Tire Size Specs?

[736cc_imp]

Anybody know the exact measured diameter of the original 2013 CB1100 Dunlop 140/70-18?
The Michelin Road Pilot 3 160/60ZR18 measured 25.55" according to Michelin. I think the Michelins look smaller in diameter but can't find the specs anywhere on the internet re: the OEM Dunlop.

[redbirds_imp]

The actual diameter of the two is very close. If the tire markings are exact, 70% of 140mm for sidewall height of the original compared to 60% of 160mm for the Michelin, 98mm sidewall height to 96mm. Total of 4mm difference in diameter or .15". The added width of the 160 makes it appear lower in sidewall height IMO.

[Lord Popgun]

736,

I have a set of original Dunlops that have not been installed. Still wrapped up in yellow tape even. I could take some measurements if you need me too.

[736cc_imp]

Popgun, that'd be great!
I emailed Michelin and got a detailed response from Michelin Girl named Lori:



11. Subject = US-EN-Michelin&Technical questions about tires
12. Message = What is the measured outside diameter of Michelin Road Pilot 3 size 160/60ZR18 ?
13. Vehicle Year =
14. Vehicle Car Maker =
15. Vehicle Car Segment =
16. Vehicle Option =
---------------------------------------------------------------------
Thank you so much, this is a very good question. After talking with one of our senior representative we have come to this conclusion. The nominal diameter is 649mm and the maximum diameter is 663mm. Meaning when the tire is cold and not been rode on, it will be at 649mm and once rode on and heated up the maximum diameter will be 663mm.

I hope this helps!

We appreciate your business and thank you for choosing Michelin.

Sincerely,

Lori
Consumer Care Department
Certified Michelin Product Expert
25.55" = 648.97mm

I think she's a 1117.6mm....

[kmoney_imp]

Popgun, that'd be great!
I emailed Michelin and got a detailed response from Michelin Girl named Lori:



11. Subject = US-EN-Michelin&Technical questions about tires
12. Message = What is the measured outside diameter of Michelin Road Pilot 3 size 160/60ZR18 ?
13. Vehicle Year =
14. Vehicle Car Maker =
15. Vehicle Car Segment =
16. Vehicle Option =
---------------------------------------------------------------------
Thank you so much, this is a very good question. After talking with one of our senior representative we have come to this conclusion. The nominal diameter is 649mm and the maximum diameter is 663mm. Meaning when the tire is cold and not been rode on, it will be at 649mm and once rode on and heated up the maximum diameter will be 663mm.

I hope this helps!

We appreciate your business and thank you for choosing Michelin.

Sincerely,

Lori
Consumer Care Department
Certified Michelin Product Expert
25.55" = 648.97mm

I think she's a 1117.6mm....

Lol. That photo is great.

[Lord Popgun]

736,

Here is what I measured. Unmounted, still in the yellow wrap tape they came in.

Front: 24 5/8 inches

Rear 25.5 inches

[DAC]

Lori looks like more of an air bag expert.

[Ferrealls_imp]

736,

You'll have to forgive me if this is more than you bargained for. Tire sizes work like this:

A 140/70-18 has a 140mm wide tire, with a 70% aspect ratio meaning the sidewall is 70% of the width, on an 18" rim. To find the total diameter use this equation

D = 2 x width x aspect ratio / 25.4 + rim size in inches.

You multiply by 2 to account for both sidewalls on (top and bottom across the diameter) and divide by 25.4 to convert mm to inches. That being said....

160/60-18 = 2*160*.6/25.4 + 18 = 25.56"

the 140/70-18 = 2*140*.7/25.4+18 = 25.72"

Difference is 0.16" overall.

[redbirds_imp]

About same difference as I came up with.

[Elipten_imp]

Finally I think I understand tire sizes. Many thanks


2014 CB1100 DLX
2013 CB1100 Std
1990 BMW K75 RT