freeranger

On my hardtail mtn.bike, my low rear cog is a 28 tooth. Would changing to a 30T make that big of a difference? I'm not going to a 32, as I have a der. which will handle the 30, but not 32 (or so the specs say). My low front cog is a 22T.

DogBoy

That's a 7% difference. Enough to notice, but nothing to write home about. Its really up to you. If your cassette is shot, get a new one and try the 30. If you don't like it, replace it next time with the 28. My $.02

Little Darwin

Assuming you have a 26 X 1.5 rear wheel, a gear calculator I just found online shows that you would move from 19.56 inches to 18.25 inches. Your new lowest gear would be about 93% of your current lowest gear.

If you need a lower gear, this would provide a reasonable gearing difference. However, your current lowest gear is quite low already, so I don't know how much this will matter in a practical way.

However, one thing to consider is that your gap between the lowest gear and the next higher gear will be increased... Whether this is a problem is a personal decision.

cyccommute 

I will agree that going from a 28 to a 30 isn't much of a change and is probably not worth the effort but if you are doing serious off-road riding, going from a 28 to a 34 will make a huge difference in hill climbing ability. It might be worth changing both the cassette and the rear derailer (and the chain) if you need a lower gear for that application.

On the other hand you might try borrowing someone's wheel that has a 32 tooth low and see if the rear derailer will shift with it in a parking lot or on a repair stand (don't go into the woods and try it or it could be a long walk home ). Or you could talk to the local bike shop guys, they might know a thing or two

sydney

Or maybe not. Probably easy enough to know if he mentioned the deraier model. And even if 'spec' is 30, it will likely handle more.

cyccommute 

Not all bike shop employees are incompetent boobs. I've run across a few that actually know something about bicycles...and a few that don't. I'd say the ones that know something are in the majority.

sydney

ok

af895

As others have said, give it a shot.

Also take a look at this page: https://www.sheldonbrown.com/gears/
...before making drivetrain changes. You can just swap cogs as opposed to buying a new cassette, usually. (see https://www.sheldonbrown.com/k7.html)

FWIW, I recently went from an 11-30T cassette to an 11-34T.
I'm in a different boat though: 20" wheel folder, only 2 front chainrings.
To get a good range of gears without sacrificing too much high or low end, I really needed that 11-34 cassette.

Looking at your setup:
Using a 26"x1.9 MTB tire
22T front ring
Now running a 28T: 22/28 gives about 20gear/inches
22/30 would give about 19gear/inches (18.9 specifically)
22/32 would give about 18gear/inches (17.7 specifically)
22/34 would give about 17gear/inches (16.7 specifically)

I think you'd be hard pressed to tell a 1-gear/inch difference but greater range never hurts.
You might seriously consider buying a long cage derailleur and going with a 34T, if you feel you really need to dig deep into the low range. Deore SGS high-normal derailleurs seem to be a great value and they handle 34T.

Hope this helps! (thank Sheldon & consider buying from Harris Cyclery if it did)

Chris

cyccommute 

Light a candle, sydney. Light a candle.