starving

My girlfriend is new to cycling. The easiest gear on her road bike has a 30-tooth chainring and 25-tooth rear cog. She has a hard time with hill climbing.

I am considering installing a 33-tooth rear cog to make climbing easier for her.

Two questions:

Would making this change make climbing much easier, or only a little easier?

Would my derailleur be able to handle to bigger rear cog?

starving

Here is a photo of the chain in her smallest gear....

Jeff Wills

1: Yes, by about 30%. This is significant.
2: Probably not. Most "road" bikes' rear derailleurs have a maximum capacity of 28 teeth, with some flexibility depending on configuration. Some people have made "road" derailleurs work on 32 tooth cogs, but the adjustment can be finicky.

It would be helpful to know what kind of bike she has, along with which components are on it. This makes it easier to evaluate any changes you want to make.

starving

Jeff, bike is Bikes Direct Windsor Wellington 2.0 with Sora shifters and 8-speed cassette and medium-cage rear derailleur. Here is a link with the specs....
https://www.bikesdirect.com/products/...ington2_IX.htm

Jeff Wills

OK- Shimano, with a triple crank on the front. That Sora rear derailleur will max out at 30 teeth on the rear... maybe. Like I said, pushing it past that makes the adjustments finicky.

Another possibility is a smaller front chainring. I think you could exchange the small chainring for one as small as 24 teeth without making any other changes. This would allow pretty easy hill climbing.

starving

Jeff, would changing the chainring require a different rear derailleur as well?

starving

The derailleur is Sora RD-3400. It says 27 maximum cog on the box. I guess I will change the chainring instead.

Jeff Wills

No. The only problem with reducing the size of the small chainring is that the chain may hang loose in the small chainring/small cog combinations. This is usually a non-issue.

IMO, that bike suffers from "over-geared syndrome". A 52 tooth chainring and 11 tooth cog is a huge high gear, useful for powerful racers but not other people. Switching the cassette to a 13-26 setup (it's 8-speed, so that's what I found quickly) and a 24 or 26 tooth small ring will give her many more useable gears and a much nicer experience.

Jeff Wills

Yeah, that's "total capacity"- the difference in sizes of the chainrings plus the difference in sizes of the cogs. With my setup that I just proposed (52/42/24 front, 13-26 rear), you'd need a total capacity of 41 teeth to make it all work perfectly in all gears. Like I said, the small/small gears need to be avoided, but it's no big deal.

davidad

Ditto on the 24t. shimano sucks with their racing triple.

HillRider

So does Campy. All road triples use 30T granny rings as OEM.

njkayaker

That indicates a 28-tooth rear cog.

starving

I know. The bike they sent me has 25 teeth. Bikes Direct can be inconsistent.

Retro Grouch 

If it was my girlfriend's bike I'd get her an 12/34 cassette, a Deore long arm rear derailleur, and a new longer chain. She'll have an easier hill climb gear, everything will shift and index the way it's supposed to, the derailleur will take up the chain slack in any gear combination, and the bike will look like it could have come from the factory that way.

starving

I could also remove the large chainring since she never uses it. This would allow me to lower the front derailleur to work with a 22 or 24 inner chainring.

Here are the specs of the front derailleur on the bike now....

"Front chainwheel tooth difference: 22 teeth or less.

Min. difference between top and intermediate: 10T.

installation band diameter S (28.6mm)*, M (31.8mm)

Chainstay angle (C) 63° - 66°

Chain line 45mm"

https://techdocs.shimano.com/media/te...9830673815.pdf

starving

Can a triple front derailleur be used with only 2 chainrings if I adjust the travel?

strock 

Yes, and if you think the crankset looks weird without the outer ring you can install a bashguard in its place.

If I could afford it, this is what I would do, too. If you're talking steep, long hills, I might install both a wide-range cassette and a smaller inner chainring.

starving

Okay, then being the cheapskate that I am, I will buy a 22 or 24 chainring, and adjust the front derailleur if needed.

starving

I will see if the smaller chainring will suffice for her. If not, I will do what you and Retro recommended.

strock 

If you have a road crankset with a 74mm inner BCD, the smallest chainring you can use is 24t.

starving

Thanks, strock. Can I take the 24 tooth chainring off my mountain bike and install it on her road bike?

starving

I suppose it is not possible to switch inner chainrings without removing the crank arm, huh?

Retro Grouch 

Probably not. My guess is the bolt circle diameters will be different.

starving

I have a crank extractor from 1987. Is it still compatible?

Retro Grouch 

Probably.