Singlespeed & Fixed Gear - singlespeed cranksets
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09-09-02, 11:06 AM
Can any crankset be converted to singlespeed in theory? If you remove the chainrings, keep the arms, and invest in a singlespeed front chainring? I'm looking at an XT crankset, and just want to make sure it will work. Does compact drive, long drive, etc. make a difference?
09-09-02, 12:33 PM
Theoretically, yes. I use standard double road crank with the chainring on the inside. I am just using a standard 42T chainring. It works fine with a 1/8" track/bmx chain and track cog fixed gear in the rear. The 1/8" (vs standard 3/32") chain is necessary for a track cog, but would not be necessary if you go with a singlespeed freewheel in the back.
The important thing is to position the chainring so that the chainline is as straight as possible, which usually means the innermost position. A compact crankset would work, but you may be limited as to how large a chainring you can get to fit the small inner bolt circle diameter. Are you thinking fixed gear or freewheeling singlespeed? If the latter, you can still use your XT crank, putting the chainring on the middle position, then put a single cog out of any cassette on a regular freehub with appropriate spacers on each side to achieve a straight chainline. Harriscyclery.com has everything you need. They are very helpful in suggesting solutions. There are often many ways to skin the proverbial cat.
Since both chainrings on a double crank and the two outer chainrings on a triple are usually attached with the same set of chainring bolts you need to get a set of short stack chainring bolts to attach only one chainring in any of those positions. Your LBS may have them or you can get them from harriscyclery.com.
09-09-02, 01:38 PM
my plan was to harvest just the arms from the xt cranks and purchase a front chainring for them if my choice. I was also planning to get a Surly or similar flip-flop hub to allow for fixed gear on one side, and freewheel on the other.
Thanks for the response!
09-10-02, 06:59 AM
Right. I figured you would be using different chainrings. The problem is that in the small chainring position the with its small BCD, is it 58? 64? mm on a compact XT crank, there is a limit to the size, ie, number of teeth you can get. Harris' website doesn't says they have them, but they don't have the sizes listed. This may not be a problem as long as you can get an appropriate chainring/cog combination to achieve the size gear you want to use. For instance my fixed gear setup is 42/17 giving me 67 gear inches. If the largest chainring you can get is say a 34T chainring you can use a 14T cog to achieve 66 inches. For a bigger gear you can select a smaller cog. The concern is what is the largest chainring you can get for that innermost position. Track cogs are available down to at least 12T; I'm not sure about 11. Harris Cyclery can advise you if your LBS can't. The point I am trying to make is that you may not be able to get a big ol' track setup like 48/14-13-12 because you may not be able to get a chainring that large with the small BCD to fit the inner position on an XT crank. Just be aware of that as you plan your setup. A cheap, used, standard 130 BCD double road crank is more of a sure thing. Which reminds me, is your bottom bracket spindle long enough for a triple? Even if you are not going to use it as a triple, you may run into problems if the spindle is not long enough. If the bolt positions for the inner chainring are solid, they may not clear the chainstay. See, there are a lot of issues to consider. I am just trying to help you be aware of them before you start buying stuff.
I am using a Sokov(? inexpensive) flip flop with the track/freewheel sides and a Surly track cog. The track cog required a 1/8" chain, but, FWIW, I am using a standard, not track, chainring. My LBS said it would work fine and it does. BTW I The wheel is a stock setup sold by QBP (the distributor your LBS buys from) on a Mavic MA3 36-spoke rim. Retails for $99. It is a very nice, inexpensive setup for getting started. If you decide you like fixed gear you can go wild later and get something like a $300 Phil Woods track hub and build a custom wheel. I am finding the one if have adequate for my purposes for the time being.
09-10-02, 07:19 AM
Getting the chainline right doesnt always mean using the inner-most chainring position. If you use a short spindle BB, then you may be able to use the outer position, with the added advantage that the pedals will be closer to the frame.
Ive setup a stronglight 80 as a 1x5 , and use the outer ring position with no problems.
Is your singlespeed for road or off-road use? Off roaders need a much smaller gear, so an MTB triple should be ideal.
09-10-02, 07:41 AM
Rainmanp, thanks for the tips! Especially about the $ 99 rear wheel. I will look into that.
Jenson USA and Webcyclery have a Truvatv stylo ss crankset with bashring for only $ 109. This seems like a pretty good deal.
My hope is to actually build a 'cross singlespeed, but there aren't many cross frames out there with horizontal dropouts. Do you guys know anything about purchasing horizontals (I think Harris sells them), and having them welded to the frame? I'd rather not have to bother with a chain tensioner.
