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Discussion Starter · #1 ·
OK so I have a road bike with 52/42 chainring, Square Taper BB and working with a 12-25 cassette.

I find that the 42 is not adequate for some inclines. So I've been thinking:

* Replace the 42 for a 39t (simplest)
* Replace the entire crankset for a compact crank like 50/36.
* If I do the above, should I also get new BB or get a square taper crankset that will be a direct fit?


What say you?
 

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campy or some lesser brand?
 

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Without knowing what kind of rider you are, what kind of riding you do, etc., I'd be inclined to just get that 39 ring, but you can score a cheap compact from Nashbar, that'll do the job. If your BB is still ok, it should go on without chainline complications.

A 52-39 with the 12-25 should give you nice gearing for general NNC-ing.
 

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Get the 39 and see if that fills the bill. Its the cheapest option. I think you can get a 38 from Excel Sports. I did that once for Ride the Rockies. It was a little more gear than a 39.
 

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Discussion Starter · #7 ·
thanks for the replies. I am a so-so rider. While I can climb some inclines with the 42, since I am a spinner, I tend to be using the larger cogs.
Recently I rode up a rather steep and long bridge with my hybrid. I had to use the bike's granny gear. Granted I did have a 3-yo at the back seat. But I cannot imagine tackling that with my roadbike with only a 42t. I saw quite a few cyclist having to push their bikes up!
So with say a 39t or even a compact, I would have atleast a fighting chance of going over this bridge.
 

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I tried to go from a standard double to FSA compact on an older bike with square taper and the chainline was WAAAAY off. You could look at both driveside cranks and see there was it was going to put the FSA crank too far out. With that in mind I probably wouldn't have opted for a square taper crankset if replacing the BB anyway.
 

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I assume your crank has a 130mm bolt circle diameter (that's what most of the old 52/42 cranks had). If so, it can actually fit a 38-tooth inner ring, you don't have to settle for 39.

A good step two in conjunction with the above might be to replace the cassette as well... inner chainrings and cassettes tend to be relatively cheap (unless you're going Dura Ace or something). Certainly is cheap compared to replacing the entire crank and bottom bracket.

Don't know how old your bike is, but 12-27 is a cassette to look into... they make 'em for 10-spd drivetrains and used to make 'em for 9-spd (and you can still get 'em). 11-28 and 12-28 are other possibilities.

38/28 or 38/27 isn't a super-low gear, but it's quite a bit better than what you've got now, and if you're fit, can get you up some pretty frickin' huge hills...
.
 

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ohvrolla said:
I tried to go from a standard double to FSA compact on an older bike with square taper and the chainline was WAAAAY off. You could look at both driveside cranks and see there was it was going to put the FSA crank too far out. With that in mind I probably wouldn't have opted for a square taper crankset if replacing the BB anyway.
Did you also swap out the correct length spindle for your new compact cranks? If not, that could be the reason the chainline was off.

To the OP, go for the 39 (or 38)...it's a cheap investment.
 

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I think you'll feel a huge difference between a 42 and a 39 (or 38) tooth ring. Going from a 12-25 to a 12-27 would help, but not a huge amount compared to the chain rings (plus, cassettes are more expensive).
 

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Discussion Starter · #12 ·
To the folks recommending cassette change, my bike is 8spd. Not sure if 12-28 is a 9spd. If that is the case, then I would have to address the brifter too.
I think I will just get a 39t/38t ring to start. It is the cheapest and easiest option.
 

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|3iker said:
To the folks recommending cassette change, my bike is 8spd. Not sure if 12-28 is a 9spd. If that is the case, then I would have to address the brifter too.
I think I will just get a 39t/38t ring to start. It is the cheapest and easiest option.
Cool. But if you ever change your mind, there is still plenty of 8-spd product out there. Heck, even 7-spd too. :

http://www.universalcycles.com/shopping/index.php?category=42
.
 

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SilverStar said:
Did you also swap out the correct length spindle for your new compact cranks? If not, that could be the reason the chainline was off.

To the OP, go for the 39 (or 38)...it's a cheap investment.
I put a new bottom bracket in after initially trying the original. Went from a 113mm spindle to a 103mm spindle as per FSA's website, so you can imagine how far the chainline was off. Chainline looks good now, but 103mm spindles aren't commonplace. FSA recommends a 103mm BB-7420 which is a FSA/TH Industries BB, and I found one at Niagara cycle. Other than that there are some 103mm Sugino BBs. Just wanted to give the OP my experience so he'd realize just because a crankset is square taper doesn't mean it's going to be compatible with the current BB.
 

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pmf said:
I think you'll feel a huge difference between a 42 and a 39 (or 38) tooth ring. Going from a 12-25 to a 12-27 would help, but not a huge amount compared to the chain rings (plus, cassettes are more expensive).
actually a 42*27 is a slightly smaller gear than a 39*25, 40.9 gear inches vs. 41.
 

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Discussion Starter · #16 ·
Hi folks, just wondering if there are much difference b/t Tiagra vs. 105 in terms of chain ring quality? the latter being double the price for a 39t. I think they are both Aluminium.
 
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