I'm posting this query because I'm not believing what I'm seeing in terms of chain wear and mileage.
Chain: SRAM PC58
Setup
48/38/28 crank set ridden 95% on the middle ring, 5% on the big ring
7 speed 13-28 XT HG cassette (7 of eight custom spaced, actually)
Suntour Command Shifters & Suntour XC Comp rear derailleur
700c x 35mm slicks @ 90 psi.
Riding Conditions
Dry, paved roads
Rider
Extra Large, 245 lb.
What I don't believe.
The chain has a bit over 1500 miles. Every 400 or miles or so its been taken off the bike, rinsed twice in clean odorless mineral spirits then lubed by soaking in generic 30W motor oil/odorless mineral spirits blended in equal proportions.
I've been expecting it to show near to or just shy of 12-1/16" distance between rivets at the 1500 mile wear point. But it still shows just a split hair more than 12" and way less than 12-1/16". I'm measuring with a Stanley metal tape measure 3/4" wide; and have measured the chain at several points with RD stretching it as tight as possible.
What I don't believe:
--Is it possible to have only worn the chain very slightly, far less than 12-1/16" in 1500 miles of riding?
--Should I go ahead and put a new chain on anyway, or ride this chain until it approaches 12-1/16" wear?
At $12 per sram pc58 chain inventoried from the winter mail order sales, the issue is not the money (grin). Rather, its a question of best practice.
I've been using Jobst Brandt's and Sheldon Brown's chain wear articles as guides.
http://www.sheldonbrown.com/brandt/chain-care.html
http://www.sheldonbrown.com/chains.html
From above link by Jobst Brandt
Chain wear is caused almost exclusively by road grit that enters the chain when it is oiled. Grit adheres to the outside of chains in the ugly black stuff that can get on ones leg, but external grime has little functional effect, being on the outside where it does the chain no harm.
The black stuff is oil colored by steel wear particles, nearly all of which come from pin and sleeve wear, the wear that causes pitch elongation. The rate of wear is dependent primarily on how clean the chain is internally rather than visible external cleanliness that gets the most attention.
Only when a dirty chain is oiled, or has excessive oil on it, can this grit move inside to causes damage. Commercial abrasive grinding paste is made of oil and silicon dioxide (sand) and silicon carbide (sand). You couldn't do it better if you tried to destroy a chain, than to oil it when dirty...
Chain Life
Chain wear depends almost entirely on cleanliness and lubrication rather than being a load problem. For bicycles the effect of load variations is insignificant compared to the lubricant and grit effects. For example, motorcycle primary chains, operated under oil in clean conditions, last as much as 100,000 miles while exposed rear chains must be replaced often.
The best way to determine whether a chain is worn is by measuring its length. A new half inch pitch chain will have a pin at exactly every half inch. As the pins and sleeves wear, this spacing increases, concentrating more load on the last tooth of engagement as the chain rolls off the sprocket, thus changing the tooth profile. When chain pitch grows over one half percent, it is time for a new chain. At one percent, sprocket wear progresses rapidly because this length change occurs only between pin and sleeve so that it is concentrated on every second pitch; the pitch of the inner link containing the rollers remaining constant. By holding a ruler along the chain on the bicycle, align an inch mark with a pin and see how far off the mark the pin is at twelve inches. An eighth of an inch (0.125) is one percent, twice the sixteenth limit that is a prudent time for a new chain.