Originally Posted by canklecat

Has anyone measured the original chain length/link number on an Ironman with 52/42 chain ring and 13-24 freewheel? I think it depends on the frame size. I pretty much start from scratch, almost never use the original chain.

Have you found a longer than usual chain length to work better? Some of those older chains really, really don't like being tight. Or perhaps the drivetrain doesn't because those chains were overstrong. Then again, I can't remember not swapping the chain out on any build.

. But this week I noticed what felt like unusual resistance, almost like binding, with the new chain in the 42T chain ring and 24 freewheel cog.
Over the summer it seemed like I was struggling more on hills, despite being faster overall. It was unusually hard to climb with the Ironman in the 42 chain ring and 21 or 24 tooth freewheel cogs. It really shouldn't be; that's a fairly straight chain line. I'd look to a bent axle or slipping QR first.

The crank spins freely. Ditto the hubs and freewheel. No brake rubbing, etc. But when I spun the crank backward I could feel unusual resistance in the 42/24 combo. Check for a bent chain ring, see if you've got a bind in the BB spindle (visually easy to see). Then, like you, I'd move rearward. First thing I'd check is the rear wheel alignment. Resistance can come from gears/pulleys/chain path, but generally is overcome by the power of our massive thighs..... Resistance at the wheel is much more noticeable, and a crooked rear wheel is scrubbing against the pavement (and sometimes the frame), so check that.

One thing I'd changed which affected chain tension was moving the rear wheel as far back as it would go in the adjustable dropouts. But that amounted to only 1/4" from the original setting. Are you using the dropout adjusters? Highly recommended, and I've found that about mid-way in the dropout seems to work well.

I disassembled and cleaned the jockey wheels again (I did this back in July). They were already a bit sluggish, so the Park CL-1 lube wasn't a good choice. For now I'm leaving them dry until I decide on a more suitable lube. But even with the dry, free-spinning jockey wheels there was still unusual resistance in the 42/24 gear combo. Even a crudded-up jockey wheel shouldn't cause that much noticeable resistance, more like chain slap or chain issues when back-pedaling. It's hard to find, but Slick 50 1-Lube is my absolute favorite for jockey wheels. I disassemble them completely, clean and put back with Slick 50 1-Lube.

The rear derailer cage seemed to be at an unusual angle, and since I was swapping to a 13-25 SunRace freewheel I didn't want to risk damage. Especially since I might go to a 13-28 freewheel later, depending on how it goes with the 39T chain ring next week. Beat me to it, but it should be betraying itself with noise if that's causing resistance. Often, the RD cage angle is a sign the wheel is in crooked. Seriously, I'm a decent wrench and I've found this on my bikes and those of others (usually 25 miles in, and 15 miles from home.)

I added two links to the KMC Z72 chain. Now there's much less resistance when spinning the crank backward in the 42/24 combo with the original Suntour freewheel, and 42/25 combo in the new SunRace freewheel. Apparently the chain tension was much too tight. It still doesn't spin as freely as it should, or as freely as my other two bikes. It sounds like that was part of it. I still think there's something else amiss. I'd really like to be looking down at that BB spindle when it's under load and not under load. Your resistance there would be noticeable. If that spindle is moving in there, the torque under misalignment is significant.

Subjectively, the bike felt a bit quicker on Saturday's ride, but that didn't include any serious hills where I'd normally need the 42/24 combo. I'll tackle that Sunday or Monday on some pesky climbs that have defied any improvement in speed.

So I'm guessing the Suntour chain that came with the bike was way off and I should have measured from scratch via the usual methods.

Anyway, just curious whether anyone else has measured their chains or has specs on the original chain length.

(Additional note: I measured the new KMC Z72 chains at 53", which should be appropriate according to various chain length calculators, accounting for the largest chain ring and freewheel cog, chain stay length, etc. But adding an inch seemed to result in less binding.)