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Compact Crank or just the inner ring?
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 2011-03-31 11:32 AM |
Elite  3779      Ontario |  Subject: Compact Crank or just the inner ring?I'm considering moving to a compact crank, but money is a limiting factor. So I'm wondering if can I just buy an FSA 34 tooth ring and put that on, or is there more to it? I'm running a 105 crank at the moment. |
| 2011-03-31 11:37 AM in reply to: #3423477 |
Expert 1322 Savannah | Subject: RE: Compact Crank or just the inner ring? If you are running a standard, most likely to BCD is 130mm. The BCD is 110 for most compacts, so most chainrings are incompatible. |
| 2011-03-31 11:38 AM in reply to: #3423477 |
Champion 19812 MA | Subject: RE: Compact Crank or just the inner ring? |
| 2011-03-31 11:40 AM in reply to: #3423477 |
| over a barrier | Subject: RE: Compact Crank or just the inner ring? Pretty sure the Shimano 105 cranks are stuck together and can't be swapped. Edit to add: I've found some nice FSA cranks on ebay over the years very cheap, new. Edited by running2far 2011-03-31 11:41 AM |
| 2011-03-31 12:09 PM in reply to: #3423477 |
Veteran 930 Morgan Hill, California | Subject: RE: Compact Crank or just the inner ring? Another consideration is that a 53/34 combo is going to make for some tough shifting between rings. Most compacts are either 50/34 or 50/36. About 16 difference is considered max practical. I've seen others explain how to make a bigger jump work, but 16 is typical. |
| 2011-03-31 12:16 PM in reply to: #3423477 |
Champion 10668 Tacoma, Washington | Subject: RE: Compact Crank or just the inner ring? Minimum for a standard crank is 38 (though they're hard to find -- most common is 39). You could get a cheap MTB crank to put in there (essentially the same as a road compact) and pull off the granny ring... |
| 2011-03-31 12:19 PM in reply to: #3423477 |
Master 1433 Calgary, AB Silver member | Subject: RE: Compact Crank or just the inner ring? I have a standard with a 12/27 - if I went compact with a 11/25 or something, is there really much point other than spending the moola?
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| 2011-03-31 12:49 PM in reply to: #3423477 |
Elite 3779 Ontario | Subject: RE: Compact Crank or just the inner ring? Okay, understand about the BCD and too much of a jump 53-34. If I find (as an example) an FSA Compact Crank, what do I need to consider before buying. Will I need a new BB (currently have Shimano) - Trek Road bike. Do I need a new front derailleur? Also, how do I check the length of my current crank so I buy the same? I have a 9 speed - are the cranks specific to a 9 vs 10 speed? Edited by GoFaster 2011-03-31 12:58 PM |
| 2011-03-31 12:57 PM in reply to: #3423585 |
Champion 11989 Philly 'burbs | Subject: RE: Compact Crank or just the inner ring? Khyron - 2011-03-31 1:19 PM I have a standard with a 12/27 - if I went compact with a 11/25 or something, is there really much point other than spending the moola?
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| 2011-03-31 1:45 PM in reply to: #3423477 |
Expert 1046 Fountain Hills, AZ | Subject: RE: Compact Crank or just the inner ring? Switching to a compact crank is easy. You can find directions online to do it yourself, but a bike shop will probably charge you only $25 and include grooming your derailleurs ... go ahead and replace your cables at same time. If you do it yourself - get a cheap crank wrench from Performance - You can use the same bottom bracket, but this is a good time to change out the BB. Be very careful threading the new BB into the frame. A BB is good for 5000 miles so you might not need to do this. If so, lube the threads of the BB with Phil grease or any high quality grease AND wrap a single pass of Plumber's Teflon Tape (the white tape) around the threads to prevent squeaking. - Lower the front Derailleur about 3-4 mm to account for the smaller diameter of the compact 34 (or 36) tooth versus the standard 39 tooth. - Whoops, don't forget the chain. You probably need to take two links from the chain. WHich means you should probably just replace the chain, since this is a good upgrade very 2000 miles or so. Most triathlon courses will accomodate a 39X27 gear ratio ... so it might be easier to switch your cassette. But if you ride your tri bike all the time, you will really enjoy a compact crank and a 12-27 cassette. THis is the set up I use on my roadie and it's nearly perfect for hilly central Maryland. Also, any Shimano 10-speed crank will work fine with a 9-speed set-up. (I don't think they make 9-speed compact cranks). Another more affordable alternative might be to get a Shimano or FSA brand 52 tooth (big ring) and 38 (small ring) 130 BCD chain rings. 52-38 rings X 12-27 cassette will handle almost any tri course except SavageMan ... and set you back only $35 per ring. But go ahead and replace your chain if you have not replaced in a while. THe length of your crank shaft (172.5 or 175 most likely) is stamped on the inside of each crank. Based on your questions ... I'd think about getting LBS help in this but it's something you can also handle on your own . Edited by jsselle 2011-03-31 1:53 PM |
| 2011-03-31 2:06 PM in reply to: #3423477 |
Veteran 361 North Carolina Foothills | Subject: RE: Compact Crank or just the inner ring? Just as a counter point ... I rode a compact crank on both my road and tri bike from 2006 to 2009. When I bought my most recent road bike - Scott CR1 with SRAM Force - I went back to standard cranks and don't regret it a bit. I also went back to a standard crank on my tri bike (Cervelo P2 SL). Where I live in Western NC, I rarely used the small 34-tooth ring, mainly because it was always possible to climb just about any hill around here in the big (50 tooth) ring (I had a 12-25 cassette). I think my average cadence dropped some with the compact crank because it was possible to mash up any hill in the big ring. Now that I am back with a standard 53-39 setup, I am back to using the small ring on some hills and I feel like I do a better job keeping a higher cadence. Also, for me, the standard crank just seems to deliver more power ... I am sure that is just a perception however. If you haven't already, I would say try a friends bike with a compact crank before you make the switch to ensure it is something you really like. Unless you live in an area where you are constantly climbing a lot of steep grades, I am not sure you'll get much benefit from a compact. Ask yourself if you would benefit from a triple chain ring on your bike, if the answer is no, you probably wouldn't benefit much from a compact either. Just my opinion however, and I am sure others will tell you differently. |
| 2011-03-31 2:25 PM in reply to: #3423477 |
Veteran 228 Knoxville, TN | Subject: RE: Compact Crank or just the inner ring? Going from Shimano to FSA will probably require a new BB. I did that and it was a completely different type of BB. Edited by tenninstr 2011-03-31 2:25 PM |
| 2011-03-31 9:12 PM in reply to: #3423477 |
Master 1862 San Mateo, CA | Subject: RE: Compact Crank or just the inner ring? GoFaster - 2011-03-31 9:32 AM I'm considering moving to a compact crank, but money is a limiting factor. So I'm wondering if can I just buy an FSA 34 tooth ring and put that on, or is there more to it? I'm running a 105 crank at the moment.
How much you looking to spend? I have a FSA compact and BB for sale. < 500 miles.
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| 2011-04-01 8:39 AM in reply to: #3424553 |
Elite 3779 Ontario | Subject: RE: Compact Crank or just the inner ring? betyoursilver - 2011-03-31 10:12 PM GoFaster - 2011-03-31 9:32 AM I'm considering moving to a compact crank, but money is a limiting factor. So I'm wondering if can I just buy an FSA 34 tooth ring and put that on, or is there more to it? I'm running a 105 crank at the moment.
How much you looking to spend? I have a FSA compact and BB for sale. < 500 miles.
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