Some information about tires

[Joesmoe]

-- @1olbull writes: "The circumference ratio front to rear is what the ECU monitors.
Use the tire aspect ratio and the wheel size to calculate the diameter then Pi x Diameter.
Once you get over a 4.3% ratio difference you risk faulting the ECU and ABS.

Example - the Exedra Max 240/55R16 is 82.9" circumference.
The Avon Cobra 140/75R17 is 79.3" circumference.
The circumference difference is 3.6". 3.6/82.9 = 4.3% ratio which is within the ECU fault ratio.
I ran a 130/80R17 up front (79.13" cir) which provided a 4.6% ratio and faulted the ECU ABS.
Now if you keep the OEM Metzeler rear 240/50R16 with a 79.95" circumference you would likely not fault the ABS with a 130 due to only a 1% ratio. I have NOT done this and DO NOT recommend a 130 front on a Roadster as it can drag the peg rails, which I have done . . . and crashed.

First you need the aspect ratio like 240/55R/16.
55% of 240mm = 132mm side wall. 132 x .03937 = 5.2 inches.
5.2" x 2 + 16" (wheel dia) = 26.4" diameter.
26.4 x pi = 82.9" circumference"

-- Tire size, difference, etc, calculator [thanks @Steel ]

 

[barbagris]

On PRE-ABS bikes it's NOT an issue. THANKFULLY.

 

[Tripps]

I thought you had a Touring, Paul?

 

[Joesmoe]

I copied what @1olbull wrote rather than quote it -- I copied it with quote marks and attribution -- what he wrote was for his bike, a Roadster with 17" wheels.

Conceptually, it's universal.

 

[1olbull]

I copied what @1olbull wrote rather than quote it -- I copied it with quote marks and attribution -- what he wrote was for his bike, a Roadster with 17" wheels.

Conceptually, it's universal.

17" front - 16" rear on the Roadster.
Nice job & gratitude!