Mongoose Stat 29" disc, $219

http://www.walmart.com/ip/29-Mongoose-Stat-Men-s-Mountain-Bike/21191093

Mongoose Stat
-Aluminum frame, size 18"
-29" wheels, fast rolling, comfortable, good selection of tires
-disc brakes.  More consistent in wet weather.  The brakes don't wear out your rims, like rim brakes do.  Brake pads and rims last longer with disc brakes.

Is the stat a decent bike?  It sells for $220, and has been on sale for as low as $160.

The aluminum frame is pretty good quality, and has some nice details, especially for the price.  It has a common 1 1/8" headtube, 68mm euro bb shell, 27.2mm seatpost.  It comes in one size, 18".  Good for 5'8"-5'11" riders.

The fork is a very heavy, cheap, steel suspension forks.  This is one of the worst parts of the bike.  The good news is that it is 1 1/8" threadless steerer tube, the most common size.

A chromoly steel rigid fork would be a good replacement.  This is simpler, lighter, no maintenance, easier to fit fenders.  You don't want shocks on a commuter bike.
This $50 Nashbar fork is a good choice.  Axle to crown: 453mm.

The Stat uses 1 1/8" stem, with 25.4mm handlebar.  These are the most common sizes.  Easy to swap out different styles of handlebars, or different length stems.
Stems are <$20
Bars are $15-35 depending on style.

The wheels use Quando aluminum quick release hubs, F&R.  It uses a freewheel in the rear.  Double wall 29" aluminum rims.  These are pretty nice wheels.
The tires are cheap, knobby tires.  They roll slow, and get flats easily.  Faster rolling, more flat resistant commuter tires are the best change you can make to this bike.  Continental, Michelin, Vittoria, Rubena make nice 29x2.0" fatty city tires for around $20-30 per wheel

29" rims and 700c rims are the same diameter, and their tires are usually interchangeable.  Both 29" and 700c rims have the same 622mm ERTO diameter.  29" rims tend to be wider to work with fatter tires.  700c tend to be narrower to work with skinnier tires.
29" tires are measured width in inches, for example 2.0".
700c is by "c", bacially mm's.  23c= 23mm very skinny.  You can fit fatter 35c and up tires on 29" rims.

These Schwalbe 700 X 40c tires are a bit narrower and faster rolling.  40mm is about 1.6" wide, so they still have some cush.
$25 for the pair is a great deal.

Fenders are another thing to think about when choosing tires.  There are not that many fenders available for fatty 29X2+" tires.  The Planet Bike Cascadia fenders are an excellent choice, but pricey at $45.

More common sizes are 700X45mm fenders, $23.  These only fit smaller width 700c tires, 44c or lower.
Going this route, you are under $50 for good tires and fenders.

The Promax cable disc brake calipers are not terrible.  One bad thing is their brake pads are not commonly stocked at bike shops.

Replacement Cheap brake pads on ebay

Better brake calipers, that take commonly stocked brake pads would be a good upgrade for this bike.
Avid BB-5., $33  These are good brakes and brake pads are readily available for them.  The are better constructed, and easier to adjust.  The promax's are not bad, though.

The brake levers have a plastic body, with an aluminum lever blade.  They work, but they are flexier than levers with an aluminum lever body.  The cables and housing on the bike are poor quality.  Better levers and cables would really improve this bike.
Shimano Acera levers, including cables & housing, $14

The 3 X 7 speed SRAM grip shifters are good.  The shift cables & housing on the bike are poor quality.  Shimano, SRAM, Jagwire make good shift cables & housings.

Shimano Tourney derailleur.
7 speed freewheel & chain.  Drivetrains usually last about 3000 miles.  The replacement parts for this bike are very inexpensive.  The chain and freewheel on the bike are cheap chinese.
The 7 speed freewheel costs $12 to replace with good quality shimano one.
Better quality SRAM chain is $8.
This bike has one of the most affordable drivetrains to replace.

The cranks are chinese, aluminum arms, with stamped steel rings.  They are not light, but they are durable.  The bottom bracket is euro threaded adjustable loose ball.  Replacement shimano cranks are around $40, and bottom brackets around $20.  Though I would expect the cranks to last awhile.

The pedals are pretty nice aluminum BMX pedals.  Most walmart bikes have janky plastic pedals, these ones are good.

