Gearing question
 

Ok, ordered a new Downtube 9FS, and am pretty happy with it with the exception of the gearing... I commute to work about 3 miles, one of which is a fairly harsh incline over a bridge... semi-steep incline up at least 100'. Traditionally I used a much heavier MTB with 24 gears and manage to get a good one where it's bearable and I can get enough speed and power without dying. On the Downtube, I'm either stuck in a muscle ravaging gear or spinning so slow I'm barely making headway up the bridge.

Would changing the gearing on it to 27 gears make a difference for me, or is it the smaller wheels on inclines I'll just have to accept? (from Downtube: "Front derailleur braze on will allow one to turn it into a 27sp bike")

How much roughly do you think upgrading the gearing on the bike would run if I did it very budget minded? Thanks.

It's not how many gears, its the ratios of those gears, a:b ..

you want to lower the range of ratios.

just putting on a smaller chainring in front is a low cost option.

Help with the math .. http://sheldonbrown.com/gears/

adding the front derailleur adds a second range for the X number of rear wheel
gears.

I shifted the gear range on our Pocket 8's down one gear by changing out stock 53T chain rings for 48T ones. Very simple but effective fix.

Lou

+1

Ok, the current Downtubes are 48T... so I'd want to move down to a 42 or something to decrease ratio?

...or maybe a 44T? Check the aforementioned Sheldon Brown Gear Calculator. It can give you the comparative "gear inches" for your current set-up vs. what 42T or 44T will do. If that comparison doesn't mean anything to you, you will just have to experiment.

I initially changed our custom Dual-Drive Fridays from 42T to 46T chain rings, so I had some idea what the 53T to 48T change on the Pocket 8's would do.

Lou

Yes. It might take some experimentation; but flat chainrings are not particularly expensive and you can typically get a very good estimate by using your regular bike with the really wide drivetrain coupled with a little math. Remember, that as you move to smaller chainrings you might have to take out a few chain links. So if you believe that either a 44 or 42 will be best, start with the 44.

I ran the math on your gears. A Downtube 9FS has a 20 inch (406) tire, a 9-speed 11-12-14-16-18-21-24-28-32, and a 48T front. Sheldon says this comes to 28/32/37.4/42.7/49.8/56/64/74.7/81.5 gear inches.

At the low end your biggest jump (16.7%) is from 28 (second hardest) to 24, resulting in 32 to 37.4 gear inches. That's not all that bad. You could change your larger gears to be closer together. For example, if you did a "Century Special" (13-14-15-17-19-21-24-27-30) you could see some more options at the low end. But beware that you're going to *really* sacrifice your high end.

FYI: The change from 53T to 48T chain rings on the Pocket 8's has not required me to remove any chain links. Both of the bikes have been ridden significantly since the modification and shift very nicely.

Lou