understanding gearing

orfeoc

Hey guys


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

artemidorus

Waht's your average speed and what cadence do you prefer?

__________________
"All that we see and seem is but a dream, within a dream..."

orfeoc

i guess i'd average around 40 km/hr, plus or minus 10 for when i'm going comfortably down hill/up hill. It would be nice to have a bit of gearing to get up to 60 comfortably, but i don't know if that's possible, espcially on a hybrid...

Scotty_Dog

According to Sheldon Brown's gear calculator, http://www.sheldonbrown.com/gears/ , at a cadence of 90 RPM:

Bad Boy: 48x11 gear combo with 700x28 tires = 50.3 KPH
7.7 FX: 50x12 gear combo with 700x28 tires = 48.0 KPH
Sirrus: 50x12 gear combo with 700x28 tires = 48.0 KPH

To hit 60 KPH, you would need to pedal at about 110 RPM.

So, actually, the Bad Boy has a higher potential top speed. That being said, the Bad Boy seems closer to a mountain bike, and the other 2 bikes are closer to road bikes. Bike weight and riding position will also have an effect on top speed.

Go test ride the bikes and then determine which style of hybrid suits your needs.

__________________
"There is alot of blather here that does not float the hooey barge." boudreaux 11/22/2005

ovalbackmarker

To hit 60 KPH you would also have to be a nationally ranked racer.

__________________
Colnago Super
Colnago Dream
Felt F4C
Softride Powerwing

orfeoc

thanks for all the tips guys, i know i'll just have to ride all these bikes to really decide but it's good to have all the info i can before i do

btw, what's peoples thoughts on internal hub gearing? one of the shop assistants suggested this as an option for there improved durability. I know that on that point they win but then're heavier (1700g compared to around 900g), have less range and they're less efficient (as well as bing hard to repair). Anyone know how much less efficient they are? is it something small like 5-10% or are we talking 20% and up?

orfeo

artemidorus

That'a a phenomenal average speed for commuting, you should race.
If you really do average 40km/h, and you are riding around Sydney on roads only, then you should get a bike with a standard road double crankset, 39/53, and a tight cassette such as 12-23 or 12-21.

__________________
"All that we see and seem is but a dream, within a dream..."