The seat and post.  The quality of the seat is not terrible, but it is heavy and has a really tacky cover.  It is one of the cheapest looking things on the bike.

The seatpost is a cheap "seat guts" style post.  These are heavy and prone to creaking and slipping.

 A 2 bolt Kalloy 27.2mm seatpost would be a good upgrade for <$20.

Kalloy 2 bolt aluminum seatpost $14

Singleworks city limit, leather, $20

Overall, the bike is not a bad choice for a commuter.  The worst parts are the tires and fork.  The brakes would be better with quality levers and cables.  Decent seat and post would save weight, look better.
Tires= $25
Fenders= $22
-------------------
Fork= $50
Levers= $13
Seat & post= $34
$144 total.

Good used commuter bike under $150 : Trek 930

"You are better off buying a slightly used, good quality bike shop bike off of craigslist, than buying a new Wal-Mart bike."

What bike to look for on craigslist?  CL is full of bikes, some good, some crappy.  Some good deals, some terrible.

One of the best types of bike for a <5 mile commuter bike, is a simple mountain bike.
Mountain bikes were a huge fad during the 90's, and millions were sold. Many have lived in garages collecting dust. You can find them on Craigslist for $50-150 all the time.

They make for good commuter bikes, when set up with smooth rolling, flat resistant tires, and fenders to keep you dry and clean.

Strong, stable, comfortable to ride.They don't get flat tires easily. Replacement parts are readily available and inexpensive. fatter tires are good on gravel, potholes, train tracks. Not as fast as a road bike with bigger diameter wheels and skinnier tires. Good bike for rides under 5 miles. Wide range gearing is good for steep hills.

This MTB is set up with swept back "northroad" handlebars, for a more comfortable, upright riding position.  Handlebars, $20-35, can really transform the fit and style of a bike.
VO Milan Handlebar 22.2 dia $25 is a popular choice.

The 930 sold for $450-500, and was one of Trek's most popular models from 1992-1999.  Trek was and is the most popular "bike shop" brand out.  "Entry level" bike shop bikes sell for $300.  The 930 was a bit higher quality.  If a $300 bike is a metro or civic, the 930 is a honda accord.  There are a lot of 930's out there.  The 950 & 970 were slightly higher end model, and are worth searching for.  They will have a bit higher grade parts.  The parts on the 930 are good quality, and the bike is more commonly found. 

The frame is the heart of the bike, and the Trek has a very nice frame.  It is made from butted, chromoly 4130 steel.  It uses top quality true temper tubing.  The frames were made in the USA, in Waterloo, WI.  The 930, 950, 970 all use the same frame.

Bike shop bikes have better quality parts.  More aluminum, less plastic and stamped steel.

Bike shop bike come in many sizes, to fit small people, and large.  Big box bikes have only one size, generally around 18" to fit average height people.
Small= 15-16"
Medium= 17-18"
Large= 19-20"
XL=21-22"



There are five 930's under $175 on seattle craiglist right now (edit, 4 of these sold in the time it took me to write this post)

Trek - Shoreline $150

This is a 1995 930.
It looks like it is an  19.5" People 5'9"-5'11" might fit this bike.
It has True Temper chromoly, triple-butted frame.  It has Chromoly uni crown fork.  Light, strong, durable, nice ride.
The wheels have shimano alivio cassette hubs and double wall aluminum rims, light, servicable, durable.
It uses shimano alivio cantilever brakes.  These are a little tricky to adjust, but are strong, well made, fit fenders easily, and the brake pads last a long time.  They are good brakes for a commuter.

The drivetrain is 7 speed Shimano STX.  Good quality, and replacement chains, cassettes, and cranks are inexpensive.

Gripshift 7 speed.  Easy to use, work ok, made of plastic.  These shifters are prone to breaking if the plastic has gotten brittle from sun exposure.
Shimano rapidfire shifters are a good replacement, under $30 for the pair with cables.

The handlebar stem, or gooseneck, is 1 1/8" threaded.  Not the most common stem size.  You can modify the fit of a bike by changing the length of the handle bar stem.  Or by  putting different bars on.

This stem is pretty long, and many people might want a shorter one, to sit more upright.

