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BlackDeuceCoupe · 09-19-2008, 09:52 PM

The inside diameter (12, 13, 14, 15, 16 ,17) doesn't really matter. It's the outside diameter that counts!

For instance, a 185/65-14 tire has the same outside diameter as a 205/40-17 tire, hence the same revolutions per mile, and the same RPM. This is a common upgrade for Honda CiViC owners - going to 205/40-17.

EDIT

Sorry! I just reread your post.

I guess we were using the same hypothetical...

So, using my example, the question becomes: Will a narrower, normal profile 185/65-14 tire give better FE than an identical outside diameter, but wider, low profile 205/40-17 tire?

I would *guess* the answer is yes... but that's just an 'educated' opinion based on participating on several Honda blogs over the years! Lower FE is a common complaint with Honda CiViC owners that switch to 17s.

Nobody gets the mileage I do with a B16A2 - I gotta be World Champ - and I credit a large part of my success to running a lighter, narrower, tire than 'normal' @ 50 PSI, and an even lighter right foot!

09-19-2008, 09:52 PM	#2 (permalink)
BlackDeuceCoupe CAUTION: May Stink!!! Join Date: Jul 2008 Location: Central Arizona (USA) Missing Posts: 225 Posts: 210 BDC's Honda CiViC HX/Si - '98 Honda CiViC HX/Si (HX Shell/Si Swap) 90 day: 40.56 mpg (US) Thanks: 0 Thanked 1 Time in 1 Post	The inside diameter (12, 13, 14, 15, 16 ,17) doesn't really matter. It's the outside diameter that counts! For instance, a 185/65-14 tire has the same outside diameter as a 205/40-17 tire, hence the same revolutions per mile, and the same RPM. This is a common upgrade for Honda CiViC owners - going to 205/40-17. EDIT Sorry! I just reread your post. I guess we were using the same hypothetical... So, using my example, the question becomes: Will a narrower, normal profile 185/65-14 tire give better FE than an identical outside diameter, but wider, low profile 205/40-17 tire? I would guess the answer is yes... but that's just an 'educated' opinion based on participating on several Honda blogs over the years! Lower FE is a common complaint with Honda CiViC owners that switch to 17s. Nobody gets the mileage I do with a B16A2 - I gotta be World Champ - and I credit a large part of my success to running a lighter, narrower, tire than 'normal' @ 50 PSI, and an even lighter right foot! __________________ .:: B16A2 HX/Si Coupe \| '98 HX shell with full '99 CiViC Si swap \| 40+ MPG Listen to the people who fail. They know what they're talking about! Last edited by BlackDeuceCoupe; 09-19-2008 at 11:50 PM..