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Slightly Opinionated
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Discussion Starter · #1 ·
Running with a 12-25 cassette. The 39/25 is the same lowest gear as my roadie and I have no problem with needing lower gearing, but wondering how it will fare on the 'cross racecourse.
 

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Slightly Opinionated
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Discussion Starter · #3 ·
I think what I'm asking is the 39 going to be a huge ring as a small ring, or should I look into finding 36t rings for my compact cranks and stick with the 48t large ring.
 

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46/36

Is a good middle ground with something like 12/26 in back. Lots of options.

If you're really strong and like to mash big gears, then 39/48 might work.

FWIW, as a top 50% 35+Cat4, I used my 46 very rarely. I considered 38t single with 12(13)/26. A lot of people run 42 single up front, but I can't realistically push that for the entire race.
 

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robdamanii said:
I think what I'm asking is the 39 going to be a huge ring as a small ring, or should I look into finding 36t rings for my compact cranks and stick with the 48t large ring.
No. I don't think so. I was running a 38 single ring last year and thought it worked pretty well.
 

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The 48T will be way too big for racing. The 39T will be fine. I run a 39 T single ring and it's perfect with a 12-27 cassette.
 

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I run a 42 single with a 12-25, if you are reasonably strong and the local courses are not crazy hilly you will be fine, however I agree with the others who say that the 48 will not be very useful because it is just too big for CX. I would try to source out a 42, 44 or 46 big ring.
 

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Iohannes fac totum
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I run 39/48 with either a 12-25 or 11-28. The 39 has been fine for CX. Don't think I've used the 48 at all in a true CX race. The 39 is a real work out on long steep mountainous dirt roads though.
 

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'brifter' is f'ing stupid
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i race w/ 39/46 and 11/23. 48 is pretty big, i don't know any pro guys that use a 48. sven uses a 47, but he's a freak. 39 or even 38 is great for the small ring. most nor-cal courses i don't shift much if at all w/ the 46. if the course has hills, the 39 works.
 

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I also use a 39/49 with a 12-25 cassette. I shift to the 39 at a few races with really steep pitches, but I end up leaving it in the 46t about 90% of the time. 46x12 is plenty big for sprinting and mashing on the flats, once I'm fit I try and shift through the gears to the 12 cog whenever there is a long flat place in the course.

I could actually see running a 44t big ring and an 11-23 cassette, with closer jumps between the cogs. 39 and 23 would be plenty low for the kind of climbs that need an easy gear in a cross race. Too bad there's not a dura ace 44t or 45t ring made...
 
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