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Restrictions on using a single Chainring

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Restrictions on using a single Chainring

Old 10-16-06, 10:34 AM
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sauerwald
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Restrictions on using a single Chainring

I am looking at building up a new bike. I commute, and would like a second bike, setup similarly to my current commuter, so that when I have a repair or maintenence issue, it is not a late night emergency. I have even toyed with the thought of making some components, like wheels, identical so that I can steal from one for the other.

The current bike is built on a touring frame - I like the long (44cm) chainstays since I haul a lot of stuff to/from work and appreciate the heel clearance, a bit longer still would be nice.

My current bike has a 9 speed Shimano hub, with a 12-26 cassette, and a triple (Campy) up front - 30, 40, 50. I use all nine of my rear sprockets, but never move from the middle ring up front. For the next bike I was thinking of using a 9 speed rear cluster, and a single ring up front. Another possibility is to go with an internally geared rear hub, but I am not yet 100% sold on that.

Looking at frames with long chainstays, I came across the Rivendell Atlantis, but they warn about how the frame must be built up with a mountain triple crank - that there isn't clearance for a double, which opened a whole new realm of worry for me.

therefore three questions:

1) When shopping for a frame and Crank - what do I look for to make sure that they are compatible?

2) Are the desires for fatish tires (I like Schwalbe Marathon Plus's), Fenders, long chainstays, and a single crank mutually exclusive, short of going to a full custom frame?

3) I assume that for the shifting to work right with a single ring up front, and 9 speeds in the back, I need to have the chainring properly positioned laterally (probably near the middle of the cluster) - how do I make this adjustment?
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Old 10-16-06, 11:01 AM
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On my road bike, it had a triple, but as I remembered never using my front derailleur on my mountain bike, I took it off and two rings with it. Some things to consider is that the probability of your chain coming off is greater if you don't have a front derailleur for obvious reasons. So make sure you have the right length chain (1" longer than your big-big combination), and consider getting a single speed chainring, like a Salsa, or a BMX because they don't have ramps or pins (which aid in shifting) making it more secure. As for mounting it for straightness, if you get a crankset with a triple spider you get plenty of options, usually it works best if you mount it where the middle chainring was.

Maybe this helps?
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Old 10-17-06, 05:45 AM
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Originally Posted by Boss Moniker
On my road bike, it had a triple, .....
. As for mounting it for straightness, if you get a crankset with a triple spider you get plenty of options, usually it works best if you mount it where the middle chainring was.

Maybe this helps?
Thanks Boss- using a triple crank and only using the middle ring would be an option, although without an Fder, I would worry about losing the chain more easily than with a crank designed as a single.
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Old 10-17-06, 05:47 PM
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Single front chain ring with no chance of chain sling = Wetzikon rings! I love mine!
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Old 10-18-06, 11:57 AM
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Originally Posted by sauerwald
Thanks Boss- using a triple crank and only using the middle ring would be an option, although without an Fder, I would worry about losing the chain more easily than with a crank designed as a single.
i run a single 36-tooth ring on my LS pisgah. i run a first generation XTR crankset with a spot chain guard in the big ring position plus i run a third eye to keep the chain from dropping, and it never has.

also, if you are looking at MTB frames keep in mind that some of the newer frames are built with a 34-tooth middle ring in mind.

at least that's the case with my pisgah so i use a 36 that's been spaced out 2mm.

my bike shifts great all the way across the cassette.

this is my only bike and i love it.

ed rader
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Old 10-18-06, 01:32 PM
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Originally Posted by FarHorizon
Single front chain ring with no chance of chain sling = Wetzikon rings! I love mine!
Ok...I'll bite......what are wetzikon rings.........???

thanks
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Old 10-18-06, 02:58 PM
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Originally Posted by squirtdad
Ok...I'll bite......what are wetzikon rings.........??? thanks
these: http://cyclocrossworld.stores.yahoo....mtasinkit.html
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Old 10-19-06, 06:00 PM
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I just build up a geared rear wheel to put on my single speed Crosscheck so I could have a couple gears. I did it with really cheap stuff from Nashbar, as well as some stuff I had in the junk box. At first I was using the same 48 tooth FSA road chainring as on the SS drivetrain, but I had some chain drop issues when shifting to the highest gear. This hadn't been a problem when single speeding, but then the chain wasn't being yanked from side to side then. I think it was a combination of hitting the ramped sections of the chainring at the wrong time, as well as not having any kind of guide or chainring guard outboard. So here's what I ended up doing.

I mounted a 42 tooth Salsa single speed chainring on the inside of my road crank and a Spot chainring guard on the outside. Had those in the parts box.

I bought a rear wheel built on a Deore hub from REI for $55.

I put an 8 speed cassette ($20 from Nashbar) on the 135mm wide MTB hub in the rear, because 8 speed chains ($13, also Nashbar) do better on single speed specific chainrings. I don't even know if a narrower 9 speed chain would work. I do have an old REI bike with a 1x9 drive train, so it's possible, but I digress.

At first I fitted an ancient friction thumbshifter on the bar. But it would only pull enough cable to shift 7 gears, so I broke down and bought a Sram 3.0 8 speed twist shifter (the cheapest they offer, $16 at an LBS). Once I actually went indexted, I had to run the derailleur cable in the stops on the frame, as opposed to running the whole way in a looong cable housing so I could just ziptie it to the frame for quick mounting.

And finally, I seem to have gotten lucky with the bottom bracket that was on the bike. It's an FSA ISIS with a 108mm length spindle. I was thinking that I might have to fit a wider one, say, 113mm wide, because of the MTB hub in back - especially running the chainring in the inboard position on the crank. But the chain line looks good and I've had no problems with it coming off. It is a bit crunchy in the lowest and highest gears, but the chain is running a quite an angle in either of those. But neither do I spend a whole lotta time in those. Gears 2 thru 7 are very smooth baby!

Finally, I've gone the internally geared hub route. And frankly, I like this better. At first I could feel the extra weight in the rear - compared to the single speed - but not as much as a Sram 7 speed hub I tried before.

I guess I better go. Good luck. DanO
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Old 10-19-06, 07:26 PM
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I would think that the only thing that would arise from using a double on a frame designed for a triple, like the riv, would be a less than optimum chainline. But since your ring would essentially be in the position of a middle ring anyway, I wouldn't see a problem. If all else fails, you could try to find a small ring and smaller freewheel to get the clearance. That was what I had to do on a single speed I built. I couldn't fit the 46t ring I wanted, so I went with a 42 and got a smaller rear cog to get the same ratio.
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