80mm stem $15

There are a few things that don't age well on bikes.  Rubber & shifters.  Tires, seats and grips get dry rotted. Good commuter tires make a huge difference.  Not getting flats.  Rolling smooth and fast.  Continental, Michelin, Schwalbe, Rubena all make nice commuter tires, generally $20-30 per tire.
Continental 26X1.75" City Ride - $18


Trek 930 Singletrack - $175 (South end)

This is a 1992 930.
It's an 18", good for people 5'6-5'10".

Good quality shimano drivetrain and cantilever brakes.  This bike uses a freewheel rear hub, instead of the newer cassette hubs.  It is a bit easier to bend an axle with freewheel hubs, but if you are not jumping, or weigh over 200lbs, you should be fine.  Freewheel drivetrains have cheaper replacement parts (rear wheel, rear cogs) than cassette drivetrains.

This bike has very early Shimano "push-push" shifters.  These are finicky and prone to failing.
Shimano rapidfire shifters are a good replacement, under $30 for the pair with cables.
7 speed right $13
3 speed left $14
Cantilever brake levers

This bike also has a threaded stem, but the more common 1" size.  The stem is shorter and more upright.  It has steel riser bars.
I think this seller is asking a bit too much for this bike.

http://seattle.craigslist.org/tac/bik/4233683770.html

This is a 1995 or 96 930 SHX.  The SHX stands for shocks.  It's a size 16" for people about 5'5"-5'8".

This is pretty good buy for $100.
Nice USA made chromoly frame.
It has early rockshox forks that don't work that well.  15 year old, entry level shocks use rubber bumpers for springs, that harden with age.  The moving parts get sloppy over time.  It is hard to mount fenders to a front shock.  You are better off with a rigid fork.

The good news is that this bike uses a 1 1/8" threadless fork, headset and stem.  This is the most common size.  Threadless is stronger, lighter, and easier to adjust than threaded is.  To adjusted a threaded headset, you need a thin 32mm or 36mm specialty wrench.  Threadless, you just need an allen key.
Threadless vs. threaded

Rigid chromoly fork - $42.50
Stems are readily available in all sizes.  1 1/8" threadless, 25.4mm handlebar clamp.  Many people like shorter length, to get them more upright.
shorter or higher rise stem <$20, or different bars.

Shimano STX 3X7 drivetrain and cantilever brakes are durable and good quality. Aluminum rims and shimanos hubs make for strong and light wheels.

This bike has commuter tires already.  It also has a decent leather saddle already.  These are common parts that need to be replaced on used bikes.

This bike would be a great commuter with the addition of some fenders, $14.

Losing the old heavy fork, for a rigid fork would be a good upgrade for $40.
You can customize the riding position to be more upright with
shorter or higher rise stem <$20, or different bars.

The last two are the same exact bike, a 1999 930, size 19.5" good for someone 5'9-6'0"

 Men's Trek 6061 T6 EXCELLENT X-MAS - $150 (Edmonds)

MEN'S TREK 930 SINGLE TRACK - $150 (Enumclaw)

Both of these bikes look like they have very little use.  They look stock, down to the tires.  The Enumclaw bike has a gel seat. The Edmonds has a rack.
The '99 gets Shimano Linear pull brakes, or "V-brakes" instead of cantilever brakes.  They are a bit more powerful, and easier to adjust.
The suspension fork on this is a Rockshox Indy, which is not too bad.  A rigid cromoly fork would be a good longterm upgrade for a commuter.  Lighter and simpler.
This bike has a threadless 1 1/8" fork and stem, the most common size.  Forks and stems are readily available.
These bikes would be an excellent commuter with some smooth rolling tires and fenders.

The handlebar stem is quite long on this bike.  Most people would be more comfortable with a shorter, more upright stem.

These are few examples of good quality used bikes, that would make excellent commuter bikes, with the addition of durable city tires and fenders.

Schwinn Admiral 700c 7 speed, fenders, rack $159

$159, the Schwinn Admiral is one of the best value commuter bikes you can get at Walmart.
http://www.walmart.com/ip/700c-Schwinn-Admiral-Women-s-Hybrid-Bike-Powder-Blue/26999382
http://www.walmart.com/ip/700c-Schwinn-Admiral-Hybrid-Men-s-Leisure-Bike-Matte-Red/26999373

The Admiral has a high tensile steel frame and fork.
It has aluminum 700c wheels, that roll fast.
7 speed gripshift and shimano derailleur.
Aluminum linear pull brakes.
Upright sweptback handle bars and a beach cruiser seat.
Steel fenders and rear rack.

