worn chainring
 

Is my chainring due for replacement?

It looks usable but certainly not new. The big-ring tooth right above the "no" in Shimano is obviously chipped. The question is it shift ok and does the chain skip on either ring?

It's skips on occasion. I know when one side gets rounded like this on my motorcycles I replace the rings, sprockets and chains.

Replacement looks pretty straight forward. Anything I should know before replacing them?
Also is it possible to change it to a compact by just changing rings?

Thanks

Changing chainrings is fairly simple as all you need is a 5 mm allen wrench and, possibly, a chaniring nut tool to keep the rear nut from turning while you loosen or tighten the bolts. You do want to match the current orientation to be sure the ramps and pins line up correctly.

You can't make a 130 mm BCD crank into a compact since the smallest chainring that will fit is a 38T and 39T rings are far more commonly available. You need a 110 BCD to allow a 34T chainring to be mounted.

Superglide chainrings come with some of those features even when new. They don't look chipped to me.

That's what I was thinking too. Check out the chainring exactly opposite the "Shimano" and see if there is another set of teeth exactly like the misformed ones. My bet is there will be.

Chainring teeth tend to look pointy when they get worn. Yours are still round on top.

thanks for all the information. I was going by my experience with motorcycles and once the teeth get that cresting wave appearance it's time to replace. On closer examination there r teeth with ridges and some are pointy, guess thats the design. I'll look at and compare a new ring with mine before changing it.

I just swithched out my 52-42-30 to a 50-39-30 and it works great left the old 30 on and just replaced to 52-42

Back in the old days, every tooth on a chainring was the same as every other tooth on that ring.

Beginning in the 1980s, however, Shimano started experimenting with different shaped teeth in different parts of the chainrings, with the aim of improving shifting.

Newer chainrings typically have some teeth much shorter than others, usually the teeth that are picking up the chain when the cranks are vertical (this is when chain tension is lowest, and is the best time to make the shift.

These special stubby teeth, often coupled with "shift assist" pins and ramps on the side of the chainrings, make a great improvement in shifting.

However, one drawback of this is that folks who aren't aware of this design will sometimes discover the short teeth and will assume that their chainrings are damaged or worn out! They aren't!

It is very rare to actually wear chainrings out, takes many, many thousands of miles with a worn-out chain. When a chainring is worn out, _all_ of the teeth show the wear, usually acquiring a hooked appearance on the sides of the teeth that drive the chain.

For further information on this, see: http://sheldonbrown.com/chains

Don't be embarrassed about this...this is a _very_ common question, so common that I have prepared this generic boilerplate response to save re-typing.

Sheldon "Superglide" Brown

Can't make a 130BCD compact but you can make it cyclocross (38-46 or 39-48). Works for me and my legs on my Novara hybrid with an 11-34.

I'm with Sheldon on this, that chainring don't look that bad to me. How is the chain for wear? Measure from the center of one pin to one roughly 12" away. If the 12" ruler mark is not on the corresponding pin your chain is worn and needs to be replaced.

My .02 (after Sheldon has far more adequately answered the Q) is that a worn ring will have a "shark fin" appearance to the teeth.

thanks for all the good info, especially Sheldon! The bike has close to 7000 miles on it. The skipping problem came for the back, resolved. Guess I'm surprised at how little maintenence the bike requires. Motorized 2 wheelers are extremely high maintenence by comparison. 1500-2500 miles on a set of tires, 10000 at most on the sprockets and chain.