Gearing?

What is your question exactly?

Gear ratios are referring to how many "teeth" you chainrings and cogs have, not how many chainrings and how many cogs your bike has.

What kind of "upgrading" are you thinking about. Do you want a whole new drive train, or just different gears based on your terrain/riding sliding (ie bigger gear ratios for time trialing and fast group riding or smaller gear ratios for climbing . . . ) Usually, and all-around cassette is an 11-23 or a 12-25.

parkerjiff said:

Trying to understand the gear ratios on my bike. the rear cog has 9 gears and the crank has two. Crank is a Tiagra Compact 50/34. Trying to understand more about this so I can upgrade.

Before you upgrade why not study your current ratios and understand why you want to upgrade and what you want to upgrade to? Make a table based on your 18 gear combinations. This can be in wheel revolutions per crank revolutions (Chainring teeth / cassette cog teeth), gear inches--this is very traditional--(Chainring teeth / cassette cog teeth X 27), or rollout inches (Chainring teeth / cassete cog teeth X 27 X pi).

There are gear calculator applications on the web, but you'll understand it better if you do it the slow, tedious way with just a calculator. Don't groan,I did it in 1971 with a slide rule. No web, not even cheap digital calculators back then. Of course, freewheels had only five cogs.

Doing this will show you your highest downhill and sprinting combinations, your lowest climbing combinations, and where you are spending most of your time on a typical ride.

Instead of doing it Bobcat's way, I would advocate measuring it by your capabilities. If you can't climb the local hills when in lowest gear, or if you can't spin the highest gear fast enough because your torso starts flopping up and down from the excessive RPMs, then you need to upgrade.

You've got a state-of-the-art compact double. A race bike would have a 53/39 in front but most people just can't max out a 50 on the smallest rear sprocket, so why go higher? (it's the number of teeth in case you didn't know.)

You could climb a lot easier with three front chainrings, such as a 50/39/30 which is a standard road triple, but the 34 is probably all you need for most hills unless you live in the mountains.

Go ahead and use it.

garage sale GT said:

Instead of doing it Bobcat's way, I would advocate measuring it by your capabilities. If you can't climb the local hills when in lowest gear, or if you can't spin the highest gear fast enough because your torso starts flopping up and down from the excessive RPMs, then you need to upgrade.

You've got a state-of-the-art compact double. A race bike would have a 53/39 in front but most people just can't max out a 50 on the smallest rear sprocket, so why go higher? (it's the number of teeth in case you didn't know.)

You could climb a lot easier with three front chainrings, such as a 50/39/30 which is a standard road triple, but the 34 is probably all you need for most hills unless you live in the mountains.

Go ahead and use it.

+1 using this method. This will prove if you need to upgrade or if your set up is correct for your terrain and capabilitys. If you do need to upgrade then the ratio calculations will come in handy to assist you in figuring out if you need to change your current cassette or your crank chain rings.