Author Topic: Road bike gearing (SRAM PG 1070 11-32 Cassette)  (Read 613 times)

jim-ratliff

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Road bike gearing (SRAM PG 1070 11-32 Cassette)
« on: July 23, 2010, 09:56:26 am »
When I bought my bike it came with an 11-23 tooth cassette and a standard compact crank (50-34 tooth chainrings).? I quickly found that was a lot higher gearing than I was strong enough or fit enough to utilize.? In my second year of riding I upgraded to an 11-25 cassette, which helped a bit but still left me wanting more without going to the expense of a triple crank (and Lynn told me only gapers ride road triples, but then I pointed at Doug's Litespeed road triple).

I have also been watching SRAM's efforts at using 2x10 groups to compete with market segments that normally used triples.? The advantage of the double crank over the triple is weight, less gear overlap, and simplicity/reliability.? SRAM introduced their high-end XX a while back, and this year introduced their APEX group for road bikes - and the distinguishing feature of the APEX group was 11-32 and 11-36 cassettes (and maybe smaller chainrings).? They also introduced an 11-32 cassette for their intermediate level road sets.

I ordered a SRAM PG1070 11-32 cassette last week and installed it earlier this week.? The lowest four gears are now 32, 28, 25, 22 which give me two gears that are lower than the 25, and based on a couple of rides it works well.? Shifting is as crisp as the Ultegra cassette, and I can now go up some of my standard hills at the same speed but with a faster and less leg wearying cadence.? I'm very pleased and thought I would pass along the info in case others wanted to try.? But there are some things you need to know.

Chainwrap- My Ultegra RD6700SS short cage derailleur was designed for a max 28 toothi cassette and can't carry enough chain to support my full range of gears.? Its rated at 33 tooth chainwrap, which is "cassette gear diff + crank gear diff" or (28-11)+(50-34)=33 teeth.? My new cassette is (32-11)+(50-34)=37.? What does this mean?? I can't use the 32 tooth cassette gear when I'm using the 50 tooth front sprocket. A good rider wouldn't crosschain that way anyway, so that's not a big restriction and well worth getting the bigger gear. There is also an Ultegra RD6700GS medium cage derailleur that has a 39 tooth chainwrap capacity, and I may decide to get that with a SRAM 11-36 cassette.

I didn't need to replace my chain, but depending on what gear you had it might be necessary.  Most shops remove some links of chain when they install a new chain (especially if you have a compact crank).
« Last Edit: July 23, 2010, 10:11:36 am by jim-ratliff »
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LivingProof

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Re: Road bike gearing (SRAM PG 1070 11-32 Cassette)
« Reply #1 on: July 23, 2010, 11:32:06 am »
Jim,
Nice write-up and thanks for sharing. SRAM's advertising bills the Apex group as the end of the need for triple cranksets. SRAM makes good stuff. It's amazing that any business case would start to compete with Shimano and Campy in the small bike parts business.

In another recent thread, Lynn and you were discussing her Litespeed Ti frame equipped with a Dura Ace Triple and (I presume) a long cage rear derailluer that permit that bike to climb with far less effort. If I rode in hilly terrain, Lynn and I could have entered into negotiations as that frame combination would suit my needs very well. Well, prior that negotiation, the Tennis Diva and I would have to strike a deal.

I found compact cranks required getting used to in 2 main areas. First, it's easy to cross-chain which you point out. Second, the jumps between gears is bigger resulting in loss of ability to fine tune the right gearing combination and I really miss having a perfect gear combination.  Both of these situations are compounded with the larger rear cassetts.

However, if you do not change the size of the chain, it's somewhat easy to change out the rear cassett to the best match depending on where you are going to ride. An option would be to have 2 rear wheels each with a dedicated cassett. The rear derailluer does not have to be readjusted as the widths are the same. The best of two worlds in one groupo!

My bad luck is that I have a 9 speed system.

I'm glad that you got this done and it should improve the pleasure of your riding!




jim-ratliff

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Re: Road bike gearing (SRAM PG 1070 11-32 Cassette)
« Reply #2 on: July 23, 2010, 01:20:28 pm »
Trivial details, but Doug's LiteSpeed triple was Campy, her current Ti bike is DuraAce (double)

I found compact cranks required getting used to in 2 main areas. First, it's easy to cross-chain which you point out. Second, the jumps between gears is bigger resulting in loss of ability to fine tune the right gearing combination and I really miss having a perfect gear combination.  Both of these situations are compounded with the larger rear cassetts.

Not sure I agree.  Compact gears are 50-34. Classic road crank is 54-39.  Net gear differences are 16 and 15, which is pretty close.  I find that I just ride the 34 whenever I'm mostly below 17mph and the 50 whenever I expect to stay above 10mph.  The gap when changing the crank is actually less if you have a larger spread between cassette gears.  As an interesting sidelight, see Sheldon Brown's "Gear Calculator" at http://www.sheldonbrown.com/gears/ for speeds at various RPM's and percentage changes between gears.
However, if you do not change the size of the chain, it's somewhat easy to change out the rear cassett to the best match depending on where you are going to ride. An option would be to have 2 rear wheels each with a dedicated cassett. The rear derailluer does not have to be readjusted as the widths are the same. The best of two worlds in one groupo!

Yes, I do have the older cassette on another wheel, but don't expect to need it. And "over analyzing" this stuff is a lot of pleasure in and of itself. Ask Lynn, it's a character trait if not a character flaw.

You could, if you wanted, do the same thing with 9 speed. I believe current Shimano mountain bike 9-speed cassettes are compatible with 9 speed road groups.
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midwif

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Re: Road bike gearing (SRAM PG 1070 11-32 Cassette)
« Reply #3 on: July 23, 2010, 04:41:19 pm »
My eyes glazed at "11-23 cassette". >:D

It's like algebra all over again. ;)
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Ron

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Re: Road bike gearing (SRAM PG 1070 11-32 Cassette)
« Reply #4 on: July 26, 2010, 08:20:45 am »
220, 221, whatever....  ::)  (movie quote)