Using gears

[Cope]

Looking at gear ratios, how does one make the best use of a set like this:

102.9 80.3 61.8
95.6 74.5 57.3
89.2 69.6 53.5
83.6 65.2 50.2
78.7 61.4 47.2
70.4 54.9 42.3
63.7 49.7 38.2

Assuming one averages at around 70 inches, as one does on fixed, and might drop to 60 or so for smallish hills, and move up to 80+ for longer flat or downhill sections, how does one get the most efficient change?

It'd be annoying to have to change both up -and- down, to go from middle to outer ring, to move from 80.3 to 83.6... so maybe one starts on the outer ring on 70.4? But then down to 63.7 might be too much?

All I do know, from older cycling days, is that one should avoid too much chain stretch, so smallest on the rear with largest on the front (ie 63.7) would be avoided.

 

[mercurykev]

When I'm using a bike with a triple chainset, I tend to spend most of my time in the middle chainring, as you can use every gear without an extreme chain angle. I only shift to the inner and outer chain rings when I've reached the extremes of that ring - based on the gears you've listed this means that in addition to the 7 gears derived from the middle ring, you'd get 3 lower and 3 higher gears - making 13 available gears. This approach also prevents you running extreme gears, such as small to small or large to large.

I hope that makes sense.

 

[Cope]

I only shift to the inner and outer chain rings when I've reached the extremes of that ring

Right. But this means moving to the outer ring, and thus to a *much* harder gear, or to the inner ring and thus to a *much* easier ring, and then a change. I guess that's just how it works.

I think I'm going to go for this instead:

102.9 70.0
95.6 65.0
89.2 60.7
83.6 56.9
78.7 53.5
70.4 47.9
63.7 43.3

This seems a better range, and less of a chain angle problem. But again... to go from 70 to 78 still means a double change. I guess it's unavoidable?

 

[jimboalee]

Here's the factory set-up on my Dawes Giro 500.
As you can see, Dawes know a thing or two about bikes.

Note- Middle ring is the one with the most combinations. In normal riding, I keep the chain on the middle ring.
Big ring is for drafting other riders, downhill and riding with a gale up my jacksee.
Small ring is for serious climbing.

PS, Its called a 'double step' chainset.

 

[mercurykev]

Right. But this means moving to the outer ring, and thus to a *much* harder gear, or to the inner ring and thus to a *much* easier ring, and then a change. I guess that's just how it works.

It is just how gear systems work. There is a technique called double shifting. For example as you shift down onto the inner chain ring, you shift up 2 gears on the cassette and vice versa on to the outer ring.

 

[Randochap]

These are the kind of questions that, ultimately, only you can answer.

Personally, I don't think about what gears I'm actually using, once I'm on the bike. I just use the ones I need.

Double-shifting is a given at some point. I don't like "big" shifts, so I'll most often drop the 10T dif between my two biggest rings at the same time as shifting up or down a cog or two. That maintains cadence. The little ring doesn't get visited often, but is there when needed

I notice your lowest gear is 38.2. Seems a bit of a waste of a triple to me. What's your granny ring?

Have a look at my gear page (keeping in mind it's "geared" toward long-distance riding).

 

[Cope]

I notice your lowest gear is 38.2. Seems a bit of a waste of a triple to me. What's your granny ring?

What's a granny ring? The biggest at the back? Or the smallest at the front?

I'm limited to 7 speed atm, and I don't want very big gaps between the gears, so I favour a closely spaced rear cassette - the downside is that it's 21 teeth on the lowest gear.

But then the biggest hill I have to cope with is 10% for 1 mile.

 

[Randochap]

What's a granny ring? The biggest at the back? Or the smallest at the front?

Smallest on front.

I'm limited to 7 speed atm, and I don't want very big gaps between the gears, so I favour a closely spaced rear cassette - the downside is that it's 21 teeth on the lowest gear.

Best worry about how big gaps on crankset are. You can still run pretty close spacing on 7-sp cassette and get up to 28.

But then the biggest hill I have to cope with is 10% for 1 mile.

10% for 1 mile? I'd certainly want a lower gear for that!

 

[Lazy-Commuter]

I tend to think about what's coming up ahead of me and what I'm likely to need to do to keep my cadence in my comfort zone of around 90rpm. I normally switch between the granny ring and middle ring when I'm on 3 or 4 (out of 8) at the back, and go to the bigger ring up front when I'm on 6 or 7 at the back.

I might combine that with an offsetting shift or two at the back, but generally not: I normally only shift the front when I can see it's going to be "worth it". If I can see I'm going to only be in the higher / lower gear for a little while, I'll just run out to 2 or 7 at the back in combination with the middle ring.

So on my commute, the bulk of it is done on the middle ring mostly combined with 3, 4, 5 and 6 at the back. Exceptions are ..

- The hill out of the village where I live. There's a bit where it switches from being a "little bit up" to "lots up" (by my standards, of course) and it's that point that I jump to the granny ring up front. I will normally have been in 2-3 or 2-4 depending on how my legs feel and so this is quite a big drop down, but it just happens to be needed!!

- A couple of bits where it's flattish, or downhill. There's one long (flatter) one of these and a couple of shorter, steeper sections. For those, I use the outer ring up the front with 6, 7 or 8 at the back depending on which way the winds blowing and how strong.

It suits me, and the exact gears used are of course varied appropriate to my level of fitness, the terrain I'm on and what the wind is up to.