tire diameter - Page 3 - Fuel Economy, Hypermiling, EcoModding News and Forum

Blue Bomber Man · 09-20-2008, 11:30 AM

As I said earlier: Your main concern should be about first finding your most fuel efficient tire, most of the best seem to fall in the 15-16" size. These tires have an overall lower average RRC (rolling resistance coefficient). Your RRC effects fuel economy significantly as this number is multiplied by the mass of the vehicle to calculate the total loss of energy.

Once you have an efficient tire it would be time to address ride height (as we already know that lower height improves both handling and aerodynamics) and then seperately deal with your gearing issues to maximize energy efficiency.

guitarterry · 09-20-2008, 12:02 PM

Quote:

Originally Posted by Blue Bomber Man

As I said earlier: Your main concern should be about first finding your most fuel efficient tire, most of the best seem to fall in the 15-16" size. These tires have an overall lower average RRC (rolling resistance coefficient). Your RRC effects fuel economy significantly as this number is multiplied by the mass of the vehicle to calculate the total loss of energy.

Once you have an efficient tire it would be time to address ride height (as we already know that lower height improves both handling and aerodynamics) and then seperately deal with your gearing issues to maximize energy efficiency.

i guess metrompg was wasting his time changing his tranny to get
1968 rpms at 50 mph on 13 in tires ( 155/80/13) instead he could have just put 16's on his car

1.5Ldave · 09-20-2008, 01:50 PM

Quote:

Originally Posted by guitarterry

again what i was wanting to know from metrompg was why he used 155/80/13 instead of 145/82/12 tires and even taller gears.

I would guess its based on the availability of tranny gears to swap in. There most likely are very limited options, so he used a taller gear that was available in the trans, and used taller tires (the 155s) to make the gearing even higher.

Red · 09-20-2008, 02:13 PM

Another thing to consider is tire selection for a 12" rim. For the most part we are all stuck buying what ever tires are manufactured. In a perfect world I'd love to run a 32x9.5x15" tire on my Jeep, but no one makes it. 13" and 14" rims and smaller tires sizes are slowly being phased out, so your choices in a smaller rim and tire selections drop.

In Darin's case I think he was shooting for the lowest RPM he could run without lugging the Metro. And he would have had the same final effect running 16s and some big arse tire as the gear swap. Only catch would be that he would be suffering from the effects of being under geared all the time. With the gear swap, he only takes a major hit when he is in his higher gears, otherwise he is accelerating more or less normally

guitarterry · 09-20-2008, 02:22 PM

What does custom gearing cost. (just top gear) some of the money ive seen spent for questionable results. This would be a definate payoff. plus like metrompg said himself, there is disadvantages in the lower gears. this would be the best of both worlds.

guitarterry · 09-20-2008, 02:41 PM

Quote:

Originally Posted by Red

Now Tire diameter, no idea why you'd want to run a 5" rim, you'd have brake problems and stuff. Bad mojo, but your call. The only benefit you'd have is that the tire would be super narrow compared to say a 14" rim and tire, and much less weight so its easier to turn. Depending on the aspect ratio of the tire, you'd still get sidewall flex. But if you are running at max load, you'll negate a fair amount of it.

Forgive me, I was bored.....

ITS AN EXTREME. Its suppose to be so over the top as to knowbody would ever confuse it with reality. ITS NOT FEASIBLE... JUST AN EXAMPLE...

Red · 09-20-2008, 05:33 PM

Quote:

Originally Posted by guitarterry

ITS AN EXTREME. Its suppose to be so over the top as to knowbody would ever confuse it with reality. ITS NOT FEASIBLE... JUST AN EXAMPLE...

I know, just messing with ya

FWIW I have heard that getting an new gear set made for a tranny costs around 1-2k. Most of that cost is due to R&D for the new gear.

guitarterry · 09-20-2008, 05:47 PM

ur funny, not as funny ha, ha but funny as in *****

dcb · 09-20-2008, 06:04 PM

If you want to save gas, keep your 4 cylinder transmission and swap in a 3 cylinder engine for a few hundred

cfg83 · 09-20-2008, 11:52 PM

Red -

Quote:

Originally Posted by Red

I know, just messing with ya

FWIW I have heard that getting an new gear set made for a tranny costs around 1-2k. Most of that cost is due to R&D for the new gear.

That's what I was thinking, +$1K at the least. Now if your pal works for a custom gear maker like they have in the NHRA ...

CarloSW2