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Lately, during the removal of my old tubular from the rear wheel, a layer of carbon stuck to the tyre. I’ve been using XXX-Light rims from Bontrager for four years now. The first tyre had been fixed with a Tufo gluing tape. The second one with Continental tyre glue. When removing the tyre a layer of carbon happened to delaminate. My dealer let me know that this was normal and not unusual, whereas the manufacturer replied that I should get in touch with my dealer. A broken off thing cannot be good for the stability of a wheel – all the more when I ride downhill at 100 kmh. Shall I further use the wheel or is it broken?
Reply by Dirk Zedler, TOUR technology expert and bicycle expert
The phenomenon is not unfamiliar to us. We stated delaminations of the upper carbon layers on wheels of our test bicycle fleet of several manufacturers. The crux with tubulars is that on the one hand the tyre has to be secure on the wheel, even under extreme conditions, e.g. downhill rides with high temperatures. On the other side the wheels are supposed to be as light as possible. After several accidents due to detached tyres, including tyres which had been glued with Tufo gluing tape and standard tubular glues, better functioning gluing systems were developed, e.g. the Conti tyre glue. If, however, the carbon rim has not been finished one hundred percent, i.e. the upper layer is not sufficiently covered with resin and hasn’t hardened as it should, carbon layers can delaminate during removal of the tyre. Without a closer inspection, however, I cannot give a final statement on the basis of your description alone. To do so, I would have to check the number of carbon layers delaminated. As far as no more than one layer of carbon is affected without any substantial severe damage, I do not see a fundamental problem in further using it. However, be sure to glue your new tyre carefully and to check the wheel more frequently in future. Tyres which have come off from bikes of your test fleet are re-glued by us very carefully or new tyres are glued – which made the wheels safe. In general, it is however advisable to check carbon wheels carefully and regularly. They might also be affected by heat warpings in the brake flanges or torn spokes.
Nuernberger Zeitung, 2020/06/03
Frankfurter Rundschau.de, 2020/06/01
May 19, 2020