Fixie, Sell me :]
 

I'm currently trying to convert an old Jamis Mtb to either a single speed or fixed.

I initially planned on going single speed, but the more I think about it, the more it seems like it would be fun to have a fixie.

I want to use it for a short errand bike (10 miles and under), and maybe LIGHT paths, also maybe learn some tricks.

My main concerns are, will it be extremely tiring (I live in a moderately hilly area) and will it use up a lot of tire (Skidding and such)?

I just finished building up my Gary Fisher Rig (singlespeed 29er) as a fixed gear, so I think I'll take this one. I have it set up with a rigid steel fork (Redline), a BB7 disc brake in the front (borrowed from another bike - I have an XT with an 8" rotor for it that needs a bleed), 165mm cranks, 39x17 gearing, and 2.2" tires.

In your case, I think it's a great idea. Mine is a lot of fun for around town riding (which is why I built it), and will make a perfect errand bike. Mountain bikes also have plenty of room for racks and fenders. I'm not having much trouble keeping up with downtown traffic (even with the 2.2" knobbies, which are on their way out). Clearance for really big tires is also a big plus, especially if it will see a little off-road use. Track bikes on the street are a lot of fun for dashing around, but an upright fixed cruiser is a whole different animal. Mine feels (and looks) like a humongous BMX bike. I can't speak much to skidding (not really my thing), but if you find hard tires and use a ratio with enough skid spots you will be fine.

Go for it.

get a flip/flop hub... if you don't like fixed, flip it over and ride SS. surly makes hubs in 135mm (mountain bike spacing)

(Reasonably) low-geared, fixed 29ers are fun, I can attest.

Also, yeah, flip/flop.

I'm not spending any money on this build (>20$), so I think a flip flop is too much...

I was gonna just weld a cog onto the back XD

if it has a disk back hub just get a ISO bolt on cog and flip the wheel... Im looking to get a single speed 26" soon, throw on some 700c wheels and keep the fron disk... for some reason I love 26" mountain bikes with 700s on instead... that are so fun, like an oversized bmx but bigger wheels...