View Full Version : Larger chainrings ?
12-25-2007, 03:13 PM
Anyone offer any advice on increasing the size of my chain rings? I currently have a 44/34/22 crankset and was looking to up it to 48/?/? Besides the rings and chain any other changes I'm missing?
12-25-2007, 03:46 PM
make sure you are still within the "T" range of your front and rear derailleurs. In other words, stay within your derailleur's capacity.
You can read up on this at Sheldon Brown's website.
12-26-2007, 10:57 AM
You'll likely need to adjust your dérailleur upwards a bit to accommodate the larger rings.
12-31-2007, 06:46 PM
most front derailers will handle a 13 tooth shift from one ring to the next, I over did it on an old mt. bike and had to use my toe to help get the chain onto the big ring.
12-31-2007, 06:48 PM
Oh yeah, if you are looking to get a higher gear, it is easier to just replace the rear cassette to one with smaller cogs.
12-31-2007, 09:17 PM
The "T" range Lynn is talking is also known as "wrap capacity" and relates to the rear derailleur. For instance, my Shimano LX long cage derailleur has 45 teeth of "wrap capacity" allowing for the stock 11-34 cassette (delta 23 teeth) plus 30/42/52 chainrings (delta 22 teeth) which equals the 45 tooth wrap capacity.
Here is a link that is short and sweet about what to watch for:
Please note the the warning in the above link, it can be serious to have a chain to short!
I run a smaller chainring in the granny position... 26T instead of 30T. This means I give up my 26>11 and 26>13 combinations because the chain is too long. No big deal and it works for me.
To make it more frustrating, there are also limitations on the steps between chainrings. This is part of the specification of the front derailleur. Most shimano 105 deraileurs will handle 12T from small to middle and 10T from middle to large. You can cheat this by a few teeth without to much trouble. Usually, symptoms of incompatability is chain-suck (where a chain wraps around the gear when shifting).
If you want to elimiate all problems and know things will work, upgrade all the chainrings equally... 22>26 34>38 and 44>48 and add 4 links in the chain.
You might also opt for a common crankset that has 30/42/52 chainring combination. If you have a standard square taper bottom bracket, these are readily available and often on sale. Most cranksets are either 170 or 175mm from center to pedal holes.
When buying chainrings, you need to know the BCD (bolt circle diameter) of your bolt pattern.
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