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Recreational Cyclocross and Gravelbiking This has to be the most physically intense sport ever invented. It's high speed bicycle racing on a short off road course or riding the off pavement rides on gravel like :The Dirty Kanza". We also have a dedicated Racing forum for the Cyclocross Hard Core Racers.

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Old 10-21-09, 11:09 AM   #1
Andy_K 
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Single Speed Question

Yes, it's about gearing. I searched and read old threads, but I think this is specific enough to be worth asking.

I'm thinking about racing single speed for the first time this Saturday. The only option I've got right now is 46x18. (Stop laughing, this might work.) I ride that ratio fixed on my commute, but I've got a freewheel that I'd be using for CX. The course I'm thinking about using this on is completely flat. It's an old golf course. I raced there last year, and the only variation in elevation, literally, will be a few trips up and down tee areas.

I fully expect to finish DFL. The single speed guys around here are fast, and I'm mostly considering racing in that category because of a schedule conflict. I would, however, like to avoid DNF because of my legs falling off.

So, my question is, if you were in my position, would you give it a try with the 46x18 gearing or would you start scouring the LBS's for a smaller chain ring?
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Old 10-21-09, 11:19 AM   #2
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I would find a used 42 for a race on grass. I aim for 62-64 gear inches for SS cross. If you don't find one just do the race but it will be harder than you think. Starting out after barriers and 180 corners will be brutal, at least that was my experience with SS cross.
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Old 10-21-09, 11:34 AM   #3
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A new freewheel is only like $20...
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Old 10-21-09, 11:38 AM   #4
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A new freewheel is only like $20...
That's a good point. I could keep the chain ring and go 46x20 and come out a tad lower than 42x18.
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Old 10-21-09, 12:05 PM   #5
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I think that you should definitely try to achieve a lower gear ratio. If you can't, you may as well give it a try anyways. But you'll probably have more fun with a smaller gear.
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Old 10-21-09, 01:31 PM   #6
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That's way too high. I would avoid racing that just for the sake of your knees. I rode my fixie to work every day for years on 52x21 and that was fine, but racing cross is a whole different thing and I would destroy my knees if I raced on something like 46x18. There's just too much starting and stopping. Even on a flat course I wouldn't do it.

I personally race 38x18 and that's about right for me. Other, stronger guys than me seem to race not-too-differently, like 39x17 or around there, maybe a little higher but not much. Even on "flat" or "fast" courses around here it's still all grass and pushing through that gdamned grass... there's just not enough length to get up to a speed where a larger ratio is going to be of any use.

But that's usefulness, I'd urge you to not race on such a high ratio just because I think you could seriously f up your knees. Sugino "standard" chainrings are affordable. If you have time to order one, do that.
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Old 10-21-09, 01:58 PM   #7
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Andy- I'm on my second season racing 'cross on a SS, last year I geared it 42-20, that was okay on all but the flattest courses. This year I replaced the (cheap, crappy, destroyed by mud) 20T freewheel with a White Bros. eno dos 17/19 freewheel, and started the season geared 42-20. After a severely vertical course (Rainier) I swapped the chainring for a 39T in time for a second hilly course (Sherwood). You found me at the end of our race laying on the ground gasping for breath, but I never actually puked, so that must have been about the right gearing.

I talked to some of the fast SS guys, and they are mostly running pretty close to 2:1, with 39-19 being a pretty common option. I will probably move the chain in to the 17T cog on the freewheel for Hillsboro this week, but I think the 39T chainwheel is going to stay.

46-18 sounds suicidal. Call or email Eric at Sellwood Cycles, he has some chainrings in stock, and is the local expert on 'cross.
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Old 10-21-09, 02:21 PM   #8
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Hey Thom, I was going to e-mail you to ask about this if you didn't show up on this thread. I'm looking at this for Battlecreek, which is very similar to Hillsboro, and if I like it I may use it again on Sunday at Hillsboro.

How was 42-20 at Hillsboro last year?
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Old 10-21-09, 03:38 PM   #9
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This might be a bit off topic, but i had an SRAM cassette that is held together with a 1.5mm hex. I took it apart and bought some pvc to slip over my cassette body to use as spacers. I was then able to play around with and get a nice straight chainline and use various cogs to see which works best for me to try out SS. This won't work with shimano as the last couple of cogs are welded together.
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Old 10-21-09, 09:43 PM   #10
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I pre-rode on my SS at Sherwood last Sunday using a 36/17 and damn near died everytime I hit the hill. I did Battlecreek last year on the geared bike and I think I will be spinning like crazy to keep up on the SS since it is so flat. I think you should be looking for a 39 or 42 depending if you're a masher or a spinner.
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Old 10-21-09, 09:50 PM   #11
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This might be a bit off topic, but i had an SRAM cassette that is held together with a 1.5mm hex. I took it apart and bought some pvc to slip over my cassette body to use as spacers. I was then able to play around with and get a nice straight chainline and use various cogs to see which works best for me to try out SS. This won't work with shimano as the last couple of cogs are welded together.
8 speed cassettes are breakable and can be used for this. Only the spacers are different.
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Old 10-22-09, 09:29 AM   #12
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That is a monster gear for sure. If there are any tight corners or god forbid mud or hills, you're toast. I just ran a 36x16 at a muddy race last weekend and was way over-geared. Next time I'll go 36x17 or 18 depending on the course and conditions.
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Old 10-22-09, 10:58 AM   #13
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Andy- 42-20 was okay for Hillsboro, in spite of being flat there was plenty of grind through the "mud", and a lot of fairly sharp turns, where the lower gearing was nice accelerating out of them.
The only course I rode last year that it really felt too low was Barton Park, where you have the long flat run through the paved parking lot.

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Old 10-22-09, 02:36 PM   #14
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OK. Thanks to everyone for talking some sense into me. The course will definitely be soggy, though I'm not sure if there's enough exposed dirt to qualify as mud. There will certainly be at least one sand trap. So I take back what I said in the original post. Feel free to laugh at the 46x18 suggestion.

I just picked up a 39T chain ring. I suppose 39x18 may give me the opposite problem on a flat course, but this seemed to be the most generally useful solution looking forward.

BTW, I'm doing this on my 1977 Gitane Gypsy Sport conversion, complete with the original Dia Compe center pull brakes.



(Yes, I have verified that CX tires will fit -- 700x35 even.)

It should be interesting. I'll post an update after the race.
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Old 10-22-09, 02:40 PM   #15
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BTW, for those in the Portland area, I ride by the Hillsboro course on my way to work. It was very muddy this morning. With rain in the forecast for Friday and Sunday, you might want to bring your hip waders.
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Old 10-25-09, 05:55 PM   #16
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My 12-year old daughter was all set to make her cyclocross debut at Battlecreek, and I was going to do the singlespeed race an hour later. Unfortunately, we weren't there 10 minutes before she starting puking. I told her you're supposed to puke after the race, but she had some sorry excuse about the flu.

So, I ended up not doing that race, but I liked the bike so well once I had it set up for 'cross, that I used it today at Hillsboro instead of my Jake.

As I said above, I switched it to 39x18. I rode it to work like that Friday, and I was spinning out all over the place. I nearly panicked and bought a 17T freewheel, but I decided to stick it out. I think that turned out pretty well.

I didn't spin out during the race and the only time (honestly) that anyone really blew by me on a fast section, it was Thom on his singlespeed. Since he was using 39-17, maybe I should have done that after all.

Anyway, I'm thinking I might take this bike to Astoria next weekend.

Here it is before the race.



Also, if anyone's wondering about how centerpull brakes on an old road bike work for cyclocross....



No worries.
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