Tiagra long cage derail, 10 speed cassette 12-28 or 11-34
10-18-19, 09:56 AM
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Tiagra long cage derail, 10 speed cassette 12-28 or 11-34
I purchased 2007 or 2008 seller wasnt sure.I have a Shimano 3x8 I have shimano acera long cage 8 speed and a 12x25 cassette that came with the bike. I purchased the Shimano Tiagra flat bar gear 3x10 and a Tiagra long cage 10 speed Derailer. I just got back into bikes after a 30 year layoff. First road bike I ever owned. But turns out my body is better suited for a flat bar so I decided to change what I have on it now. I’m still trying to figure what works better the 11-34 cassette or the 12-28 because of the long cage Derailer. I can’t return them now. No return policy on eBay
from these sellers.
from these sellers.
10-18-19, 10:10 AM
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a long cage RD can handle either of those cassettes without issue.
Count the teeth on your large and small rings then subtract the small from the large. Next, subtract the small cassette cog tooth count from the large cog tooth count. Last, add the difference for both the chainrings and cassette together. If that total is less than 41, then you are good. The stated capacity of a Tiagra 4700 long cage RD is 41 teeth.
Also, technically the largest cog a 4700 RD can handle with a triple system is 32t. I doubt 34t would be an issue though because Shimano is conservative with their published max numbers for cassette cog max.
Example-
crankset is 50-39-30. So 20t difference.
cassette is 11-34. So 24t difference.
Added up, thats a 44t difference and officially it wont work. It may work just fine in practice though. If it doesnt work, then to fix the issue a new crank with a smaller large ring could be used. Or a smaller cassette could be used.
Count the teeth on your large and small rings then subtract the small from the large. Next, subtract the small cassette cog tooth count from the large cog tooth count. Last, add the difference for both the chainrings and cassette together. If that total is less than 41, then you are good. The stated capacity of a Tiagra 4700 long cage RD is 41 teeth.
Also, technically the largest cog a 4700 RD can handle with a triple system is 32t. I doubt 34t would be an issue though because Shimano is conservative with their published max numbers for cassette cog max.
Example-
crankset is 50-39-30. So 20t difference.
cassette is 11-34. So 24t difference.
Added up, thats a 44t difference and officially it wont work. It may work just fine in practice though. If it doesnt work, then to fix the issue a new crank with a smaller large ring could be used. Or a smaller cassette could be used.
10-18-19, 02:12 PM
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I run a 10-speed Tiagra short-cage with a 12-28 cassette. With your long-cage derailleur you can run any cassette Shimano makes. Which you choose depends on terrain. Changing a cassette takes about three minutes and the tools cost about $20 .... less than half that if you make your own chain whip (as in, just use an old chain.)
I run a 50-34 crank set and with 12-28 I can make it up most hills but I live in Flatahoma, where "long, steep hills" are a quarter mile at 5 percent---and rare.
Mathematically, as @mstateglfr notes, you can handle a max of 32 teeth, but ignore that. Your RD can handle the 11-34. His math is correct---not disputing that--but as he notes, "Shimano is conservative with their published max numbers for cassette cog max."
Seriously, with that triple, 12-28 ought to work for everything except mountain-climbing .... unless you are fat, old, and weak like me, in which case you can fall back on the 11x34.
Whichever cassette suits whichever ride, you have all the gearing you should ever need.
I run a 50-34 crank set and with 12-28 I can make it up most hills but I live in Flatahoma, where "long, steep hills" are a quarter mile at 5 percent---and rare.
Mathematically, as @mstateglfr notes, you can handle a max of 32 teeth, but ignore that. Your RD can handle the 11-34. His math is correct---not disputing that--but as he notes, "Shimano is conservative with their published max numbers for cassette cog max."
Seriously, with that triple, 12-28 ought to work for everything except mountain-climbing .... unless you are fat, old, and weak like me, in which case you can fall back on the 11x34.
Whichever cassette suits whichever ride, you have all the gearing you should ever need.
10-18-19, 02:26 PM
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I've well over 15k miles on a Tiagra long cage with an 11-34 cassette. Not a problem. I could run a longer B screw and easily get away with a 36 cassette. Unless you live in Flatlandia you're probably gonna want that 11-34.
-Kedosto
-Kedosto
10-18-19, 05:59 PM
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Good news. I just installed a Sunrace 11x36 , 10 speed cassette and new chain on my friends bike. Tiagra 4700 GS cage. Didn't even have to adjust the "B" screw. Crankset is a 34/50, so that puts the capacity right at 41 T. He is an older rider (82) and the bike came with a 11x32, he needed some lower gears to climb with me (72). KB
