Does 10sp really wear faster?

[Grant McLean]

Dave from Highlands Ranch, CO wrote

"The thickness of cog teeth has changed over the years. Cogs haven't been 3/32" (2.38mm) wide for a LONG time. 8 speed Campy cogs are only 1.9mm thick. Campy and Shimano 9 cogs have nearly identical thicknesses of 1.75 and 1.78mm. Campy and Shimano 10 cogs are 1.70 and 1.60mm respectively. Shimano 10 cogs are 10% thinner, while Campy 10 cogs are 3% thinner than 9 speed."

Yesterday Dave a I were discussing some of the measurements of drivetrain components, in relation to wear. I suggested there are some myths around the "10sp wears out faster" idea, and thought that some measurements would help show why I think this is largely false. Lets review what can be measured:
1) All chainings are 2.0mm wide regardless of how may cogs are on the rear. 2) Even the narrowest 10sp chain is 2.35mm wide at the bushing, and has to be this wide, in order to roll on a 2.0mm chainring. Therefore, even the narrowest bushing is wider than any chainring or cassette cog.

Lets look at the cog thickness for a second. Why are they thinner? 'Cause there is more of them!! Take Dave's 8sp example. 1.9mm thick x 8cogs is a total of 15.2mm of cog width. Take 10x 1.6mm and you've got 16mm of total cog with. Even more, you will likely get more miles from a 10sp cassette than an 8sp one because it has more useable combinations.

Take an 8sp 12,13,14,15,17,19,21,23 and a 10sp 12,13,14,15,16,17,18,19,21,23. If you mostly ride in the middle combos, (i certainly do) you have additional 16 and 18 tooth cogs to select while riding, thus reducing the number of miles spent on the 15, 17, and 19 tooth cogs. You might expect a 30 - 50% increase in the total number of miles you could ride before those heavy user middle cogs get worn out.

Am I missing something?

Grant

[e-RICHIE]

snipped:

Am I missing something?
Grant


FRANK: Let me understand, you got the hen, the chicken and the rooster.
The rooster goes with the chicken. So, who's having sex with the hen?

GEORGE: Why don't we talk about it another time.

FRANK: But you see my point here? You only hear of a hen, a rooster and a
chicken. Something's missing!

MRS. ROSS: Something's missing all right.







from
http://www.seinfeldscripts.com/TheRye.htm

[Dave]

I wouldn't argue that longer life isn't possible with a 10 speed cassette, but it could just as well be that the extra cogs are nice to have, but seldom used. Shimano 12-25 an 12-27 users who've been without a 16T cog finally have an extra in the middle where it will get used. Others will only get an extra cog at one end or the other, which will not extend the cassette life. I always used a 12-21 9 speed, which has both a 16 and an 18. When 10 speed first came out, there was no 12-23 available, so I got an 11-23 and skipped the 18T cog. The 11T was worthless for a lightweight spinner, so I switched to a 12-25. Never have missed that 18T cog after using 10 speed for more than 5 years.

I think the point that you are missing is that a cassette is worn out when only one or two cogs skip after a new chain is installed. Those cogs are the same ones that wore out first on an 8 or 9 speed cassette. Replacing two cogs can involve buying two sets of paired cogs and the cost can be nearly as much a whole new cassette.

I thought you wanted an accurate analysis of the surface of each cog. Used the same number of miles, a 10 speed cog and chain will wear out a bit faster.

Some shimano 10 users are reporting very poor life from their chains. This makes no sense to me, since the chain is only 5% narrower. I haven't found that to be the case with Campy, but my maintenance technique is apparently a lot more effective than others. I expect to get at least 5,000 miles from a chain and even then, mine won't measure 1/16" wear per foot.

[Dude]

I don't open a can of worms but I can tell you that the shimano chains most definately wear out faster.

You're lucky to get 1000 miles out of them.

[vaxn8r]

I don't open a can of worms but I can tell you that the shimano chains most definately wear out faster.

You're lucky to get 1000 miles out of them.
Mine start slapping around a bit at about 1,400 to 1,500 miles.

[Ti Designs]

Some shimano 10 users are reporting very poor life from their chains. This makes no sense to me, since the chain is only 5% narrower. I haven't found that to be the case with Campy, but my maintenance technique is apparently a lot more effective than others. I expect to get at least 5,000 miles from a chain and even then, mine won't measure 1/16" wear per foot.

Let's spell it out. Chain wear is a function of friction, surface area and material. The amount of friction isn't changing much and the material is about the same, so it's mostly a function of the two parts which come into forced contact with eachother - pins and inner roller surfaces. The 8-speed Shimano pin was 7.2mm wide, the 9-speed pin is 6.5mm wide (a loss of over 10%), the 10-speed pin is 5.6mm wide (a loss of just over 16%).

The chain is clearly the weakness in the system here, but it can drag the whole system down with it. Chains don't really stretch, the pin wears into the roller surface, giving that pivot a little extra room. This also throws off the distance from pivot to pivot. With an increase in this distance you see an increase in leading edge force on the cog or chainring as they pick up new chain links, thus the increase in wear due to a worn chain.

The bottom line is that changing chains on the new systems is like putting gas in the tank - it's part of the cost of putting on the miles.

[Sandy]

I replaced my Shimano 10 speed chain at 4,000 miles. It really wasn't needed, but I thought that a new chain would help prolong the life of the cassette. I have about 8,000 miles on my bike (and the 10 speed Dura-Ace) and have replaced shifter cables and rear shifter(under warranty). The rear hub's axle broke and it was replaced under warranty. Chains tend to last well for me.


Sandy

[jerk]

yes.