bark_eater 

I bought a set of steel chainrings off ebay. Their 52-36T 116 bcd and I was excited to find a cottered crank "compact double set". On inspection the inner 36t chainring has more wear than the outer and a new chain "lifts" a bit more than the outer. Any ideas on how to quantify wear on steel rings? My concern would primarily be wearing out the chains and freewheels faster, but practically speaking the 36t chainring is the most unobtanium consumable in the drive train. I can get some pictures tomorrow. Thanks

bikemig 

Is it possible to wear out a steel chainring? Obviously the answer is yes but those things are pretty tough.

bark_eater 

I've seen some pretty worn rings, but I don't think I could wear this one out in my life time. I just don't want to have to feed this ting to many freewheels. That's not even a big deal as long as they keep making cheap 5 speed freewheels.

clubman 

I had a pre war Hercules with a saw toothed chainring that had to go. It could cut your finger. This is the bike with a poor replacement as the original had the name Hercules in the webbing.

oldlugs

I always just figured a chainring was good so long as it didn't slip and no teeth were missing.

bark_eater 

I tried to get pictures but lost them... using drill bits as gauges I was able to get a 1/16th bit under the rivet on the 52t ring and a 5/64th bit under the rivet on the 36t ring. I'm not sure what that all really means, except try and ride the 52t ring until I need to engage the grannie gear....

bark_eater 

The engineers answer...

bark_eater 

Here are some pictures. The 52t ring is loose enough for a 1/16th drill bit to squeeze in. The 36t will allow a 5/64 drill under the rivet. Playing with the chain it looks like the amount of slop is halved when the chain is tensioned for one side as it is when the cranks turn. I don't know what that all means, except save the 36t as a granny for the hills...

Johno59

Only the 3 o'clock position on the chain ring reveals meaningful data. Did Elvis write a song along those lines?
Go to the 3 o'clock position on the chain ring. As the furthermost point from the 9 o'clock position on the rear sprocket you can gauge the amount of wear on your entire drive. Pull the chain away from the teeth at the 3 o'clock position on the chain ring . If you can see half of a tooth, change the chain (cheapest option).Repeat procedure with new said chain. If the half tooth still appears your chain ring is toast. Replace and happy days.
If it still jumps - change the rear sprocket as well.
You now have a completely new drive.
Oil every day and it will stay that way, neglect the oil and you will be back sooner or later.

miamijim

If mounted on a bike pull the chain tight at 3:00. If you can see light at the tip of a tooth the rings are toast. Or 12:00 as in your pics..

I've never compared new large n small rings side by side but I'd guess the chain will pull further away on the small ring as there're fewer teeth engaged. That small ring has a bizzillion miles to go as both tooth 'bevel's' and machine marks are clearly visible. Pedal away....

Teeth on that particular ring are beveled in two directions, from the inside in and from the front/back towards the tip.

Reynolds 

Those rings look OK to me. Probably still good for many years of use.

ClydeClydeson

Rings can wear to a point where the shape of the teeth changes visibly. Those rings do not look like that. You expect to see a difference between the front and back edge of each tooth, and a bit of an extended flat section between. Neither are visible there.

My first question: is that a new chain? Because lifting off the chainrings is one way to determine if there is wear in the chain, and the same chainring can be used over the life of many chains, if the chains are changed regularly.

bark_eater 

It's a new chain. The industrial sprocket web link put 10% of tooth width worn away as the replacement point. MKII eyeball and a Harbor Freight caliper puts the small ring at 10% compared to a NOS Nervar ring. The Nervar ring has chromed over burs on the teeth so that's probably a pessimistic comparison. I'm assuming that there's an tolerance spec for 1/2" chain.


Here's an illustration from the link. If a roller is 7.75mm in diameter adding 10% gets you 8.525mm. 8.5 mm drill bits are available, I wonder if one could be used as a No-Go tooth gauges?

I get the idea of the 3 o'clock test, and having the chain tensioned back to the sprockets, will reduce the amount of slop, so there would be less lift than with how I have the unmounted chainring and drill bit. I tried tensioning the chain in the proper direction and it looked like the gap was significantly reduced, but I only have 2 hands...

miamijim

Dont tensioin it. Just pull at 3 o'clock. Its a bike sprocket not a rocket ship. Dont over analyze.

ThermionicScott 

The only meaningful test is whether the chain skips under load. End of story.

bark_eater 

There was no mention of pixy dust. I looked...

https://www.renold.com/company/lates...worn-sprockets

cudak888 

Not far from the truth. Curious what quality of steel chainring/cranks the OP has though.

-Kurt

zandoval 

When they are worn enough that I can see changes, I replace them. They seem to last longer if riding on clean roads. Dirty roads = Dirty chains = Worn out cranks... Ha

bark_eater 

Their Cylos (sp?) and I got to say the rule of thumb push back is a little weird.....

PugRider

I thought I first saw it at Sheldon's, but I'm having trouble finding it. But one tip I recently discovered is to use a loose roller from a chain, pick it up with a set of needle-nose pliers, and fit it into the chainring. If it seems nicely nestled in there, then the chainring is good. If the valley is wide and the chainring teeth don't really come up the sides of the roller, then it's worn out. Hard to describe, but it's really obvious if you do it with a chainring you know is good, and then test it out on one you think is bad.

bark_eater 

I gave that a try, and a roller in a new chainring has zero play. Referring back to the diagram, it looks like if there is any play with the roller at the bottom of the trough, the wear point may have gone beyond 10%, but I have no idea how accurate that illustration realy is. I played with a drill index a bit more, and where there is visible wear further up the tooth an 11/64 bit would lock in to the groove, above the bottom. The next thing to play with would be the 2 5/32" drill bits approximately 1/2 a roller diameter to space a caliper off the bottom of the valley. That would be ball park, but even with spacers exactly 1/2 the rollers diameter the measurement will be off as it will be a straight line tangent bellow the PCD radius. The greater the diameter of the chainring the less this is a factor....

Reynolds 

There's a Rohloff sprocket wear gauge, I guess you can use it on a chainring too.




I made one but it wasn't of much use - when it said "worn out sprocket, replace" you could as well see that by eye...

bark_eater 

I've been meaning to get one of those. The instructions say that they only work to 21T. Roller chain and sprocket technology must be getting close to 200 years in use, so I'm sure this has been covered before. I just need to find the right critical application that is relevant to 1/2" chain drives.

Sluggo

Can you turn the chainring over and use the unworn side?

Hobbiano 

Check out the pictures of worn out vs new chainrings here: https://www.bikeforums.net/bicycle-m...isualized.html
Yours look closer to the new end of the spectrum to me. I don't think you need to actually measure it to come to that conclusion.