Bicycle Mechanics - Crankset Dillema. Need advice.
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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?
08-09-10, 01:45 PM
This depends on how "not adequate" it is. If you think 3 teeth less would do it, then by all means just drop down to a 39 and pedal on. If you feel you're going to need more, then yes, go with a compact double, I would advise square taper as there isn't a reason to change your bb unless you are having issues with it.
08-09-10, 03:32 PM
The lowest you can fit on a 130 BCD crank is 38. They do exist and generally come on cyclocross bikes. I think that coupled with a 12-28 cassette would solve your issues.
08-09-10, 04:09 PM
+1 on the 28 cassette. Three teeth there will help more than on the front.
08-09-10, 04:42 PM
I had the same problem back when I was stationed in CT. The hills that I was riding up were a bit too much for my 42 tooth ring. I swapped it out for a 39 and that made life more bearable.
I have not bought into the compact crank craze but perhaps in another 10 years or so I will revisit this. I think it is because I can gauge in my head what it feels like to ride in a 53 tooth ring and a 39 tooth ring across a range of rear cogs (11 tooth all the way to 26). I just can't mentally gauge the lower tooth rings of a compact crank...maybe I am selling this idea short but so far I have been doing ok.
As far as your bottom bracket, it will be easier to keep it and your existing crankset and just replace your inner chainring unless:
1. Your bottom bracket is shot
2. Your crankset is shot
3. Your chainrings are riveted in place vice bolted in place
4. You might find it more economical to replace the crank with one with a 39 inner ring than buy just a ring.
5. You just really want to buy new gear.
If you find yourself staring at item #4 above then make sure your current bottom bracket is compatible with whatever crankset you plan on buying (JIS/ISO tapers, length and symmetry of the bb axel).
Good luck with this.
08-09-10, 06:00 PM
In the 60s 42 - 26 was what gear they climbed the Alps in , Merckx and all those guys..
Classic Campag Road cranksets were 144 BCD . track cranks still are.
08-09-10, 06:06 PM
Well to start with we are not all cut of the same cloth that Eddy Merckx was made from.... :D
Biker, you're going to want to start by figuring out what the BCD (Bolt Circle Diamter) is for your crankset. That will tell you pretty quick if a 39 or 38 is the smallest you can get. But for the same or nearly the same cost you could get a 12 to 28 cassete and get more change for your money.
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