when to replace chainrings

[Johan Bornman]

This could get interesting' date=' Johan go easy on the youngster.. Rather sign him up for a workshop, esp seeing that he is part time in a bike shop. Allegedly.

[/quote'] OK, OK, OK. Sorrie Bushman.

 

But...(and I'm waiving a big finger here). There's a big difference between a foam and cream cuppaccino. The latter is technically just a hot milkshake, the other is the real thing.

 

 

 

 

[Aquatic]

Ha ha,good one..wait a minute,my post got edited! And bushman is another forum member not me! Now for some cappucino. . .

[brussel]

OK part II

 

 

 

I replace my cassette, chain and pulleys as they were all pretty shot after 6000km of hard MTB riding. Chainrings are OK except the large one.

 

 

 

Riding in the big ring out of the saddle I get chain skipping. It cant be the cassette/chain/derailleur as it is all new and in perfect alignment.

 

 

 

Can you get chain slipping on the chainrings?

[droo]

Yes, it's just less likely than on the smaller cogs. And it can be a real beast if the chain derails, stem + nads =

[Johan Bornman]

OK part II

I replace my cassette' date=' chain and pulleys as they were all pretty shot after 6000km of hard MTB riding. Chainrings are OK except the large one.

Riding in the big ring out of the saddle I get chain skipping. It cant be the cassette/chain/derailleur as it is all new and in perfect alignment.

Can you get chain slipping on the chainrings?[/quote']

 

Check your gear settings, especially the limit screw, it sounds as if the derailer cannot move enough over to the right.

 

You can get gear skipping on the chainrings, but then the teeth are almost flat. You say it looks OK and since you're an old hand at technical stuff, I trust your eye.

 

Chains only skip on the chainrings if there is physically nothing to grip them. The chain enters the chainring under tension and is forced onto any misformed tooth, no matter how bad. If skipping does occur, it is a krrrrrrrrrrrrrrrrrrr affair, with no intermittend skipping, just full-on slipping and going nowhere.

 

I'll look for the problem elsewhere, particularly the settings.

 

 

 

 

[Bat-ass]

i gave old Peugeot Mirage to my gardener ,, and one day he came to me holding his "package"... tells me he cant ride uphill because of the chain??? so i took the bike for a spin up the road, and also can back holding my "crown jewels"... apparently the chain can skip on the chainrings!!! P.S. it was the same chain + chainrings from 1987!!

[Johan Bornman]

Yes guys, I agree that it can skip, but my point is that a visual inspection should very quickly tell you if the chainring is the culprit or not. This is what a worn ring looks like. Note, it doesn't skip until it gets to this point.

 

http://www.bicyclinglife.com/images/WornRings.jpg

[brussel]

Johann the settings on both derailleurs are perfect shifting is crisp both up and down. Skipping only happens in the big ring when I put major pressure on the system when I am out the saddle. It is also worst in the 17 sprocket for some reason, not at either end of the travel of the derraileur.

 

 

 

I have a spare 44 so maybe I should try it. Here is a pic of my current one:

 

 

 

brussel2009-09-03 10:03:20

[Johan Bornman]

That one is fubar.

 

Just compare it to the new chainring above.

 

 

[Johan Bornman]

Comparing these two pictures made me think....why does Brent's chainring skip when it is in better condition (not much, but still) than the one in the picture?

 

In the chainring in the picture we see teeth (cogs) that are visibly smaller than the one in Brent's picture, yet it must still have been rideable, otherwise it wouldn't have worn that far.

 

The answer, I'm think, lies in the "wrap" of the chain. The very worn one is a road bike ring, probably a 53. The other one is a MTB ring, probably a 44 (?)

 

That means, with a 3/4 wrap, the big one engages 40 teeth and the small one, 33 teeth.  Percentage wise, a 21% better wrap, hence the extra grip.

 

Also, the smaller one would be transmitting higher torque loads.

 

What do the chain gurus think?

 

 

[wiMPers]

Hi Johan,

Please check your PM.

(I know it is late but would you mind if I give you a call, it is rather urgent?)

Thanks,

Willem

[crasher]

I think the angle of the photo makes it look worse on the distant teeth(right side of photo)

But comparing the teeth on the left side of the photo to my almost new SLX outer ring then I dont see a huge difference between the 2 and would say that ring although slightly worn would still be ok

 

look on this new one below how flat some of the teeth are

 

Johan Do you really think that one is totally knackered as if so that means I am prob only going to get 1200 or so km's out of mine which is a lot less than I was expecting

 

I dont have the knowledge or expertise in assessing these items but when doing the comparison I really cant see why it is so bad when compared to a new one?

 

 

 

 

http://www.chainreactioncycles.com/Images/Models/Original/38186.jpg

[TNT1]

 

Chainrings only need replacement if:

1) The teeth are so worn' date=' you worry that they will cause the chain to skip

 shark fin soup.

[/quote']

 

Funny... I have some old, no, really old and worn campag rings...

 

[brussel]

part III

 

 

 

Ok so I road up the rode a few times... definitely the chain slipping on the rings and not the cassette. I replaced the big one and viola all solved...so it is FUBAR but does not look that bad? strange but true!brussel2009-09-04 01:38:23

[droo]

Sorry boet, but that thing looks poked.

 

 

 

The difference is that the "shark fins" on the new one are pointing the other way, which is opposite to the drive direction (if you get my meaning?)