New or modify?

Should I have posted this in another category?

You are in the right category, just bad timing. Its the first weekend around here with no snow and warmer weather so most of us are out riding instead of sitting at the computer. I tend to ride early so now I have a little time to kill.

In your situation, I wouldn't do much to your existing bike. Maybe get wider tires or something like that. The best thing in your situation would be to get a hardtail off eBay or Craig's List and use it for your off road or rough road rides. The reason that I am suggesting this is that you will be compromising the road ride of your road bike if you set it up for off road riding, and no matter what you do to it, it will not ride as good as an MTB would. If you are good with your hands, then a nice used MTB and a little TLC would be the way to go. If you do want to go with larger wheels and tires, make sure that there is enough room between you seat stays and between the chain stays to accommodate the larger wheel/tire.

Thanks! Still a few feet of snow on the ground and roads covered in sand around here. I dont think I am going to be riding much off road yet. I should rephrase that to full time road but we have some bumpy roads. I am most likely going to try larger tires for now.

I looked your bike up on Bikipedia and it shows that it comes with 28c tires, so you should be able to go that wide at least. Most road frames (and brakes) will only take a tire that wide, but you might get lucky. I put 28s on my road bike last year and I like them so far. I'm not doing potholes, but I find that I can ride through some mud when necessary. I agree with kd that you shouldn't put a lot of money into this bike. Modifications to a (lesser, no offense) frame are often expensive and may not result in the bike you want.

I'll find out exactly which tires I have now. I did buy new tires last year because I needed new ones.
At the time I hadn't thought about bigger tires.

No offense taken! I realize the sirrus is entry level. Heck, when I bought it used I only knew there were road and mountain bikes, that's it.
I'll upgrade at some point. I can't justify spending thousands on a bike when I don't even know what the components are.
I may buy a new bike next year. I'm itching to try a cyclocross. I keep hearing lots of comments about that bike and how it's what I'n looking for.

Does anyone have any experience with the trek montare as a road bike with slight off road use? Too overkill?

If you keep an eye on eBay and Craigslist, you may be able to find a Surly cyclocross bike or frame; go to their website and check out which model(s) you might want. Also check out the frames at Velo Orange. Not strictly cyclocross, but maybe what you're looking for; wider-tire-capable at any rate! These are the more reasonably-priced alternatives. For the next level, and a lot of information that may be of interest to you for the type of riding that you decribe, check out the Rivendell website. Cheers, Steve.

Thanks. Never heard ot those but I will check them out.

What's your budget?

Are you handy enough so that possible modification includes moving components from the current frame to another?

Do you currently have a MTB?

IMO, a suspension fork is probably overkill AND a rigid fork will probably suffice for most unpaved road conditions.

For now, I am thinking about spending 600 slightly used and waiting for the right deal to come along.
I always find the deals!
Perhaps a bit more, but like I mentioned before, I'm just starting out. Maybe in 2-3 years from now I'll but a $1500- $2000 bike.

I don't have a mtb. I don't see myself riding that much offroad often.

I am somewhat handy. Once I learn the first time I could figure it out.

I don't think you're going to gain a whole bunch by going to a full on cross bike - especially if you're just riding the odd graveltrail in fair weather. If you're venturing out in the mud, rain and snow then a bike with bigger clearences and cantilever brakes would be the way to go.

The Sirrus came standard with 28mm tires - so a good tire in that width, properly inflated will pretty much take all the potholes you can throw at it. Your wrists however, may not. The key is to use a good tyre.

I replaced the tires that were on the bike last year with something similar to semi slicks. They have a bit of tread on them.

They are 25mm, which is what was on there. Perhaps I should try 28?