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 email@example.com. Today’s column offers tips on disc brake pad compound options and what to do if your pads are contaminated. Daniel also reviews how to take care of loose Sram GXP bottom bracket bearings.
I have a set of Tektro disc brakes that are really loud. I think the pads might be contaminated with oil or misaligned. I tried to equal out the wear on the pads with sandpaper and get rid of any contamination by washing them with soapy water, lemon juice (a freerider mag I read said that lemon juice was a good brake pad cleaner), and isopropyl alcohol, but none of that helped. I also interchanged pads front and rear but that didn’t help either. Would metallic pads be quieter? I hate annoying other riders with my loud brakes. From: Hill
It doesn’t matter whether they are metallic or organic, once your brake pads are contaminated, they have to be replaced. Whichever pad compound you choose, just be sure to keep oils, soap, and degreasers away from them. Water and dirt should be the only things that should ever be allowed to touch your brake pads. I won’t even touch the braking surface of the pads with my bare fingers! Metallic pads will give you the most stopping power. They are a little bit noisier than properly working organic pads but are far quieter than a contaminated organic pad, or an organic pad that causes loud vibrations throughout your frame.
I recently bought a Kona Big Kahuna 2013 that came with a Sram X7 2×10 crankset. The bottom bracket shell is 73mm and I noticed that there was no spacers on the drive side or the non-drive side of the GXP bottom bracket. I also noticed a gap between the crankset and the drive-side of the bottom bracket, is this normal? My friend owns a Kona Kahuna 2012, it came with a Sram X7 3×10 crankset, the bottom bracket shell is 73mm also, no spacers, and there’s a gap between the crankset and the drive side bottom bracket on his too.
When you hold the right and left crankarm together with your hand and jiggle it, there’s play between the bearings and the crank and the plastic cover on the drive-side of the bottom bracket pushes outward. I put two spacers on each side of the bottom bracket and it stopped the play, and now there’s no gap at all between the crankset and the bottom bracket, and it spins smoothly. Is this setup advisable? Can it work on my bike too? From: Tan
You have the spacers setup correctly on your bike. There does not need to be any spacers between the bottom bracket shell and the bottom bracket cups when using a Sram GXP crank with a 73mm English bottom bracket. The gap that you see on the drive side is normal. Any play that your friend may be experiencing in his crank is due to worn bottom bracket bearings. Using spacers, like your buddy has on his bike, can mask this problem by taking out some of the play. The right thing to do is to install a new bottom bracket. They are fairly inexpensive and easy to install. If you are riding frequently and hard in inclement weather, one year is about how long you should expect a steel OEM bottom bracket to last. Chris King makes a great bottom bracket that you might consider if you are looking for something that lasts a bit longer.
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. When he is not riding, wrenching, or writing he enjoys spending time with his wife and two children.