Mathematical Info for Wheel/Tires Conversions...

I was looking into maybe upgrading wheels... To get those super sport tire sizes... It's just an idea, but I wanted to share with you guys...

The bike in question is a 1998 KZ1000P. This bike comes with 110/90R18 front, and 120/90R18 rear... I was considering going with the standard 1000cc super sport wheel and tires sizes, 120/70R17 front, and 190/55R17 rear...

What is the difference???

Well, the tire sizes give you all the information... Width (Metric) 110/Height 90/Radial R/and Wheel Size 18... 1st, you divide the Width by 25.4 to get the with in inches. 2nd, Multiply by 0.XX Height... 3rd, multiply by 2 to get the upper and lower height of the tire... 4th, Add the wheel size.


KZ1000 Front 110/90R18 - 110/25.4 = 4.33 * 0.90 = 3.89 * 2 = 7.79 + 18 = 25.79
ZX1000 Front 120/70R17 - 120/25.4 = 4.72 * 0.70 = 3.30 * 2 = 6.61 + 17 = 23.61

Difference in width 0.39" inch wider - Difference in diameter -2.18 inches shorter

KZ1000 Rear 120/90R18 - 120/25.4 = 4.72 * 0.90 = 4.25 * 2 = 8.50 + 18 = 26.50
ZX1000 Rear 190/55R17 - 190/25.4 = 7.48 * 0.55 = 4.11 * 2 = 8.22 + 17 = 25.22

Difference in width 2.76" inches wider - Difference in diameter -1.27" inches shorter

The difference in width on the rear end is significant, 2.76" inches, divided by 2 it's 1.38" inches to each side... This means start planing how much room you need to clear the swing arm to the right, and chain to the left....

Now to balance the front to rear ride height change... The front is -2.18 inches lower, The rear is -1.27" inches lower... This tell us that the front end is 0.91 inches lower than the rear...

2.18" - 1.27" = 0.91" inch... To restore balance the front end has to come up... Most bikes like being on their nose a little... But 0.91 is a bit much!!!

NOTE: This is a base line... As each tire manufacturer measure their tires with their own ruler... But it's a start... Knowledge before you start spending your money buying parts that may not work for your project...

Luis

After some quick research I found Pirelli Night Dragon tires... A 130/75R17 front tires, and the choice of 180/60R17 and 200/55R17 rear tires...

KZ1000 Front 110/90R18 - 110/25.4 = 4.33 * 0.90 = 3.89 * 2 = 7.79 + 18 = 25.79
Pirelli Front 130/75R17 - 130/25.4 = 5.12 * 0.75 = 3.84 * 2 = 7.68 + 17 = 24.68

Difference in width 0.79" inch wider - Difference in diameter -1.11" inches shorter



KZ1000 Rear 120/90R18 - 120/25.4 = 4.72 * 0.90 = 4.25 * 2 = 8.50 + 18 = 26.50
Pirelli Rear 180/60R17 - 180/25.4 = 7.08 * 0.60 = 4.25 * 2 = 8.50 + 17 = 25.50

Difference in width 2.36" inches wider (Or 1.18" inches to each side.)- Difference in diameter -1.00" inches shorter...

To balance the front to rear ride height change... The front is -1.11 inches lower, The rear is -1.00" inches lower... This tell us that the front end is 0.11 inches lower than the rear...



KZ1000 Rear 120/90R18 - 120/25.4 = 4.72 * 0.90 = 4.25 * 2 = 8.50 + 18 = 26.50
Pirelli Rear 200/55R17 - 200/25.4 = 7.87 * 0.55 = 4.33 * 2 = 8.66 + 17 = 25.66

Difference in width 3.15" inches wider (Or 1.58" inches to each side.)- Difference in diameter -0.84" inches shorter...

Now to balance the front to rear ride height change... The front is -1.11 inches lower, The rear is -0.84." inches lower... This tell us that the front end is 0.27 inches lower than the rear...

Luis