Bicycle Mechanics - Shimano 2300 RD vs granny cog
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02-21-12, 10:43 AM
Will it work? I've cast about and I think it could, but I don't have a definite answer. I've never been steered wrong here so please indulge me again.
I have a Shimano 2300 Rear Derailleur, a single 44T front ring, and a Shimano Hyperglide 8-speed cassette with 7 cogs 11-28, with 8-speed downtube shifter. I want to use 8 cogs up to 30T or 32T.
I found a RD 2300 spec sheet which says:
Total capacity 35 teeth or less
Largest sprocket 26T
Smallest sprocket 11T
Front chainwheel tooth difference 22T
Total capacity I take to mean the number of teeth difference between large-large and small-small so I'm way under that, and with just one ring the last one is irrelevant (right?). But what about "largest sprocket"? It's working fine as is with a 28T sprocket. Can that be stretched to 30? 32?
02-21-12, 11:08 AM
You might be able to ge away with 30T or 32T largest cog.
Using a single chainring is in your favor. When I've exceeded the largest cog rating, bumping had occurred in small/big, but not middle/big.
Keep the chain on the shorter side of the potential range (try Sheldon's big/big + 1" method) and flip around the RD's b-tension screw so that its head butts up against the RD hanger.
02-21-12, 11:28 AM
The only way to be sure is to try it and see, but just because you are getting away with 2 teeth bigger than the rated sprocket size does not mean that you will get away with 6.
02-21-12, 02:20 PM
Since it's questionable, if it were you would you risk 8 or 10 dollars for a sprocket and an hour of messing with to find out? Given that it's a "like to have" instead of "really need", and the chain angle for the additional gear is also going to be a little "iffy".
02-22-12, 03:24 AM
So, you're using just 7 cogs of an 8-speed cassette? Is there a spacer behind the largest cog? I'm making sure you have an 8-speed-plus freehub and not a 7-speed-or-less freehub.
02-22-12, 06:47 AM
Yes, all it would take is removing the spacer and putting a sprocket in, a longer chain and adjusting the rear derailleur.
02-22-12, 06:52 AM
Heck if you remove the spacer and put in the larger cog, you're not out much if it doesn't work, right? I mean in essence you'll be where you are now but with a non-functional 8th cog instead of a spacer.
05-19-12, 07:51 PM
I'm resurrecting this old thread to report how it turned out. (Don't you hate it when you search a question, find a discussion for it, and there's no resolution?)
I had put this off until I wanted to get a spare rear wheel, to do both at once. For some reason I went with an SRAM 830, 11-30, instead of a Shimano Hyperglide. In short, the 2300 Rear Derailleur handles a 30 tooth sprocket like a champ! I didn't lengthen the chain, which I think was a half link long to begin with.
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