Bicycle Mechanics - SRAM Force With A 12-36 Rear Cassette Help

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epicycle
05-25-12, 05:59 AM
I ordered a 12-36 SRAM PG 1070 rear casette for my bike for a really hilly 200k I'm training for this summer. My bike currently has a 53-39 front and a 11-26 rear. My question(s) is whether or not I'm going to need to buy a new rear derailleur to handle this new cassette or whether the SRAM Force one already on there can handle it. I assume it's a standard mid length derailleur (I'm not sure how to tell). Any suggestions on one to buy if I do need one? I'd like to stick with SRAM if possible.

Another question, what would you rate the difficulty in changing out these cassettes? I have only read how to do it and I'm not scared, I just don't want to break my parts. I'm worried about the adjustments I'd need to make to my rear derailleur to handle the larger rear cassette.

Oh yea, I also picked up a new chain as I figured that would be needed with this new setup and it couldn't hurt with mine being 2 years old anyhow.

Thanks for the help!
Sean


BikeWise1
05-25-12, 06:43 AM
Your road derailleur will not work with that cassette. You need a ATB rear derailleur. You also need several special tools to remove your cassette, and yes, you may need to make minor adjustments to make it shift right. The chain was a good call. Old chains and new cassettes do not play well together. It bears mentioning that if you desire to be able to swap back and forth between road and ATB cassettes, you will need to adjust chain length each time, unless you simply leave the ATB derailleur on all the time, which is fine....

My advice is to compose a few good searches based on what you want to achieve. Park Tool's website is helpful as well.

pmt
05-25-12, 06:44 AM
Send the cassette back and get a compact crank. That's far more useful, and far less disruptive. Get an 11-28 cassette; the 50/11 top gear is higher than 53/12. Plus the 34/28 is only a tiny bit higher than 39/36. Shifting will be better all around.


HillRider
05-25-12, 06:48 AM
Changing a cassette is relatively easy if you have the correct tools, namely a lockring tool and a chainwhip. As to the rear derailleur, i'm not that familiar with SRAM but I'd be amazed if your Force rd will work with that big a cog. I'm pretty sure you will need either an Apex or one of their MTB rear derailleurs. Finally, you will have to size the new chain properly and will need a chain tool to shorten it if needed.

It is likely that you will have to tweak the derailleur settings if, by some chance, your current rd does work and it is certain you will have to set one up from scratch if you need a replacement. The Park Tool web site has tutorials for all of these jobs.

epicycle
05-25-12, 08:55 AM
The only thing I don't like about that gearing mix is the number of duplicate gear combos (4) according to my spreadsheets. I'm not opposed to a compact crank at all, is there another rear cassette that would work? Would the compact work with the 12-36 without changing out the rear derailleur?

Barrettscv
05-25-12, 09:02 AM
The only thing I don't like about that gearing mix is the number of duplicate gear combos (4) according to my spreadsheets. I'm not opposed to a compact crank at all, is there another rear cassette that would work? Would the compact work with the 12-36 without changing out the rear derailleur?

Anything larger than a xx-28 cassette will require a different derailleur. The Apex, Rival and Force mid-length cage rear derailleur, AKA: WiFLi, will take a xx-32. A MTB rear derailleur will be needed for anything larger than 32.

njkayaker
05-25-12, 09:33 AM
The only thing I don't like about that gearing mix is the number of duplicate gear combos (4) according to my spreadsheets. I'm not opposed to a compact crank at all, is there another rear cassette that would work? Would the compact work with the 12-36 without changing out the rear derailleur?

There are two properties related to cassette/derailleur compatibility.

1) the chain capacity: bigger cassettes need derailleurs that can take up more change (long cage derailleurs).
2) the derailleur movement has to match the angle of the cassette. Cassettes with a narrow range have a shallower angle; cassettes with a wide range have a steeper angle. If you use a short-range derailleur with a wide range cassette, the derailleur will be too far away from the smaller sprockets when it can clear the big sprockets.

HillRider
05-25-12, 12:42 PM
Would the compact work with the 12-36 without changing out the rear derailleur?
No, the rear derailleur does not care what's up front, only what it has to deal with in terms of cog size.

ThermionicScott
05-25-12, 01:31 PM
The only thing I don't like about that gearing mix is the number of duplicate gear combos (4) according to my spreadsheets. I'm not opposed to a compact crank at all, is there another rear cassette that would work? Would the compact work with the 12-36 without changing out the rear derailleur?

What's wrong with duplicate gear combos?

HillRider
05-25-12, 01:36 PM
What's wrong with duplicate gear combos?
+1. Do you really need 20 or 30 unique combinations?

epicycle
05-25-12, 03:18 PM
Looking at the options it seems like the SRAM Force rear with WiFli might be the cheapest and most ideal route. Replacing the front is pricier than I thought it would be and the WiFli rear would allow for the 11-32 rear cassette which would work well with my current 53-39 front.

The only issue I see is that the Force with WiFli isn't available anywhere in the US that I can find. Anyone know when it's set to be available? Any technical reason I wouldn't want to go with the WiFli Force over the compact 50-34?

Thanks again for the help everyone!