I had just bought a new mountain bike and really enjoyed my first few rides on some trails near my house. At first I couldn't be more pleased with it. The bike rode great and was a huge improvement over my old one. Unfortunately, I quickly noticed a problem when climbing up hills. After each pedal stroke I heard a rather loud and annoying "creak". I'm used to most normal bike noises, but this one had me worried.
Of course a "creak" is usually caused by two parts of the bike rubbing together under pressure. The real question (and not so simple one at that) is which two parts. I could simply ignore it, but that is almost certainly a bad idea. Creaks always seem to get worse over time and can end up in something breaking catastrophically. I can still remember when a "creaking" stem on my bike suddenly snapped into two pieces (an experience I don't recommend).
After several disappointing experiences with local bike mechanics, I had already decided I was going to do all my own minor bike repairs. I was especially concerned about this particular problem because it only showed up while climbing steep hills. I couldn't make the problem happen on a bike repair stand or with the rear brake on. This meant that it wouldn't be easy for a bike mechanic to troubleshoot in their shop. I could easily see myself having to take the bike to the shop several times as they tried various "fixes". All the more reason to do it myself.
If you Google "bike", "creak" and similar terms you will find an overwhelming amount of information. Turns out "creaks" are a really common problem with multiple causes including:
- A cracked frame
- Bottom bracket shell / Bottom bracket bearing cups
- Chain ring bolts
- Crank arms / crank spindle
- Pedals / crank arms
- Rear wheel quick release too loose
- Seatpost / seat post clamp
- Saddle / saddle rails / saddle clamp
- Handlebar / Stem / Headset
- Loose rear cassette
I'll go over the steps I took to diagnose my problem, how I eliminated the easy stuff, then what I did that eventually fixed the problem (hopefully) for good.
First up, how I started the troubleshooting.
Step #1: Isolate the problem by "diagnosing from the saddle"
Given the variety of causes of creaks (or any problem really), it makes sense to try a few experiments in order to get a better idea of what might be the cause.
The first thing I tried was to see if the creak happened while I was "standing" and climbing. Sure enough, the creak continued even with my weight completely off the seat. This eliminated my saddle, seatpost or seatpost clamp as the cause.
The next thing I tried was climbing without putting any stress on the handlebars. This isn't as easy as it sounds, but I was able to get pretty close. Again, the creak remained. This eliminated my handlebar / stem and headset as a likely cause.
Both the seatpost and stem are really common causes of creaks (and easy to eliminate or confirm). In any case, my problem was clearly elsewhere.
Step #2: Eliminate the easy to fix stuff first
Since I had narrowed down the problem as much as possible while riding, it was time to start examining the bike in more detail on a bike stand.
Some "fixes" for "creaks" are easier than others. At some point it makes sense to simply try the easy stuff first no matter how unlikely. Save the complicated fixes for later when all else fails.
The first thing that I tried was to reinstall the pedals in the crank arms. Pedals are notorious from causing creaks when they are not installed correctly (plus they are under a lot of stress). I removed the pedals, cleaned the pedal threads, applied anti-seize (not grease), and re-installed them. I also was careful to tighten the pedals to the correct torque. Sadly, the creak continued. However, now I at least know the pedals are installed correctly and shouldn't cause me any problems down the road.
Next I checked some of the other less common causes. I checked my rear cassette and didn't notice any side to side play. Also, the rear wheel quick release was tightened with the proper force. I checked my rear spokes and didn't notice any that were loose or overly tensioned.
Finally, I checked my frame for any obvious cracks. I didn't spot anything (thankfully, as new frames are really expensive!).
Step #3: Make an educated guess
I'd pretty much taken the diagnosis as far as I could without actually starting to take the bike apart. Given that the "creak" sound appeared to be coming from around my cranks, I guessed that the problem could be one of three things in that area (chain ring bolts, bottom bracket cups or my crank arm). All of these involve taking apart the crank completely.
Note that even though the creaking sound seemed to come from the cranks, many people have discovered that sound can be transmitted along the frame of the bike. People have sworn that the sound is from their cranks and yet it ended up being something else entirely (like a loose rear cassette). Since I eliminated those causes already, I was ready to proceed with the cranks as the likely culprit.
Step #4: Do your homework before you pick up a wrench!
The first thing that I did was review the chapter on cranksets in my Park Tools' Big Blue Book of bicycle repair. It is an easy read and has a specific section that covers my style of crank and bottom bracket (FSA's MegaExo). However, any general bicycle book is bound to be slightly inaccurate even if it provides you with most of the background you need to get started. For the latest, most accurate instructions you need to keep digging.
