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Old 05-13-13, 04:44 AM   #1
muni50
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Deore LX FD - max chainring?

Hi,

I have a Deore LX Front DErailleur.

I am looking to replace the crankset because the chainrings are worn and also I have a stuck pedal. The chainring is 52-42-30 (in the crank is written FC3304 and in the largest chainring "Shimano SG A-52). In the rear, I have 8 speeds.

I am struggling to understand the compatibility between FD and crankset (and rear cassette?) Here are my issues:

1. From Shimano's page the specs for the DEore LX FD, it says 'Applicable front chainwheel = 44/48T' . How can this be, if I have clearly been riding with a 52 chanring? Should I buy a new cranset with max 48 or 52 teeth?

2. I would like to have actually only 2 speeds instead of 3. What are the considerations apart from the 48/52 question above? DO I need to change anythign in the back cassette e.g. from 8 to 9? Do I need a new FD or will the Deore work with 2 speeds?

Thanks a lot!!
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Old 05-13-13, 04:45 AM   #2
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By the way, I do not know if it helps but I think I got the Deore LX FD around 2006, in case the DEore's have changed in recent years.
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Old 05-13-13, 08:29 AM   #3
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Do you never use the small ring now? If not, you might be interested in a compact double. Yes, it will work fine with the double. You will have to readjust it upon installation of the new rings. Since it works well with the 52 now, there is no reason it won't continue to work just as well. No - you don't have to change anything in the back.
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Old 05-13-13, 08:37 AM   #4
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OK, sounds promising, I do use the small ring, buy not so much. just for my education, I am confused why would the specs of the deore lx say that applicable front wheel was 48T where my 52 ring fits just fine, even with quite a bit of leeway left. For that matter, it seems most MTB or trekking shimano fd's have the same 44/48T max 'restriction'. Can anyone explain?
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Old 05-13-13, 09:00 AM   #5
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I've had this same issue your talking about, except with road bike derailleurs Ultegra, 105, and Tiagra. Far as I know Deore is a MTB group set, and is designed to work on a triple crack set, maybe Shimano didn't list the road crank you have not thinking it would end up on one. But as you noted it is working, do you really need a 52 anyway ? I realized yesterday that I'm never going to need the 50T front, and 11T rear I have in this lifetime. I have a base line Deore shifter on my front crank, with a Tiagra 10 speed derailleur & a 50-34 compact crank. (Sram Rival), this setup came stock on the 2013 FX 7.6.. And it sux's at shifting, have had 5 different mechanics looking at it, and only one could make it shift half ass, about the same as I could get it with hours of adjusting. In my opinion TREK screwed up and installed a Deore MTB shifter, on a 10 speed road derailleur that is compatible with a compact crank. Here is WHAT should have came on the bike : http://www.amazon.com/Shimano-Tiagra.../dp/B005LKXA4W and I will be ordering one. Why do you only want a double crank, less weight ? Given everything is working correctly, and if you never use the 52 front with the smallest rear. Just replace it with a 48-38-28.. (not knowing your rear cassette size). In theory your current set up would not work with a double road crank , from my experience.

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Old 05-13-13, 09:24 AM   #6
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Quote:
Originally Posted by muni50 View Post
Hi,

I have a Deore LX Front DErailleur.

I am looking to replace the crankset because the chainrings are worn and also I have a stuck pedal. The chainring is 52-42-30 (in the crank is written FC3304 and in the largest chainring "Shimano SG A-52). In the rear, I have 8 speeds.

I am struggling to understand the compatibility between FD and crankset (and rear cassette?) Here are my issues:

1. From Shimano's page the specs for the DEore LX FD, it says 'Applicable front chainwheel = 44/48T' . How can this be, if I have clearly been riding with a 52 chanring? Should I buy a new cranset with max 48 or 52 teeth?

2. I would like to have actually only 2 speeds instead of 3. What are the considerations apart from the 48/52 question above? DO I need to change anythign in the back cassette e.g. from 8 to 9? Do I need a new FD or will the Deore work with 2 speeds?

