Bicycle Mechanics - Chainrings, cogs, and chain widths

I know that some single-speed/fixed-gear cogs are made specifically for 3/32" width chains and others for 1/8" chains. That makes sense, but I was told by an experienced bicycle mechanic that for either width chain you use the same chainring, and that doesn't make sense to me. Is it true that chainrings don't care about chain widths but cogs do, and if it is true, why are the cogs more sensitive to different width chains than chainrings?

Jim

chain sizing (width) in accordance with no. of speeds in back is mostly dictated by very tight cog spacing in back...particularly with 9-10 speed cassettes. Tolerances and spacing in the rear is more critical to prevent rub with X-chain combinations versus up front.
George

I know that some single-speed/fixed-gear cogs are made specifically for 3/32" width chains and others for 1/8" chains. That makes sense, but I was told by an experienced bicycle mechanic that for either width chain you use the same chainring, and that doesn't make sense to me. Is it true that chainrings don't care about chain widths but cogs do, and if it is true, why are the cogs more sensitive to different width chains than chainrings?

JimThere are chainrings and cogs made specificially for the wider(inside width) chain.

chain sizing (width) in accordance with no. of speeds in back is mostly dictated by very tight cog spacing in back...particularly with 9-10 speed cassettes. Tolerances and spacing in the rear is more critical to prevent rub with X-chain combinations versus up front.
GeorgeIt's single speed/fixed gear George. Hint: no cog spacing,cross chain and derailer rub issues.Also, it's about inside width,not outside.....regards...s

X-chaining in context of running acute angles off the single front chainring across the rear cassette...rear cog clearance and chain width (internal) sizing is more critical in the rear due to spacing. As to your point sydney about chain rings and cogs made specifically to wider inside width of chain...yes and no. Many front chainrings and different size chains can be used together as the poster stated. To answer your question a bit more succintly Jim...if you have a single chain ring up front where the chain does not shift to an adjacent chain ring, chain sizing up front in terms of match between chainring tooth width and internal chain width is less critical. The reason why front chainrings in general on double and triples are less chain width specific is due to their spacing between rings which is much wider apart up front than in the rear where it is more critical that the internal width of the chain closer match the width of rear cog teeth to prevent rubbing due to X-chain angles as I stated previously.
HTH,
George

X-chaining in context of running acute angles off the single front chainring across the rear cassette...rear cog clearance and chain width (internal) sizing is more critical in the rear due to spacing. As to your point sydney about chain rings and cogs made specifically to wider inside width of chain...yes and no. Many front chainrings and different size chains can be used together as the poster stated. To answer your question a bit more succintly Jim...if you have a single chain ring up front where the chain does not shift to an adjacent chain ring, chain sizing up front in terms of match between chainring tooth width and internal chain width is less critical. The reason why front chainrings in general on double and triples are less chain width specific is due to their spacing between rings which is much wider apart up front than in the rear where it is more critical that the internal width of the chain closer match the width of rear cog teeth to prevent rubbing due to X-chain angles as I stated previously.
HTH,
GeorgeTake a pill and turn on the comprehension switch Georgie. He's not running a cassette. There is no cross chain issue,unless he has totally hosed the chainline.There are 2 inner chain widths in common usage. The 3/32 no workee so good on the chainrings and cogs specifically designed for the 1/8" width(single speed,and track). You can however run the wider chain on the narrower stuff or a mix of wide and narrow. FWIW Georgie, all derailer chains are the 3/32" nominal inner width.It's the outer width that gets narrower with greater nummber of cogs. I think you need to bone up on some of this stuff.....regards,s

not today...will let you wallow.

not today...will let you wallow.Honestly...it was a simple question with an easy answer.

There are 2 inner chain widths in common usage. The 3/32 no workee so good on the chainrings and cogs specifically designed for the 1/8" width(single speed,and track). You can however run the wider chain on the narrower stuff or a mix of wide and narrow.
That's exactly what I wanted to know. The bicycle in question is an Azuki that was converted to a fixed-gear. The rear cog was designed to be used with a 1/8" chain, but, since the bicycle originally had a derailleur, the existing chain was 3/32". We switched to the 1/8" chain, but the mechanic said not to worry about changing out the front ring. Your comments agree with his, and even better, the bike works like a charm with the present setup. Thanks very much for your input.

Jim