The answer to this is normally yes, as long as you can get a finger between any part of the tyre and whatever’s closest to it to allow for growth at speed. Whether it’s a good idea or not is another matter. The bike and tyre manufacturers do a lot of testing, using very experienced riders, to find the best fitment for that bike. The only change I have found to be useful is to fit a 190/55 to bikes that come with a 190/50 as standard. This raises the back of the bike slightly and gives a bigger footprint at full lean. Makes the bike feel a bit sharper generally. Can make the bike a bit less stable so not recommended on bikes without a steering damper. It generally has the same effect as going down to a 180/55 but without the reduction in width.
Why does my front tyre wear out on one side, not in the middle?
This is because the road has a camber for drainage. In England or Australia, it’s the right-hand side that wears out first, in other countries it’s the left hand. This problem has got worse with modern dual compound tyres. It doesn’t happen on the rear because of the wider flatter profile.
Should I fit Sports, Supersports or Sport Touring tyres to my sports bike?
I’m only talking about sport bikes here because if you have anything else you should only fit Sport Touring or Touring tyres. These bikes do not have the ground clearance, suspension or brakes to take advantage of anything stickier, so don’t waste your money. On a sports bike, you need to be realistic about your riding. Modern Sport-Touring tyres, such as the Bridgestone T31or Michelin Road 5 are as grippy as Supersport tyres from ten years ago and last twice as long. If you only ride on the road, you don’t need anything more. If you go mental through your local twisties and do the occasional track day in the novice or Intermediate group then a set of Sport tyres such as Continental Sport Attack 4’s or Bridgestone’s superb S22 would be good. If you’re in the fast group at track days and want something that would work well on the road as well then try Bridgestone’s RS11 Racing Streetor maybe Continental’s new Conti Race Attack 2 Street. These are just examples, all manufacturers make suitable tyres, just buy the ones you like the feel of best, the performance of all well known makes is very similar these days.
What pressures should I run?
On the road run the pressures in your handbook. If these differ from the tyre makers recommendation, go with the tyre manufacturer. If you’re riding in really hot weather drop the cold pressures a bit. On the track you’re looking for about 37 psi hot with road tyres, this translates to 30-31 cold in the front and 29 cold in the rear. With road legal race tyres, recommended pressures vary a lot, so check with your supplier. The latest Dunlop and Bridgestone race tyres, for example, run at 18-22psi hot in the rear! Don’t ask your mate the bricklayer, ask the manufacturer or tyre dealer.
Can I mix tyres?
Usually yes. On the road it’ illegal to put a crossplay on the back 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.