[gentledental4u]

Hey all, I'm about ready to get my 20 inchers and just curious what to expect in terms of gas mileage...so on avg, how much did you lose after the switch?

oh, also is the odometer going to be off after upgrading? like is it going to be slower than actual or faster than actual if my odometer reads 60 mph?

 

[xJoeMama78]

MPG loss will depend on the weight of the wheels and tires. The more they weigh, the more you lose. Speedometer/odometer accuracy will depend on the overall height of the tire and wheel. If it's taller than stock than you will read slow, if it's shorter you will read fast. You can calculate it here:
http://www.miata.net/garage/tirecalc.html

 

[Danielc409]

Like 1-2 at the most. I used to get somewhere around 360ish before my light came on, I'm down to about 330 depending on my driving .. somewhere around that.

 

[peter01592]

who cares about gas anyway =b

 

[MagikDraggin]

MPG loss will depend on the weight of the wheels and tires. The more they weigh, the more you lose. Speedometer/odometer accuracy will depend on the overall height of the tire and wheel. If it's taller than stock than you will read slow, if it's shorter you will read fast. You can calculate it here:
http://www.miata.net/garage/tirecalc.html

Like the man said....if the tire/wheel is taller than the OEM tire/wheel, the wheel will rotate LESS times over a given distance than the stock wheel will rotate....therefore resulting in SOME (not much) increase in gas mileage.

There are a lot of factors besides just the weight of the wheel/tire to consider, such as rolling resistance, and whether most of your driving is stop and go, or primarily on the highway.

Generally speaking, the few additional pounds that a new set of wheels MIGHT add, prolly won't affect the gas mileage to where you would actually be able to consistently calculate that difference.

And also as the man said, a larger diameter tire/wheel will cause the speedometer to read slower than you are actually going....and that difference will be slight at low speeds and get proportionally worse the faster you go.

So, if you are in the habit of going "ten over" the posted speed limit on the highway, you might actually be going 12-13 over, where then the highway gestapo's will probably get you for it.

 

[avs]

It's hard to say. Depending on how much city vs highway driving you do. Generally speaking, when going up in wheel size you will increase hwy mileage and decrease city gas mileage.

 

[Sultan]

Yeah thats the price you pay for getting 20's but its nothing mind blowing so it shouldn't bother you.... i would just get them

 

[Joey J]

My speedometer is like 1mph off with my new wheels.

 

[MrLogan13]

I lost about 1 mpg.

 

[needforaccord]

Like the man said....if the tire/wheel is taller than the OEM tire/wheel, the wheel will rotate LESS times over a given distance than the stock wheel will rotate....therefore resulting in SOME (not much) increase in gas mileage.

What about the fact that all your gearing will be higher and that you will have to push the engine harder to have the car get going? Or the extra weight/ rotational inertia of the wheels/tires? Or the extra traction/friction of the tires? Do you still believe the mpg will go up?

 

[Clutch34]

I want 20's as well, just gotta save up for them now lol I'm not as concerned about the gas mileage hit than I am about the speedometer. Is there anyway I can get the speedo re-calibrated so that the speed that shows up is the speed I'm traveling at?

 

[Danielc409]

I want 20's as well, just gotta save up for them now lol I'm not as concerned about the gas mileage hit than I am about the speedometer. Is there anyway I can get the speedo re-calibrated so that the speed that shows up is the speed I'm traveling at?

It's not going to be off enough to be a concern as long as you get the correct tire size etc.

 

[next_milenium]

I really didn't notice much difference as far as MPG is concerned. Don't get a very heavy 20" wheels and you should be ok (for example, my 20" wheels are actually slightly lighter than stock). With 245 35 20 tires, the speedometer is off a little but not enough to worry about (I think it's less than 2 MPH difference).

 

[MagikDraggin]

What about the fact that all your gearing will be higher and that you will have to push the engine harder to have the car get going? Or the extra weight/ rotational inertia of the wheels/tires? Or the extra traction/friction of the tires? Do you still believe the mpg will go up?

Yep!

However, I take it you skipped over the part where I mentioned rolling resistance and whether or not the majority of driving would be done in town stop and go, or mostly on the open highway.

In town, it may go down, but not an appreciable amount. On the highway, it may go up, again not an appreciable amount. This isn't rocket science...we aren't talking about a lot of extra weight, or a big difference in overall wheel/tire height here.

I get amused when I read something like "I got 1 mpg less, or 1 mpg more, after putting on 20" wheels". Jeez, you can get get a one or two mile per gallon difference, simply if the outside air temp goes up or down 20 degrees...or the air density/relative humidity goes up or down 20%...or you're driving into a 20mph headwind, or have a 20mph tailwind.

Most people I know, when they change to 20" wheels, end up getting tires with a lower sidewall dimension, to compensate for the additional increase in diameter. They don't want their ride to end up looking like a 4x4 pickup truck.

IOW, there really isn't much need for concern over what effect on gas mileage going from OEM wheels/tires to some 19's or 20 incher aftermarket ones. Unless the driver is really into drag racing his Accord....then some of those factors you mentioned might come into play in regards to his 60 ft, ET, and trap times.