banquo372

so about 2 months ago i got a brand new trek 7.1 FX and its been making this clunking noise pretty much ever since i bought it. i took it to the lbs where i bought it and he keeps adjusting the derailleurs because he thinks its that but i dont think it is. im very new to bikes and i have no idea how to fix anything so i need your help.

https://www.flickr.com/photos/8868329...in/photostream

theres the video and sorry its kinda windy and it was filmed at night. also it is not the bottle cage or water bottle as the noise happened before i added that to it. this happens randomly both only when i go up hill and down hill while pedaling but never while coasting or when i pedal it with my hand while lifting the rear wheel up.

bike works perfect other than the noise but it is very very annoying to see a brand new 500 dollar bike do this. i know its impossible to diagnose the exact problem online but any suggestions are welcome.

fietsbob

Walk more..

pierce

oh boy, lets play 20 questions... lets see, I'll open with the first 2...

is the noise happening at the cranking speed or the wheel spinning speed?

does it happen when you coast, or only when you pedal?

banquo372

Speed of cranking speed and only when i pedal

dawes56

I had a noise like that... after about a month I discovered it was coming from my helmet straps..it was
in time with pedaling.

Good luck.

Pete

banquo372

yeah ive heard so many stories of these noises coming from silly things, but unfortunately i do not wear a helmet while i ride my bike. i really need to though. thanks for your reply though dawes56!

banquo372

also one more update: its not coming from either of my saddle or my pedals. i just rode it and it still made that sound while standing and earlier today i regreased my pedals and made sure they were tightly on.

pierce

well, that video is pretty much useless...

ok, next 3 questions...

does it only happen in some gears, or in all gears? try at least the middle and big gear in the front, while using a middle gear in the back.

does it happen only when you're pedaling hard, or even if your almost coasting and pedaling very lightly?

if you pick up the back wheel while stationary, and pedal with your hand, can you find the source of the noise?

banquo372

yeah i apologize for the crappy video.. it happens in some gears but it doesnt seem like all of the gears do that. the noise is very apparent in the gear combo that i most often use which is 2nd in the front and 5th on the back and also alot while im in the 3rd front gear.

it usually happens while i begin to accelerate from a turn or if i am completely stopped and i begin to go again. also it happens alot going up the hill too.

it doesnt happen at all while i pedal with my hand.

pierce

ok, so its load dependent. I assume by '3rd front gear' you mean the big chainring ?

does it always happen at a particular point of the pedal cycle? like, when the righthand (drive side) pedal is all the way back, or all the way forward?

banquo372

yes sir, big chainring.

ummm im not sure, i tried to look to see if it does but i didnt pay too much attention to that. it happens with each pedal stroke though. but i think it makes the noise when each pedal goes forward. so ill pedal forward with right foot *noise* go forward with left foot *noise*. so pretty much with every downforce the noise occurs.

just out of curiosity what would be the issue if it did occur at a particular point? would it be an issue with the chainring then?

pierce

hmm, if its happening TWICE per full turn of the crank (eg, once per pedal side), I'd be looking at the bottom bracket, and or crank-to-bb attachments.

is it sort of a "Crink" or 'creak' sound?

pierce

ah, test for BB. bike stopped next to sturdy stationary object like sign pole or something that you can hold onto. sit on stopped bike. with pedals at 3 and 6 o'clock, stand on pedals and bounce your weight a bit. spin pedals backwards 18 degrees so the OTHER pedal is forward, and bounce your weight. hear any klink or kreak sound? its a BB related issue. you might 'feel' this creak/crink in your feet too, it will usually only happen once for each time you put one pedal forward and put your weight on it.

banquo372

if i were to describe the sound its more of a clunk, similar to the sound when the chain engages the freewheel when you start pedaling from a stop or a coast. its not a creaking noise but more of a thump. when i first rode the bike i at first thought it was a distant hammering of construction workers. but i will test out your BB test that you mentioned.

