understanding gearing

orfeoc said:

Hey guys,

I'm looking into getting a new bike and i'm wanting to understand the difference between gearing. I'm buying a hybrid like the trek 7.7, specialized sirrus comp or cannondale bad boy. So i ride 99% of the time in the city on tarmac. Few hills and i never use the granny gear (my gears are actually broken and don't go down that way). I find i am limited by not being able to go fast enough with the gearing i've got on my stock trek 980. However i don't know if this is a big deal as really at that speed, 50km/hr your fighting so much wind that maybe its a waste to get gearing that can take you faster. Anyway, i digress, I spoke to one guy here and he said the specialized bad boy has a gearing better for climbing rather than going fast. Its got a Shimano CS-HG50, 11-32 and a Shimano FC-M470 Hollowtech, 26/36/48 . How does this compare with the trek 7.7fx's Shimano 105 50/39/30 and Shimano 105 12-27, 10 speed . I assume the trek is alot faster, but from those figures there doesn't seem much differnce, the crank having only about 3-4 more teeth (?) on the trek 7.7's setup.

What should i be looking for in a fast gearing hybrid mountain bike, city riding in sydney australia with no long hills, what sorta of gearing ratios?

thanks guys

orfeo

hello again...I was waiting for someone to reply, but here goes...

It's not directly related to the number of teeth but the diameter of the chain ring/cogs...in reality, there are only about 9 distinct gear ratios on a bike, regardless how many "speeds" you have

So, a bike with a 26T granny will have more torque than one with a 30T...slow, but will climb easier, even with a 32T cog

at the high end, a 50T chain ring is 4% larger than a 48...so even with a 12T cog, it will run faster than a 48/11...not much, but there will be a small advantage...more work, though

orfeoc said:

Hey guys,

I'm looking into getting a new bike and i'm wanting to understand the difference between gearing.

Hi,

As you already have a bike, and know its spec's to boot, go HERE: and crunch the numbers. Then repeat with the numbers for the bike you're looking at. Now think back to your current bike, and how you feel about its characteristics, do you feel like you're spinning out, any gears you never use, any steps between gears that you feel are too big/too small, ASO...

You might want to take a special look at the "speed vs cadence" chart to avoid overstressing your knees, particularly if you think you could go faster.

JM01 said:

...It's not directly related to the number of teeth but the diameter of the chain ring/cogs...

Which is a bit of a moot point, as long as we are all using chains with the same pitch. No. of teeth will determine diameter and is an easier number to use as a reference.

JM01 said:

.. a bike with a 26T granny will have more torque than one with a 30T...slow, but will climb easier, even with a 32T cog...

...assuming the same size wheels and crank length...

JM01 said:

......in reality, there are only about 9 distinct gear ratios on a bike, regardless how many "speeds" you have..

You know, that's like asking how many shades of grey you can fit between white and black, but I agree that most bikes have a couple of redundant/repeat gears.

Speed is relative - cadence is where its at. Try to find your optimum cadence (usually between 60 and 120 rev/min of the pedals). Too slow and you're pulling muscles or going way too slow. Too fast and you're tiring yourself out before the end of the ride. Change the gears in the front (smaller for going up hill - larger for downhill), and adjust the cogs in the rear to make your cadence go up or down. But find out what's right for you.

orfeoc said:

Hey guys,

I'm looking into getting a new bike and i'm wanting to understand the difference between gearing. I'm buying a hybrid like the trek 7.7, specialized sirrus comp or cannondale bad boy.
orfeo

UPDATE...

I finally gave up on my 7.5fx and switched to a Scott Speedster S60...the 2007 flat bar has exactly the same frame, gears, tires, and specs as the the roadie version with drops, but way more comfortable