I'm thinking about converting my '03 GF Tarpon to single speed this summer, to use to get around campus next year. One of the things I noticed is that the crank is sort of one piece - it doesn't seem like I can take the individual chainrings off. It's just a basic Suntour crank with 3 chainrings. My question is do I need to get a new SS-specific crank and bottom bracket? What do I need to be concerned about as far as compatability between a new setup and my existing bottom bracket frame housing?
Single Speed Mtn Bike Conversion
- Thread starter MechE
- Start date
As far as I can tell, it's a 3 piece crank on your bike:
http://www.fisherbikes.com/archive/model/13
3 piece crank is called 3 piece because it has 2 arms & the spindle part:
I think there are several ways you can go (from cheapest to most expensive):
1) If the chainrings don't bolt off from each other, you could try to cut them off. Although I believe they should bolt off .. it should be the same set of bolts that hold it to the crank that hold the chainrings together. Then you can use some spacers or something to try to get the chainline straight.
2) Take the 3 chainring combo off and put on a new single-speed chainring. These have taller teeth so the chain stays on better for single-speed. Single speed and multi-speed chains are also different.
3) I don't think you need to go this far, but you could get new crank arms that fit your current bottom bracket, or get a crankset/bottom bracket combo .. along with a single speed chainring.
RNG1
Well-Known Member
I did the same thing with an old bike I had before I got my single speed. I also had the same issue with the chainrings that the small one unbolted but the large one did not. I used it in the middle ring with a pretty cheap conversion from performance that worked pretty well for just casual riding once you got the spacers right to make the chain path as straight as possible. I never used it for hard off road as I didn't trust it but it sounds like you wouldn't be either. If you want the conversion kit you can have it for a few clif bars.
Mech, your chainrings are all riveted together. Technically, you could leave the others on and "rig it" if you really want to. I would say just find a set of cheap cranks and buy a seperate singlespeed chainring without ramps on it. That won't run you a lot. There are a few little hangups on your bike, however.
First, you have integrated shifter/lever combo. It will still work, but you're gonna have shifters on your bike without any gears. You could just buy a set of levers for 20 bucks and be done with it.
Second, I'm goin on memory here, but I believe that bike has an e-style derailluer that gets pressed in behind the bottom bracket. You will have to remove that and space out accordingly if you stick with that bottom bracket.
Third, This is the bigger problem for you. Stock, that bike had a freewheel style rear hub. To run a singlespeed conversion, you need a freehub style rear hub.
bottom brackets are 68 or 73 mm. You have to measure your frame to see what you got. If you are going the three piece style, you can go with any crankarm you like. Some manufacturers are helpful and tell you the specific bottom bracket spindle length for that specific crank to optimize chainline(typically 50mm). Shimano is usually very helpful with this. With a single speed, chainline isn't as crucial because you can adjust the chainline if needed through the spacing in the rear wheel if you are using a standard 7,8, or 9 speed hub.