Motorcycle Safety & Driveability: wide front tyre, honda shadow vt600, tyre sizes

Question
I had changed the front wheel on my Honda Shadow VT600 from a 2.15" x 19 " rim (with a 100/90x19" tyre) to a 3.0 or 3.5" x 16" rim. (with a 130/90x16" tyre).

When testing how it feels at low speed on the road the steering is very heavy when turning tight circles e.g. doing a u-turn.

From my calculations of the tyre sizes it is only very slightly smaller than before (22mm overall).

I have tried to understand why this is and have tried lowering and raising the the front forks. It did not seem to make any difference.

I would appreciate any advice you can offer. Thanks for your time.

Answer
Emilio,

There are two forces that are causing the front end to respond sluggishly.

First, the motorcycle turn is initiated by the leaning of the front tire onto the side which is smaller diameter width) than the center of the tire. Since you not have a wider profile tire it will require leaning the motorcycle a bit further to accomplish the same amount of turning response the taller and narrower tire provided.

Second, you are on the right track by guessing that the smaller radius (19 versus 16) wheel has now changed the effective wheelbase of the motorcycle by shortening it slightly. The length of the wheelbase directly affects the turning agility of the motorcycle.

I do not have any suggestion for making adjustments that will return the handling to the previous condition. On many motorcycles changing tires with even the same size tires but using a different brand that may have a slightly different profile ( the roundness of the tire if you placed your thumb on one side of the rim and your finger on the other side to make a half-circle is the profile I'm talking about) that can slightly effect the way a motorcycle responds. The changes you made are significantly different from the factory configuration.

I suggest you use caution when riding the motorcycle and practice off-road with cornering and stopping to become accustomed to how the motorcycle will handle. The best way to restore the handling and safety of the motorcycle is to reinstall the correct size rim and tire.

Thank you for the question. Please let me know how you make out with the project. Please be careful.

Tom Wright