For people that drive 70 daily.

[asleepz]

As we all know, our CB7s were set up for the 55mph speed limit back in the day.

Has anyone ever put larger tires on their accord to get the RPMs back closer to that RPM range 55-60 works in..

If so, how much bigger did you have to go

How did you recalibrate your speedo.

[93accordexcoupe]

my rpms work fine at 55-60

did our cars not come with big enough tires from the factory? i think they were 60s or 65s werent they?

[pwrusr]

As we all know, our CB7s were set up for the 55mph speed limit back in the day.

Has anyone ever put larger tires on their accord to get the RPMs back closer to that RPM range 55-60 works in..

If so, how much bigger did you have to go

How did you recalibrate your speedo.

That just sounds like more touble then it's worth. The extra rotating mass from the larger tires make the engine work harder to spin the tires. That really kills any advantage you'd get from the larger tires.

[The G-Man]

I see no problem in cruising at 3200 rpms at 80 mph.

[blackcb7]

I see no problem in cruising at 3200 rpms at 80 mph.

x2 its great

[wed3k]

i cruise a bit below 3k when im at 80

[InvaderTrax]

Your RPM's will be the same no matter what size tire you have. You just think they're lower because your speedometer says you're going 80 when you aren't

[DilutedImage]

Your RPM's will be the same no matter what size tire you have.

A larger tire has a larger circumfrence, which causes the car to travel further with every rotation. Do you really think that a 20" tire would go the same distance as a 40" tire, in one rotation? Not even close. Remember geometry? P=2[pi]r ...

20" tire:
P=2[3.14159265359...]10
P = ~62.83" traveled in one rotation

40" tire:
P=2[3.14159265359...]20
P = ~125.66" traveled in one rotation

Look at the formula for the circumfrence of a circle; a tire that's twice as tall will go twice as far. So, increasing the tire height will also increase the distance per rotation. It's not opinion; it's math.



EDIT: I decided to be a little less harsh, so I edited this a little.

[DilutedImage]

You just think they're lower because your speedometer says you're going 80 when you aren't

The RPMs have nothing to do with the speedometer. If that were the case, then an idling car would show 0 rpms.

[zipcreature]

You can search for a "tire calculator" online; I believe www.tirerack.com has one. I use it alot, because with my 50 series tires on, my speedo is something around 1.6% slow.
Hope this helps.

- Zipcreature

[Spartan1987]

my rpms work fine at 55-60

did our cars not come with big enough tires from the factory? i think they were 60s or 65s werent they?

It depends on whether you got the 14" steelies, or the 15" alloys.
All though some of the 90-91 CB's came with 14" alloys.
IDK I just replaced my steelies with Prelude wheels, see my members ride page for pics.

[Spartan1987]

A larger tire has a larger circumfrence, which causes the car to travel further with every rotation. Do you really think that a 20" tire would go the same distance as a 40" tire, in one rotation? Not even close. Remember geometry? P=2[pi]r ...

20" tire:
P=2[3.14159265359...]10
P = ~62.83" traveled in one rotation

40" tire:
P=2[3.14159265359...]20
P = ~125.66" traveled in one rotation

Look at the formula for the circumfrence of a circle; a tire that's twice as tall will go twice as far. So, increasing the tire height will also increase the distance per rotation. It's not opinion; it's math.



EDIT: I decided to be a little less harsh, so I edited this a little.

Dang man talk about the math major dropping it hard.

[DilutedImage]

Dang man talk about the math major dropping it hard.

Haha, nah, that's just basic math .. . I learned that ish in sixth grade ...

[shimnacracer]

Yup thats all taught in 6th to 9th grade classes. Most of us just choose not to remember it . So what if the rpm's are a little higher at your cruising speed on the highway...just means you'll burn a little more gas. And with bigger tires thats more rotational mass which takes more energy which also will burn more gas.

just my 2cents

[ParoXoN]

Yup thats all taught in 6th to 9th grade classes. Most of us just choose not to remember it . So what if the rpm's are a little higher at your cruising speed on the highway...just means you'll burn a little more gas. And with bigger tires thats more rotational mass which takes more energy which also will burn more gas.

just my 2cents

The extra gas lost to spinning up tires of a greater mass and diameter will be minimal. (To a point, of course.)

In fact, depending on how one drives, larger, heavier tires might actually save gas. (Forcing the vehicle to accelerate slightly more slowly will reduce the amount of fuel consumed during acceleration. (Look at the area under the curve.) To my knowledge, the engine does not add more fuel to increase crank torque when it feels it is accelerating too slowly.)

Quick question:
How much fuel is actually injected into each cylinder per fire? Then we can actually see how much fuel is saved by changing tire sizes and see if it's worth it