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Old 09-26-08, 06:48 AM   #1
mazpr
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Swapping compact small chain-ring



Is it possible to swap the small chainring (34t) for a 38t?

Which brand or specs should I follow? I go onine and see so many of them, visited Sheldon making it more confusing with all the specs and numbers on his website.

Does the front derailleur needs to be changed if I go for a different combo, 37-52 just to say an example?
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Old 09-26-08, 07:28 AM   #2
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Hi mazpr. If all you want to do is swap the small chainring for a slightly larger one, you shouldn't have to do anything to your front derailleur. And the only measurment you need to worry about is the bolt circle diameter of your chainrings - 130mm is standard but double-check yours before you buy new ones.

If you wanted to swap your compact cank for a standard 53/39 setup, you would have to check whether your front derailleur is compatible with that gearing. The main concern is that the deraileur cage needs to be tall enough to accommodate the top of the largest chainring and the top of the smallest one.

Rich
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Old 09-26-08, 12:55 PM   #3
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Yes. Your crank has "110BCD" right on it so get a 38T that is 110mm BCD. Inner rings of double cranks usually dont have any ramps or pins so you can probably get any old ring.

You usually only need to lower/raise the front derailer if you get a different size big ring. You still may need to tweak stops and/or angle with a new inner ring, though.
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Old 09-26-08, 05:29 PM   #4
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Here is a picture of the front, it is has some grain as I cropped it and zoomed the image a little. By thw way, this bike is very fast, lol.

Hey, thanks for the replies, I thought about swapping but was not sure if it could be done or not. I usually shift to the small gear on intersections, but the one I got right now is too drastic. I think a 38 will be a smoother transition.


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Old 09-26-08, 06:19 PM   #5
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Harris Cyclery shows 110bcd chainrings at a couple pricepoints from 33 tooth to 52 tooth. Take your pick.
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Old 09-26-08, 06:45 PM   #6
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Quote:
Originally Posted by mazpr View Post


Is it possible to swap the small chainring (34t) for a 38t?

Which brand or specs should I follow? I go onine and see so many of them, visited Sheldon making it more confusing with all the specs and numbers on his website.

Does the front derailleur needs to be changed if I go for a different combo, 37-52 just to say an example?
Any 110 bcd in 38t, will work.
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Old 09-27-08, 11:29 AM   #7
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http://www.jensonusa.com/store/produ...Chainring.aspx

Does it matter it says MTB?

All the rest is the same; 110 / 38T and "seems" to be similar...

The price is not bad at all for less than 20... The pull down menu will show its less for the 38, default is around 25.

What confuses me a little is that some say 110mm 38T for 9-speed and others for 10-speed. Is there any difference at all or is it marketing hype?

http://www.excelsports.com/new.asp?p...r=5&site=qbike

http://www.jensonusa.com/store/produ...Chainring.aspx

How come some of them be 9/10 Shimano and others just be 9 shimano?

I ask many questions, I hope people here are patient enough. I know I can grab the phone and start calling the different shops, but man... Many times customer service is just pure horse relish.

Last edited by mazpr; 09-27-08 at 01:57 PM.
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Old 09-27-08, 04:15 PM   #8
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If you have a 9 speed cassette, then either a 9 or 10 speed chainring will be fine. The 10 speed may be a little bit thinner, so a nine speed chainring may not work with a 10 speed chain and cassette.

You might want to order a chainring bolt tool while you're at it, the $5.00 or so it costs will save you some frustration when you go to do the swap.
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Old 09-27-08, 06:36 PM   #9
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Originally Posted by c_m_shooter View Post
If you have a 9 speed cassette, then either a 9 or 10 speed chainring will be fine. The 10 speed may be a little bit thinner, so a nine speed chainring may not work with a 10 speed chain and cassette.
My experience is with an 8 speed chain on 9 speed rings but I imagine the relationship between 9 and 10 would be the same. What I found was that the 9 speed ring was actually thicker because of more pronounced ramps. This caused an issue with an 8 speed chain in certain gear combinations as the chain would catch on the ramps. Where the chain sits on the chainrings, the width appears to be the same. For an inner ring, catching on ramps is moot point though (your chain will never be on the inside of the ring).

A 9 or 10 speed ring should work just the same for you.
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