SimonLee

hello. i just replaced my chainring and bike chain. when i ride my bike and pedal harder or fast i heard my bike making a grinding sound. any ideas what is causing this?? also how long do aluminum alloy chainring last (miles)?

tagaproject6

Tighten everything properly. Lube everything that needs to be lubed. Try again.

epiking

Take a close look for adjusment and lubrication of bottom bracket and pedals.

Retro Grouch 

Front chainrings normally last a long time. If yours was worn out, that would be a sign to look for other wear on the bike like, for example, the bottom bracket..

SimonLee

my chainring is new and also bike chain is new usually come lube already??? yea i check and tighten everything. oh yea i forgot to mention my single speed bike uses a chain tensioner since it has vertical dropouts do you think maybe the chain is too long,

ursle

Chains come greased, you want to remove it and apply chain lube, "or not"
Check the length of the old chain and cut the new chain to the same length.
3-4 to many links is a no-no

Retro Grouch 

Such an innocent sounding comment. Excuse me while I fix some popcorn.

SimonLee

could it be dirt on the rear cog or on the roller of the chain tensioner??

SimonLee

anyone know what might be wrong??? does aluminum chain-ring on new bike chain always will make a grinding sound???

JanMM

What kind of bike? What kind of gearing setup?

SimonLee

old school marin 1996 hybrid bike. was multi-speed now converted to a single-speed bike that uses a chain-tensioner 48/14 gear ratio. not sure if the chain tension is too tight or dirt on my rear cog. my chain-ring and bike chain is new. my chain tension i think is fine when i walk my bike and it hits a bump on the road the chain moves and shakes slightly.

JanMM

No.
Is the chainline reasonably straight from front to back?
Can your chain tensioner be adjusted to a bit less tight to see if that makes a difference? It needs to be tight enough so that the chain doesn't come off the chainring or cog.
Cleaning and lubing couldn't hurt. Including the tension device.

SimonLee

the chainline is straight from front to back. my chain-tensioner can be adjust to a bit less tight. i think it is okay because when i lift my bike and put it down on ground the chain jump up and down slightly a tight chain will not jump up and down or move a single bit. i haven't lube it yet since the chain is new. but doesnt it come lube already???

Phil_gretz

(1) - Grit. In my experience, the "crunching" sound from an otherwise silent drive train is from grit in the rear cog. You've admitted that you didn't clean it. So, let's get this straight...

You went to the trouble of installing a new chain and front chainring, but couldn't be bothered to clean the rear cog?

Clean it thoroughly, as well as the tensioner pulleys, with solvent and a rag, until you can't wipe another bit from any tooth or indentation between.

(2) Chainline. The second culpret is edge-wise contact between the cog teeth and the chain at the lower point where they meet. Your chainline might "appear" straight, but might be several mm off. Use geometry, an accurate millimeter scale measure, and a centerline reference point to determine where your front chain ring is and where your rear cog is. These measurements are made from the bike frame centerline to the cog/chainring tooth centerline. How far off is it really?


These two things, when corrected, should remove your issue.

PG

SimonLee

i did the first thing you mention. the 2nd thing you mention still dont understand how to measure. do i start from the chainring and measure to the rear cog?? any sites or good pictures i can look at??

Phil_gretz

You will have to apply simple geometry. The plane of each set of teeth must be measured independently, from the centerline of the bicycle to the plane of the chainring or cog. For example, for the front chainring, you must measure the diameter of the seat tube (in mm), then divide by two. That's half the width of the tube (A). Next, measure the distance (in mm) from the same outer edge of the seat tube to the mid point of the width of the chainring teeth. Rotate the crank and make this measure at several points. Average the measurements (they may differ by one to a few mm). The average becomes the distance from the seat tube to the center of the chainring (B). Add (A) and (B), and you have the chainline measure in mm.

Phil_gretz

The rear takes a little more math. There are several ways to do this, but the most straightforward is to take the distance from the outside of the non-drive side locknut to the outside of the drive side locknut. It's best to make this measurement with digital calipers set to the metric scale, but you can use a mm-scale ruler if you are careful. With calipers, you can make the measure with the wheel off. With a ruler, do it with the wheel mounted in the rear dropouts.

Measure the distance (C). This is the outer locknut distance of your rear hub, which will be in the neighborhood of 120mm-130mm, depending on the wheel that you're using. Now measure from the drive-side outside of the locknut to the center of the rear cog teeth. Similarly to the chainring, make this measurement a few times around the cog and average the result. This distance is the in-board centerline of the cog (D).

Take the (C) measurement and divide by two = C/2. Next take the inboard cog distance D and subtract it from C/2. That is the rear chainline measure, or C/2-D=rear chainline. Compare this to the front chainline measure, and you'll know how far off you are and which of the two you need to change to get better alignment. Some folks will accept 5mm or so error. I'd suggest that <2mm would be better.

Hope that this helps you.

PG

OldsCOOL

Grinding sounds can come from a crunchy rear hub needing fresh lube and adjustment. If the rear hub bearings are rough it will transmit sound up through the bike components and make you wonder just where it's coming from.

Pull the rear wheel and hand-spin/rotate the axle in your fingers feeling for any "dry spots" or anything feel that isnt smooth.

SimonLee

thanks Phil i'll give it a try.

SimonLee

Thanks old school for the tip.