Commuting - Fixing up a MTB to commute!

I want to try and get out riding more. My current 80's touring bike does not have the breaks or tire clearance, even with a 1 3/8 treaded tire in front I do would not feel safe making the commute these past few weeks.
So...last night I bought a 1999//2000 GT Rebound MTB. 4130 Cromoly, heavy I guess. It cost $60.
The bars are great with several positions for my hands and I like the frame.
1)Here is where I am debating: Shifters are "shot" according to old owner, they are Shimano Altus.
Do I find old new parts or upgrade?? I like working on bikes but have stayed away from shifters/drivetrains so far. Have converted to SS, and messed around with other fun stuff.
2) Shock 2.2 max Fork does not have hole for fenders(poor design?), with center pull breaks is there a reasonably inexpensive way to switch forks???
3) There was no seatpost, my 28.6 seatpost I had laying around came close, but is too big, I can not find specs for seatpost on the internet.
4) Tires, what do commuters out there suggest who commute over 15miles a day on a MTB(on mostly pavement)(I will search since I know this information is already here).
Thanks for any advice for getting me out on the road more!!
Happy Holidays, Matt.

The good news is you want to bike commute. The bad news is for $100 you could have likely found a different used mountain bike that would have required a lot less work to be a capable commuter machine. As it stands, you're going to likely spend quite a but of cash making this bike work the way you want it, especially if the shifters are really shot. Shifters are pricey.

1) I'd start by replacing cables and lubricating the shifters and derailleurs to see if that helps the shifting woes. Otherwise, a new set of twist-grip shifters can be had for under $50. Decent trigger shifters will probably cost more than twice that amount. Not all shifters are compatible with all derailleurs, so you might want to ask in the Bike Mechanics forum for input on what shifters will work with your current setup.

2) If your bike has a hole in the fork right above the wheel for a reflector mount, that can be used as one of the fender mounts. There are some fenders (you'll have to search or let someone else dig them up) that can be strapped to the fork or otherwise "clipped on". As a last resort, there are small splash guards that strap to the downtube behind the front wheel. If you want fenders, they are better than not having anything. I don't run fenders on any of my bikes.

3) Sounds like you need to take a trip to a bike shop (we call them LBS for short - Local Bike Shop). This would be a place that has bicycles as their primary business, not a sporting goods store or a discount warehouse that happens to sell bikes in a Toy Aisle.

4) I like Forte Slick City (http://www.performancebike.com/shop/profile.cfm?SKU=15304&subcategory_ID=5425) tires ($7 or so each at performancebike.com) but they're for pavement only. I tend to avoid "hybrid" mountain bike tires that have big knobs on the outside and smooth tread in the middle. Forte VersaTrac (http://www.performancebike.com/shop/profile.cfm?SKU=2307&subcategory_ID=5430) tires run okay on pavement because there's not much gap between the tread blocks on the center. They also work fine on singletrack and snow. They're not as fast as a higher pressure city tire, though.

Thank you, I guess step one is to take apart shifters. If they are shot I will start to think SS,
I live in Flatland. Worst case I shorten chain and use it for my purpose, to ride
on a stable bike in the winter to work.
Sorry,the seatpost I tried was 26.8, now that I look at this again.
I have not had luck with LBS is Indianapolis, what I have learned has come from
here, the other usual internet spots, and books.
I have not seen many $100 bikes that need few alterations around here, maybe $150 on ebay and then there is risk.
Thank you for tire advice. I am hoping to put on new tires, a rack, fenders, and seatpost for less than $100.

I'll just chime in on the tires. I have http://www.performancebike.com/shop/profile.cfm?SKU=14789&subcategory_ID=5430 Forte Versa Trac/K (Kevlar layer) and I *really* like them. I commute 12mi daily with them and they are the best tire for the money, IMHO. I can't say enough good things about them. Right now my commute involves about 500 feet of riding on the dirt should of a road (because of construction) and last week it was VERY muddy because of snow. The tires handled it fine. When these wear out, I'll get another set.

The bike I've been using the past 2 winters set me back 100 even from a bike shop last year, and at the time there were several other $100 options for good used bikes. Perhaps the fuel hike and holiday season have driven used bicycle prices up in the last year.

I'm pretty sure you can get all those things for under $100.

