OrangeBike

First time sizing my own chain, want to make sure this is correct. Chain is a SRAM PC870 (love that PowerLink).

From smallest gears:


To largest gears:


Thanks.

Pars 

Possibly a little tight in big-big, not that you would intentionally use that. Did you do the one link overlap per Sheldon, on big-big and NOT run thru the derailleur? About half-way down here.

due ruote 

In the top pic your chain looks slightly slack; in the bottom one, your rd looks like it's gasping for breath. Taken together, I'd say you're at the limit of your rd's chain wrap capacity. Given that the pictured combinations are both gears you should avoid, and it will shift onto the large/large combo, you are probably OK. If anything I would add a link and see if the chain is too slack.

ThermionicScott 

I might have left it a link longer, too. Like my barber always said "it's easy to take off more, but it's harder to put it back."

Lascauxcaveman 

better make two,be easier that way

But yeah, I'm with you. I'd rather be reminded not to use the small/small combo (by having the RD jockeywheels bumping on the chain) than to be reminded not to use the large/large combo (by breaking my RD).

OrangeBike

I started with the full length of the new chain, since it was only a couple longer than the old.

Took off two to match the old, slack enough to hit the chainstay on the smalls.

Took off two more and ended up with this.

By two I mean an outer and inner combination of links, crossing three pins.

Rides well enough...

OrangeBike

If I put a straight edge on the chain with the smalls and I am slightly slack as it is, am I good to go?

ThermionicScott 

"Slightly slack" is always fine on a derailleur bike. You don't ever want it to be so taut that the chain is as straight as a ruler.

due ruote 

OK, what's a link? I thought it was an inner/outer pair. But maybe that's not right. If each inner or outer segment is a link, then what should we call a half link?

Lascauxcaveman 

Oh, I don't know, really. I just think everytime I see someone saying "try taking a link out" someone else always says, "Well, you have to take a a pair." It was just my turn to be the smartass this time.

Although, when you buy a new chain, it always says something like 114 links or 116 links on the package. That would be 57 or 58 links, if you were talking pairs.

dddd

Looking at the photo, I would myself move the derailer claw hanger forward about 1/8", since it looks like there is yet plenty of grip surface on the dropouts and because the chain appears so tight on the big/big so as to possibly cause slow ("tight") shifting off of the largest cog.

There are many reasons why never to use the small/small combination (I said many), but why does anyone advise against using the big/big? It's one of the most-useful gears in the entire range, given that it allows the rider to avoid ceding momentum with a front downshift when cresting a hill.

Note that a sufficiently-long chain is needed especially with older single-sprung-pivoted derailers like the OP's, otherwise the chain gap may become sharply larger as the largest cog is engaged. Too much gap requires the derailer to overshift the largest cog in order to make the shift, which risks putting the chain over into the spokes!
Additionally, largest-cog-size limits of the particular derailer must be respected, especially when these are bigger than published figures from the manufacturer.

But, with any sort of modern chain (why use anything else!), there should be absolutely no other concerns about crossing the chain from big-to-big, given that these older bikes typically have longer stays and narrower cog stacks. Only if the bike is so poorly set up so as to have the crankset outward from where the chainrings are centered within the freewheel's width (which is common enough) ...but even with an outwardly-positioned crankset I still use the big-big even for sustained climbing. It's not like the chain or cogs are going to wear out prematurely, that just doesn't happen(!), but using the small/small combo increases and/or contrates loading and/or wear greatly on the entire load path (through the frame and all), as well as chipping up the chainstay paint right away.

Admittedly, there are bikes out there with front derailers not optimized for using the entire range of cogs while in the big ring, but careful adjustments, narrow chain (and subtle, carefully-considered cage tweaks where needed) can easily gain full use of the freewheel's range without ever having to "trim" the front derailer's shifter.

End of rant, but I use the entire spread of even 8, 9 and 10-speed cassettes in the big ring, even on bikes with short 40.5cm chainstays.

OrangeBike

I also find that on any bike I ride, I'm on the big ring all the time. I rarely need to downshift to the smaller one. I am also guilty of the big/big sin.

OrangeBike

Tell you what, I will take a picture of it with the two links (out and inner) back in and see what everybody says.

If that's too loose and this is too tight, then dddd's suggestion of moving the derailleur forward a scootch is the way to go.

repechage

Im a small ring guy, having to race a 44 x 14 top gear way back conditions one that way.
That said, when its time for a big cookie, its 53. Gotta listen to John Howard.

dddd

With a modern chain, You'll need to add a second PowerLink in order to lengthen the chain. Re-riveting modern derailer chain usually results in an extremely weakened sideplate retention at the affected pin.

I wouldn't place two PowerLinks next to each other, since their tolerances are measurably different from the rest of the links. What I do in such instance is to splice in a typical remnant piece of perhaps 6-10 links, so that the two PowerLinks are not so close to each other.

For your test purposes, you can simply engage the two ends of your chain with the chainring, leaving a 2-link gap that is toward the front of the bicycle. The free ends can be held in place with nothing more than a loop of wire, string or a twist-tie and will not fall out of place on the chainring unless the chainring is rotated.
You'll have to do all of your "shifting" by hand, moving the thankfully-clean chain to the cogs/rings that are to be evaluated for chain "tension".
But doing it your way (with a re-installed pair of links) is also fine, for testing, just not for any serious riding to follow.

OrangeBike

That's exactly what I was going to do.

Ditto on the second PowerLink. If the next step up in length is the way to go, I'll hit the LBS and grab one.

miamijim

As long as possible in the small/small. Add more links until the rear jockey wheel centerline is just a tick below the front most centerline.

OrangeBike

This is small/small with the extra two links back in. Chain rests on the chain stay.


Here's the big/big.


Here's what I mean by two links.

Here's how I did it.

OrangeBike

As far as the derailleur being maxed out, on the big/big, the body of the derailleur is at full lock (I dunno what to call it, car term) but the cage plate/pulleys still have plenty of twist left in them. They're far from being maxed out.

In case anybody is searching, this is a first generation Campagnolo Record.

ThermionicScott 

That big-big looks a lot nicer.

OrangeBike

I can honestly say I will never be on the smalls, I'd have to be towing a sled up a hill... but this does put me in a pickle as I now have to lengthen this chain or replace it, I don't have any scraps laying about.

miamijim

You could always bail on that RD...

OrangeBike

Nope, came with the bike. Keepin' it real.

due ruote 

Not sure I understand this. The small/small is far from your lowest gear.

You said earlier you are almost always on the big ring. Why not go with a closer ratio freewheel like maybe a 14-24?

OrangeBike

Oops, yeah, misspoke there...