sbslider

I recently (1 month ago) replaced my bottom bracket with a BB UN-55. Seemed to go together fine, and I thought I followed the installation instructions. Bike running nicely again.

Within the past week or so I have been getting creaking from my bike. Decided to check out the bottom bracket installation, seemed like the drive side was not tight, so I tightened it to ~70 foot pounds. I no longer have the installation instructions, and have not been able to find them online. I also tightened the non drive side to 50-60 foot pounds. Cranks back on, and it rides very nicely again. So I went for an hour ride, including a 1500' climb. As I approached home I started pedaling hard up a hill and noticed what seems to be the beginning of the creak returning.

I did a bit of research and found some folks prefer the Tange Ln-3922 over the Shimano part. While I am not excited to toss a month old bike part, I am thoroughly annoyed by a bke that creaks when I pedal it. I realize you all can't be sure I have diagnosed the problem correctly, but in general would I likely be free of this creaky pedaling problem if I switch to the Tange part? And is the installation tool (funky ribbed socket) the same?

RoadGuy

Did you put grease on the bottom bracket threads and in the adjustable (non-fixed) cup before you installed them?

FBinNY 

given that the BB is so new, it's possible, or even likely, that the creak is the lockrings moving up and down in the frame. If you remember that the threads were very loose and the rings threaded in easily, that would tend to confirm this.

This cause can often be solved using a fibrous pipe dope on the threads. The fiber material fills the available space preventing movement.

If you want to confirm my theory, apply a drop or two of penetrating oil between the cups and frame (no need to take apart), and go for a ride. If it resolves or if the sound changes, then you know the problem and can take care of at your first convenience. If the creak resolves, wait a while and see how long it stays quiet. If a while, you can repeat the treatment for another temporary fix, or deal with it at your option.

Bill Kapaun

You might also look up proper torque specs!

AnkleWork

Did you use a torque wrench to attach the crank arms?

Al1943

+1
70 ft/lbs sounds way too high.

Does the creaking continue while standing on the pedals or only when seated?

LesterOfPuppets

+2. BB cups don't need quite that much torque.

I'd guess it's from crank bolts not tight enough before it's BB cups not tight enough.

hueyhoolihan

i agree. i would look at the crank/spindle connection. there may even have been some slight rounding involved after the new BB was installed, which could make things difficult to fix.

if, after tightening, the creak goes away, i would recommend re tightening them after each ride for a while until the creaking goes away for good.

cale

I used to carry a wrench with me on rides because of loose cranks. Sometimes buying a new crank isn't a priority especially when giving the bolts a nudge on a regular basis isn't tough maintenance.

sbslider

I will try to hit all the responses.
I applied anti seize to the cups, not grease.
I tried the penetrating oil, no help.
I could not fing torque specs for the cups, so if you know please pass them along.
I did not have a bit for my torque wrench for the crank bolts, but now I do. I can not find documentation for the truvative 8 mm bolts, when I find that I will torque them properly and see what happens.

edit - started by torquing to 40 foot pounds, bolts did tighten a bit but I still hear a creak under heavy load.

sbslider

I found the torque rating stamped on the bolt (nice), 35-40 nm. This translates to 30 foot pounds max. So I am again guilty of over torquing, but still have a creak.

davidad

Torque Specifications - Bicycle Tutor

mtbikerinpa

Torque of the arms notwithstanding, the arm interface should be cleaned thoroughly and inspected for deformation. Any lines or deformations can lead to problems under load. All it takes is under-torquing and one hard ride to put enough damage in to cause problems.

sbslider

Nice, this is a keeper, thanks!

sbslider

I removed the cranks earlier today and leaned them before reinstalling. I did not inspect for lines or deformations super carefully, but I did not note anything unusual. What the heck, I removed them again. I can see what I would call an imprint the the mating between the spindle and the crank. Definitely no significant deformation, but a noticeable "print" of the spindle on the crank. Is this normal?

note: bottom bracket cups properly torqued now.

mtbikerinpa

It does not take much to make a creak. The usual rule of thumb is if the deformation can be felt with a finger nail it's borderline/reject. If it will keep the surfaces from making a fully square mate it will allow some movement and thus a creak. This is also a related issue that prompted industry designs toward multi-spline variations.

sbslider

So time to toss the cranks or live with some creak under load?

