Chain Length

[stosh]

How do I figure the proper chain length when I'm using an 8spd rear casset. and a short cage rear der. ?

[JRogers]

There are scientific ways to do it. usually I just do the "biggest" gear combo (big ring and lowest (biggest) cog) plus two links.

[kidwoo]

Originally posted by JRogers
There are scientific ways to do it. usually I just do the "biggest" gear combo (big ring and lowest (biggest) cog) plus two links.

I thought that WAS the scientific way.

[mtbdirteater]

Originally posted by stosh
How do I figure the proper chain length when I'm using an 8spd rear casset. and a short cage rear der. ?

Well, let me tell you a story about a couple of chain links.

And this doesn't matter if 8 or 9 speed. And we're assuming your derailleurs are adjusted perfectly (what other way is there!) . Some people say big-big + two links, but I don't, because then my loose chain drops all over the place. Some people (not too many any more I hope) say remove enough links so you can't get big-big, ...and then if/when you accidentally shift into that no-no cross-chained combo, you either rip and bend chainrings and teeth off or bend your rear derailleur hanger or break it off. Self destruction is not cool. I the dark in the middle of the frozen forest. So there has to be a happy medium.

So I say (and do) just enough chain to pull my rear derailleur tight and straight in the no-no big-big combo. (I use a short cage on my two-chainring bike, and a long cage on my three-chainring XC bike. (Both are 9-speed 11-34 rear, but this doesn't matter either here). That way no damage if accidentally shifting into that combo (and it grinds noticably a cassette gear away from it, so you know). You don't need any more chain than this, if you have extra and your rear derailleur is pointing straight back in the other no-no cross-chained small-small, you are going to bounce your chain off more easily, especially rough techy stuff, hard impacts and in the mud.

We didn't talk chain guides here, 'cause that's another topic, but same goes, just enough chain to make it through the guide and big-big, with a tight chain. Not so tight that you bend or break something or rotate your non-ISCG chain guide mount (yet another topic), but snug. You will have to play with this with a decent chain tool. Park Tools makes a slick one (not the little bitty one).

So the two-link theory is great for building and assembling the bike in the shop, but not so great for keeping the chain on the gears while riding it. As far as I'm concerned, this goes for DH, XC, road bikes, and everything else except single speeds (other than you want your SS chain fairly snug where the rear hub bolts without using something like a Singlator chain tensioner if possible).

I also happen to notice that chain length usually doesn't change if swapping a long for short cage derailleur if you still want the possibility of being able to run it through all gears (big-big with a tight chain).

Cheers,

Dave

Edit: I spell like Al Gore

[Tootrikky]

It is a pain in the ass. Another trick is put your mech in the middle of yo cluster and in da middle ring up front (if 1 ring then omit this step) then shorten chain to point where if you drew a line throught the derailleur pulley axles it would be perpendicular to the ground (assuming bike is level of course). I find both methods are flawed and that it is best too always err longer when cutting the chain, cause it is easy to shorten a chain, while hard to lengthen.

[Brian HCM#1]

I use the granny gear, small cog combo. Then pull the chain till you see the derailleur moving down. Remove the necessary links and valla your done, and you'll have proper chain tension in ALL gears.

[stosh]

Thanks guys!
I got the chain length pretty well set. I did big ring and big ring and added 2 links. That was to much after I ran it through the rear der. so I subtracted one link and it seems to be prefect. Now I have to tune the der's better.

OH and it seems the 8spd shifter pod I purchased off ebay was 7 speed not 8 like they had said.... oh boy.... So now I have to purchase another set... GRRRRRRRRR!