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Tech FAQ: CX Tubular Sealing, Thru-Axle Loosening, Flats, Road Link

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Have a question for Lennard? Please email us [email protected] to be included in the technical FAQ.

Dear Lenard,

I have a few pairs of Challenge Pro and Team Edition tubulars glued to the rims using Effectto Mariposa Carogna. Work and family obligations cut into my pre-season prep time last season and I didn’t use tent seals on the sidewalls. A few tires with light cream sidewalls looked pre-treated, but the darker tan versions did not.

After a lot of mud and pressure washing in the pits last year, a few of our tires are showing faint desiccation lines on the sidewalls. They hold air and look structurally sound, so I would like to use them for a second season as tubular tires are rare at the moment. Any reason not to treat the flanks now, year two? I’m thinking of using a Gear Aid product called Seam Grip. Do you have any other tips for extending the life of the casings in their second year of use?


Also read: Tested: The fastest bicycle inner tubes

Dear Eric,

Yay! The cyclocross season is near again and I love the questions about it. Here’s the answer from Cyclocrossworld founder Stu Thorne, who has run the Cannondale/Cyclocrossworld team for years and is as familiar with sealing CX tire sidewalls as anyone anywhere:

“We’ve never had much luck putting sealant on a used tire. I felt it was a bit of a band-aid at the time, and trying to squeeze another year out of a tire wasn’t something we did very often, as we used fresh glue every year . Sealing a tire was always done when it was new and never done on a Challenge, because they used more latex on the sidewalls. The Dugasts we used years ago absolutely had to have putty. So I would say give it a try if you want, and maybe it will extend the life of the tire a bit, but I wouldn’t expect much.


Dear Lenard,

I read your August 1 articles about thru axles coming off. I had this problem on two bikes, both have cam thru axles. I think I finally figured out why this is happening. On both cam-style thru-axles, when the cam is fully open, the handle and thru-axle are locked, which means that if you turn the handle, the thru-axle rotates (of course you have to tighten the thru axle), however when the cam is closed, the thru axle can spin freely (I assume it’s designed that way to allow a person to close the thru axle and then rotate the handle to the location wish).

Also, the knurled nut that the cam clamps against is not part of the thru-axle. So once the thru-axle is tightened and locked, the actual thru-axle can rotate while the cam lock and knurled nut stay in place. The thru axle on my Devinci gravel bike has a slight worn groove on the right side. So my theory is that the freewheel bearings can develop some drag, and when I pedal, the thru axle loosens up. Anyway, I’m curious if this looks correct to you or do you think something else is causing the problem.

To M

Dear Tom,
I hadn’t thought of that before, and your reasoning makes sense. On a front axle, unless the hub bearings are seizing up, I don’t see how that could cause the thru axle to loosen. On the rear, however, I can see how the scenario you’re suggesting could cause the axle to come loose.


Dear Lenard,

I can totally back up your answer to Mark’s question about apartments from scraps of wire. When I commuted regularly, I got one of these apartments at least once a year. My route passed through industrial areas. Flats were never blowouts but slow leaks. I had to use needle nose pliers to remove the wires. The wire was never perpendicular but at an “almost tangent”.

I think these wires are “everywhere” and I think they get stuck on a tire and work there.


Dear Lenard,

I also have the misfortune of having punctures caused by thin metal wires. I believe these wires are almost always the remains of shredded car and truck tires. As such they are usually steel/magnetic so could their orientation on the road be vertical due to static charging? Just a thought, thanks for reading.


Dear Stuart,

It’s an intriguing thought. They are probably usually well anchored to the road, thus dissipating the load. In low humidity on concrete or asphalt, I imagine there may be a static charge that straightens them after a dry tire has passed through.

Dear Lenard,

My favorite thing about the Tech FAQ is how an obscure random topic can attract more reader feedback and additional in-depth analysis from you. While reading the last question and answer on flat steel wires (8/30/22), I remembered something I had seen in the early days of online cycling forums (Usenet newsgroups). The late Jobst Brandt was there, both for writing authoritative explanatory articles and for not willingly suffering fools. He wrote that steel wires are more likely to cause rear punctures because the wire (or other sharp debris) can be kicked up by the front tire and then puncture the rear. (Source) I wanted to share this and see if this reasoning makes sense to you.


Dear Keith,
Cool! I’ve always had a lot more flat tires at the rear than at the front. I have generally associated it with the higher load on the rear tire and often the higher level of tread wear on that tire. This is an interesting concept that the front tire could turn sharp objects around so that the rear tire would be impaled. Too bad Jobst is no longer with us to offer pearls like this.


Dear Lenard,

I read your article today with great interest on the application of the Wolf Tooth Road Link to achieve greater gear capacity

I have a pair of 2015 ish road bikes with SRAM Red ETAP (not AXS). One is short cage with a 52/36-11-28, the other WIFLI with a 52/36-11/32. Would love to have bigger climbing ranges on that one (Shenandoah is right here…!) without sacrificing the 52-11 for those critical sprints. I know I can spend $700 to get an upgraded derailleur, but that’s a lot of money. Will the Wolf Tooth Road Link do this for me? Is there another alternative?

put on

Dear Don,

Yes, the Road Link will allow you to use a larger rear sprocket. Of course, the further you move the rear derailleur away from the cogs, the less sharply it will shift on the smaller cogs, so your shifting during “those critical sprints” might suffer.

Other solutions? Well, you can often get your rear derailleur to accept an extra tooth or two on the larger cog by turning screw B more. This also results in slower shifting on the smaller cogs because the jockey wheel top is farther from the gables.


Lennard Zinn (, our longtime tech writer, joined VeloNews in 1987. He is also a custom frame builder and supplier of huge non-custom bikes , a former U.S. National Team rider, co-author of “The broken heart” and author of numerous books on cycling, including “Zinn and the art of road bike maintenance,” “DVDas good as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Introduction to Cycling: Maintenance Tips and Skill Building for Cyclists.”
He holds a bachelor’s degree in physics from Colorado College.

Follow @lennardzinn