Modern bikes are assembled from components by many different manufacturers (brakes, shifters, hubs, etc). You can get service information from your bike vendor, but sometimes they just have information about the bike frame itself. Any information they do have about components is often generalized so I would recommend using the specific component manufacturers' info first.
My frame is made by Gary Fisher and my Crankset is made by Full Speed Ahead (or FSA). Specifically I have the FSA "Carbon Pro Team Issue" Triple Crankset with their matching MegaExo BB-9000 bottom bracket. I went to both the Gary Fisher and FSA websites to get their service procedures / info.
Yes, I know some of you may snicker at me for "reading the instructions" (almost like cheating), but it more than paid off as you'll see below.
One other note: The only reason I checked the Gary Fisher website was to get the torque setting for the bottom bracket. Although FSA specifies the torque for reinstalling the bottom bracket, so does Gary Fisher (and they are a bit different!). More on this later.
Step #5: I disassembled the cranks and found four problems!
Here is a nice diagram of the FSA "Carbon Pro Team Issue" crankset and the FSA MegaExo BB-9000 bottom bracket:
Disassembly was relatively easy as I already had all of the tools I needed. Right away I spotted several problems, some more important than others:
Problem #1) Grease was smeared over everything inside of the bottom bracket (spindle, splines, alloy center sleeve). This is (IMO) both unnecessary and messy (the bottom bracket uses sealed bearings and the bottom bracket shell is also sealed).
More importantly, grease was used between the spindle splines (#9 in the diagram above) and the mating non-drive crank arm (#11). See this warning note from FSA instructions:
Problem #2) As I unscrewed the bottom bracket cups, I noticed that I had to use a lot of force to get them off (way more than I expected given the correct torque). My guess is that the cups were either over-torqued or they had started to seize. Note that even if you use grease on the threads, grease can dry out over time (which is why anti-seize is better). Over torquing the cups is a major problem because it could strip the threads and it creates too much pre-load on the bearings (both are very bad). I doubt the creak was caused by this, but I'm glad I found this problem.
Problem #3) I noticed that the chain ring bolts didn't have any grease on them. FSA does recommend using grease. This could definitely be one source of the creak. However the bolts didn't appear to be over-torqued and weren't loose (so at least that was good).
Problem #4) I noticed a missing "rubber shell spacer" as indicated in the diagram below:
It took me a while to figure out if this spacer (also called a crush washer) was important or not. Turns out it is mostly cosmetic and merely fills the gap between the bottom bracket cup and shell. Nevertheless, it seems like a good idea to have this in place to keep crud out of the threads.
Step #6: Get ready to reassemble everything
I had most of the tools I needed (see my previous post on do it yourself bicycle maintenance), but I still needed to order a few special things:
- Park Tool SPA-2 Pin spanner wrench -$10 (for the final nut)
- Park Tool BBT-19 bottom bracket tool - $18 (for setting proper bottom bracket torque)
- Loctite 641 retaining compount - $20
- FSA Mega Exo BB Crush washer MS145 - $3
BTW: For a good laugh and a step I DON'T recommend, read about my little experiment using acetone to clean bike parts on MTBR.COM (a great website!).
Step #7: Assemble the crankset, doing it right this time
Here are LOTS of pictures and comments from the assembly that show how much detail is actually involved in putting together the cranks correctly. This was actually pretty fun and went rather quickly.
Here are the chain rings and parts disassembled and cleaned:
I applied anti-seize to bolts and mating surfaces (using a q-tip because it is messy):
I assembled the chain rings and torqued bolts to 12 N-m (per FSA manual).
Here I hit a bit of a problem since my Park Tool TW-2 torque wrench (shown below) isn't accurate at the lower 20% of it's scale (which includes 12 N-m). Instead I used my smaller Park Tool TW-1 wrench to set the torque to 7 N-m (the maximum of it's scale), then manually added about 1/8th of a turn. This is probably close enough to the proper torque (I'm not about to buy a third torque wrench).
I was particularly concerned about over-torquing the rather weak alloy chain ring bolts. They have a reputation for easily being stripped (and in fact, I did strip one by accident). Be careful!
I cleaned and applied anti-seize to bottom bracket shell (both sides) before installing bottom bracket.
