Worn chainring

[Big T]

I've fitted a new chain and cassette to my audax bike and on the ride to work this morning, the chain was jumping in the middle ring of my Campag triple, whenever I set off from standing. I presume the chainring is too worn for the new chain.

So it' looks like a new middle ring. I'm assuming Campag triple middle ring is still 135 bcd. Is that correct?

Spa have Zicral rings at £24 and Dural rings at £12. Is Zicral really worth the extra?

Last question - I have a virtually new 44 campag ring. The current chainset has a 42. Would it affect the gear changes if I fitted the 44, especially changing from middle to small ring, which is a 30? I'm not too bothered about the increase in gear inches with the 44, as I have the granny ring for climbing steep hills.

[Stradageek]

The Dural ring is likely to be plain (no rivets and lifters) to be used as the inner of a double. You need to specify that you want a Zircal 'middle triple' ring to make sure it doesn't have the same limitations. The guys at Spa kindly pointed this out to me and my new 42T middle is working perfectly.

I defer to the experts for an answer to your second question

Cheers

Stradageek

[Mick F]

The BCD of the middle ring, is the same as the outer on a Campag Triple.
Campag Triples are 135mm BCD middle and outer, and 74mm BCD for the inner.

For info:
To find out the BCD, measure between adjacent bolts and multiply by 1.701
http://sheldonbrown.com/gloss_bo-z.html#bcd

In order to get good shifting from middle to outer, you need the rings "timed" and you need ramps and pins.
If I were you, I'd fit your spare 44t ring and try it. You may be lucky and it may save you a little bit of dosh. You have nothing to lose.

If it doesn't work too well, you need a new middle ring. Get the best you can afford IMHO.

[Big T]

I've fitted the 44 (which is actually a TA ring) and will see how I go. This ring doesn't have the ramps and pins so the change isn't that crisp but I spend most of my time in the middle ring anyway.

[nickpaton]

In order to get good shifting from middle to outer, you need the rings "timed" and you need ramps and pins.

Mick, could you explain what you mean by "timed", is this the same as having the correct alignment between the rings?

With this in mind I've just replaced middle 36T chainring on my Spa Cycles XD-2 Crank with an identical Stronglight Dural 110 BCD. Unfortunately I stripped the crank down without noting the relative positions between the existing chainrings so had to start from scratch again.

All 5 quadrants around the middle chainring between the mounting bolt holes are identical, ie no alignment "rise" on one of them, and other than the position of the pins themselves around the ring there's no indication as to how it should be aligned WRT to the larger outer one.

The only way I could work out the alignment was via this picture on Spa's site, and having set it up as close as possible to the picture, changing between the chainrings is actually very smooth and so I presume must be correct.

However there must be some information somewhere that shows how the rings should be aligned, but I'm blowed if I can find it.

I hope this isn't another of my questions that has the answer starring everyone except me in the face

[byegad]

Zircal lasts me at least twice as long as Dural, so I buy the Zircal.

[nickpaton]

Zircal lasts me at least twice as long as Dural, so I buy the Zircal.

But is over twice as expensive - typically £10 versus £24 (Spa Cycles 110 BCD 34-44T)

However it will cut down on more frequent servicing.

[Mick F]

In order to get good shifting from middle to outer, you need the rings "timed" and you need ramps and pins.

Mick, could you explain what you mean by "timed", is this the same as having the correct alignment between the rings?

A plain cog or chainring has all the teeth the same all the way round.

What the manufacturers do, to make changes sweeter, is the "profile" the teeth at a certain arc or two on the cog/chainwheel to allow easier shifting up and down. They form a "ramp" to allow nice chain transfer. The chain doesn't object too much to "sliding off" the profiled teeth when pushed by the derailleur mech.

My chainrings - for instance - have little marks on the face that when you mount the rings on the crank you line them up. Sprockets will only go on in the correct position of course so you don't have to worry, but chainrings can go on in any position on the spider.

If they are "timed", it's better to fit them correctly, but if you don't - or your rings aren't timed - it's not the end of the world.

The outer ring and perhaps the middle ring has pins fitted that help the chain lift from the lower ring to the higher ring. They obviously need to be in a correct position to fit in with the profiled teeth.

[nickpaton]

Many thanks for the information Mick.

TBH, having looked at the chainset again, I'm not much the wiser as there doesn't seem to be any marks or profiled teeth etc.

I'd probably need to remove the crank and chainrings for a closer look, but as the chain now moves more smoothly between the rings I don't want to play around with them just for the sake of finding some "theoretical" marks - also I guess it's not great to frequently remove the crank off the shaft.

However, I still come back to there being no information about all this, especially on Stronglight's site for instance, even though it may be fairly obvious information to some people!

[meic]

Almost every chainring that I have seen will have a little arrow engraved or a protrusion of metal on the ring that indicates where the crankarm will be when you fit it.

You can see the protrusion at the bottom of the right hand ring in this picture.

http://www.spacycles.co.uk/products.php ... b0s149p292

On the left hand ring you can see the hole (which takes a little thing to stop the chain jamming between crank and rings) to indicate where the crank goes.
Actually it has two such holes but only one will line up on any one crankset, the other lines up on a different design crankset.

On "plain" rings it doesnt matter and you can rotate them to even out tooth wear.

[nickpaton]

Almost every chainring that I have seen will have a little arrow engraved or a protrusion of metal on the ring that indicates where the crankarm will be when you fit it.

You can see the protrusion at the bottom of the right hand ring in this picture.

http://www.spacycles.co.uk/products.php ... b0s149p292

Thanks Meic

I've got the plain version of the RH chainring (ie not the Compact one), and each quadrant between the mounting holes is the same - can't find a decent picture anywhere to show the one.

The outer ring has a bolt in it which I did remember (before stripping) set its position to be in line with the crank arm.

Possibly as it's a cheaper Dural version, Stronglight treats it as a plain ring which can be mounted on any hole.

[andrew_s]

Zircal lasts me at least twice as long as Dural, so I buy the Zircal.

But is over twice as expensive - typically £10 versus £24 (Spa Cycles 110 BCD 34-44T)

However it will cut down on more frequent servicing.

My experience is that the wear difference more or less matches the price difference. However a problem I have had with the Dural rings is that the tooth edges can burr over and promote chainsuck. Chainsuck can be quite damaging to your frame, as well as a black hands nuisance at the time.

[531colin]

As somebody already said, the outer ring has a peg to stop the chain dropping between the ring and the crank.....after that I line them up as shown

[nickpaton]

Thanks Colin

I guess you meant by lining them up, that the cog teeth number labels are lined up as shown.