Bicycle Mechanics - commuter crank set conversion from 24 to 8

I live in missoula mt and i have just recently become a full time bicycle commuter. i am riding a recently purchased trek pdx and i am looking to start making some alterations. The first thing i am looking at doing is converting from a 24 to an 8 speed. as far as i can tell there are 2 avenues i could go down that would work but i just cant decide which to take...

The most important thing for me is not loosing my chain. i ride in traffic allot and the commuter education level here is pretty low as well as the street quality.


1. i could just take off my front derailleur and shifter and all that and just run with the one cog. i obviously would have to get a chain guide or keeper or something to keep the chain on. this appears to be the less expensive route, however i think there are a few things to worry about. im not sure that i want run full time on either of the chain rings my bike has up front. it has a 48 and a 38 and i was thinking it would be better to run a size some where in between. hills are not a issue here.

2. i can get a new chain ring up front. i would still want to get a guide or chain keeper to make sure i dont drop my chain while im getting flipped off and honked at by ignorant drivers. The problem here though is do i have to buy new cranks, bottom bracket, chain, hardware, cassette, ect ect to get my new set up rolling.

Im pretty sure that its fairly obvious that i need to go with option two but i dont want to have to spend a fortune doing it. does any one have any suggestions or advice? thank you very much.

You can screw in the 2 limit setscrews on the fd to center it over the middle chainring .
pull the cable and shifter,

and either ignore the other 2 rings , or take them off. the middle location is the single ring chainline , Middle of the rear cluster between #4 and #5 of 8

some 5 bolt cranks have chainring guards to that wraps take place of the outer , 110, of note,
to 42 or 44t [cyclocross stuff]
[AFAIK, the 4 bolt ones are rather small]
And there is a chain minder thing that clamps to the seat-tube
to keep the chain from coming off on the inside ..

If I were you, I would just lock the front derailleur in place with the limit screws and remove the fornt shifter and cable and housing. 38 teeth is a very good size. According to Sheldon Brown's Gear Calculator (http://sheldonbrown.com/gears/), a 38 tooth chainring with an 11 tooth cog will get you going 22mph at 80 rpm... and 33 mph at 120 rpm.

THe advantages to this are (1) cost, (2) simplicity, and (3) gives you a chance to evaluate the setup and decide if gear changes need to be made.

Option three would be learning to properly adjust your FD, so you don't lose your chain. You are keeping the RD, so chain slack and a changing chainline will always be there, and a well adjusted FD will do better at keeping the chain on than just a chainring.

I think im going to try to find a five bolt crank set with 40-42 teeth and get a chain retention system/guide. eventualy i would like to upgrade the rear derailleur and crank set b ut probably not until next year. first i need to find some riser bars, clipless pedals and shoes and a messenger bag.

Im pretty sure that its fairly obvious that i need to go with option two but i dont want to have to spend a fortune doing it. does any one have any suggestions or advice? thank you very much.

3. Visit the Park website and learn how to adjust your front derailleur:

http://www.parktool.com/blog/repair-help/front-derailleur-adjustments

or find a youtube video to watch.

With extremely small granny rings you might want a chain catcher (Third Eye Chain Watcher, N-Gear, Deda Dog Fang, etc.) but adjustment alone is usually enough.

Also watch for chain rings that wobble as they rotate which can be due to bent rings or incompletely seated crank arms (the lower end of the torque spec may not be enough) which may preclude adjustment for reliable shifting without dropping the chain in some combinations.

What do you guys think about this one with a puals chain guide
http://cgi.ebay.com/NEW-VUELTA-SINGLE-SPEED-TRACK-FIXIE-BICYCLE-CRANK-SET-/170418268871?pt=Cycling_Parts_Accessories&hash=item27adb86ac7

As others have said, the cheapest, fastest & easiest solution is simply to lock your FD with limit screws in the middle rings.