Radial tires on Gen 1 stock wheels

[Fire-medic]

There's a 15 "radial, but there for 100cc plus scooters. There's nothing that would match the height of a stock rear.

https://www.yamaha-motor.eu/lv/lv/products/scooters/sport/tmax-2023/techspecs/
Front suspension systemTelescopic fork
Front travel120 mm
Rear suspension systemSwingarm
Rear Travel117 mm
Front brakeHydraulic dual disc brake, Ø267 mm
Rear brakeHydraulic single disc brake, Ø282 mm
Front tyre120/70R15M/C 56H Tubeless
Rear tyre160/60R15M/C 67H Tubeless

Rating of 67 is 308 kg, H rating is to 130 mph

308 kg is 678 lbs. so couple that with the front tire's weight rating (letter 56=493 lbs), total of 1171 lbs and it should be OK. I think if you look at your steering column bike gross vehicle weight rating it's < that.

a profile of 70 vs stock 90 means the tire will be shorter in height and more rpm's, so it's like changing your gearing for more acceleration. Just what a VMax needs! Like Jeff Bridges says a yellow light means, in the movie Starman: "Go faster!"

 

[Patineto]

L0L Yes. And with a 5 inch wheel you'd probably run the engine at a red line doing 20 miles and hour and wondering what the hell is going on - an example just to paint the picture. But great acceleration! - maybe if you'd compensate with a 5 foot wide tire for grip? Hahaha What it meant is the relation between engine rpm's (and rear tire rotations) and the bikes speed, shown on speedo correctly, will change. So, again, looking at this the other way, if you like cruising around at certain speeds will make the engines rpm higher at that speed. Bringing them down will lower the speed, and you will want to keep the engines rpms lower. With different sizes rear tire rotations will change. So, at the receiving end, while working correctly and showing the correct absolute speed - it will be showing a relative error. Two bike with different wheel/tire sizes will show different speeds under identical working conditions. In other words, you want be able to judge the speed by keeping an eye on the tacho as you used to relate them.

THe critical measument is the CIRCUNFERENCE...

You can have a massibly tall 15" Tire with a greater diameter than a 17" with a skinny sidewall

 

[Patineto]

This chart is for bicycles but the concept can be extrapolate
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