Big difference between 32- and 34-tooth cassette cog?
 

My commuter Felt SR91 came stock with 52-42-30 crankset and an 8-speed 12-25 cassette, but the lowest gear (30/25) is not low enough. The ride to work is about half flat, but the other half is a long steep climb, and I end up walking most of that section on the way home.

I'm pretty new to the concept of adjusting gearing, so this is a pretty basic question, I think. I plan to change out the cassette for lower gearing but I'm not sure if I should go for an 11-32 or an 11-34. Is there a big difference between a 30/32 pairing versus a 30/34 pairing?

A gear inch calculator tells me this:

30/25 = 32.0 gear inches
30/32 = 25.1 gear inches
30/34 = 23.5 gear inches

... but practically, I don't know if the difference between 25.1 gear inches and 23.5 gear inches will be significant to my legs, since I've never experimented with this before.

It looks like there might be some tradeoff in shifting smoothness if I go for the 34-tooth, so I am leaning toward the 32-tooth.

Thoughts?

Thanks so much...

Change your 30 T chain ring to a 24 T.

http://i256.photobucket.com/albums/h...39-24001-1.jpg

There won't be all that much difference. The biggest consideration is that you'll need a new chain either way and probably a different rear derailleur.

You may be able to go to an 11-28 cassette without a rear derailleur swap, but probably still need a new chain unless you are very careful. If you go big-big gears without a longer chain, you could do some serious damage to the rear derailleur.

"Change your 30 T chain ring to a 24 T."

Well, the thing is, changing the cassette seems simpler and cheaper, and creating a 24/25 pairing only gets me down to 25.6 gear inches. Also, I'm pretty sure my front derailleur wouldn't be able to handle the 18-tooth jump from the 42-tooth ring to the 24-tooth ring.

I hadn't thought about chain length -- thanks for that advice...

And the wheel. And the bike. And you...

If one makes you walk and the other lets you ride, it is a big difference!
Seriously, it looks like the Tiagra mid cage rear derailler can handle a 32t cog and no more.

Speed difference at 90 rpm between 30/32 and 30/34 is less than .5 mph. Like others have said, not much difference there, but combined with a smaller chainring, you could ride much steeper (and slower) while maintaining a decent cadence. I regularly ride up 12-13% grade switchbacks with 24/32 combo, which is slow, but quite easy.

Wow, that's quite high gearing for a hybrid.

Here's something else to consider. The Shimano 11-32 cassette has a pretty even shift sequence.

11-13-15-18-21-24-28-32
+2 +2 +3 +3 +3 +4 +4

The 11-34 has an even nicer sequence (same as the 11-30) up until the final shift which is a huge bailout.

11-13-15-17-20-23-26-34
+2 +2 +2 +3 +3 +3 +8

The SRAM 11-32 has a tighter midrange, one tooth higher from the Shimano, with smaller shifts and then two big shifts at the bottom.

11-12-14-16-18-21-26-32
+1 +2 +2 +2 +3 +5 +6

Yeah, that last step is a big leap.

The difference between 32 and 34 doesn't feel as much as between 13 and 15. In the lower geared cassettes a four tooth gap is normal, the 32/34 would be like a half step.

I have an 8sp 11-30. I've been running without using the 11 for the last several months and have found that I don't miss it at all. I just ordered a 13t first position and an 11-34 cassette. I'm going to try a 13-34, with the last three steps being 26-30-34.

Because the % difference is smaller than 13-15. the Mega Range shifts 10 teeth 24>34.

Having toured for a while when asked for freehubs, I thought Shimano's K cassette , back in the 7 speed era was Perfect 24,29, 34.


Though I was Fine with my 13 to 34- 6 speeds 24, 28, 34.. didn't even have the Hyperglide tooth profiles so common Now .


50-40-24t triple crank .. Now My Road and Cross Bike have the same gear-set in Campag's 135, 74 bcd.

Older Bike, Over the BB cable route, its a 52,42, 26.. lower tip of the FD clears the cable to the RD that way.

My thoughts are to go with the 34 tooth. It will come in handy in the future if you happen to ride up any really steep roads. If that meant changing out the rear d and the chain, so be it. That might be an extra $50 or $60 bucks.

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