Technical FAQ
Photo: Dan Cavallari | VeloNews.com

Technical FAQ: Will frequent indoor riding damage a carbon frame?

Bicycle manufacturers offer advice on using a carbon-fiber frame with an indoor trainer. Plus, can tire sealant corrode raw aluminum?

Have a question for Lennard? Please email us veloqna@comcast.net to be included in Technical FAQ.

Dear Lennard,
As winter approaches, lots of us are getting ready for smart trainer season. In the past winters I’ve paired my Serotta Ottrott with my Wahoo Kicker. However, I also have a full carbon frame (Colnago C60) and was curious how advisable it is to mount carbon frames onto the fixed bindings of trainers. I’ve heard that it can void warranty, but I see many videos of people riding carbon frames on trainers. Is this a case where carbon frames actually won’t handle the specifics stresses related being mounted on trainer or are manufacturers just being overly cautious? Does the carbon frame compatibility vary by manufacturer?
— Greg

Dear Greg,
Here are some responses from carbon frame manufacturers to your question.
― Lennard

From Specialized:
There is certainly something to this concern. The loads into a bike frame are totally different in the rear triangle on a trainer compared to riding on the road. In the FEA (i.e., Finite Element Analysis, a predictive computer modeling method of how a structure will react to applied forces) world we would say the constraints are different. We have a special lab test to double check for this situation since the ISO/CEN test is not an adequate predictor of trainer frame fatigue.

The popularity of Zwift over the past few years has certainly driven many of our riders to train indoors. I would recommend that a trainer user verify with the manufacturer of their bike via owner’s manual and web that their particular bike is suited to sustained indoor training usage.

A final note, since users are generally swapping out the rear wheel to put the bike on the trainer, there is a potential for problems and abuse of the bike. The rider should regularly inspect their bike and make sure the trainer use isn’t damaging the bike.
— Mark Schroeder
Engineering Director
Specialized Bicycle

From Alchemy:
I don’t see any reason not to [use a carbon frame], given that you are using the correct QR or axle mount. I use mine in a trainer all winter without worry or effect.
— Matt Maczuzak
Alchemy R&D Director
www.alchemy.bike

From Calfee (who repairs carbon frames of all brands):
There may be some older trainers that attach to the frame or dropouts in a manner that could damage the frame. But we’ve not seen any repair requests for such a thing. And it’s another easy excuse to not honor a warranty.
— Craig Calfee
Calfee Design, Inc.

From Ridley:
Using a Ridley on a trainer does NOT affect the warranty and the frame.
— Jochim Aerts
CEO Ridley, Belgian Cycling Factory
www.cyclingfactory.be

Tire sealant and corrosion

Photo: Rodger Steeper

Dear Lennard,
I have had two Fulcrum 2-way fit rims that have failed in the same way (see photo). It seems that the inner surface of the rim corrodes at the site where the serial number is etched into the anodized surface, leading to a hole that creates a leak such that the rim does not hold air with a tubeless tire. I have used only ammonia-free sealants (Slime tubeless sealant or Stan’s) allegedly designed for tubeless tires, but I suspect it is the sealant in direct contact with the aluminum at the etching site that is causing the corrosion and eventual failure.

Is this a common problem with tubeless rims, and should we be coating any etched areas with some kind of protectant before using these wheels? Would it be safe to place a piece of tape over the hole or use a tubeless rim strip to cover the hole to correct the problem?

Do you have any suggestions for sealing the hole to make the wheel usable again? The hub, rim and spokes are in good condition, so I would like to keep it in service if possible.
— Rodger

Dear Rodger,
You discovered a fundamental issue, namely that sealants will attack raw aluminum where there is no anodization to protect it.

Fulcrum (and Campagnolo—same company) 2-Way Fit rims are specifically designed for tubeless and require no rim tape, as they have no spoke holes penetrating the rim bed. The factory etched through the anodization in order to put in the serial number, and that became the place that the sealant attacked, since the raw aluminum was unprotected. Here are some answers to your question from sealant makers.
― Lennard

From Stan’s NoTubes:
It’s not the sealant; it’s any liquid. All sealants have water in them, and his unprotected areas are allowing it to corrode. (Not very good aluminum.) He can spray paint or use any tape that will seal the inside of the rim. Electrical tape will conform to almost any shape. He could even use fingernail polish or anything that will create a coating.
— Stan Koziatek
Founder, www.NoTubes.com

From Effetto Mariposa:
“Exposed aluminum doesn’t work well with the water contained in any sealant.
The best way to protect rims is adhesive tubeless tape (like our Caffélatex tubeless tape, one of the lightest in the market, 5.5 g in size M for a 29″ wheel).
A good tubeless tape is the best choice. While any adhesive tape will work in the short term, you really want a tape tested to stick to the rim even with the constant action of the liquid sealant.
— Alberto De Gioannini
Founder, Effetto Mariposa

Photos: Adnan Kadir

Dear Lennard,
My wife has a set of wheels with DT R460 rims. Over time, tire sealant (in this case, Bontrager TLR) gets into the rim body. When it hardens and breaks loose, it rattles inside the rim. It isn’t audible when riding, of course, but it’s easy to hear when I’m wheeling the bike around the garage.

There was a lot of sealant in the rim (see photos). At least I think it is sealant – it looks more like crystalized crack. Blasting it out with a garden hose did the trick. I think what happened is that the seal around the base of the valve was not very good and sealant gradually leaked into the rim. There was a period where the tire had a slow leak with no obvious source and eventually adding more sealant plugged it. I suspect this was it.

By the way, this rim actually had three layers of Stan’s tape on it.
— Adnan

Dear Adnan,
Thanks for the cautionary tale. People often don’t pay enough attention to the seal of the valve with the rim. Brushing sealant around the base of the valve before installing it can avert some problems like this.
― Lennard


Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder (www.zinncycles.com) and purveyor of non-custom huge bikes (bikeclydesdale.com), a former U.S. national team rider, co-author of “The Haywire Heart,” and author of many bicycle books including “Zinn and the Art of Road Bike Maintenance,” “DVD, 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 in physics from Colorado College.

Follow @lennardzinn