Spoonrobot 

I'm debating running a regular gear ratio with tiny chainring/cog. I've got a 36t ring and 14t cog sitting around and I'm curious if anyone has run something like this for any length of time? Its 69 inches so it will work great around here as far as the actual ratio is concerned.

Any issues with excessive wear? I've been getting 1200-1500 miles out of my chains and 7000-8000 miles out of my cogs, this is with pretty normal 46 chainring and 17/18 cogs.

I ask because even when the ratios are essentially the same the ride feels a lot different. I spent about a year on 46/18 and loved it, often going to 46/17 for flatter rides. Gearing felt good, easy to spin, nice power on the hills and really matched my riding style. When I switched to 52/20 which is about the same ratio (70 inches) I hated it. The ride felt sluggish and I never felt like I had a good spin, maybe due to the added mass in the extra chain links and larger ring/cog? I'm not sure, anyway if you have input that would be great.

Thanks

TejanoTrackie 

I don't see any advantage and can definitely say from racing on the track with a 14T cog that it wears out a lot faster than a 17T or 18T cog. Also, the 36T inner chainring on my geared bike wears out a lot faster than the outer 52T chainring. As to one setup with the same ratio feeling different than another, I really can't see this being the case, since the mechanical advantage is the same regardless of the sprocket combination, and mass differences are tiny. Also, mass matters only when you are accelerating.

bieterman 

Tejano,

Can you speak as to what percentage of your miles are spent on the 36t vs. the 52t? I don't doubt that a smaller chainring would wear relatively faster than a large one, I'm just curious if it sees more spins with the chain than the large ring, and if that can reasonably be factored in.

Thanks

TejanoTrackie 

It's probably 50-50. I basically don't shift the front a lot. I pretty much maintain the same cadence whether I'm on the big or small chainring, so there is no significant difference in the number of revolutions. The thing to understand is that the tension on the chain and therefore the loading on the chainring teeth increases as the chainring size decreases, which is the main reason that smaller chainrings wear faster than large ones. This is why tiny granny gear chainrings on mtbs are usually made of steel, rather than aluminum.

SquidPuppet

Something is amiss here.

With 700 x 28c

46 x 17 = 72.4 GI
46 x 18 = 68.4 GI
50 x 20 = 66.9 GI

That's a significant difference and you should feel the difference.

The odd thing is, the 50 x 20 should have been much easier to spin, not harder. Almost 8% easier.

Bandera

TT is correct, wear will be accelerated on 36X14 68GI vs. a 48X18 70GI on 700x23.
Small chainring & cog combinations will be particularly finicky about chainline & chain tension as well.

Traditional FG road gearing works well for a number of reasons.

Not unless you are the cycling equivalent of the Princess & the Pea, it's a lower ratio than 46x17 not the same.

-Bandera

Stun

Yes. I think the 18 in back is magical for good chain tension and reduced wear. I have one on a ss bike right now and it just keeps going and going...

Spoonrobot 

Look back at my original post. I was running 52/20, which is 69.6 with 28c tires.

Although it does appear I was comparing 46/18, 46/17 and 52/20. What I meant was that 46/18 felt great, 52/20 felt like garbage. Also, 46/17 felt great.

I'm not ruling this out as being a psychosomatic issue. But now that I think about it the 52 ring was steel and the 46 was aluminum. Other than cog & chain everything else on the bike was exactly the same. Probably still within the realm of statistical noise but I do wonder. Anyway, thanks for the input all. I'm going to go ahead and stick with what I like and get another 46 ring since they're super cheap anyhow.

79pmooney

Many, many miles of fix gear riding here. The vast majority on 42 and 44 tooth chainrings. (Gears from 67 to 72 with 70 being the most common.) Sopme time on a 48 with a big cog. The big ring/cog feels a bunch smoother to me. Also does wear better. In recent years I have been doing the vast majority on my riding on a 42 or 43 on my new fix gear, but that is driven entirely by the need to go to very low gears for serious climbing; a goal the bike was designed for. A track standard low (using track quality 1/8" drive) is 42 x 23 (44 BCD rings and a lesser Surley? cog. I use EurAsia cogs for all the rest down to 12 teeth. (I ride the 42-12 on serious descents. I wouldn't want to do serious miles on that 12; $50/per would add up fast, but that 94" gear is a blast on real descents!)

I know I could save money riding bigger cogs but that low gear issue ie a real limiter. And my knees say I should ac cept the $$s spent on drive train wear. Good thing is that with 1/8" and quality parts, it still is a very long lasting system. But going from ~17 teeth everyday to 13 teeth? That is 17/13 = 30% higher chain tension spread over significantly fewer teeth. (Crudely: say 1/2 the cog shares the load, then 8.5/6.5 = again, 30% more load seen per tooth. 130% X 130% = 69% more wear. (Yes this is high since in both cases the last tooth engaged sees most of the load; it in not spread evenly. But that first 30% you cannot argue with.)

Another factor is that chains run more reliably over bigger chainrings and are less likely to be throw off with rough roads and chain slack. (And chain slack or unacceptable loads on BB and hub bearings are a fact of life with cheaper, not so round cranksets.)

Ben

SquidPuppet

LOL. I checked the numbers ten times to make sure I wasn't goofing, and I did anyway.

But guess what? 52 x 20 at 69.6 GI is still a lower ratio than 46 x 17, so it should have been livelier.

I'm going with the psychosomatic vote.