tjax

I got out today and went around the block. I notice that when I am in a low gear I hear a scrubbing sound through half a rotation of the pedals. What is this, should I worry about it????

If it is a problem can I fix it or should it go to a LBS? Would like to have it fixed so when the pneumonia is gone I can go for some more awesome rides if it is an issue.

Thanks,
Here is a smiley

Erwin8r

We need more details. Where is the front derailleur? I presume by low you mean the large cog on the rear? If you have the front on the large ring and the rear on the large ring, you are "cross chaining" and there will probably be some noise. Not a good idea to run this way (and same for the opposite--small rear/small front).

tjax

It is when I am in my lowest gear in the back and mid gear in the front. I don't know a lot of terms yet.

Tel0004

It does sound a bit like cross chaining, although if that was the problem, you would hear it throughout the whole pedal rotation.

Cross chaining is when you have the chain at a bit of an angle, due to being in the lowest gear in the back, and the highest, or mid gear in the front (the reverse is also true).

I try to avoid using the lowest gear in the back, when I'm in the middle gear/top front gear. Shift up to your second gear in the back and see if the noise goes away. Then try to avoid the lowest rear gear when in the middle front gear. Instead drop into your granny gear, and shift up the back so you can get the gear you want.

chasm54

The answer to your question is yes, there is obviously something wrong. Whether that is major, and needs fixing, or minor and merely requires some small adjustment, we cannot tell on the basis of your description. If you put the bike on a stand (or just turn it upside down if you haven't got a stand) and turn the pedals by hand you may be able to see what is going on. If not, ask someone who knows what they are doing to look at it.

There are hundreds of useful videos on bike maintenance on youtube.

Rowan

What sort of shifters do you have?

Some (Shimano road levers, for example) have a trim function for the front derailleur; it shifts the derailleur by a tiny amount either in or out so the chain ceases to rub on its side plates.

The movement is not enough to create a shift on the chainrings. The chain can rub on the derailleur at the extreme ends of the cassette (ie, the biggest cog or the smallest cog).

tjax

They are Shimano shifters. Its a Trek 1.2 if that helps at all.

tjax

I'll try that out in a bit and see if I can see what the cause is.

10 Wheels

You have a new bike.
Your bike shop should be able make some adjutments for no charge.

psalm

If it's only half of the rotation you might be hitting something. I had a similar issue. Every pedal stroke I kept hearing a rubbing sound. Turned out the zip tie that held the magnet on my crank arm had shifted, and it was hitting my fame pump.

cyclist2000

you really need to determine where the sound is coming from. If you have a stand or some kind of rack, you can spin the wheels and see if they spin freely or is there some resistance that prevents the wheels from spinning freely. if that is not the problem then spin the cranks and see if the chain makes noise when moving the cranks.

skilsaw

I would have to see the bike and hear the sound to figure out what it is, and how to fix it.

Your scrubbing sound is somebody elses growling sound, scratching sound, rubbing sound...
I don't trust a mechanic who says my car needs $1000 worth of work based on me saying it goes "tickety-tickety-tickety"

If it is a minor adjustment on a newish bike, the shop where you bought it might fix it for free. It is one of the benefits of supporting your local bike store.

Rowan

You can trust me. That sound is stuck hydraulic lifters. And it will cost $1,000 to fix.

tjax

lol

tjax

Upon further investigation the chain moves to the side and rubs the side of the piece of metal that shifts the chain, in mid rotation. SO it appears something is mis aligned because half of the rotation you can see the chain rub on that piece.

EDIT: I'm taking it to my LBS as you guys suggested, they were very nice to me when I bought it, I'm sure they will look into it for me.

chasm54

It's called the front derailleur, FD for short. Sometimes referred to as the front mech.

CraigB

Specifically, it's the FD's cage that the chain is rubbing on.

otis66

This was happening to me last year. When my bike was on the big chainring and the largest sprocket the cable would tap my shoe and I would hear a clicking noise every time my right foot passed near the front derailleure, "click, click, click ,click. It would only make the noise when I was riding the bike. When I checked my bike on the stand...no noise. I repositioned the FD cable and the problem was fixed. On another occasion I had a tiny piece of gum stuck on my tire that also made a noise only when I was riding the bike.
Also check that there is nothing interfering with your brakes, and check that your wheels are seated correctly in th frame.

tiger187126

seriously check out the trim feature. try shifting the front gear and see if the noise goes away. i took mine into the shop for a "grinding" noise and they showed me that one click or half click meant i turned the trim on and then a second or full click shifted it and the noise disappeared.

sorry if that phrasing sounds weird, but i don't fully understand it. i equated it to double clutching, where you're preparing the gear for change but i have no idea if that's true.

Myosmith

Trim might help, but if the chain is only rubbing during half of the crank rotation, something is still wrong. Check to make sure that the bottom bracket is properly installed and solid and that the crank arms are firmly attached. Also inspect for bent chain ring or loose chain ring bolts. There should be no play anywhere in the crankset.

TJClay

Without a doubt it's the the Flux capacitor

tjax

+1 hahahahaha

tjax

Well I took it to the LBS The wheel was not "true" (no idea what that means). And it was pulling the chain into the cage half a crank. $15, a newly "trued" wheel later, and a couple trim adjustments I had a perfectly running bike. I need to learn a lot.

Rowan

Wheels are meant to run straight when you spin them, and if they do, they are true. If they wobble, they are out of true.

But the explanation as you have portrayed it is not correct. A wheel that wobbles on the rim, won't have any influence on the chain whatsoever.

Anyway, all's well that ends well, so if your bike is running perfectly... go ride it!

tiger187126

i could see a non trued wheel rubbing somewhat and making noises at the point where it's bent out towards gear side, but yeah i'm not sure with this explanation.

either way, have fun riding and now you know what to look for if you hear noises again.