Hello everyone!
I’m gonna swap out my 130bcd standard crankset (53/39) with a 110bcd compact (50/34). But before I do that I wanted to know if I need to shorten my chain or get a new one. I have a 11-28T cassette currently installed in the rear wheel and the compact is slightly used (150 miles or less).
Please let me know.
Thanks,
Roland =^.^=
If your chain is just long enough now, then you’ll probably be fine. If it is a little long now, then it might be too long after the swap.
Just mount it up and see. If the little-little combo causes the rear derailleur to fold all the way up, remove a link or three.
I’d remove 2 links from the chain just so that the chain isn’t really slack when you’re on the 34 front ring.
Length aside, I’d ask how many miles you got on it currently? As we keep adding more cogs and the spacing continues to get narrower, the tolerances get tighter and chains get correspondingly thinner, so the recommended service life for a 10- or 11-speed chain these days is about half what we expected out of a 6/7 speed chain back in the day. So, might be a good enough excuse to just go with a new one anyway, especially since an older chain will accelerate the wear on a new(er, I know you said ~150mi) set of chainrings you just invested in. Obviously in that case you’d need to take out a few links from a brand-new chain regardless, so it’d be just as easy to remove 4-5 (or whatever) as doing 1 or 2 from your current chain.
Unless your chain is currently at the long end for your setup, you’ll be fine leaving it as-is.
If the dérailleur’ strange is maxed out in the 34X11, just remove 1-2 link pairs.
All depends. I purposely set mine up that they are just long enough on a 53-28 setup. This allows me to go from compact-standard and 11/23 to 11/28 or anything in between without messing with the chain. If your do need to shorten it I would be careful not to make it too short so you can’t swap back to the standard crankset in the future. Also, I will 2nd the caution that if the chain has some miles on it just replace it. Lack of chain replacement gets expensive when you start ruining chainrings and cassettes.
First check with a chain-checker as to whether the chain is stretched or not. These are simple to use and cheap.
When the compact crank is on, have the chain on the 34 chainring at the front and the smallest cog on the rear cassette. In this configuration the chain has the least amount of tension on it and still should be clear of the underside of the rear derailleur. If not, split the chain and take out as many links as needed to clear the underside of the RD yet still have the RD applying tension to the chain.
Per ST article:
"Here’s where the magic begins. You’re in small-small. You want to find the appropriate chain length that allows the chain to just clear the rear derailleur cage and pulleys. If the chain is too long, it will look like this:
See the contact? That’s bad. That means you can’t use the small-small gear. Of course, you’re not really supposed to use it anyway, but reality knows otherwise (people do it).
You manipulate the chain length simply by holding it in your hands and pulling on the left half (this will pull the bottom pulley down). Pull it to where the chain slightly clears everything – like this:
Let me say this clearly so we all understand: THAT’S IT! That’s how you size a chain properly…"******
It depends on who they measured your chain when they put on the existing config. It’s simple to test.
If so, no need to shorten it. If not, don’t bother shortening, get a new chain. Chains are relatively cheap and are one of the most disposable parts of your bike (if you want your cassettes to last!)
For my money, if I were making this switch, I’d just use it as an excuse to change the chain anyway.
See the contact? That’s bad. That means you can’t use the small-small gear. Of course, you’re not really supposed to use it anyway, but reality knows otherwise (people do it).
I suppose on a tri bike that might be the case, but my TT bike has the chain sized for the big ring. I can only use about half the cassette with the small ring but that’s enough. Derailleur tension sucks power.
Thanks for the tips guys! I ordered some tools to do this swap properly and will post an update.
See the contact? That’s bad. That means you can’t use the small-small gear. Of course, you’re not really supposed to use it anyway, but reality knows otherwise (people do it).
I suppose on a tri bike that might be the case, but my TT bike has the chain sized for the big ring. I can only use about half the cassette with the small ring but that’s enough. Derailleur tension sucks power.
How much power?
all of it… when the chain snags and tangles in the mech…
How much power?
Not that I think it matters, but ~600W at initial takeoff, and less everywhere else.