LesterOfPuppets

I've gotten slightly creaky cranks to go silent by slightly overtorqueing crank bolts.

I find a lot of times freshly installed square tapers will creak a bit after riding a few miles on them, so I install, ride about 5 miles mostly standing to pedal, do a couple bunnyhops, then come back and tighten crank bolts again.

mtbikerinpa

Sometimes you can get that to work. As long as you do not overtorque the bolt itself and snap it, the arm can take a significant amount of torque past specification. If the bolt breaks however, its a real bug to fix. The bolts don't drill well and the bb spindle is very hardened so it doesn't tap well. Try it conservatively up to say 50-55 ft lbs and see if it changes. Wouldn't go past 60 though.

sbslider

Well it seems like the process has narrowed it down to either the cups or the crank/spindle interface. I suspect the latter. I just put it all back together again, and for the moment no creak. Since the creak loosened/properly torqued the bottom bracket, and removed/inspected/re-lubed the crank/spindle interface and properly torqued. If it begins to creak again, I will try the over torque. Regardless after a couple of days of commuting I will torque the crank bolts again.

Kimmo 

If you've cleaned the threads and greased all the mating surfaces of the BB, it shouldn't creak (especially when over-torqued a bit) unless there's something obviously wrong...

The square taper interface can sometimes creak too, but many folks (myself usually included) don't grease it, while others do. If you're in the former camp, you could try a bit of grease; AFAIK there's just a bit of a risk you'll deform the cranks very slightly and narrow your Q while putting your chainline a tad inboard if you go very hard on the crank bolts (reducing the friction on the tapered interface is understood to allow more of the fastener's torque to stretch the crank interface over the BB spindle).

hueyhoolihan

if indeed the crank's square hole has been rounded, more force than that specified by the manufacturer may need to be applied in order to fix the problem, as noted by LesterOfPuppets.

in essence, the crank hole has to be reformed by forcing the slightly rounded portion deeper on to the tapered square spindle. a type of poor man's cold forging, sort of. i've done this, and it worked on a vintage dura-ace crank that had been slightly rounded and was creaking like an old man's knees.

and if the crank arm is rounded there is no reason not to give it a try. after all, one would have to throw it away anyway. might as well try to save it, even if it breaks in the process. i wouldn't worry about the spindle, it's steel and the crank arm is aluminum. it has nothing to fear.

FBinNY 

To the OP.

The types of creaks you report can come from either he crank/spindle interface, usually on the left, or from the bottom bracket to frame interface (among others). Knowing which is the key to solving your problem.

Trained ears can often tell the difference, but not always, so you need a diagnostic method, such as the penetrating oil trick I outlined earlier. Another diagnostic is if you tried anything and it helped for a while. That would point to wherever you worked as being related. You mentioned that the bottom bracket seemed loose, and tightening seemed to help for a while, so I went with that. But working on the BB means the cranks were removed and replaced, so they're not eliminated.

Rather than take things apart and risk over-tightening them in an effort to be sure (or out of frustration), see if the penetrating oil trick works. You can also use it between the crank and spindle, but save that for a last resort, since that interface should be dry, or have the least film possible.

One place nobody mentioned that fools lots of people into struggling to fix the wrong thing is the pedal/crank interface. Whenever I treat a "BB or crank creak" I start by removing both pedals and replacing them with plain pedals known not to creak (I have a spare pair just for that). Or you can removing, cleaning and greasing the threads and flat face area on both cranks and pedals and replacing then tightening tight. Had you not pointed me toward the BB early on, I would have sent you there first.

sbslider

Good points FB, I agree. If/when the creaking comes back I will try the penetrating oil again. Thanks for the tip, that is a great diagnostic tool. I think that this point the pedals are a non factor based on what seems to have had an affect.

davidad

Don't retorque the crank arms. If it is done properly it is not necessary. Installing Cranks by Jobst Brandt