illusiumd

Well I've been breaking my new Soma ES 64cm in and the one thing that's bugging me is the shifting. Currently I got a SRAM PC-1050 Cassette 11 - 27 paired with a SRAM 68mm 180mm 50-34. It seems like I'm shifting too much (especially with how windy Chicago is). I'm either on the top three rings back/large front or on the bottom two/small front. (can someone explain to me how to say that in bike speak?) Is there a cassette I can get that will even this out so I'm not shifting from extremes?

bigfred 

Are you sure that's an 11-27 and not a 12-27? I'm not aware of Sram producing an 11-27. 11-25, 11-26, 11-28, 11-32, 12-25, 12-27, 12-30. Could you have a quick check before we discuss this further?

TrojanHorse

Your comments don't really make sense to me - if you look at a gear calculator (like this one: Mike Sherman's Bicycle Gear Calculator) and you put in a 12-27 cassette and a compact crank, you get the image attached



The two ranges don'tn really over lap the way you're describing (ie if you find yourself wanting an easier gear than 50/27 and you shift to the small chainring, you'd probalby find yourself in about 34/19 or so). There's a tremendous amount of overlap between 12 to 20 mph.

Your experience may depend on what cadence you're using too - the attached picture assumes 80-100, which is a pretty reasonable range for most road cyclists.

One possible solution for you if you find that you don't need the top end of a 50 tooth chainring is to install a smaller "large" chainring like a 46 tooth ring. That will create even more overlap of course, but it will also get you up off the largest cog of your cassette.

Another thing to look at is your front shifting - I shift my front all the time. It's easy & fast and doesn't bother me at all. If yours is less easy then i could see wanting to minimize it but perhaps just getting it adjusted will help you out.

CliftonGK1

11 or 12 on the low end isn't going to matter based on what the OP says.

OP - You're picking your worst 5 cross-chained combinations for either ring based on what you're explaining. Small chainring, and 2 smallest cogs; or Big chainring and 3 biggest cogs.
You should be able to get the same gear inch combination of the small/small combo by choosing your big ring up front and a cog from the middle of the cassette in back, same thing with the Big/Big combo; a small ring up front, middle cog in back should get you the same gearing without cross chaining so badly.

Assuming a 12-27 standard cassette, the 50 ring gives you 49, 55, and 63 gear inches using the 27/24/21 cogs. Those same gears can be had with your 34 ring and 19/16/14 cogs (or, close enough.)
Similarly, the 34 ring gives you 75 and 69 gear inches in the 12/13 cogs, which can be accomplished with the 50/17 and 50/19 combos. They're approximate (as in, within 2 gear inches) but plenty close.

bigfred 

I agree with you about the fact that a 34/50 X 12-27 drivetrain provides all those ratios without the need to cross chain.

Why asked about the 11 or 12 tooth high gear was that it does impact on what I was going to follow up with.

And, that is: That the OP is probably suffering from a very common ailment of the 34/50 compact gearing. IF he's using a 12-27 cassette in combination with that crank combo he has a single gear overlap before he falls into what most of us would consider unacceptable crosschain combos. And, depending on cadence, that cross over occurs right in the 16-17mph range. Which is where a lot of recreational cyclist spend a lot of time. Subsequently, they either spend a lot of time performing double (front & back) shifts and running up or down the cassette or they accept crosschaining more than they should.

Check out gear calculator for the 34/50 vs running a 14 tooth spread on the front like 36/50: https://www.gear-calculator.com/#KB=3...0&UF=2130&SL=2

That probably does a better job of demonstrating what I'm talking about than I can describe. That 34X14, 50X21 overlap is a bit narrow.

Black wallnut 

My suggestion is to learn to spin at a faster cadence.

sstorkel

I'm not sure why people worry about cross-chaining these days. I cross-chain all the time and I've never noticed an issue: no excessive chain or cassette wear, no problems with shift quality, etc. I avoid combos that cause the chain to rub on the front derailleur excessively (only the small-small and big-big combos for me), but everything else is fair game as far as I'm concerned...

illusiumd

Thanks all, yes BigFred it is a 12-27 - it said 11 on my invoice but I counted them just now. So this is my first step into gearing and it makes my head hurt. I took my bike into the shop cause the cassette was slipping from my favorite gear ... he tightened up the barrel adjuster? a little but he did say it looked like I was wearing that gear down -> big/front third-biggest back. I'll have to spend more time trying to concentrate on these comments once I get more coffee

bigfred 

Chain rub would be a certain indicator to me that I'm in an inappropriate cross chain situation. My primary reason for worrying about it is increased chain wear as a consequence of the tortured path in an age where we already suffer accelerated wear. If set according to Shimano specifications I'm certain to suffer constant chain rub in the most extreme cross chain combination and intermitent rub in the next cog, depending on ring runout and frame flex.

I also, don't worry about cross chaining for short periods. If I need a big/big gear to get over a small rise or small/small to get through a short flat on a longer climb, I'll use them. But, for the most part I still attempt to avoid them. And, a 16 tooth front differential subsequently results in a lot of front ring changes while in the region of 25-30 kph.

bigfred 

If you look at the gear calculators presented by either myself or TH you'll start to get an understanding of where your issue stems from. With a 16 tooth difference between chainrings and a reasonable close ratio cassette you're left with a precious narrow overlap between the two front rings. That occurs right in the speed range that a lot of recreational cyclists find themselves at.

My solution:-) Simply ride more, get stronger and FASTER. Problem solved:-) Once you're spending more time above 30kph, you'll find less need to be in that big/big combo and only shifting into the small ring for extended climbs. How's that sound?

salreus

Shifting to me has a lot to do with wanting a constant resistance when I pedal which means I shift often. And because I don't have lots of experience and strength in order to deal with that extra resistance that slight incline or wind is providing. But to me, I am new and shifting often also allow me to get more comfortable with my bike and is helping me keep a good cadence and focus on other aspects of riding.