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Technical FAQ: Valve stems, wheel migration, and more

  • By Lennard Zinn
  • Published Jun. 4, 2013
  • Updated Jun. 5, 2013 at 2:36 PM EDT
There are a variety of options for valve stems, ranging from short to long and with or without valve extenders. Photo: VeloNews.com

Valves and wheel migration

Dear Lennard,
I have a set of American Classic wheels with 34mm deep section rims. In your opinion, is it better to run long-stemmed tubes or use regular stemmed tubes with a valve extender? If you like extenders, which ones do you prefer?
— Charlie

Dear Charlie,
From your use of the word “tubes,” I assume you mean that these are clinchers. In that case, long valve stems on the inner tubes is the best solution.

Unlike with tubular tires, the issue with inner tubes, at least butyl ones, is that very few of them have removable valve cores. QBP’s Q Tubes have them, but that’s about it that I’m aware of, other than expensive latex inner tubes. With a short valve without a removable valve core, you’re stuck using a straw-type valve extender, which is certainly a step down in ease of use and reliability from a long valve stem.

If your tubes have removable valve cores, then you can use a double-threaded valve extender, which screws in where the valve core was (after you remove it, of course), and then you screw the valve core into it. It behaves exactly like a long valve stem. This is generally the solution required for tubular tires, since the choice of valve stem length is usually minimal or nonexistent.
— Lennard

Dear Lennard,
I have a road bike rim with the valve stem valve slightly off center. I’ve been getting flats and was wondering, is there a way to re-align the hole?
— Don

Dear Don,
You can carefully file the hole with a round file to move the wall of the hole over enough that the valve can be centered. Obviously, don’t file any more than you have to.
— Lennard

Dear Lennard,
Two Mavic rear wheels (older Kysrium and newer Carbone) when installed on my BMC Team Machine, migrate toward the non-drive train chain stay (once I start pedaling) and will eventually rub; no problems with Zipps on the same bike.

Mavics are fine on 2005 Giant TCR … any ideas why this is happening?
— Stephen

Dear Stephen,
I would guess it’s a combination of the texture at the ends of the axles and the wear inside your right dropout.

This is a common thing to have happen with mountain bikes with aluminum dropouts and certainly has a lot to do with the move to through axles rather than hollow axles with quick-release skewers on the rear of mountain bikes. The axle will tend to seat forward into the dropout slot. While I have also seen it happen with steel dropouts, it’s much more common with aluminum ones. On many bikes, half of the thickness of the dropout is the dropout itself, and the other half is the derailleur hanger bolted onto the outside of it. And the axle stub only sticks out to half the thickness of the dropout, so even replacing the derailleur hanger has no effect, since the axle does not stick out far enough to be in its groove. While I haven’t seen it happen with carbon dropouts, and I don’t know if your BMC has them or not, I can certainly imagine it happening with them as well.

My guess is that if you look inside the right dropout, you will see wear toward the front of the slot. If you hold the end of the axle in there, you will find that it has more freedom to move forward on that bike than on your Giant. And I further hypothesize that the gripping surface at the ends of the axle faces that meet the dropout faces are significantly different. I would guess that the Zipps have a larger area of contact than do the Mavics and hence are less able to slide forward under pedaling pressure, due to this higher friction. Furthermore, the clamping force on the skewers you have on the Zipps may be higher than on your Mavics.
— Lennard

Dear Lennard,
I have just bought a 2012 Cervelo R5 and put the ENVE 3.4 clinchers on it. With the 25 mm tires, the clearance to the frame is super tight. In fact whenever I ride on any dirt, you can hear the frame scraping the little bit of dirt off the tire. What is a safe, or better yet unsafe, level of clearance? And does it help to decrease air pressure or would the added tire width just exacerbate the issue? I love each of the pieces separately, but they are making me nervous together.
— John

Dear John,
Reducing tire pressure would make little difference, I suspect. The tire’s width would not increase where the tire passes the stays, and it would probably not decrease significantly, either.

Once you wear through the clear coat, you are actually wearing down the carbon. An “unsafe level of clearance” is an amount that in normal use results in wearing through the clear coat and into the carbon.

If you were to put a 23mm tire on that wide rim, it would still give a broader contact patch than on a standard rim, and you could still probably run the 25mm in the front for better handling on dirt descents. You certainly would not want to stop riding dirt roads, but, for whatever it’s worth, I’m happy enough riding a lot of dirt on 23mm tires (with standard rim width).
— Lennard

Campagnolo factory tour

Dear Lennard,
I just read your recent article about the Campagnolo factory and was really surprised that the workers were not wearing any safety gear, especially not even any eye protection. Is this common in Italy?
— Leo

Dear Leo,
Here’s the response from Campagnolo:

Campagnolo is involved on a daily basis in complying with Italian and European rules as far as safety, environmental and health issues in our working places is concerned. Such rules are among the most restrictive in the world. Furthermore, we are active in prevention and protection, aiming at continuous improvement to achieve a zero risk level. In Italy/Europe, the approach is first to cut or reduce factory risks and then to protect workers from any residual risk. So, all workers are provided with individual protection tools and garments as for the existing rules.

Following the actual standards and guidelines, activities to safeguard workers safety have to privilege first of all the areas with operating machines and tools to reduce as much as possible or to eliminate any possible risk. Then, every worker has been instructed, has available, and is using specific individual protection tools based upon a specific risk assessment and the specific manufacturing process he/she is following. For instance, in the Mechanical Workshop every worker involved in production is requested to wear safety shoes and a specific working suit. If needed, depending on the kind of production and based upon specific risk assessment, the worker might be requested to wear gloves, protective glasses, anti-noise headset, etc.

Considering all the measures applied in the factory, since the residual risk is close to zero, the people visiting the factory and following the indicated yellow routes on the floor are not requested to wear any protective shoes.
— Lorenzo Taxis
Group Marketing & Communication Director
Campagnolo Srl

Dear Lennard,
Your article on the Campy factory tour brought back some of my fondest memories. I was working in the south of France in the summer of ‘99. I used to see groups of Postal riders on the roads in and around Nice. Anyway, I emailed Campagnolo and asked for a tour and, lo and behold, they granted me one. My fiancé (now wife of 12 years) and future mother-in-law experienced a most wonderful tour of the factory. I swear they showed me everything! I think I heard angels singing when I walked in!

Best memories: factory bikes with campy parts; seeing the pro bikes (testing after a season); and seeing little old Italian women polishing cranks (while smoking cigarettes with 1 inch of ash hanging off!).

Thanks for the great article. I still hope Campagnolo can be competitive in today’s market. I haven’t ridden Campy since friction shifters.
— David

Tip for noisy rollers

Dear Lennard,
It has been a particularly miserable spring here in Western Canada, and I have, as a result, spent a lot of time indoors on rollers (fortunately there’s lots of ice hockey on TV). In the last few weeks, however, my aluminum rollers developed what started as a squeak and eventually grew to a horrible squeal. I couldn’t figure out how to get rid of it: new tires, old tires, higher/lower pressure, do a road ride and then come back in — and there’s no really helpful advice on the Internet, except to turn up the volume on the TV. It was driving me nuts.

Anyway, I finally solved the problem by putting a little bit of candle wax on the drums (I use an old set of wheels/tires, so I wasn’t particularly concerned about what the wax would do to my tires). Not only is the squeal gone, but my workout corner in the basement now smells faintly of vanilla! So, this may be a standard solution that most everybody already uses, but in case there was another reader out there suffering with noisy rollers, I thought I would pass along my experience.
— Ben

FILED UNDER: Bikes and Tech / Technical FAQ TAGS: / /

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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