How do you know what your gearing is?
 

I was reading in the "touring" forum about changing gearing. I have a 2005 Trek 4300. Anybody know the standard gearing for this bike(is there such a thing?)

How do you know what your gearing is??? H0elp, I feel so uninformed!!

thanks,

Gabe

What's on it what is standard.: teeth on front chainrings,and teeth on rear cogs. So why do you want to change it?

Bicycle gears are traditionally expressed in "gear inches." To understand gear inches think back to the high wheeler days. The bigger front wheel, the faster you could ride. When the safety bicycle was invented with a chain drive and wheels the same size, the formula for gear inches was invented so that its gearing could be compared with that of a high wheeler.

To get gear inches, first count the number of teeth on each sprocket on your bike.
Gear inches for a road bike= the number of teeth on the front chainring / the number of teeth on the rear cog x 27 inches. Do that for every gear combination on your bike and you'll find out there is considerable overlap in the gearing available for each of the front chainrings.

Gear ratios higher than 100 gear inches are very fast. Many riders can't use then effectively unless they are going downhill. Gear ratios in the 30 gear inch range are only useful on road bikes for climbing hills. Mountain bikes often have hill climb gears in the low 20 gear inch range.

To get an easier hill climbing gear, you need to put either a bigger cog on the back or get a smaller chainring for the front. Practically speaking, it's usually easier to change the rear cogs.

According to Trek's website:


According to SRAM's website (http://www.sram24.com/newtechdoc/eng...MTB_MY04_E.pdf):

Gearing can be a very involved subject and requires understanding of cog ratios, wheel circumference, pedalling speed (cadence) and road speed.
Bike manufacturers tend to give a very wide gear range to cover a wide range of cycling terrain, speed and rider strength.

In general, experienced riders try to fine tune their bike's gearing to match their needs, by swapping chainrings and cogs. Before doing this, you should plan your requirements for terrain, speed, comfort, duration of ride, wind, etc etc.

At the moment I'm doing short triathlon and criterium type club racing, on relatively level roads, with light winds. So I don't need a lot of range in my setup. I'm riding a 25 year old bike with 7 speeds on the rear (that's plenty for my use). I have 49 Teeth and 42 Teeth on the front chainrings (yes only 2), and 13,14,15,16,17,18,19 on the rear. This gives me a very close selection of gears so I can keep an optimal cadence regardless of the road conditions, within the expected racing speed range of 24 to 52 km/h.

In the usual race speed range of 30 to 40 km/h I have a perfect gear to choose from, for almost every 1km/h increment.

BUT............ I would be hopelessly lost in hilly terrain, as I don't have gears for climbing or decending.
So if I go away to a race in a hilly area I change my front rings to 52/42 Teeth, and change my rear wheel to 12,13,14,16,18,21,24.

The finer points of choosing exactly which cogs to use, requires careful study of a gear chart and considerable experience. Even then, there will always be arguments about gearing.

In my experience, most owners of 18, 21, 24 or 27 speed bikes only have 5 or 6 gears in the most used speed range. Most of the gears are wasted. That's because the manudacturer can't predict your exact usage, so they give you more than you need.
To get the most out of your bike you can get rid of a lot of gears, and tune the rest to your needs.

So, sort out what type of riding you want to do, and ask an expert to design a system for you.

Bobthe....

Try these:

http://www.campagnolo.com/sviluppo.php

http://www.sheldonbrown.com/gears/index.html

http://www.panix.com/~jbarrm/cycal/cycal.30f.html

Cheers...Gary

Go to Sheldon Brown's site for an informed discussion on gears and all things cycling. He also has a great gear table for calculating your own ratios.

www.sheldonbrown.com/harris