The truth about chain strength? 8-spd vs 9-spd vs 10-spd?

Question

I spoke recently with a well known wheelbuilder. The issue of chain durability & strength came up. He claims that an 8-spd chain has no advantages over 9-spd chains in this regard.

Huh? So is it myth? Are 9-spd chains really as strong as 8-spd chains? If so, what is with the stories (or tales) of 8-spd chains being less prone to unexpected breakage...as well as showing much less wear over the same amount of miles?

Answer 1

I haven't experienced or really heard of any strength issues between the different chains, but there is *definitely* a difference in longevity.  Notsomuch between 8- and 9-speed, but the 10-speed chains wear out much quicker.  I've only used Ultegra and Dura Ace 10spd chains and didn't notice a difference.....haven't tried any of the Sram or Wippermans on that bike yet.

Answer 2

most chain failures i have seen are not a matter of a chain breaking from pedalling.  usually they fail where a pin hasnt been installed well, or where excessive chain rub has wore the head of a pin off.  usually there is a reason they come apart.  the way the torque is spread around the chainring or cog, it would be almost impossible to apply enough force to actually break a fresh, correctly installed chain.  chains fail because of impropper pin installation or wear.

Answer 3

Back in the day when we all rode bikes with 5 speed rears, there was a ton of hubbub about chain strength by narrowing it to allow a 6 speed drivetrain, so engineers simply increased rear spacing and used the same chain.

Then came the scandalous Ultra 6 and Ultra 7 where the rear spacing was maintained but the chain and the cogs were made :::gasp::: thinner! Well, it worked.

Time went on, spacing went wider, cogs went thinner, chains went narrower. It seems that the main issue with the modern setup is chain stretching and cog wear, not strength.

EDIT: 8 and 9 speed chains are virutally identical... there are very few chains that are "8 speed only" or 9 speed only". There are a number of 10 speed chains that are 9 speed versions with thinner link plates. These tend to stretch and deform over time. It is even possible- on some drive trains- to use an 8/9 speed chain on a 10 speed but these systems are uncommon and older.

To reiterate, 8 speed chains are often marketed as 9 speed chains with no differences. Some 9 speed chains are 8 speed with thinner link plates (which may address the strength issue). Some 9 speed chains are marketed as 10 speed chains with no differences while others have narrowed cog spacing and thinner link plates.

I mutter about this (with myself) constantly when speccing a certain chain with a certain drivetrain to fit into performance and cost considerations while designing a new bike. Yes, even chains are given big consideration on your bike.