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Old 01-05-14, 08:50 PM   #1
vanbiker
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Lower gear wanted, change cassette or inner chainring?

I built up a fun road/cross bike this fall - its great for riding pavement to the trail areas, then gravel roads or mild single-track, then back home on the pavement. I used a 7800 Dura Ace triple drivetrain from an older road bike, and it works fine but I would like a lower bottom gear for those steep sections of slippery single-track. Currently have std 30-42-52 chainrings with an 11-30 cassette. My questions: Will a SRAM 12-32 cassette work well with my D.A. chain and derailleurs? Should I switch the inner chainring instead, say to a 28t? If so, will any model Shimano inner ring from a triple fit and be compatible on my D.A. crankset? Thanks for your expertise! BTW its a Salsa Vaya frameset with a disc brake wheelset with 35mm Clement adventure tires....so far just a kick to ride.
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Old 01-05-14, 10:47 PM   #2
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If the want for a lower gear is often then explore the cassette change. Whether you'll squeeze a 32T cog above the guide pulley might depend on the frame hanger length and careful chain length VS using the big/big crossover.

If the lower gear need is only sometimes and then for a while (long hills) then I'd favor a smaller inner ring. A 28 or even a 26 should be able to be done. Again chain length and avoiding some cog combos might be needed.

But you can also go down in the middle ring. This affects much more then either a cassette or inner ring change. Andy.
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Old 01-05-14, 10:53 PM   #3
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You will need another crankset or a new TA middle adapter ring. Go to the bottom of the page. http://www.peterwhitecycles.com/chainrings.asp
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Old 01-05-14, 11:02 PM   #4
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I had 48/38/28 chain rings and a 12-28 cassette on an old trek 820. Really a hybrid gearing these days. I rarely used the large chainring and really wished to save my old knees by spinning up the hills in my neighborhood. I changed to a mountain bike crankset 42/32/22 and kept the cassette the same as the rear DR topped out at 28. Now I use the largest chain ring a lot and climbing hills is a breeze. I highly recommend it.
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Old 01-06-14, 12:35 AM   #5
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I think the cassette option is preferable for my purposes. The guide pulley clearance could be a problem though; as I was tuning it up today it seemed there was almost no clearance on the current 11-30 cassette when on the big cog. The bike is a "touring" style frame though, so it seems it should be made with a sufficiently long r.d. hanger. I will borrow a friends cassette and give it a whirl. Thanks.
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Old 01-06-14, 06:32 AM   #6
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Before buying anything, take the time to figure out what gear ratios you have now and what ratios the proposed change will yield.

A 32 rear cog will definitely yield an easier hill climb gear than the 30 that you have now but it might not be enough for you to notice the difference.
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Old 01-06-14, 07:08 AM   #7
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vanbiker, There is little net difference between +2T in the rear or -2T up front. I do like the idea of losing the 11T at the rear, good luck on the clearances.

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Old 01-06-14, 08:21 AM   #8
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You cannot change the granny chainring on the FC-7803 for a smaller one. Shimano uses a "tripilizer" middle chainring on that crank and the granny is bolted directly to it with a 92 mm bolt circle and a 30 T is the smallest that will fit. A larger large cog or a different crank are your only options.
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Old 01-06-14, 10:10 AM   #9
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Older DA with a triple off the middle ring i'm hearing is not going to take any smaller ..

TA, France, makes a different 130 bcd middle ring where 3rd is a smaller BCD.


Then again consider: lose the crank for a Ultegra where the 3rd ring bolts are on the crank spider.
or even something else entirely, without the race bike high gearing .

Last edited by fietsbob; 01-06-14 at 10:15 AM.
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Old 01-06-14, 10:17 AM   #10
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In general a different inner chain ring is the right choice.

It will allow a lower gear without compromising your spacing and cost less than a new cassette.

Shimano used a 92mm BCD inner chain ring for 7803 which makes that non-viable. I'd change the crankset and pair a smaller chain ring with 13-14-15-16-17-18-19-21-23-26 or 12-23 before I ran a mountain bike cassette even if that cost a few hundred dollars more.
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Old 03-09-14, 06:02 PM   #11
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After exploring options, I finished installing a new crankset today, a velo-orange triple compatible with 10-speed that has 48-34-24 rings. I used a 122.5mm cartridge b.b. and everything went well, I even used my old ultegra f.d. and it works fine. Took it out for a pavement + single-track ride this afternoon and it was great. I have a 24/30 gear for trail climbing along with a 48/11 for cruising. Awesome. The front shifting isn't quite as quick or quiet as it was with the d.a. crankset but it works well and is a blast to ride. The V-O crankset is beautiful, in a retro-way.
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