jcwitte

I have a Trek 520 that was new in August 2005 and I use Speedplay Frogs. It has about 2500 miles on it. I just changed out the chain and greased the pedal bearings. I know the chain should last longer, but I wanted a fresh chain and some spare links for my upcoming loaded tour. Now, there is an intermittent grinding sensation in the down stroke on each side. I do not hear anything, but it is annoying. It usually comes up when when pushing higher gears rather than while spinning. I didn't mess with the bottom bracket at all and the vibration/grinding sensation didn't start until after I changed out the chain and greased the pedals.

wonkemtel

you didn't mess with the BB, but could it be the BB?

maybe not...just close to what just happend to me.

powers2b

Repack or replace the BB bearings.

Enjoy

jcwitte

What happened to you and how did you fix it? Something with your BB? I have a Shimano LX FC-M580 Crankset (44-32-22) with an integrated BB.

HillRider

Did you get the proper width chain? A too wide chain could interfer with the adjacent cogs and produce the noise. Is the chain rubbing on the front derailleur cage? Limit screw adjustments should fix that.

jcwitte

I have the correct size chain. There is no rubbing on the derailleur. Also, there is no "Noise" it is just a grinding "Sensation" that I can feel with my feet every once in a while (mostly as I push the higher gears and then nothing when spinning).

Landgolier

Sounds like a bb, but you said you repacked the pedal bearings so maybe it's there. Swap the pedals with a friend's bike and see which one has the grinding.

jcwitte

There's an idea. I have some platform pedals on my beater bike. I can swap them out and hopefully find the problem. Thanks for the idea.

jcwitte

Okay, It's not the Pedals and I checked the bottom bracket and it all seems to be fine. I did compare the old chain to the new and the only difference is that the old chain was a Shimano HG73 9spd chain and the new chain was a Shimano HG93 9spd chain. I thought that one 9 speed chain is the same as any 9 speed chain as far as size and fit go. Is there a big enough difference between these two chains that it is the problem?

jcwitte

I just found out that the HG73 is for LX/105 and the HG93 is for Ultegra.

Is the difference in Ultegra versus LX/105 really that touchy that it would be the cause of the grinding sensation?

Ed Holland

jcwitte - could the sensation be described more as a vibration or buzz than a grind? I have noticed this with new stuff, sometimes after chain cleaning too, and always in the higher gears as you describe. It is -I believe - simply a resonance in the chain. The top portion of chain is under tension, like a musical instrument string and is "plucked" each time a link is released from the rear sprocket, a process that can never be completely smooth because the chain is comprised of descrete segments.

Perhaps this offers an explanation?

Cheers,

Ed

jcwitte

I'll keep this in mind as I ride it next (here in a few minutes) and see if it feels more like a vibration. I think (hope) you are probably correct. After all, I just replaced the chain. If it gets worse, I'll just take it in to the LBS and see what they think.

Ed Holland

...yes, I intended to add that if it is just resonance in the chain, you do not have a problem. If you are able to "drop" the chain from the front rings so that the pedals can spin freely, you can also check for play and/or roughness in the bottom bracket bearings. Needless to say, there shouldn't be any!

Cheers,

Ed

jazzy_cyclist

I actually have always had this to some extent, but I only notice it when I'm in 53/12 or similar configurations. I don't get to this gear very often, so it's never been an issue, but I am curious about it. I don't think it's the BB, as I have removed and replaced it with no effect. I have a DuraAce chain on essentially a 105 group.

The Great Stonk

last few times ive been confronted with this problem in my workshop its been people using a new chain on an old cassette, or an old chain on a new cassette.

the grinding may verywell be the worn rear sprokets not meshing properly with the new, unstretched chain. - to test, put the rear gears into whatever gear you use most often, and then try to lift the chain directly away from the sprocket with your fingers, if you can, and it comes up a fair way (where you can alsomost see the teeth) you NEED a new cassette, or else the new chain will just get grinded untill its stretched as much as your old one.

Evilbee

An HG93 will run just fine on an LX chainring. My guess would be running a new chain on worn chainrings/cassette is the cause (as above).

jcwitte

The rear cassette shouldn't be too worn. I bought the bike new last August and rode my other bikes through the winter. I have also been pretty good about cleaning and lubing the chain, and I replaced the chain well before the "chain checker" tool showed much wear. I'll check the rear derailleur adjustments and make sure everything there is good and then hope it goes away or at least doesn't get any worse. Otherwise I'll bring ask the LBS next time I'm in there.

jazzy_cyclist

I'll be curious as to what you find out. "Grinding" is much too strong a term for what I've experienced - it's just not as smooth as spinning in a lower gear. I know that in my case, it's not a worn cassette or chain.

jmraspa

you know, this same thing happened to me, and i was freaking out that there was something wrong with the bottom bracket, the drivetrain, something. i was about to rip the bottom bracket, check the bearings, and repack it. wisely, i took it to the local co-op first to ask for advice, and the guy took it for a quick ride around the block.

"did you hear the sound i was talking about?"

"yeah, it's your tire. it's a little crooked and is rubbing against the chainstays."

check even the obvious things.

jur

This Q comes up from time to time. Ed's answer is probably closest to the truth. In my case it happens in a certain speed range. I have swapped chains, chainwheel, bottom bracket, crank arms, pedals, changed to SS, but no difference. It can't be anything else anymore. The vibration in the tensioned part of the chain suggestion was also put forward in the past.

robmcl

I am finishing a rebuild project where I replaced almost the whole drive train and today I was adjusting the shifting. I am almost done except that I have a clicking sound coming from my rear cassette. What I found out was that some of the teeth in the middle cogs where hitting or catching the sides of some of the chain links. Because you replaced your chain ( as I have also), I wonder if that is what your problem is too. I have not had a chance to do this yet but I think all that needs to be done is adjust the limit screws so that the rear derailer is more centered within the chain links.

ppc

I experienced the same grinding feeling when I changed my chain once. It wasn't so much grinding as a weird sort of "crunchy chain" sensation under load. My cassette was good, it turned out it was the chainrings. I had cleaned the chain regularly, and changed it as soon as the Parks chain tool indicated the first signs of chain stretch, but the 2 outer chainrings were toast anyway. They weren't cheap rings either, they were alu Specialite-TA rings, but apparently they were made of cheese-metal. The granny ring, a no-name steel 22T, was perfectly fine.