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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 01-22-07, 02:56 PM   #1
pathdoc
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DIY singlespeed crank question

I have a 1997 Bob Jackson Messina, beautiful lugged frame that's going to be converted to a singlespeed. The cranks are Shimano Ultegra which came with the 8 speed groupo. My large chainring is a 53 and my smaller one is a 46. I'd like to move the 46 over to the outside and use it as my drive gear. I'll be using the ultegra rear cassette that's already on the bike. Is there any reason I can't simply mount the 46 on the outside of the crank where the 53 current lives?
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Old 01-22-07, 02:57 PM   #2
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Here is a pic.
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File Type: jpg bob jackson medium.jpg (66.5 KB, 119 views)
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Old 01-22-07, 02:58 PM   #3
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I'm also switching to bullhorns, cheapies from Nashbar.
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Old 01-22-07, 02:59 PM   #4
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I'm going to warn you there will be those who say not to convert such a lovely, well assembled bike.

The chainline depends on which rear cog you choose to run.
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Old 01-22-07, 03:00 PM   #5
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Originally Posted by pathdoc
Is there any reason I can't simply mount the 46 on the outside of the crank where the 53 current lives?
no.
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Old 01-22-07, 03:03 PM   #6
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No trouble at all. I am assuming that you are going to use spacers on the 8 speed hub with a cog, which makes chainline a non-issue.
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Old 01-22-07, 03:03 PM   #7
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Thanks for the warning. This has been my main bike for 9 years. I have purchased a 16t and an 18t singlespeed cogs which will slide onto the cassette as well as spacers.
Chainline should be easy to setup. I hope to get the chain length just close enough so I don't have to resort to a singulator/tension pulley setup. My dropout are somewhat horizontal.
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Old 01-22-07, 03:10 PM   #8
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Sucks to the people who think you should only convert crap frames. I say do whatever makes you happy---just don't hack off that derailer hanger!
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Old 01-22-07, 03:11 PM   #9
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Quote:
Originally Posted by pathdoc
Thanks for the warning. This has been my main bike for 9 years. I have purchased a 16t and an 18t singlespeed cogs which will slide onto the cassette as well as spacers.
Chainline should be easy to setup. I hope to get the chain length just close enough so I don't have to resort to a singulator/tension pulley setup. My dropout are somewhat horizontal.
You may need to use a half-link if you are unlucky with chain tension. You could just use the old rear derailleur as a chain tensioner if need be.
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Old 01-22-07, 03:12 PM   #10
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check your chainrings. if they're ramped and pinned, you might consider getting ss specific ones. after all, for ss stuff, you want your **** designed *not* to jump off the teeth and onto the next. cause, there's no next ring or cog.
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Old 01-22-07, 03:12 PM   #11
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I will not under any circumstance do anything to this frame that is irreversible.

That was my other question. Is there any reason not to use the existing cranks. They have very little wear.
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Old 01-22-07, 03:37 PM   #12
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No reason not to use existing cranks. Just don't post any photos of it when it's done.
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Old 01-22-07, 03:54 PM   #13
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Quote:
Originally Posted by pathdoc
I hope to get the chain length just close enough so I don't have to resort to a singulator/tension pulley setup. My dropout are somewhat horizontal.
i've found this calculator to be extremely accurate:

http://eehouse.org/fixin/formfmu.php
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Old 01-22-07, 03:58 PM   #14
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you may need shorter chainring bolts, but you probably knew that. Little suckers are surprisingly expensive.
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Old 01-22-07, 04:07 PM   #15
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Only due to market forces. But $6 is hardly expensive for most things these days.
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Old 01-22-07, 04:12 PM   #16
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Where could I find shorter bolts?
Thanks in advance.
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Old 01-22-07, 04:14 PM   #17
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Any lbs that sells bmx stuff.
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Old 01-22-07, 04:18 PM   #18
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Sorry if this is a hijack, but I am curious if anyone has found a normal hardware store substitute for short chainring bolts and/or spacers. Believe it or not, but I have two bikes where those damn little bolts were the biggest investment.
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Old 01-22-07, 04:22 PM   #19
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Yeah, most shops will have them. Get steel, Al are a pain and a haircut saves more weight. I paid $9 for a set once because I needed them on the spot, and even though I was like "Come on, you and I both know these are like $2.50 in the QBP catalog," I had to cough it up. $5-6 would be more normal. I've also put washers on or used the other chainring as a spacer to get bikes rolling when I didn't have a set on hand.

Edit re: previous post, I've found that washers and regular chainring bolts are the easiest way out, if you can't find the right size washer you might have to file a flat place on them to get them on the spider. You can also grind down regular bolts if you have a grinder, filing would work but you'd be there for a while.
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Old 01-22-07, 04:37 PM   #20
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I have an old mountain bike crank in the garage. It may have an extra set of bolts on it.
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Old 01-22-07, 05:08 PM   #21
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Hey thanks. I would guess shipping would make it not worthwhile.

I manage to strip ones off junkers where I can. And I have bought sets too. They are pretty easy to come by. But it irritates me that I get charged 10.00 for something I know is worth pennies.

(In case anyone is wondering how many sets of bolts I need, it is because I seem to be always building up another bike for myself as well as another one to sell. )
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Old 01-22-07, 06:09 PM   #22
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washers around those bolts where the other chainring would go would be a way to not buy singlestack bolts.

pathdoc, when's your walker getting here?
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Old 01-22-07, 07:37 PM   #23
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Walker is still in progress and will be one of Don's featured frames at NAHBS.
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Old 01-23-07, 07:08 AM   #24
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I've got a crankset that I pulled off a bike someone else had singlespeeded where the chainring is held on with regular bolts, and nyloc nuts. Awesome.
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Old 01-23-07, 07:40 AM   #25
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What I do is pick up an extra 3 or 4 sets whenever I buy something from danscomp. They have the single-stack bolts for $5 or so. The only LBS around here that has them charges $20 for a set.
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