 9-speed chain with your 7800 crank. You don’t write about your RD. Can I use a Wippermann with my 7800? I like the idea of being able to take my chain off regularly to clean it without breaking it. If yes, which Wippermann would you recommend?
Michael

Dear Michael,
Yes, you certainly can use one on your 10-speed Dura-Ace rear derailleur. I would recommend the Wippermann 10-speed chains, like the 1008 (nickel-plated) 1011 (hollow-pin); 10X1 (stainless steel); or 10TR (titanium rollers, cutout plates and hollow pins). By the way, my RD was a 7700—9-speed Dura-Ace.
Lennard

Speaking of Wippermann chains . . .
Dear Lennard,
In the photo you published on velonews.com of your bike/crank/front derailleur, you appeared to have installed the Connex link incorrectly.

My understanding is that, as the chain is traveling in the forward motion, the Connex link should look like a “V,” and when the chain is on the bottom traveling toward the rear derailleur the Connex look should look like an inverted “V.”

Is this catch worthy of a signed copy of your book?
Mark

Dear Mark,
Thanks to you and the others who pointed out that I had installed the Connex Master Link upside down. It never occurred to me to look at the directions, since I have installed so many SRAM, Lickton’s, and Taya (and Wippermann) master links in the past without problems. The instructions clearly show the preferred orientation; still, I must say that I never had any noise or shifting problems with it in the upside-down configuration.

Wippermann’s U.S. agent says the side of the asymmetric link with the more constant radius is the side that goes against the cranks: “If it’s installed upside down, it’ll work, but you’ll hear an annoying tick as it rolls over the smallest cog on your wheel.” A picture of the proper setup and an installation tutorial is available at

IRC says beads refined
Lennard,
Since you have twice mentioned the tight fit of the IRC Serac XC UST tubeless tire in your technical columns, I feel I should respond. Since you conducted the product test of the IRC Serac XC UST tubeless tire, approximately two years ago, we have significantly refined our tubeless tire beads to make them work as well as anything on the market. That includes ease of mounting, air retention and abrasion resistance.

Bead thickness was a past issue in ease of tire mounting. The specific technology is proprietary, but in a nutshell, we have reduced the bead thickness to allow for both tire beads to fit easier into the center channel of a rim. A smaller bead allows for an easier tire mount. IRC has invested many hours of R&D to refine our tubeless tires from when we first received UST certification over three years ago to now.Joe Staron, IRC Tire

And Bontrager chimes in
Lennard,
I saw this on the VN website the other day:

“I have had trouble mounting tires on Bontrager UST rims, which were standard rims that became UST rims by means of a permanent plastic rim strip that sealed the spoke holes. The problem, as far as I could tell, was that the rim ledges for the tire beads were standard diameter, but once they had the rim strip over them, the circumference was increased and required the tire to be stretched farther. Furthermore, the rim valley was narrower and shallower, due to the rim strip taking up room throughout this area as well, making it harder for the fat UST beads do drop down into the center, particularly both of them at the same time, which makes pushing the bead over the rim wall at the opposite edge of the rim easier.”

Your description of the rims and strips we make is a bit off. The rim is not a “normal rim” in the sense that you convey. It is specifically designed to work with the strip for tubeless applications. The bead seat diameter of the rim with the strip installed, measured at the (radially) outerward facing surface of the strip, is the same as other UST wheels.

The same goes for the inner dimensions of the channel in the center of the rim and strip. The dimensions of these features are the same as UST standard parts when they are assembled. The tire beads will fit into them and the tires will mount in the same way as with other UST rims.

The rim and strip are designed together so that the tire mounting surfaces of the strip conform to the UST standard in every way. The attached images show how this works.

That said, there were some early production rims that were made with an improper diameter, a bit too large. Even small errors in this dimension cause the tires to be very difficult to mount.

The symptoms of a large rim are as you describe when you try to mount a tire; the beads don’t seem to drop into the central channel far enough and make the opposite bead tough to get over the rim wall. You probably tried to mount tires on one of those. That is not an issue with our tubeless wheels when they are made to the proper diameter and the tire is made to UST standards.

Onto the tips:

Wetting the beads of the tire and/or the mounting surfaces in the rim is important because it makes a better seal against the rim and slides easily onto the bead seat. I use a diluted mixture of common dish soap and water and spray it on or use a sponge to wipe it on. The soap solution whets the tire surface and strip well. Plain water out of a water bottle will do the job out on the trail too.

Using a sealant in a tubeless tire makes them almost invincible. The sealants are okay as a tire-mounting lube if you have to use them and are careful. But the coagulant particles and fibers in some of them are large enough to cause a leak at the bead if they get trapped in there. Rinsing or wiping the old sealant out of the rim and off the tire when you have them apart prevents leaks.

Prestretching the tire on a normal rim overnight also makes it much easier to mount. This is especially true with some tire companies’ bead designs, which tend to be bulky and a tight fit in the rim channel in the best case (an example of which you pointed out with the early IRC designs).

Mount the new tire on any standard MTB wheel or rim you have around, using a tube. The wheel doesn’t have to be anything current or fancy. Inflate it to 50 psi or so, and let it sit around overnight. The aramid fibers in the bead will stretch a little, typically enough to make a tight tire go on much more easily by hand afterwards. Do this to a new tire as soon as you get it. If you aren’t going to use it right away, then pack it into your spares after you stretch it so it is easier to mount at the races.

I always carry a tire tool to help remove and replace a stubborn tire. I don’t get many flats with a tubeless tire, and the tires I use will come off by hand, but weird things happen out there and there is no sense taking a chance to avoid packing 10 grams of plastic in your tool bag. Wrap the tire lever with a few inches of duct tape in case you need to boot a tire.

Don’t forget to tighten the air inflation valve by hand so you can remove it and use a tube if you do puncture.
Keith Bontrager


Technical writer Lennard Zinn is a frame builder, a former U.S. national team rider and author of several books on bikes and bike maintenance including the pair of successful maintenance guides “
Zinn & the Art of Mountain Bike Maintenance” and “Zinn & the Art of Road Bike Maintenance.”Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn. Zinn’s column appears here each Tuesday.