Tires, tyres, skins
 

Hi Folks: I'm just in the process of breaking in a new GSA, road stuff for a few klicks. I want to install a set of tires that will give me reasonable performance on and off road. Any suggestions?

Your money or your life
 

Continental TKC 80

I believe you should fit the tires where they will most reduce the risk of loosing control when cornering or braking.
If you do high speeds on the highway then fit good road tires and take it real slow if you end up on dirt.
If you travel on bad dirt road conditions, even for small portions of your journey, but there is a real risk of loosing grip then fit off road tyres and take it real slow on the highway.
There is no single tyre that will ever be great at doing both, but since you asked I believe the TKC80's come the closest. Not great at being a road or off road tire but the best at trying to be both.

I always go for the off road tyres because dirt is why I do love biking so much, highways for me is only the means of getting to the dirt and sometimes I will even take a dirt road to get to the dirt if one is available.
Fitting off road tires mean that I normally have to keep speeds moderate when on the hard surface.
My number one choice is Michelin Desert but then these won't fit standard BMW's so I fit a specially modified rear wheel.
Take note that these tires are real dangerous on tar at any speeds over 130km/h and I don't just mean the reduced tire contact to the road on account of the large gaps between the blocks but the Desert front will make you loose control of your bike even when riding in a straight line.
Second to the Desert I can also recommend the Michelin T63 which have the same treat patten as the Desert rear but the front is not so aggressive so it is a lot safer at higher speeds on the asphalt, not as durable and great in really loose stuff though.

Never let tyre life determine the choice of tire because this mean that you regard your life and health less than that of your wallet and coincidentally if you do come off on account of not using the right tires, your repair bill and hospital bill can be much more than a set of tires, that is if you do come out alive on the other end.

Something I have also realised is that the most dramatic modification you can do to improve a bikes off road capability is to fit the right type of tires. It is also the cheapest and most easily done.