Singlespeed & Fixed Gear - Chainring Size vs. human body build and height

Yeah, I know this is a totally dorky thing to ask, but when I was at the track last night I got into a conversation with an old, experienced trackie (who seemed to totally know what he was talking about) and as we got talking about gearing, he said that he'd "prefer", with my height and build (about 5'9", haven't weighed myself in a couple years, but would estimate about 145-150lbs.) that I be riding with a smaller size chainring. In other words, e.g., instead of riding 48x15 it would be BETTER for me to ride 45x14 because of the front plate being smaller, even though the gearing is essentially the same.

My question is why? Why would he say this? How does height/build affect this? I would have asked him, but we were both on the way out and I was in kind of a hurry and didn't get the chance. Maybe next time if no one here has any answers.

i can't possibly see why. I would keep the 48 because that chainring is probably more versatile for you if you were riding track. As Jose R has said, you will more likely go up in gearing once you build up strength and confidence.

It's all about leg speed.

Correct me if I'm off-base here but the only difference I can see is this. The thought behind larger chainring and cog is longer wear due to more contact area. Here is where my question is, More contact area would equal more resistance, right? And resistance would make you slower, right? Can someone shed a bit of light on this?

I'd be astonished if there was a serious issue here. Bigger rings w/ same ratio give marginally more weight (chain is longer, too), and wear slightly slower (and put less stress on chain), I think. Nothing most of us would ever notice.

Ooops! I misunderstood the question. Larger rings will last a bit longer and look cooler.

I was thinking about this question today, and I still can't quite figure out why he would base the size of the drivetrain on the relative physiology of the individual rider.

The essential differences between same ratio combinations, but different cog/chainwheel sizes, is:

Small cog/chainwheel = quicker/faster acceleration, less weight = good for sprinting

Big cog/chainwheel = less friction, better efficiency = good for mass-start, points, pursuits

The above also implies that the small C/C combo will wear faster than the bigger combo (as was stated above).

But, there is also other criteria to consider before making the choice of drivetrain sizes:

What type of racing will you be focused on? Do you fancy yourself a sprinter? What type of track? Kissena is 400m with 20+ degree banking which allows for bigger gearing in general. What type of racing goes on at Kissena on Wednesday nights or the special events on weekends? What is your budget for components? TA and Shimano makes 45T track chainrings. $60 and $82.50, respectively. Then $20-30 for the cog.

This is the reason most hardcore trackies bring multiple rings and cogs to the track. Each event is different and calls for different approaches in terms of bikes and components.

For your body weight and height, I would assume he doesn't believe that you could turn over a 48T fast enough to cover any attacks in a race; and that a 45T gives you a quicker turn of speed to be more competitive. But its still a generalization, and the answer is much more individual.

It would be great if we all had an array of component available to us when we head over to the track and had a mechanic to make the changes. If you have the resources, then it would be good to try out his suggestion and see how a 45x14 feels over a 48x15. If you don't, then let things be as FF suggests, 'cause its cheaper to buy a cog than a chainring.

http://www.delaunecc.org/track.htm

http://www.velonews.com/tech/report/articles/5832.0.html

There is no difference as far as it being the same ratio. A ratio is a ratio. If they are identical, then it doesn't matter what you got up front or in the back. It is still the same lever. A smaller combo is less efficient if you want to really start breaking down into physics. More wear as well with this system. The weight you save is negligible. It's only going to be a few grams. You won't save too much metal. The 48 will give you more versatility than the 45. IMO, go with the 48.

Sounds like a bunch of BS to me, one things for sure, I refuse to "microdrive" my drivetrain, unless its a track event I wont run anything less than a 16t cog, reason being wear and safety, the more teeth the chain has to grab on the rear the happier I am.Besides, a 52t chainring isnt anywhere near big enough to cause clearance problems when I bunnyhop curbs.My usual setup is a 52/17 or 52/16, works just fine.Im 5'11" and about 160lbs w/o messenger gear on.

I was thinking about this question today, and I still can't quite figure out why he would base the size of the drivetrain on the relative physiology of the individual rider.

The essential differences between same ratio combinations, but different cog/chainwheel sizes, is:

Small cog/chainwheel = quicker/faster acceleration, less weight = good for sprinting

Big cog/chainwheel = less friction, better efficiency = good for mass-start, points, pursuits

The above also implies that the small C/C combo will wear faster than the bigger combo (as was stated above).

But, there is also other criteria to consider before making the choice of drivetrain sizes:

What type of racing will you be focused on? Do you fancy yourself a sprinter? What type of track? Kissena is 400m with 20+ degree banking which allows for bigger gearing in general. What type of racing goes on at Kissena on Wednesday nights or the special events on weekends? What is your budget for components? TA and Shimano makes 45T track chainrings. $60 and $82.50, respectively. Then $20-30 for the cog.

This is the reason most hardcore trackies bring multiple rings and cogs to the track. Each event is different and calls for different approaches in terms of bikes and components.

For your body weight and height, I would assume he doesn't believe that you could turn over a 48T fast enough to cover any attacks in a race; and that a 45T gives you a quicker turn of speed to be more competitive. But its still a generalization, and the answer is much more individual.

It would be great if we all had an array of component available to us when we head over to the track and had a mechanic to make the changes. If you have the resources, then it would be good to try out his suggestion and see how a 45x14 feels over a 48x15. If you don't, then let things be as FF suggests, 'cause its cheaper to buy a cog than a chainring.

http://www.delaunecc.org/track.htm

http://www.velonews.com/tech/report/articles/5832.0.html

Good words!

S/F<
CEYA!