 Like most walmart bikes, it only comes in one size.  The men's model fits people 5'6"- 5'10".  The women's model fits 5'2-5'-6".

Walmart does not assemble bikes very well.  The same kid that puts together the BBQ grills, puts together the bikes.  Most bike shops are pretty honest.  Bring the bike to a shop, tell them you will be riding it to work and would like it safe, and they will take care of you for under $50.

One of the best features of the Admiral, are it's good quality, aluminum 700c wheels.  It has an alloy quick release front hub, and solid axle nutted freehweel rear.  700c aluminum rims can fit a wide selection of road, touring, and commuter tires. However, the schwinn tires that come on the bike are very cheap, do not take high pressure, and are prone to flat tires.  The best thing to do to this bike to make it a more reliable commuter is better tires.  Nothing ruins your day like flat tires.

Plan to buy better tires.  Good commuter tires are Continental, Schwalbe, Michelin touring.
These Vittoria 700X32c tire are slightly skinnier than the stock 35c tires.  $30 pair.
This is a great deal on Schwalbe Marathon 700x35c tires.  They are very tough to flat, and very long lasting.
Some of best commuter tires you can get. Blue Sky has them $40 for the pair.

The beach cruiser springer seat is made for cruising, not pedaling.  The springs are heavy and squeaky.  The seat is very wide and rubs on your legs when pedaling.
The seatpost with cheapie seat guts is heavy and prone to slipping and creaking.
I would suggest a better seat for $20-30 and an aluminum seatpost for $15-20.

http://www.blueskycycling.com/product7576_46_-WTB-Freedom-Econoline-Saddle.htm $33

The Avenir Classic has real leather cover, for $30.
http://www.amazon.com/Avenir-Classic-Series-Saddle-Black/dp/B003RLDH0E

Singleworks city limit, leather, $20

Kalloy 2 bolt aluminum seatpost

Seatposts come in many sizes.  It is important to check the size of your post to make sure you get the right size.  Luckily, the size is stamped at the bottom of the post.  Remove your post and look for marking:

This example, not the Schwinn, is stamped 26.8.   Post sizes are diameter X length.  This example post is 26.8mm.  Common length is 350mm or 35cm.  400mm is long.  250-300mm is short.  You can always cut a long post down.  Common diameters are 25.4, 26.0, 27.2, etc.  Make sure you get the right size!
Amazon is a good place to buy a post.  Search "kalloy" and "27.2" or "25.4" or whatever the correct size is.

The admiral uses a aluminum quill stem.
It's steel handle bars are swept back. They give you an upright, comfortable position.  Good for short trips.  If you are riding longer distance, lower, less swept back bars would put you in better position to cut through the wind.  The steel bars are quite heavy, and aluminum bar saves a lot of weight.
http://store.velo-orange.com/index.php/components/handlebars/vo-milano-handlebar-22-2-dia.html
It uses a gripshift 7 speed shifter, good quality.
Aluminum V-brake levers, also decent quality.
The brake and shift cables and housing are poor quality.  The cheap housings flex a lot, makes your brakes feel mushy and shifting vague.  Jagwire, Shimano, Sram make quality cables & housing that will drastically improve shifting and braking of the bike.
Brake cables & housing, $13

The aluminum V-brakes are functional, but not great quality.  The stock brake pads are very hard plastic-y compound.  The brakes themselves have play on the bosses and cheap plastic spring adjustment.  I would suggest upgrading to Shimano Acera brakes fore $14.  Not much more than $8 brake pads.

The drive train is basic, durable, and replacement parts are inexpensive.  The drivetrain is the crank and chainring, the chain, and the freewheel.  Drivetrains typically last around 3000 miles.  That sounds like a lot, but if you are riding 5 miles to work each way, that 10 miles a day, 300 days.  Tires, brake pads, and drivetrains are consumables.

It uses a steel one piece crank and steel sprocket.  This is heavy and crude, in comparison to three piece aluminum cranks that come on bike shop quality bikes, but it gets the job done, and is durable.  This style of crank is common on beach cruisers and kid's bikes.

The 7 speed freewheel costs $12 to replace with good quality shimano one.
Better quality SRAM chain is $8.
This bike has one of the most affordable drivetrains to replace.  The steel chainring, while heavy, is durable.
The Shimano Tourney derailleur is basic, and replacements are about $14.