Ask a Mechanic no image

Published on April 28th, 2011 | by Evan

Ask a Mechanic – Wet Wheels, Mystery Creaks and Bottom Brackets

This is the second edition of a weekly column we’re running here at Art’s Cyclery 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 daniel.slusser@artscyclery.com.

Question: I own a trek Speed Concept 2.5 and my question is about the bottom bracket. It’s a SRAM Apex groupo and there seems to be noise coming from the crankset and there is maybe 100 miles on the bike. Is the Apex lineup a cheap set? I have heard the bearings in the bottom bracket aren’t very good. Your thoughts on the apex group?   From: Jamey

Answer: I’ve actually never dealt with a properly installed, non-defective component that was part of a mid-level groupo that made noise simply because it was designed to meet a specific price point. As such, I highly doubt that the creak on your Apex equipped bike is the result of poor production values. With SRAM in particular, it is my opinion that the biggest difference between the various road groups is simply weight as the performance is remarkably similar throughout their range (something I think SRAM should be commended for).

The first thing to do is to go through the checklist that I have typed out below. That said, high-end Trek frames made in the last few years make use of their BB90 standard. My experience with this standard is that the interface between the bearings and frame have little to no interference fit (depending on production run and year model) and can result in bearings that wobble in the frame and can occasionally cause noise. With that said, check out my instructions below and see if they are of help. Beyond these suggestions, the unique BB interface on your bike could be the issue.

How to fix that annoying bottom bracket creak

I will be honest with you; no one likes dealing with this type of problem whether they are a rider or a mechanic. That said, an experienced mechanic can likely get to the solution a lot faster and with minimal fuss. Something to keep in mind with all audible issues on a bike is that they come from a variety of sources.

Nearly every customer that has come to me with a creak issue over the years insists that the bottom bracket is to blame. They are technically right the majority of the time. Nevertheless, I would estimate this correctness to occur slightly less than 50% of the time. This means that the source of the creak usually lies elsewhere.

So, when diagnosing a creak I follow a basic procedure to narrow down the cause of the problem. First, I check the bike over to see if anything is obviously loose and do a basic safety check. I will correct whatever problems I find and then test ridethe bike only after removing various noise causing accessories such as pumps and bags.

If the creak is still there I check three specific areas of the bike in order to narrow down where the creak is emanating from. First, I ride the bike in the saddle and apply as much force to the pedals as I can safely while pulling the rear brake. Riding the brake keeps speed to a minimum so that if something fails catastrophically, my face won’t meet the pavement at a speed greater than 5 mph! If I hear the creak and it is unclear what the source is, I will do the test again but pedaling out of the saddle this time. If the creak goes away I know that the creak is coming from the seatpost or saddle.

Park Polylube is a great all-purpose grease for use on metal-to-metal interfaces.

The fix for this is simple and requires greasing or applying carbon paste to the components in this order with a quick test after each step: 1st the seatpost and seat collar, 2nd the seatpost head assembly and the junction between the saddle rails and the saddle shell. One or both should fix the issue.

If the creak persists when pedaling out of the saddle, the next area to check is the cockpit. Straddle the bike and torque on the handlebars radialy from side to side alternating the twisting force. If you still hear the creak then first grease the front skewer where it passes through the hub as this is a common cause of creaking, especially with Mavic hubs. If this doesn’t fix it then apply carbon paste to the stem and handlebar interface and re-torque it to spec. Still creaky? Grease the headset assembly and you have checked off the front end of the bike.

Now, only if your bike is still creaky when out of the saddle and not creaky when you perform the handlebar twist test, then the creak may be coming from the bottom bracket. However, if it sounds like it may be coming from the aft portion of the bike it may be a good idea to grease the rear skewer and the interface between the derailleur hanger and the frame. Before pulling the cranks and bottom bracket, make sure your pedals are greased and torqued. Then, torque the chainring bolts. If everything is secure, then you can begin disassembly of the crank and bottom bracket.

The Park BBT-9 Bottom Bracket Tool will remove any out-board bearing bottom bracket.

When you remove the bottom bracket, feel how much effort was required to unscrew it if it is an English bottom bracket. This is a good indicator if this is the problem. After removing it inspect the bearings for excessive play or rough spinning. If it is worn out, replace it. Now clean the threads on the frame and bb and re-grease them before reinstalling it to the manufacturers recommended torque value. Grease the spindle of the crank including the splined interface between the crank arm and spindle before reinstalling and re-torquing.

If all of this has failed to cure the problem, make sure there is not excessive wear to the chain or drivetrain and check for stiff or bent links in the chain that you may have missed in your initial inspection. All that remains after this is to grease the cassette and the freehub body. If that doesn’t solve the problem, get a second opinion to see if others can reproduce the problem. If they can’t, then you should schedule an appointment with your doctor who will then follow a more complicated set of instructions to resolve the issue.

It is important to remember that every bike makes noise, including mine, and it is something that has to be dealt with to a degree. The vast majority of these noises are completely benign, but it is always a good idea to get them checked out just to be safe.

Question: I had to load the bikes on the back rack of my truck and then drove for 14 hours in the rain. After unloading the bikes and starting to clean them, there ended up being quite a bit of water in the rims on both bikes. I had to take off the tires and tubes and shake the water out of the valve hole. I let the wheels sit inside with the valve stem pointed down overnight before remounting the tires and tubes. Any thoughts on why this happened or what the chances of this causing any long term damage are?     From: Chrisitain

Answer: It seems that the high pressure of the air flowing over the car forced the water into the spoke holes and/or the valve in the rim and then trapped it inside. You did the right thing to get the water out as this accumulation can really slow you down as well as cause corrosion and other issues inside your wheels.

The corrosion issue is most likely to come up if your wheel has brass spoke nipples, as this material corrodes much faster than alloy nipples. Once the corrosion has set in the nipples become brittle and fail.

You may need to replace your rim strips if your wheels get soaked.

With respect to your method for removing the water, I would suggest removing the tire, tube, and rim strip in order to allow the water to drip out of the spoke holes on the inside of the rim where gravity can help with the process. Another reason to remove the rim strip is if you are using a porous rim strip like Velox cotton rim strips. Once wet, the adhesive can go bad thereby allowing the rim strip to move out of place during a tire change exposing the sharp edges of the internal spoke holes to your inner tube causing a puncture. Even if this does not happen, cotton can absorb twice its weight in water and can add unnecessary rotating weight to your wheel. Finally, once the rim strip is saturated with water it is nearly impossible for it to dry out while encased between the rim and tube. This eventually leads to mildew that becomes a nasty surprise that will greet you at your next tire change!

The combination of circumstances that caused this problem for you is of course uncommon and unlikely to occur in most situations. However, the only way to avoid this should this situation crop up in the future is to put the wheels inside the vehicle or use a rear mount rack where the water will have a harder time getting in.

 

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.

Share Button

Tags: , , ,


About the Author

After a stint at Art's Cyclery's sister company Running Warehouse, Evan joined the Art's staff as a buyer in 2009. Evan has a Journalism degree from Cal Poly, San Luis Obispo and when he's not on his bike, which isn't very often, you'll probably find him surfing.



Back to Top ↑