I have tires that are just like the VersaTrac (not kevlar) which I turned into ice tires (http://kc-bike.blogspot.com/2007/12/tricks-of-trade-make-your-own-studded.html). Like rykoala I'm going to pick up another set eventually, probably the kevlar version.

Nice Blog and pics!!. I have looked at a couple homemade DIY sites and yours has great detail.
Maybe the tires that came with this bike will get studs for Chrismas!

Be forewarned, these studs were too long and I will have to grind or cut them down to get better traction. Cheers and happy trails!

Replacing those altus shifters should be no problem.
8 speed stuff.
http://www.nashbar.com/profile.cfm?category=6000104&subcategory=60001195&brand=&sku=20851&storetype=&estoreid=&pagename=Shop%20by%20Subcat%3A%20Shifters%2FBrake%20Levers%20%2D%20Mountain
You probably have 7 speed.
http://www.nashbar.com/profile.cfm?category=6000104&subcategory=60001195&brand=&sku=21482&storetype=&estoreid=&pagename=Shop%20by%20Subcat%3A%20Shifters%2FBrake%20Levers%20%2D%20Mountain
Cables will be your more expensive part. Those should probably be replaced b/f the shifters if they don't slide well.
If you have a 1 1/8" fork, I think that this fender would work:
http://www.jensonusa.com/store/product/FE409A07-Sks+Shockblade+Fender.aspx
Try to find one that has a fitting that gos into a 1 1/8" steerer tube. Otherwise, you could kludge one up or get a new rigid fork. You will be learning a lot, though, or spending a lot (relative to your $60).

How to you tell if they slide well? Like I said I have never messed with gears,
except to strip them to a SS.
VES, That shockblade fender looks like a good option. Not Cheap, but I bet
I could make a pvc diy fender with a similar concept. The fork is threaded, but I have not measured it.
I still can not find a thing for specs on the seatpost. Since 26.8 was just to big, I
guess I try to measure myself to see if it is 26.2 or 26.6. Any advice on how
to measure tenths of mm??

If you are a teacher, take it down to shop class and ask to use the calipers. If not, take a piece of paper, wrap it around the post, carefully mark where it overlaps, measure the diameter, and divide by pi.

To check cables:
Put bike in easy gear (large cog in the rear). Shift into hard gear without moving pedals. Cable should now have so much slack that you can pull the housing out from the frame stops. Then, you can slide the housing along the cable. If the cable is rusty or it is very gritty, you you should replace the cables. Many people would recommend replacing the housing with it.
If the cables do not appear rusty, and there isn't too much friction, you can lube the cable and inside of the housing (use triflow if you have it. thin oil may work). Try to clean any crap out of there. Some times the last piece of cable (near derailleur) gets dirty, and you can get away with just replacing that.

You can probably undo a couple little screws on the shifters to lift the housing off. Then, you can grab the cable right near the shifter (loosened in step above), shift around and see if the spool moves freely and stops in nice solid clicks. If it doesn't, you could try to lube it with some oil. Even though they aren't 'serviceable,' a little oil can make it work better.

Cables are $3 - $5 a piece. Housing is $1.50 to $3.00 per foot. Shifter housing is different (parallel strands) than brake housing (coiled), so don't mix and match - you might make sure that the previous owner didn't use the wrong housing. If at the lbs, get ferrules and cable crimps with the cables. The most cost effective way to do cables/housing for a single bike is often to order a cable / housing set from online.
A friend once had the shockblade. It was solid and pretty nice. I had a $7 special from Nashbar that I eventually threw away, b/c the mount was retardedly crappy. To figure out your fork size, measure your stem o.d. I think that a 1" fork will have a 7/8" I.D. (stem O.D.). A 1 1/8" fork should have a 1" stem O.D.

I do agree with others that this might be a little costly / time consuming project, but if it fits and you like the bike - go for it.

Yes, a math teacher, without a shop in the school. I like the circumference idea, since I do not have the seatpost I can roll paper into the tube. Thank you for the idea, and the specific help on shiffters!!!! T his problem solving stuff is as much fun as riding. I went with this bike because I now commute on old steel road bike, there is something nice about taking a spill and knowing your frame is rock solid, and your not late for work!!!

I loked over shiffters, front is fine, back has a broken bolt running through the gears, sort of flowered shaped. Probably not something I could fix, shimano no longer has specs on these...so I will try to replace with similar shifter.