Road Cycling - interesting analysis

I recently purchased a new bike and went from two to three chain rings. Furthermore, my cassette changed. I had a three gear range on my old bike that represented my sweet spot for motoring on the flats. I wanted to know what gearing combinations on the new bike were equivalent to these three gears. Here's the graph that I created to answer the question. It's probably self-explanatory, but if any part of it is confusing, please ask so that I may clarify.

The other benefit of this analysis is that I know exactly which modification I need to make to my cassette to get my sweet spot back.

The Bianchi is my old, two-chain ring bike while the Tommaso is the new three-chain ring bike. The gearing sweet spot has a yellow box around it. The blue shaded regions are the "optimal" regions for the chain ring (i.e. the regions that provide little lateral chain flex).

so essentially what you're saying is that f or you the triple presents no real benefit

so essentially what you're saying is that f or you the triple presents no real benefit

Not really. I ride on hilly terrain frequently and will definitely use the gearing in the lower range. If you look at the chart, you'll see that the triple adds four gears on the low end that I didn't have on the double.

30X19
30X21
30X23
30X25

-mark

It is a convention to talk about gear ratios in gear-inches, so you can compare pedal-to-wheel ratios for any combination of cogs and wheel size.
You also have to discount the non-usable gears.

I wouldn't have thought that the 'optimal' regions would be the same region on the cassette for each chain ring. Optimal for the 30 ring would be more like 17-25 (or even 14-25) sprockets, and the 52 ring the 12-17 (or even 12-21) sprockets... wouldn't it?

Interesting analysis, though. You've confirmed what I expected to be the case with triples - there's no point in having a cassete with the range and spacing of a 12-25. The triple ring will easily allow you to run more of a straight-block cassette (12-21, 13-23 etc) - this'll still give you decent climbing gears, while at the same time allowing easy fine tuning to find the 'sweet spot'.

so essentially what you're saying is that f or you the triple presents no real benefit


I was thinking the same thing. :)

I was thinking the same thing. :)
It gives him no advantage on the flats, which is what his 'optimal' analysis is about. No big surprise there - I doubt anyone gets an advantage from a triple on the flats.

There are still lower gears for the hills = potential advantage if geneman has been struggling a bit with the Bianchi gearing.

Knock, knock.... I'm back again! Looks like at least on the flats you're most comfortable running at or about 64 gear inches. Since you've got your sweet spot nailed, it's time to gear your Bianchi at 64 inches and ride it fixed..... ...You'll be most happy..... ;)

.......and the drumming continues......

I wouldn't have thought that the 'optimal' regions would be the same region on the cassette for each chain ring. Optimal for the 30 ring would be more like 17-25 (or even 14-25) sprockets, and the 52 ring the 12-17 (or even 12-21) sprockets... wouldn't it?.

Nice catch ... you're absolutely right. I thought about this the day that I made the graph a month ago and never changed it. It certainly changes the range of usable gears. However, because the middle chain ring is not centered relative to the cassette, the lower gears (including the 25) still offer little deflection when on the middle ring ... which is a plus.

And once again, your revelation on the other thread concerning switching cassettes to a narrower range is quite relevant.

Thanks,
-mark

Knock, knock.... I'm back again! Looks like at least on the flats you're most comfortable running at or about 64 gear inches. Since you've got your sweet spot nailed, it's time to gear your Bianchi at 64 inches and ride it fixed..... ...You'll be most happy..... ;)

.......and the drumming continues......


By the time you say it another 10 times, I'll finally be convinced. I'm thick that way.

The problem with the Bianchi was that the frame was slightly too large for me to begin with. So if I were to make a fixie, I would do it with another frame entirely.

Who wants a 58cm Bianchi Sport SX with 105 cranks? It's tange9 tubing and dates back to the late 80's. It has a few rust spots on the top tube (from sweat) and the area around the binder bolt is a bit suspect. Finally it's got a nice 140mm modolo quill stem that's pretty much fused to the fork at this point.

Maybe I'll list this in another thread as a project bike. We all know how rabid Bianchiphiles can be.

-mark