[ZHendo]

hey guys,

i could just have made a little mistake i'll notice tomorrow when i'm not exhausted, but it's worth asking the question. anyways, i'm trying to put on my new short cage x.9. i've been told that chain length is judged by wrapping the chain around the front ring (i only have one) and the biggest cog in the back without going through the derailleur, and then adding 2 links from when the 2 ends meet. i'm also running an e13 srs guide though, so will that lead to a need to change the chain length? i tried the method stated above, and the chain is too short and is overextending the derailleur. basically, my old chain was too long and i was too lazy to change it, and now that i have my new derailleur, i want to get everything set up correctly. my front ring is a 36T and i'm running an 8 speed cassette with a 28T cog as the largest.

 

[BmxConvert]

What I do when installing a new chain/derailleur or chainguide is remove the coil spring from my frame leaving the shock in the frame. Now compress you shock as if it were bottomed out. Shift your rear derailleur into the largest cog. Snake your chain through the chainguide, around the cogs and through the der. cage. From there I pull my derailleur to it's limit, and add 1-2 links. This ensures that if I need to remove a twisted link or something later on, I can still ride the chain and know it will be safe with the frame bottomed out.

Kind of a hassle, but it's worth it.

-Kevin

 

[MattP.]

When I size my chain, on a FS, I put it on the smallest ring on the the front, and the smallest cog on the rear, and determine how long it can be without the chain overlapping on the derailleur. Generally, I can take a couple links out, but I would rather be safe then sorry w/ chain growth and what not.

Running a 36T up front, and a 28T in the rear, w/ a short cage may be pushing it. I would use my method, run the chain as long as possible without it overlapping.

I was running a 34T dual ring in the front, and a 34T in the rear on my Nomad with a short cage, and had sized the chain just so it wouldn't over lap, but when I was in big+big and the suspension activated, the dérailleur snapped right off.

EDIT- though u said DRS. W/ an SRS, just loop it through the guide and derailleur, put it in the biggest cog in the back, and run it as long as possible w/o rubbing on itself.

 

[.Pit Steelers.]

I always just take out 3 links, thats it.

 

[Dartman]

The big + big + 2 links trick works fine for hardtail bikes with no guide or road bikes.

Once you add in chainline growth (the distance from the BB to the rear axle) from the suspension going through its travel and wrapping around chainguides and such it's pretty much trial and error.

BMXConvert there has a good way of figuring this out by removing the spring and cycling the suspension to find the greatest distance BB to axle. If you don't take this into account your drivetrain will explode when you bottom out the bike.

 

[miuan]

I always just take out 3 links, thats it.

Nice advice.

I agree being safer than sorry is always good. However, too much caution makes your chain longer than you would desire. You may end up with too angled cage, unable to keep your chain tight in high speeds/low gears. Your suspension will never bottom out on the largest cog unless you have a stupid low road cassette and pedal uphill to a drop to flat. Finally you save a couple of grames as well

 

[.Pit Steelers.]

Nice advice.

I agree being safer than sorry is always good. However, too much caution makes your chain longer than you would desire. You may end up with too angled cage, unable to keep your chain tight in high speeds/low gears. Your suspension will never bottom out on the largest cog unless you have a stupid low road cassette and pedal uphill to a drop to flat. Finally you save a couple of grames as well

I said thats what i do, not what he should do ufa.

 

[miuan]

I said thats what i do, not what he should do ufa.

Excellent. So you can get MTB chains in various lengths, there are a lot of possible chainring / cassette setups, plus you have to consider your mech cage length, preferred cogs, CS length and its growth. I'm not going to say you are doing a stupid thing, though I fail to find any logic there. Just don't interfere with people searching for a complex, thought out answer, saying you don't care.

 

[DirtyMike]

I do a cross between MattP and BMXconvert. In that order, I try to leave my chain as long as possible without is slapping and overlapping, that way if there is a problem on the trail I can fix it and not worry about it, at the same time when I am done, I take My spring ff, and make sure its long enough, also I do that to get an idea of how much chain I can remove and still be safe on the trail. Your chain length is going to be pretty critical with the gearing you have matched with a short cage, I run a 36/27 and I run a Medium X9, perfect combo for the dirtbag

 

[cycleryshop]

big + big + 2 is the way SRAM and Shimano both say to do it. since you bike is a hardtail, the chainguide will not make any difference, think of it as a bigger chainring.

big, big, +2 is correct.

 

[ZHendo]

thanks guys, i'm having the problem on my hardtail, so i'm not too worried about things exploding.

 

[BmxConvert]

big + big + 2 is the way SRAM and Shimano both say to do it. since you bike is a hardtail, the chainguide will not make any difference, think of it as a bigger chainring.

big, big, +2 is correct.

Still a bad rule of thumb. You need to check that small-small(despite being a gear you should never ride in) doesn't leave the chain loose and overlapping.

I know I didn't point it out in my suggestion, but its something that needs to be done.
You really should never ride in small small or big big(if you run a 3-ring combo), so these gears allow room for sacrifice if your chain length cannot be varied, it's very rare that it can't though.

-Kevin

 

[Fulton]

What I do when installing a new chain/derailleur or chainguide is remove the coil spring from my frame leaving the shock in the frame. Now compress you shock as if it were bottomed out. Shift your rear derailleur into the largest cog. Snake your chain through the chainguide, around the cogs and through the der. cage. From there I pull my derailleur to it's limit, and add 1-2 links. This ensures that if I need to remove a twisted link or something later on, I can still ride the chain and know it will be safe with the frame bottomed out.

Kind of a hassle, but it's worth it.

-Kevin