18t Front Cog's

[trialsguru]

ok, when the whole 18t front cog thing came about people were saying that chain snappage would be increased, its been a little while now and lots of people are using them and i wanted to know if the chain snapping thing has happened, do chains break faster or is there no difference?

cheers!

[JTM]

Do you mean 16t............? lol

They do significantly increase chain snappage imo. But with a KMC theres not much chance of that. Prob best to change chains every 6 months or so though, just incase

[Mark W]

JTM speaketh the truth. Theoretically, it'll increase chain-wear, especially if the chain-ring material is significantly harder than the chain? However, as JTM also said, chain's should take it. Saying that, I sheared a KMC Kool link literally in half doing a tiny little gap. Note: Replace chains before they get to that stage; mine was a year and a half old :ermm:

Park's chain measurer device should be useful for that I guess...

Anyway, yeah, not much help I guess but I haven't noticed the amount of faceplant vids go up so I'm guessing they're holding up.

[chocolatefoot]

sorry if you already know this but

say you run 22-18, theres much more chain so the stress is less per link than runnin 16-13 or watever, i thort bout gettin super pro burns for ma bt but a decided not to because of the chain snap issuses involves and the chain has to curl round the cogs more because the are small whitch causes more wear.

you can measure chain wear by streaching the chain right out then measurin it.

then push it together, it should still b in stright line though and take the mesurement, do this when you first get it so you can compare the wear :ermm:

tom

[Mark W]

It's not so much the general amount of chain, more that the way the load is spread. If you're running a 22t front ring, you've got your Force divided by 11 teeth ('cos it only contacts the ring for half of it). With the smaller 16t chain rings it's F/8, which doesn't sound much, but imagine you're putting 1.4Kn of force through something (which is near the breaking point of a Kool), when you do 1400/11 it gives you 127.272N per tooth. However, at F/8 it's 175N per tooth. It's not a huge increase, but it IS still more than it was. This explains why chains are more likely to snap, and also the increased wear rate you'll experience.

The above calculations aren't accurate to any real degree (apart from the final outcome of the sums, but the original values aren't), but they give you the idea.

Mark.

[trialsguru]

im thinking about running 18-16/15 at the moment im running 20-17 do you think that seeing as im only losing a few teeth the loads involved will be similar?

[JT!]

I would have thought the main reason for chains snapping on ffs is that the chain is going round more, well all the time in fact. So it would whare that way.

[trialsguru]

i wasnt thinking of running ffw, i was going to get tensiles with an 18t fixed cog

[JT!]

i wasnt thinking of running ffw, i was going to get tensiles with an 18t fixed cog

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Oh, i see.

I wouldn't have though it would have made that much difference.

Chains only cost £10, if you replace them every half a year, there shouldnt be a problem.

[cultiv8ed ::Chris::]

i am running 15 - 13 at the mo seems alright

[Ali C]

I used to snap ordinary chains quite often on a 22-19 set up. I was worried about using a 16-14 set up due to the snappage issues, but when I got the smaller set up, I also got a kool chain and its been the least hassle of any drive chain I have used.