| Try it and see if you like it. It's really a question of handling preference, but there are some side issues.
Keep in mind is that (unlike the back tyre), the front tyre wears most quickly at it's edges. So over time, the profile gets progressively steeper and the steering gets more tippy; that is, it falls into the corner more readily. Starting with a 120/60 or a 120/65 section tyre reduces this wear-induced effect.
Further, a lower 60-profile tyre has a shorter height so it doesn't flex as easily. This increases the severity of the loads transmitted to the wheel rim, suspension and handlebars. This in turn, increases the likelihood of alloy wheel damage, so a 70-series tyre will be kinder to magnesium wheels.
Your tyre s are an integral part of your suspension so when you go from a 60 to a less-stiff 70 tyre, the resultant handling change will probably benefit from front suspension setting modifications. Increased front compression damping may be in order to offset the less-stiff 70-series tyre. Also, turn-in is slower with the 120/70 but this is easily compensated for by adjusting rear ride height
Also, the increase in the outside diameter of the tyre will cause your already inaccurately high-reading speedometer to read more accurately and will change your ride height so you may want to compensate by repositioning the front forks.
The decreased loads to the handlebars and increased sidewall flex combine to give you less (better?) feedback on the state of the front suspension and the traction condition at the front tyre.
All this may better suit your riding style. Or not.
Some, like myself, find a less-nervous front end to be more appealing for the road so we run a 70-series tyre. On the track, the better road surfaces make the benefits of a lower profile 60-series tyre more obvious.  |