Looking for tire profile change information

[pjar]

Earlier this year 98lee suggested I change my Battlax BT-45 from a 120/90-18 to a 130/80-18 for my K75 (105k and going strong). He mentioned it should keep the diameter very close (about 3/8" shorter) and it would give me about 3/8" wider tread. It would give me the same width and diameter as an S.

My question is this. What are the benefits of the tire profile change?

Better/worse mileage?
Faster/slower wear?
Improved handling?
More stability in wet conditions?
Does it have a significant effect on the speedometer reading?

As you can see I'm inexperienced at this stuff (physics wasn't my favorite subject).

By the way, i think the BT-45's are great tires. Feel confident in the corners and have a peace of mind at high speeds.

Many thanks to any input offered.

Pete

 

[EMSimon]

Shoulder Height 120/90 = 108mm
Shoulder Height 130/80 = 104mm

Total difference in diameter: 2x 4mm = 8mm = less than 1/3" (less than 3/8")

The larger footprint may result in less pressure/area thus less wear.
Wider tires usually are worse in handling. They make steering more difficult and the lower sidewall of the 130/80 may make the sidewall stiffer.
Your fuel mileage will decrease because of the lower tire (speedo reading is "fast")

All this is very theoretical and only BMW riders will ponder this. You may not recognize any difference. Get the tire that is more commonly available and less expensive.

 

[pjar]

Shoulder Height 120/90 = 108mm
Shoulder Height 130/80 = 104mm

Total difference in diameter: 2x 4mm = 8mm = less than 1/3" (less than 3/8")

The larger footprint may result in less pressure/area thus less wear.
Wider tires usually are worse in handling. They make steering more difficult and the lower sidewall of the 130/80 may make the sidewall stiffer.
Your fuel mileage will decrease because of the lower tire (speedo reading is "fast")

All this is very theoretical and only BMW riders will ponder this. You may not recognize any difference. Get the tire that is more commonly available and less expensive.

Thanks Mike, I appreciate the input. I imagine that breaking may be slightly improved due to the increased surface are on the road. You are correct about the cost. The 130/80's are about 5% more expensive.

Pete