Cyclocross - Questions about a single crank 'cross build for a n00b
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12-11-11, 10:39 AM
I have done two (2) CX races this past fall, with travel and family stuff preventing more. So my experience is limited, but I have big plans.:D
I noticed that I never went to the big ring on my bike - I have a 46/36 double, and a 12/28 on the back. Rode both races entirely in the small ring. Probably could have done it in the big ring, since my bike doesn't mind cross-chaining big/big.
I commute on my cross bike, and am wanting to put together (if cheaper than buying new) a bike for racing. I am wondering if a single ring on the front would be a good approach, particularly since I can even go to 12/30 with a Tiagra cassette (have no familiarity with SRAM or Campy, so cannot talk to those).
Does this make sense? With a 46 or thereabouts on the front, and the wide range on the back, it seems I would have everything I would need. And I might actually have fewer chain drops when I do my magic on the course (found that one can bounce the bike hard enough to drop the chain, or at least I apparently can). And I like the mechanical simplicity.
What do you folks think? Does this make any sense?
12-11-11, 11:25 AM
Single Crank? what about the other leg?, it needs a crank arm too :lol:
Parts exist to fit a 42 or 44t chainring , and have 2 chainguards
or one and a chain-minder, inside ..
Course dependent of course.
just a 46t ? you never need the smaller ring? what a guy !
(apparently that is not the case,)..
yea there are toothless discs to replace the big ring too ..
even a 36 or 38t,
I got a 110- 38t one for my IGH bike.
cyclocrossworld.com has nice ones black anodized several BCD.
Cheaper, just finish filing off the teeth off a worn out chainring.
12-11-11, 11:32 AM
No, whatta cassette! I've been to lazy so far to calculate the gearing, but with a 46 front and 30 on the back, I should be pretty good. I commute using my 46/36 with the 12/28 cassette, and never use the small ring - and I have a couple of killer hills to climb.
I'm just "supposing" right now, may not be worth it - it would restrict me a bit from riding with my mtn bike buddies, with THEM I will need the granny gearing!
12-11-11, 01:32 PM
I used a 44t and a 12-27 cassette for all my riding. It's a great range of gears. I used two Salsa Crossing Guards to keep the chain on the chainrings. That worked perfectly.
12-11-11, 01:39 PM
I've gone one step more simple and gotten rid of the choices in the rear, too.
I use an S300 single up front, which is basically a Truvativ/SRAM S300 double with a Salsa Crossing Guard for the outer ring. I leave the rear alone and depending on course conditions I swap out the chainring between a 38t and a 44t. The height of the 3rd Eye chain watcher is enough that I don't need to adjust it between swaps to keep the chain from hopping the inside (which, on a singlespeed frame with track ends is rare).
12-11-11, 02:38 PM
A single ring is good. You should be able to ride anything with the 46 and the 12-28.
The chain WILL drop off unless you take some measures.
If you don't want to buy anything just use a your front derailleur.
Paul Component makes the sweetest device for this purpose.
I went to a single ring setup this season with a 36T in front and 12-27 in the rear. There were a couple of times when I thought I shouldn't have given myself such a low option as the 36x27 because whatever my lowest gear is I end up using it a lot. A 46x30 gear is about the same as a 36x24, so that should be OK. The 12-30 cassette has some kind of big jumps between gears at the low end, and the bigger front ring multiplies those jumps even more. I think a 42T ring would be better.
I've got my commuter set up right now with a 46x34 double and a 12-30 cassette. I use the 34-30 gear for the hill up to my house, which gets as steep as 20% at one point. For everything else on my commute I can use the 46T ring, so for commuting I would expect that your 46x12-30 gearing plan work work out unless you've got any major hills. I think a 42T ring would work too, though you'd start to spin out around 26 mph with that.
As for chain control, there's a company in Tualatin that makes very basic outer ring chain guards at a good price. You can check them out at http://www.bbgbashguard.com/. I used one of their chain guards this year and am entirely happy with it. On the inside I used an N Gear Chain Stop (http://www.universalcycles.com/shopping/product_details.php?id=1806&category=54). I dropped my chain in the first race in which I used it, but I think that was because I set it up with too much clearance. I closed the gap a bit after that and haven't dropped the chain in nine races since then.
12-11-11, 06:18 PM
I'm thinking of doing the same thing. I've had trouble shifting on the front and ended up (quite successfully) using the 46 for the initial sprint, and then dropping to the 36 for the rest of the race. I too end up in the bottom end of the cluster for most of the race, but am planning on working on that during the off-season. I'm not sure the weight penalty of a double ring setup is worth it, so I'm thinking of going for a single 42t CR with a K-edge chain-catcher/bash-guard setup. I'm running a 12-27 rear cluster, but may look into a 12-28instead. Salsa does this gear ratio cluster stock on their Chili Con Crosso. If I have trouble in training, I'll swap it for a smaller chainring / bashguard combo. At least I won't have the shifting problems from this season.
12-19-11, 09:34 PM
First off BB-Bashguard is the way to go. I ran 1 x 9 for two seasons and tried multiple combos.
What ended up working best was 44 in front with an 11-32 in the back. I ran a short cage xt derailleur. The bigger jumps in the back worked well for me because it reduced the multiple shifts.
I used a JumpStop chain guard for the inside. Which are priced great and a super company to deal with. Highly recommend.
This gearing can also be used (and I did) for fast group road rides (just add slicks), commuting and training.
If it were soley C-X racing, I may step down to a 36t ring for more clearance. I only spun out my 36/11 once this year (at Ranier) and I was honestly pretty freaked out by the whole thing.
BTW, don't expect any weight savings over a 2x setup unless you do something really different. I ran a single barend with CaneCreek levers and it was a little lighter than as setup with my SRAM Rival.
Hope that helps.
12-20-11, 01:31 AM
hill too steep?, shoulder the bike and run,you will probably pass
people trying to pedal up it.
12-20-11, 10:30 AM
I too have done this on my cyclocross/commuter. A single 43T up front and a 11-36 with a long cage derailleur on the rear. So far it's really working well for me. There are some big jumps in the cassette, but it doesn't really bother me in this particular application.
12-20-11, 11:41 AM
I used to run a 43 - 12-27 and that was fine. Anything lower gears in a cross race just get off and run. The paul chain guide is nice but you can still drop your chain from the underside. Nothing beats the inner outer chain guard combo.
Of course the other option is to just keep the double and only use one ring ;)
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