I hand threaded the right (drive) side bottom bracket cup (with middle spacer and one 2.5mm shell spacer). Note that I applied a bit of grease on the tiny middle spacer o-ring seals to help keep them from drying out (seemed like a good idea).
Now I torqued the right side cup. FSA specifies a torque range of 39 to 49 N-m. Gary Fisher specifies a torque range of 32.9 to 40.7 N-m (Yes, they are different!). I thought I'd play it safe and chose 35 N-m. It is a little low for FSA, but still felt plenty tight for me. I'd rather err on the side of not damaging the frame:
Now I inserted the inner alloy center sleeve from left (non-drive) side. This sleeve will press against the inner race of each of the bearings.
When the left cup is later installed, the difference between the cup torque and the (opposing) crank fixing screw torque should determine the final pre-load on both bearings (since they are sandwiched between the two). This is another reason why torque is so important. Improper torque will result in improper bearing pre-load and early life failure of the bearings (IMO).
Now I hand threaded the left side bearing cup into place. When fully threaded into the frame, the left side does NOT mate flush with the frame (unlike the right side) because it will be held apart by the greater width of the inner alloy sleeve. This leaves a "gap" that is filled in by the crush washer (which you can see below).
When you torque the left side not only will the cups be secured into the frame, but the inner alloy sleeve will be applying an unopposed outward force on both inner bearing races. When the cranks are later installed with the crank fixing screw, an opposing force will push the bearings back from the other direction.
Now I torqued the left side to 35 N-m.
Now the bottom bracket is fully installed. If you rotate one bearing, the other will spin too as they are now physically "connected" and pressing against each other via the inner alloy sleeve.
NOTE: Isn't the hollow bottom bracket design with it's external bearings cool? I think so.
Now it is time to install the cranks.
Be sure to THOROUGHLY clean the spindle and crank splines so that there is absolutely no greasy residue to interfere with proper Loctite 641 adhesion. I used Simple Green first, then finished it off with two or three washes with electronics contact cleaner. FSA recommends Acetone, but some suggested this might be better (see my link about my "accident" with Acetone above).
I installed the first of two metal o-rings on the crank spindle before sliding it into the bottom bracket.
I GENTLY slid the cranks into the bottom bracket. There is an inner bearing dust cover that you need to make sure you don't damage on the opposite side of the bottom bracket.
Next, I installed the second metal o-ring
Time for the Loctite 641:
Here you can see that I applied a thin layer of Loctite 641 (orangish color) to the inner and outer surfaces of the splines.
I pressed on the left crank arm until it was flush with the bearing cup.
Here I applied blue Loctite 242 (medium strength thread locker) to the crank fixing screw. I installed the inner washer too (part of the self-extraction assembly).
Next, I hand threaded the crank fixing screw
Now it is time to torque the crank fixing screw. FSA specifies a torque range of 44-54 N-m. As this is 5 N-m greater than the torque for the bearing cups, I assumed that I should add 5 to the 35 N-m that I used. Again, I figure it is the difference (5 N-m) between the two torques that creates the final bearing pre-load.
So I torqued the fixing screw to 40 N-m. This is plenty tight and the blue loctite should keep it from ever coming loose by accident.
Here I inserted the last washer and nut (for the self-extracting crank fixing screw - nice and simple design!)
Now I used the pin spanner wrench to snugly tighten the nut.
IMPORTANT: Now leave the bike undisturbed for 24 hours for the Loctite 641 to fully cure. I waited about three days just to be sure.
Step #8: Test ride and no more creak!
Now for the fun (and nerve racking part), the test ride to make sure it is fixed! After all that effort, I admit to being more than a little worried. However, I told myself that I had learned a whole lot in the process and was definitely confident that my bike cranks were reassembled correctly (fixing a number of problems and preventing further issues down the road).
The good news is that there is no longer any creak. The only bad news is that I'm not totally sure which of the steps that I performed above was the final fix (only the nerd in me really cares). If I were to take a bet, I'd put my money on the use of loctite 641 v.s. grease. My second guess would be the use of anti-seize on the chain ring bolts. In any case, the problem is now fixed and my cranks should be good for probably thousands of miles to come. The only follow up that I need to do is to check the torque on my chain ring bolts after a few rides to make sure they are staying tight.
I could have taken my bike into a shop to have them fix this, but based on my experience I doubt that many mechanics would have gone to the trouble I did to fix the problem. I would have been out time and money with no guarantee that they would eventually find the right fix. Furthermore, it reinforced my opinion that a bike is a precision machine that deserves quite a bit more respect that it usually gets!