Can I mix tyre brands?

Usually yes, it’s not illegal to mix motorcycle tyres but it’s not ideal.

On the road it’s illegal to put a crossply tyre on the rear with a radial on the front, but not the other way round. The speed rating should also be enough for the bike’s maximum speed, not the speed you normally ride it at. Other than that the law has nothing to say on the subject.

However, your bike has been developed with specific tyres. Some bikes are more sensitive to different tyres than others, the ST1300 being a case in point. The main problem with mixing brands of a tyre is that you’re on your own. The manufacturers obviously can’t test every combination of tyre on every bike, so you are the test rider. Your bike will definitely handle best with a new set of matched tyres approved for that bike. In the real world, this isn’t always practical, and nothing terrible is going to happen if you fit for example a Michelin rear with a Dunlop front. However, if you have a newish sports bike, you’ve spent a lot of money on a great handling bike, why blunt it by fitting worn mismatched tyres? This goes double for fitting racer’s castoffs, most bikes feel terrible with these fitted. These days tyres are designed to wear out in pairs, the fronts generally having much softer rubber than the rears, so the old trick of fitting a sports front and a sport touring rear isn’t really necessary anymore.

Finally, remember that modern tyres are fantastic things, with more grip than you think, whatever type you have fitted. If you’re in a corner too hot and you think you won’t make it, don’t stand the bike up and run into something solid just lean it over some more, your tyres will grip and you’ll almost certainly get around OK.