Welcome to our Ask a Mechanic column where our expert mechanic Daniel Slusser answers your bike maintenance questions. If you have a question for Daniel, please post it on our Facebook Wall or e-mail Daniel directly at firstname.lastname@example.org.
Question: On a recent ride I was taken out by a distracted driver and laid down my bike. The damage doesn’t look too bad. I am riding a Specialized Tarmac SL2 with all stock parts. I am concerned about the possibility the carbon may be damaged and I want to know what to look for so I can be sure my bike is still safe to ride. From: Jacob
Answer: You have my sympathy Jacob. Cyclists are unfortunately treated as third-class citizens with respect to transportation in the United States. Pedestrians are of course the second-class citizens. It seems like motorists can run down cyclists with near impunity while only receiving a fine for their misdeeds. Pedestrian homicide is merely frowned upon and likely to result in a felony charge of some kind, while killing another driver will certainly land you in serious trouble. Before this rant gets out of control I will do my best to focus my aggression on getting you riding again.
Ok, focus… You need to make a thorough inspection that includes removing the handlebar tape, handlebar, stem, and fork from the bike. Inspect each part along its entire length while paying special attention to clamping areas and the fork crown. I use a flashlight to help expose any cracks that may be hiding among the black fibers. Any areas found that are cracked, crushed, or dented should be replaced. As expensive as this may be, it is far cheaper than medical bills or reconstructive dental work.
While you have the fork off, shine your light inside your headtube to look for any potential damage that was invisible on the outside. Then check the rest of the bike over from stem to stern and look for anything that is damaged or out of place. The flashlight is your friend on this task as well if your bike is painted a dark color.
If you still don’t feel good about the bike after looking it over your Specialized dealer can offer you a crash replacement frame and fork at a deeply discounted rate that often is close to half-off the retail price. Just keep in mind that carbon bikes are amazingly strong. It takes either a truly massive hit to do one in or a very focused smaller impact that is far less common. A careful inspection will help you avoid the latter of the two.
Soldier on Jacob and keep smiling.
Question: I need some lower gears for my road bike for some extended steep roads I will be doing on my next riding trip. Currently, I am running Ultegra 6500 10 speed shifters with a 50/34 compact crank and an 11-28 cassette. Is there anyway I can use a mountain cassette? Do I need a triple derailleur? From: Chris
Answer: Bass… How low can you go? Death row? If that reference got past you then click here. There is an easy solution to your problem that will enable your dreams of masochistic climbing bliss along the world’s steepest roads.
What you need is a 9-speed mountain derailleur to replace your Ultegra unit. Don’t be tempted to try a 10-speed mountain derailleur as they utilize a different cable pull ratio and are incompatible. The 9-speed derailleur will work with cassettes with a 36t low gear which will give you a more than low enough gear for any paved road.
Keep climbing Chris, all the way to the stars!
Daniel Slusser is a professional bicycle mechanic with over ten years of experience. He holds a bachelor’s degree in business administration from HSU and a master’s degree in history from Cal Poly University. When he is not riding, wrenching, or writing he enjoys spending time with his wife and two children.