Bicycle Mechanics - How wide of a tire can i use?

Hey guys, I was wondering if I would be able to use a larger tire on my bike. It is a 2006 Lemond Reno with Shimano Tiagra, 32h alloy wheels and 700x25 tires stock. I am thinking about changing to a 28 but I do not know if it will fit. I am not only worried about it fitting on the rim which I think it will but I have heard the frame wont clear it. Anyone have this bike and use larger tires?

Let me add my own related question: Can I use larger tires on my wheels? I have Bontrager Race Lite Discs that are 622 x 13 with 700 x 28 stock tires. I was wondering about putting 32s on these rims.

According to Sheldon Brown's tire sizing chart (http://www.sheldonbrown.com/tire-sizing.html) you shouldn't even have 28 mm tires on 13 mm wheels, but I believe the LeMond Poprad comes stock with the same wheels and a 32 mm tire. Captain Brown does say the sizing is conservative, but any actual experience would be helpful.

Turboem1, that won't help you with frame clearance questions. For that, I've just gone to my LBS and we've grabbed wheel/tire combinations off of other bikes to see if they will fit. (Also, apologies for a blatant thread hijack attempt.)

I took the front wheel off a Trek Pilot that has a 700/28 tire on it and put it on my LeMond Vesaille with room to spare. I think the fork is the same as your bike. Both tires are Bontrager, I think tire sizes vary by manufacturer so try the make and model you would be buying.

Turboem1 - it'll generally work fine to have 28c tires on narrow road rims, as newbojeff is doing right now.
For clearance, you can just look at how much space is above the 25c tires and get a sense of whether a larger tire will fit. Most racing-design road bikes won't take larger than 28, and often will max out at 25c. But you should be able to get some sense of clearance under the frame and brakes by just eyeballing.

There was a recent thread on this topic, and you should be able to find it using the search. I think it was specifically about Mavic Open Pro, the standard narrow racing rim.

Yeah, measure the existing clearancs first. The vertical space up to the brake-bridge and the fork-crown. Also measure lateral clearance at the front of the chain-stays. That's the limitation on my bike and I can only use up to a 700x26c tyre.