Trunk Monkey

First time post… I’ve got a (mostly) cross bike I built to use as commuter. There isn’t much in the way of CX in my part of the country (Wichita, KS) but I was thinking about entering a couple for the experience. My bike is currently set up as a 1 x 9 (49 tooth front w/ 11-34 cassette rear, Shimano HG80). I do really not want to go w/ more than 9 speeds and I’m sure my 49 front is too big for racing CX.

I’m looking for suggestions as to what I should change the front to. It seems most double fronts for CX are either 36-46 or 38-46. Splitting the difference puts me at 40 or 41, both of which seems small for some reason. Is there a “standard” for a rear setup such as mine? Being in KS also makes me feel the bike should be geared a little faster.

Any help?

Thanks.

patrickinvt

hey - with that cassette, a 42t will give you enough on the low and high ends. very few courses will give you a chance to use 42x11 very much and if 42x34 isn't low enough, you'll probably be running anyway! also keep in mind that just because you can push big gears for one lap doesn't mean you'll be able to do it for 45-60mins - cx can be a real slog sometimes and you'll appreciate lower gears.

vcnz

I would go for 46 or 44, not smaller. With 34 on the back nothing is going to stop you.
Hope you have a rear der with cage long enough

fietsbob

Cyclocrossworld.com for racing, gets the flanges made mostly in 42, and 44.
and a 38t ... i got the 110 -38,, though, it went on an IGH bike.

42-27 low in competition, Lower? then the 2 feet gear should be faster.

Trunk Monkey

Thanks for the input I appreciate it. My current plan is to use a 44 or 43 tooth ring that I just remembered that I have. I know at least 1 CX race is held in a particular park. Even though I'm not sure how the course is set up there are lots of trails I can try it out on. There are also some nice MTB trails not too far from me. I am unaware of any competitions held there but it should be interesting. They are well kept trails but relatively mild mannered (it is the Great Plains after all).

At the very least I'm starting in the right neighborhood.

Good point that I forgot about. My short cage is already maxed out by my cogs (literally). I was unaware of this until you prompted me to check. I'll have to remove some links from the chain. I'll probably just add another quick disconnect link to make swaps easier.

flargle

49:34 is a lower gear than 42:27, and 42 x 12-27 is a popular single-ring setup.

I'd just race the 49 and go from there.

Trunk Monkey

I like your attitude. The thing that got me considering the swap was the "width" between ratios with the 49 tooth. It's something I notice riding paved roads around a pretty flat city. The 49 tooth also halls balls when paired to the 11t cog. There is literally only one place in town that I can really use it (down hill run). It's awesome to pass cars while speeding on a bike. Realistically I don't even need 49t on my current setup but I did buy it because I was tired of maxing my old setup on that run. I have no business running that fast on a CX course. Just because one can doesn't mean one should... I kinda doubt I could though.

Andy_K 

There are two schools of thought with regard to spacing between gears. One school says that wide spacing is good because you accelerate a lot more often than you spin and cruise (the latter of which never happens in a CX race) and the big jump puts you at a faster speed when you feel the need to shift. The other school says that wide gearing discourages you from upshifting when you should. Which one is right probably depends on your personal tendencies.

Personally, I like tight spacing so I raced most of this year with a 1x10 setup using a 36T ring on front and a 13-25 cassette in the rear. If you're reading that and thinking I must be really slow, you're right but not for the reason you may be imagining. The 36x13 gear is higher than the 42x16 gear that Adam Craig used to win the SSCX national championship (and that's a monster of a SSCX gear). I spun out the 36x13 in exactly one place in 14 races this year, and that was a long, smooth straightaway with a slight decline. A cadence of 120 gets you over 26 mph in that gear, and that's a speed that you almost never see in a CX race (at least, I almost never see it).

The other thing I'd like to say is that if you do get a smaller chain ring, you should also consider a different cassette. A tough CX course has a way of pushing you onto your smallest gear. No matter how high your smallest gear is you can probably will yourself to keep going, but if you aren't in your lowest gear it is very hard to keep yourself from downshifting when you're deep in the pain cave. Having a low gear available makes you slow, and that's the real problem with my gearing as described above.

bicyclridr4life

I used to live in Wichita. Where is a down hill? I do not remember any "hills" other than the overpasses in Wichita.

Trunk Monkey

Prepare to be disappointed... Hillside Street runs N/S, starting on Douglas and south to about Pawnee (both run E/W), approaching Hillside from the east gives a relatively good run. It's nothing overly dramatic and the run is fairly short but if you hit the lights right at Hillside the speed can carry you far enough to put s mile on your face and you can easily keep up with and pass traffic. Overpasses for the canal route work good too but there are usually traffic lights on either side. Pretty much all of theses will allow you to max out a 49/11 gear (for a short distance) if you push to get there.

Nothing compared to real hills even in KCKS. I've seen those and thought they looked ridiculous but the city is too congseted to even consider that type of speed in town.