# Switching to a 11-28 to a 12-30...do I need a new chain.



## Typetwelve (Jul 1, 2012)

Ok...with the 10 speed Ultegra stuff on sale, I picked up a 12-30 to replacement current Ultegra 11-28. Running a 52/36, I never run 52/11 and make sure not to cross chain (although it does happen from time to time). I don't do the high speed downhill stuff and I'm too mortal to chug along in that combo. I figured I'd rather have the 30 rear than the 11...

Now...the 36/30 would be handy...very handy for some of the short, steep climbs I find myself in.

Either way...I know the common advice is to replace the chain with the cassette but this current chain is an Ultegra and it only has 1000 or so miles on it. If it were beat up, I may replace it but at this point, I feel it's barely even broke in yet.

So...this leaves me to my question. Will my current chain length suffice? I know for a fact that 36/30 will be fine...but what if I accidentally go full granny on accident and attempt to run 52/30? Is a +2 in the rear gear enough to cause a problem figuring my current 11-28 setup?

If it is...I can get a new chain, it's just an added expense I don't want to add if I don't have to.

One last thing...I will continue to run a 11-28 on my trainer wheel. If i do swap the chain, will running the trainer set cause a problem? One word of note...I do not run the larger rear gears on the trainer. With my current set, I stick to the 11-15 rear range and switch between the large and small front. I've never touched the 28 on the trainer nor will I.


----------



## looigi (Nov 24, 2010)

There's no way to know without seeing and actual setups. By going from 28 to 30 cog, the length of the chain run increases by one link (1/2"), since the chain only wraps halfway around the cog. It's likely your current chain is long enough but you'd have to check. If you need a longer chain, (you can only change chain length in 1"increments) running it on the 28 cog is not the concern, since it will run fine on the cogs smaller than 30 on the 12-30 cassette. The concern will be if it's too long for the cross chained condition of running on the small ring and the 11 tooth cog on the 11-28 cassette. Again, you would need to check, but it's likely it will be OK.


----------



## Typetwelve (Jul 1, 2012)

looigi said:


> There's no way to know without seeing and actual setups. By going from 28 to 30 cog, the length of the chain run increases by one link (1/2"), since the chain only wraps halfway around the cog. It's likely your current chain is long enough but you'd have to check. If you need a longer chain, (you can only change chain length in 1"increments) running it on the 28 cog is not the concern, since it will run fine on the cogs smaller than 30 on the 12-30 cassette. The concern will be if it's too long for the cross chained condition of running on the small ring and the 11 tooth cog on the 11-28 cassette. Again, you would need to check, but it's likely it will be OK.


Thanks for the reply. I'll get the cassette sometime in the next 2-3 weeks (yay probikekit customs wait time!). I'll just pop it on and see how it goes. Like I said, I rarely crosschain...especially the 36 front, which I will never run to the 11 cog. With my compact crank, 36/11 would chatter off the front derailleur quite a bit...if I need that kind of gear ratio, I'll run the 52 up front and try a 17 or 15 rear for close to the same thing without rubbing...

On that note...possibly this is common knowledge, but the 52 front runs much smoother than the 36...I try to stay on the large ring as much as possible (again, unless I'm climbing)...


----------



## JCavilia (Sep 12, 2005)

It's highly unlikely you'll have any problem. If your chain was sized to be barely long enough, it's possible you'd need to lengthen it, but it's probably not. 

You can test now, before you get the new cassette. Shift to the big-big combination and push on the derailleur cage to see how much slack it's taking up. If it moves more than the slightest amount, you're probably fine. As loogi said, you only need a half inch.


----------



## fun2none (Mar 16, 2010)

My neighbor runs full Ultegra 6700 group with 11-28 cassette and short cage rear derailleur. He just exchanged the 11-28 for 12-30. It works fine on his bike.


----------



## Guest (Nov 9, 2013)

.....


----------



## cxwrench (Nov 9, 2004)

lighthouse54.1 said:


> Generally speaking a chain should be set so that the deraileur cage is verticle to the ground when the bike is in it's highest gear. (big in front and small in back). That is ideal. Then shift up to the large cog in back and leave the chain on the big ring in front. Look to see if the deraileur is over extended. If not your ok. If it is then you can add a link and make it work but take some precision from your fine equipment or buy a new chain and a large cage deraileur and do it properly within manufacturer specifications.
> 
> Your new set up has a total capacity of 34 (52-36) + (30-12) = 34 You have to look up your deraileur at shimano.com to see what the capacity is. I am going to guess it is 33 but I am just basing that guess on what information you gave us.


I think you need to fine-tune the way you advise people of chain length. And throw the words "carefully shift to the large cog" in *bold*. And "over extended" _generally_ equals "broken". Either the chain is long enough so the derailleur can make the shift or it's not. There is the rare occasion when the cage gets pulled all the way up to the stay and will still work, but it will be very rough. Usually it's one or the other. Depends totally on the length of the chain stay. 
The best way to size chains is small/small. As long as your drivetrain components are within the capacity specs for the rear derailleur you're using, it's the safest method. Especially if you're going to be swapping wheels and they have different cassettes.


----------



## looigi (Nov 24, 2010)

lighthouse54.1 said:


> Generally speaking a chain should be set so that the deraileur cage is verticle to the ground when the bike is in it's highest gear. (big in front and small in back). That is ideal. ....


Where did you get that? What determines chain length requirements are the extremes, big-big, small-small. That's where trouble will occur if it's not right. Big rig and small cog says nothing about what happens at either end.


----------



## MikeWMass (Oct 15, 2011)

lighthouse54.1 said:


> Generally speaking a chain should be set so that the deraileur cage is verticle to the ground when the bike is in it's highest gear. (big in front and small in back).


I would question this. I want my derailleur to be almost fully extended in big-big, and able to take up slack in small-small (although I never use that combination). If I had to choose, I would let it be too slack in small-small, as it beats putting the derailleur into the spokes if I accidentally (or on purpose!) shift into big-big. Where the cage is in big-small is of absolutely no concern to me.


----------