Thanks a lot!!
Also depending on wear, you should probably change the rear cassette and chain also..
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Old 05-13-13, 09:54 AM   #7
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Hi thanks for reply. As I understand the 10 speed stuff is differently spaced to the 8, 9 speed stuff, so was the problem maybe just in the shifter? In my case, I won't be putting any 10 gear stuff. My shifters are not deores, I'll update what they are when i go down to check.

Also, what does it mean 'compact' crank set? Can there be crank sets with same name, but different due to one being g 'compact' and the other not?

T hanks!

Also, I anyone knows the 48 spec vs 52 conundrum, I'd love to know!
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Old 05-13-13, 11:16 AM   #8
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If the bike came like that from the factory I wouldn't worry about it since OEM's are usually conservative about that sort of thing. I don't know how a FD would know the difference between a 48 or 52T chainring (they're very simple devices.) With FD's I thought the only consideration was the the number of teeth it needs to go from the highest to lowest chainring on the crank.

As far making the front shifter into a double that is very easy to do. They would just mechanically lock out the third position using the limiter screw on the derailleur. This is exactly how they do on the new Trek 7.5FX (Deore front shifter with a compact double crank.) I did the same thing on my last road bike when I converted it from a triple to a double crank.
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Old 05-13-13, 01:52 PM   #9
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Quote:
Originally Posted by muni50 View Post
Hi,

I have a Deore LX Front DErailleur.

I am looking to replace the crankset because the chainrings are worn and also I have a stuck pedal. The chainring is 52-42-30 (in the crank is written FC3304 and in the largest chainring "Shimano SG A-52). In the rear, I have 8 speeds.

I am struggling to understand the compatibility between FD and crankset (and rear cassette?) Here are my issues:

1. From Shimano's page the specs for the DEore LX FD, it says 'Applicable front chainwheel = 44/48T' . How can this be, if I have clearly been riding with a 52 chanring? Should I buy a new cranset with max 48 or 52 teeth?

2. I would like to have actually only 2 speeds instead of 3. What are the considerations apart from the 48/52 question above? DO I need to change anythign in the back cassette e.g. from 8 to 9? Do I need a new FD or will the Deore work with 2 speeds?

Thanks a lot!!
1) front ders are the least complicated mechanical item on a bike. the difference is in the cage. a road der will have a larger curvature to match the larger ring diameter. a compact mtn f der will have a smaller curvature to it. as long as you dont want to use a compact mountain der to shift to a 52 ring, you can probably make it work. most f ders have a bit of leeway through height and angle adjustments. you can also the bend the cage if you know what youre doing. also road and mtn ders have different cable pull and ders for triples have more travel.

2) try not to think of cranks as for "road" or "mountain." try to think only of the gearing you desire, the crank length you need, chainline, and compatibility. in your case the main issue would be chainline. a double would require a narrower bb spindle. depending on the crank you get, it may come with a new bottom bracket so your issue is solved. if you want to keep your old bb, you have to find a triple with the same bb interface as yours.

you dont need a new f der if you stick to a crank with similar size rings and the performance was acceptable to you

i think a 24/36/46 110bcd crank is ideal for most people. this is considered a compact road but is a very traditional size used by tourers and mountain bikers. the benefit is the abundance of chainring sizes, and the wide range of very usable and realistic gears. if you dont need the granny, remove it. i would recommend a crank without built in granny tabs for that.

"compact" refers to the bolt circle diameter. different bcds allow for different min size rings. your current 130bcd allows for a min 39min. a compact road has a 110bsd which allows a 34 inner and something smaller than a 52 outer ring - something many people find useful

btw, are you aware that the left side pedal loosens by turning to the right? that might be the source of your stuck pedal.

http://www.rivbike.com/Cranks-Chainrings-s/41.htm

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Old 05-13-13, 03:08 PM   #10
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Also depending on wear, you should probably change the rear cassette and chain also..
http://forums.bicycling.com/eve/foru...5/m/2581088885
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