Bicycle Mechanics - Newbie questions - Can I "convert" my Trek 700?

I have an old (I think it's a 1992, based on some internet research) Trek 700 Multi Track Hybrid. Not a lot of miles at all, still riding on the OEM gumwall tires, with plenty of tread left. I'd like to get back into riding, but a bit more trail oriented. Instead of spending $$ on a midlife crisis shiny new mountain bike, I'd like to ease into it by making my Trek a bit more trail-worthy. The rims are marked Araya PX-45 700C and tires are marked 700 x 35C. Here's my question - can I just swap in a pair of more aggressive, knobby tires on the rims? Other than strength issues, is there any other difference between my rims and a mountain bike rim, like size or bead, that would prevent doing that? It looks like I have plenty of clearance for a wider/taller tire.

If this upgrade works, I might consider swapping in a suspended fork to replace the rigid fork. Again, is this "do-able"?

Thanks in advance for your help.

Depending on how much clearance your frame and brakes have to the wheels will determine how agressive of a tire you can mount. You shouldn't have much problem though.

Check out these tires (http://www.nashbar.com/results.cfm?category=121&subcategory=1256&storetype=&estoreid=&init=y&pagename=) for suggestions of good tires to mount to your Trek. Something in the $12-20ea range is a good price to get a tire that will hold up for you. You'll want to get a 700c tire, width of 28-35mm. The wider will provide more grip, but higher rolling resistance (making it harder to keep the speed up).

A couple photos of your bike or a link to one that looks simular will help us determine what will work on your Trek. A rigid fork is most likely possible, but probably not worth the cost.

I have an old (I think it's a 1992, based on some internet research) Trek 700 Multi Track Hybrid. Not a lot of miles at all, still riding on the OEM gumwall tires, with plenty of tread left. I'd like to get back into riding, but a bit more trail oriented. Instead of spending $$ on a midlife crisis shiny new mountain bike, I'd like to ease into it by making my Trek a bit more trail-worthy. The rims are marked Araya PX-45 700C and tires are marked 700 x 35C. Here's my question - can I just swap in a pair of more aggressive, knobby tires on the rims? Other than strength issues, is there any other difference between my rims and a mountain bike rim, like size or bead, that would prevent doing that? It looks like I have plenty of clearance for a wider/taller tire.

If this upgrade works, I might consider swapping in a suspended fork to replace the rigid fork. Again, is this "do-able"?

Thanks in advance for your help.
You can definitely put knobbier tires on your bike! Just remember that you need 700C tires, while most knobby tires are for 26" mountain bike size.

Unfortunately, it's pretty much impossible to upgrade your bike to a suspended fork, since (a) you have 700C sized wheels and (b) you almost certainly have a 1" steer tube. There are suspension forks meant for MTBs with 700C wheels (29'ers), and there are suspension forks meant for old MTBs with 1" steer tubes, but I don't believe a combination exists. A new bike would probably be your best bet at that point.

The old Rock Shock Metro was available with 1" threaded steerer. My LBS has a NOS one for $75.

The old Rock Shock Metro was available with 1" threaded steerer. My LBS has a NOS one for $75.
Good to know... sounds like there's hope for a suspension upgrade! Is that roughly equivalent to a Judy TT fork for 700C wheels?

ok, just so I understand and again, forgive my ignorance - my 700 wheels are different than a standard 26" wheel on a mountain bike? So mounting 26" MTB tires on my rims is simply out of the question? I need 700 x ?? tires, no if's and's or but's (?)

ok, just so I understand and again, forgive my ignorance - my 700 wheels are different than a standard 26" wheel on a mountain bike? So mounting 26" MTB tires on my rims is simply out of the question? I need 700 x ?? tires, no if's and's or but's (?)
Correct! 700C wheels are the size typically used for road bikes, while 26" wheels are the size typically used for mountain bikes. Hybrids are split, some go one way, some go the other. Tire sizing is very confusing... fortunately 700C and 26" are the standard sizes for *nearly* all modern adult sized bikes.

A 26" MTB tire simply won't fit on your wheels. Fortunately, there are PLENTY of knobby tires for 700C wheels... thanks to so-called 29'er mountain bikes and cyclocross bikes (cyclocross is a crazy ass sport that chiefly consists of racing road bikes in mud in December :)).

29'er tires: http://www.nashbar.com/results.cfm?category=121&subcategory=1252&storetype=&estoreid=&init=y&pagename=
Cyclocross tires: http://www.nashbar.com/results.cfm?category=121&subcategory=1256&storetype=&estoreid=&init=y&pagename=

29'er tires tend to be wider than cyclocross tires, and to be knobbier. Here's a cheap, knobby 'cross tire that you might want to check out: http://www.nashbar.com/profile.cfm?category=121&subcategory=1256&brand=&sku=17802&storetype=&estoreid=&pagename= (I've never used it myself)

ok, not exactly what I was hoping for, but at least I now know what I'm dealing with. I have options, but within limits.

Thanks all for your speedy help!

I'm sure that there are many more 29'er and 'cross tires besides the ones that Nashbar sells. Check PerformanceBike.com, HarrisCyclery.net, your LBS, etc. 29'ers are a growing market, so there will be new models coming out soon, I'm sure.

PS- If you think of going for wide 29'er tires, check to see if your rims are wide enough to handle them well: http://sheldonbrown.com/tire-sizing.html#width

If you put a too-wide tire on a too-narrow rim, the tire will squirm a lot and you won't enjoy it :)

Without taking the headset apart, can any "Trek techies" out there verify my steerer size from a spec sheet? I have looked online and not found those details anywhere.

I have confirmed this is a 1992 model. Someone is selling the exact bike on ebay right now:

http://cgi.ebay.com/TREK-700-MENS-MULTI-TRACK-ROAD-OFFROAD-BIKE-BICYCLE_W0QQitemZ270017430217QQihZ017QQcategoryZ98084QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Without taking the headset apart, can any "Trek techies" out there verify my steerer size from a spec sheet? I have looked online and not found those details anywhere.

I have confirmed this is a 1992 model. Someone is selling the exact bike on ebay right now:

http://cgi.ebay.com/TREK-700-MENS-MULTI-TRACK-ROAD-OFFROAD-BIKE-BICYCLE_W0QQitemZ270017430217QQihZ017QQcategoryZ98084QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Any Trek hybrid made in 1992 would have a 1 inch steer tube.

I'm not sure when 1-1/8" appeared on the scene, but it was only for mountain bikes with suspension forks until around 2000. It's also clear from the ebay picture that it has a 1 inch steerer, since it has a threaded stem. Very few threaded stems in the 1-18" size.

You will probably be able to fit 700 X 38 mm tires without having them rub the frame or forks. Try riding them on your local trails before you think about the expense and weight of suspension fork. Bar ends would add to comfort by providing alternate hand positions.