Jude

So I've got this bike, had it a few years and it's served me well as a commuter and I've done a few long rides on it. It still needs plenty of upgrades - tires being the main thing - but I'm thinking, since I use it for commuting on Philly streets where the roughness of the ground has more in common with riding on trails than on roads, of getting some fatter tires. I currently have 25mm.

Now, a few things. It has 27 inch wheels, which limits my tire selection. I also don't know how fat of tires the frame and fork will allow - there seems to be around 45mm of clearance in the relevant area, but I've also got to allow for fenders wide enough to cover the tires. Finally, the brakes on it are presumably what came with it - DiaCompe brakes, no other information given on them. I don't know how fat of tires they would allow, either.

So, basically, given the frame, and the fact that I want to add fenders to it, what are the fattest tires I could hope to get on there? What are the fattest I could get without swapping out the brakes? What are some good 27 inch tires for commuting? And what are some good fenders to put on there?