Speed difference between 18" and 16" rim

I understand the way different sprockets result in different low-end and top-end speeds, but is there also a difference in speed that comes with rim size?

I have an 18" rim on my 1980 KZ750 E1, but I also have a 16" rim from a 1981 KZ750 H2 available, and I'm wondering which would make it faster off the line. I'm thinking the 18", is better since it's covering more ground per revolution at the sprocket.

Also, it's a 4.00 rim — does anyone see why I couldn't fit a 130 tire on it without distorting the sidewalls?

Yes rim size matters. However, it usually does not equate to a 2 inch diameter difference in the tire's outer diameter because the 16" rims tend to get much bigger tires. The end result of the change is usually much smaller than the rim change would indicate.

My 18" rear tire measures 80.4 inch in circumference.
At 5500 rpm I'm going 70 mph.
If I changed to a 16" rim with same wall-height on the tire, the circumference is 74.1 inch.
At 5500 rpm I'd be going 65 mph.

But if the tire is bigger such that I only lose about 1 inch in diameter instead of 2, then at 5500 I'll be going 68 mph.

If I ate an apple and it tasted like a Pear would it be a banana? Smallers going to travel faster.Gearing would make the best sence,Bigger tires will give more ground contact for better traction.I like oranges that taste like grapefruit, I call them pinapples.:woohoo: .:laugh: .:woohoo: .:dry: .

chrispysaki wrote:

I understand the way different sprockets result in different low-end and top-end speeds, but is there also a difference in speed that comes with rim size?

It is the overall wheel size that matters. A smaller rim probably will have a smaller wheel diameter, depends how fat the tire is.

chrispysaki wrote:

I understand the way different sprockets result in different low-end and top-end speeds, but is there also a difference in speed that comes with rim size?

I have an 18" rim on my 1980 KZ750 E1, but I also have a 16" rim from a 1981 KZ750 H2 available, and I'm wondering which would make it faster off the line. I'm thinking the 18", is better since it's covering more ground per revolution at the sprocket.

Also, it's a 4.00 rim — does anyone see why I couldn't fit a 130 tire on it without distorting the sidewalls?

Just to clarify, where all else is equal, the smaller overall diameter tire, will be faster off the line.

In this illustration, tire A will be faster off the line than tire B.

It's akin to comparing hole shots between 1st gear and 2nd gear.

Good Luck!

taller tire will help on top side,but willhurt acceleration

i have 16 and an 18 rear rim that both go on my bike sometimes back and forth.....mostly i like a spoke three tier 16 rear though.....i have gone through two 16 and one 18 rear tire on each this year....if i give johnny two apples how many will martha have........big tire ..top end little tire low end...big tire me likey ...little rim ..me likey more....spins up outta rear end steered corners better for my type of throwing bike around.....and sets into the corner on rear end english better imo.....sucks more on the freeway....where i spend 3 % of my riding...

here we go again??????