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Technical FAQ: Tips for sealing ’cross sidewalls against moisture

  • By Lennard Zinn
  • Published Jan. 29, 2013
  • Updated Jan. 29, 2013 at 7:21 AM EDT
A Dugast Typhoon sidewall sealed with Aquaseal by Stu Thorne. Notice how the Aquaseal goes over the edge of the base tape and even the tubular rim cement squeezing out from between the base tape and the rim. Photo: Lennard Zinn | Velonews.com

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.

Treating sidewalls doesn’t have to be a pain

Dear Lennard,
I saw on VeloNews.com that the new Dugasts come factory pre-sealed. Do they still need Aquaseal? If so, how do you do that?
―Chris

Dear Chris,
According to Stu Thorne, manager of the Cannondale-Cyclocrossworld.com team, “They are sealed better, but as insurance I Aquaseal them. I can get two seasons out of them this way. I would love to dispel the belief that Aquasealing them is a huge pain in the ass. Takes me five minutes max to apply.”

Dugast has always recommended Aquaseal (called Aqua Sure in the EU).

Thorne carries out his method with the wheel and glued-on tire in a truing stand. He takes a tube of Aquaseal (he uses the big tubes), and squirts a fat bead all of the way around the sidewall as he turns the wheel in the truing stand. He smoothes it with a latex-gloved hand all of the way down to the edge of the rim and up to the edge of the tread. He has a curved, plastic concave scraper that he has fashioned to fit the tire sidewall right up to the edge of the rim from the tread. He uses this to squeegee off the excess Aquaseal.

Make sure that the gap to the rim is filled so that water cannot get under at the base tape. With pure cotton tires used in wet conditions and frequently washed with power washers, introduction of water can lead to rotting and failure of the cotton threads.

Not all teams do this. Rapha-Focus mechanic Troy Smith says that his team instead coats Dugast tire sidewalls with liquid latex, rather than Aquaseal, so the tire won’t become as stiff.

Also, a common thing for American riders to use is McNett’s Tent Sure. This is a urethane tent floor sealant for coating worn-out areas in waterproof-coated synthetic fabrics. It is thin and easy to brush on with the included foam brush. I have found, however, that it does not hold up very well, even in our dry Colorado environment with a lot less washing going on than in Belgium.

I exploded my Tent-Sure-coated rear Dugast Typhoon that was less than a year old on the final lap of our state championships. I had coated it with Tent Sure, although not for some time, and the tread on the tire looked quite new. However, I ignored the crisscross pattern of darkened groups of cords on the sidewall, which I believe was a sign of rotting in the cotton cords. I also ignored the general fuzziness of the sidewalls, which indicated abrasive wear that had thinned the already-thin cotton cords. Lesson learned.

Christine Vardaros, an American racing cyclocross in Belgium, also reports that a number of Belgians have told her that they use Invisible Terrassen to seal their cotton tubular sidewalls.
―Lennard

A thinner option

Dear Lennard,
Just wanted to send out a tip for ’cross tire sidewall sealant. Most use Aquaseal, which you have even described as thick and difficult to apply. There is an identical but thinner product called Seam Grip (http://www.mcnett.com/Seam-Grip-Seam-Sealer-Outdoor-Repair-P133.aspx) also by McNett. My day job is in the outdoor recreation industry. We use aqua seal to repair neoprene, or anywhere we need a thick glob for the application because it doesn’t run much after application. For tent fabric repairs or to waterproof seams, we use seam grip, which is just a bit thinner and runs a little if you put it on too thick. I’ve found that seam grip is much better on sidewalls as it is much easier to apply quickly, neatly, and in a thin layer. As far as I know they have identical ingredients, just different viscosity out of the tube.
—Josh Whitmore, Globalbike Wipes Cycling Team

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Lennard Zinn

Lennard Zinn

Our longtime technical writer joined VeloNews in 1987. He is also a framebuilder, a former U.S. National Team rider, and author of many bicycle books, including Zinn and the Art of Mountain Bike Maintenance and Zinn and the Art of Road Bike Maintenance, as well as Zinn and the Art of Triathlon Bikes and Zinn's Cycling Primer: Maintenance Tips and Skill Building for Cyclists. He holds a Bachelor’s degree in physics from Colorado College. Readers can send brief technical questions to Ask LZ.

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