dynaryder

First thing I'd do is tighten down the pedals and cranks. Here's some helpful info if you don't know how:
https://www.parktool.com/blog/repair-help

Next,just to rule it out,I'd lube the rear derailleur's jockey wheels. Just put a drop or two of chain lube in the little axle in the center of each pulley wheel. Might fix it,might not,but takes only a couple seconds,won't do any harm,and will rule something out if it doesn't work.

banquo372

alrighty thanks for your suggestion ill definitely give it some grease. would you recommend any grease? i need to buy some and never have experience with it

evilpulse8

Sounds to me like you are either cross chaining or the front derailleur is rubbing against the chain. I had a similar problem with my road bike on my rear dura ace derailleur. Somebody had bumped the derailleur in the garage and bent the derailleur arm and hanger. check that rear pulleys that they are aligned straight with the cassette.

pierce

I use green marine waterproof grease, available in most any auto parts or boat store. it comes in cans or in grease gun tubes. I have a grease gun for trailer hubs, so I just squirt a gob out of that onto a clean paper towel when I need some.



others: if its twice per pedal turn, I doubt its anywhere near the rear end. re: oiling derailleur idle pulleys, I don't like to put oil on the outside of those, take the little axle screw out, there's probably a bushing and two dust caps, clean all the parts, and put grease on the bushing and inside the dust covers, then reassemble. for sure, bent rear derailleur hanger inspection should be a regular thing, it just takes a glance at it to see its aligned or not with the rear cassette when its on a middle cog. if it is bent, its better to take the hangar off the bike and straighten it with a vice and a small crescent wrench instead of trying to unbend it via the derailleur.

dynaryder

For the jockey wheels just use chain lube.

Tsagg

From my admittedly limited experience with bikes, my guess is a subpar component in the crank or BB. With so many grades of components, it is the main reason I paid more to go to a 7.5 FX...to get the higher end components. I'm hoping I am wrong and you can successfully get the bike tuned at LBS once the source is found. Good luck!

Burton

Could be the crankset wasn't torqued properly and is flexing enough under load to contact the derailleur or just to make a noise on its own. Doubt that the crankset itself is out of round otherwise the problem would be continuous. Its a warranty issue - have the shop retorque the cranks just to be sure. If its that and it goes too long they'll have to replace them anyway so its preventative maintenaince.

giantcfr1

My turn to have a guess. On my road bike I had a noise that I swore was coming from my BB / Crank area. The guys riding with me said the same. It was when I accelerated or on an incline. Two bike shops also told me that it was from either my BB or Cranks. Anyway, at the one shop I took the cranks and BB out, greased where necessary, and rebuilt it. The noise was still there. Then it dawned on me...check the cassette. I took the back wheel off, and bugger me, the cassette was loose. Problem fixed.

frantik

You've asked at least two questions that he answered in the initial post...

RollCNY

Easy test for loose crank arm or BB. I have only had it work well on square taper BB's, but I think that is what you have.

Be off the bike, on the drive side. Line up the drive side crank arm with the seat tube. Wrap your hands around the crank arm and the seat tube and squeeze. You won't necessarily feel anything more, even if the BB is loose.

Rotate the crank 180 degrees so that the non-drive side crank is in line with the seat tube. Now grab that crank arm, and squeeze it toward the seat tube. If something is loose, you will usually see decent movement.

If something does move, keep repeating the test to isolate.

zandoval 

I finnaly found one of those Thunk Tunk type sounds to be iminating from my freewheel - Its a long story that involved the systematic upgrade and repair of vairous parts of my 80s UNIVEGA - Each adjustment resulting in eliminating one particular sound but the most anoying and fleeting sound was as yours - Not my casset but my freewheel - I just changed it out for another and have not isolated just why it was making that sound - I suspect that some of the small bearings in the free wheel have failed or gauled...

Hey good news is that I have been over my bike in explicit detail and now it rides smooth as real butter...

Tuto Ballencia...