09-10-02, 02:20 PM
Many, if not most older 10 speeds had horizontal dropouts. I have a mid-80s Bianchi, an early 80s Schwinn and a mid-70s Trek that not only have horizontal dropouts, but the lugs and other construction details look almost identical. An old frame like that would be good and sturdy and not necessarily all that heavy for what you want. Horizontal dropouts were the norm for old single speeds with nutted axles to help get good chain tension. Frames continued to be made that way even after derailleurs made chain tension a moot issue. When quick release wheels came along, vertical dropouts made it easier to drop those wheels out for quick changes.
If you just want a good inexpensive crankset, without rings, go check out the Sugino AC130 cranks at chucksbikes.com. The only drawback is that he only has 175 mm. On a fixed gear it is considered better to use shorter cranks, even as short as 165 to reduce the likelihood of grounding a pedal going around a corner. Remember, with a fixed gear those pedals are alwasy moving so you can't just keep the inside pedal at 12 o'clock going around the bend. And grounding a pedal on a fixed gear often leads to a crash where a grounding on a freewheeler might not.
If you can pick up a nice Schwinn or Trek of appropriate size for 50 bucks or so you might have your frame and cranks right there. Even if the Schwinn has 27" wheels there is often enough adjustment in the brakes to accomodate the slightly smaller 700c wheel. The pads only have to move down 8 mm (the difference between the diameter of a 27" wheel and a 700c wheel, 630-622=8) or about 3/8". You just have to look at these little details.
All this talk is giving me the itch to finish the conversion of this old Trek to fixed gear. Just picture it. Repaint the frame flat black with black bar tape and a black rack- stealth urban fixed gear commuter. Or should I go really really high gloss black? I just can't decide. I'm just waiting for Rainbabe to get over the silly notion that 3 working bikes is enough. "How many bikes can you RIDE at one time?" Like that's even a relevant consideration. :D
09-10-02, 05:05 PM
Originally posted by RainmanP
I'm just waiting for Rainbabe to get over the silly notion that 3 working bikes is enough. "How many bikes can you RIDE at one time?" Like that's even a relevant consideration. :D [/B]
All non cycling enthusiasts are this way!:p They can never understand why we'd need so many different bikes.
Your suggestion is a good one, and I have been keeping an eye out for a good used vintage frame for a little while now, but ideally, I'd like to have a cyclocross/touring setup to allow for canti brakes and larger tires. It will most likely spend it's time as a singlespeed rather than a fixie.
This raises another question: Are horizontal dropouts or track forks preferred when building a singlespeed or fixed gear. Is one suited better for one or the other. track probably make removing wheels tough, so are there drawbacks for each one?
09-10-02, 06:31 PM
I haven't experienced a bike with track dropouts. I'm not sure there would be that much difference. It seems like getting the wheel out of forward facing dropouts is just a tiny bit more convenient. Have you read Sheldon's articles on fixed gear topics? Makes for very informative reading.
09-10-02, 11:52 PM
You CAN get fix gear cogs in 3/32 or road thickness- I have several.
The advantage of "track" or rear-facing dropouts is- It is impossible to pull the rear wheel into the frame if your hub works loose in a heavy acceleration.
On my fixie "set-up I left BOTH chainrings on the crank, so I could use the 53 for power workouts and the 42 for "spin" work.
09-12-02, 06:51 AM
Hey, thanks for the good ideas! What brand are the 3/32 track cogs you are using? Shimano? When I asked my LBS to order a couple for me they didn't tell me there was an option and got me Surly which are the thicker type.
Using the double chainring sounds interesting. Are you using the same cog in the two different gearings or do you flip your wheel. Is there enough horizontal adjustment on the track dropouts to accomodate the two different gearing combinations?
You can use your existing XT crank. If you have a couple of bb laying around with different spindle lenghts you can play around with the chainline. A frame with vertical dropouts to set up a single speed without a chain tensioner is difficult. You have to make sure that your front ring and rear cog ratio is exact to the chainstay length in relation to the number of chain links.
On my wifes bike for example I missed by a HALF a link! Made all the difference though I had to use a tensioner.
Originally posted by Hunter
On my wifes bike for example I missed by a HALF a link! Made all the difference though I had to use a tensioner. In that case, you can get a Half-link and ditch the tensioner. Sheldon sells them, although to the best of my knowledge, they only make them for 1/8" chains - no big deal though. Friend of mine did this and was able to set his vert. drop frame up w/o using a tensioner.
Also, check http://www.peak.org/~fixin/ for a gear calculator that will tell you what gear combos will work on your bike w/o a tensioner. Works pretty good, but things like chain stretch and chainring wear can make a difference too.
09-05-05, 06:14 PM
awesome link thanks!
I will never let this thread die... muaha... ha...
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