wheel size make the car run different?
 

Ok if you don't have an automatic fit then I guess your out of the picture for this question anyway...............I have an 07 fit and its my DD so driving around 50mph my RPM's are around 1500............... now that I have put my 92-93 gs/gsr 14' wheels on my fit it seems like the motor is running at a higher RPM going 50mph its around 2000-2100 rpm..........its not much of a difference but my car used to be very quite but now its much louder and its getting on my nerves........just wondering if anyone had the same problem or know what I should do

thanks

Re: wheel size make the car run different?
 

its probably because youre not really going 50mph anymore. plug your tire sizes into this link and you will see.

http://www.miata.net/garage/tirecalc.html

Re: wheel size make the car run different?
 

it has nothing to do with an automatic or manual, you've changed the side wall size of the tire. probably smaller now.

Re: wheel size make the car run different?
 

^ Like he said. Smaller wheels have to spin faster to achieve the same speed.

Re: wheel size make the car run different?
 

I think you are all wrong ;)

Change in wheel and tire size can change the circumference of the tire. And that would lead to a change in speed read from the instrument. The odometer will also be wrong and if you have an mpg reading in the car computer it is probably wrong too after the new wheels.
How much off all those instruments are depends on how much diffrence the circumference on the new tire is going to be compared to the old one.

But change in tire wall size and type (steel or alu) or size of wheel will change the weight of the wheel. Most likely does NCintegraLS has a heavyer wheels than before. Thus the engine have to work harder to maintain the same speed as before.

But that would probably only be on a CVT like mine. Doesn't the 6spd Auto have fixed speedratios? Thus the engine rpm and speed should be the same whatever size wheels?

I know that the instruments was indicating wrong speed and wrong distance on my car when I changed new wheels. I had 165/65x14 stock tires tires and the new one is 205/40x17. According to the tirecalculator that is 2% larger circumference on the new tires compared to the stock tires. Thus the distance on the instruments in the car would be 2% shorter. And the speed will also show a lower speed.

After a tank of fuel I discovered that the mpg reading was way to high I started investigating this. I have measured with an GPS and found out that the speed is now spot on, as before it was a bit higher than real speed. And the 2% decrease in distance was comfirmed with the GPS.

Re: wheel size make the car run different?
 

6 speed auto? What? Smaller wheels/tires, more revs per miles, less mpg. It's pretty simple.

Re: wheel size make the car run different?
 

What you're probably hearing is increased road noise due to using a different tire model, not additional engine noise.

This is correct, but F0NIX is correct as well - the instruments won't indicate any change. The speed indicated on the speedometer is calculated by a sensor that counts the revolutions of the differential in the transmission. Anything downstream of the differential in the drivetrain, such as the wheels, can still affect actual ground speed without any indication on the instruments.

In other words, if you change the overall tire diameter, your actual ground speed will be different than the indicated speed but nothing displayed by the instruments will change. For any given indicated speed the engine RPM will remain the same as before, but your speedometer and odometer will be off.

The only way to affect the relation between tachometer and speedometer readings is by changing gear ratios inside the transmission.

Re: wheel size make the car run different?
 

Bingo. :thumbup:

Re: wheel size make the car run different?
 

Basically, youve changed your final drive ratio. Measure the diameter of the stock tires and size some new tires to match that with 14" wheels. Easy.

Re: wheel size make the car run different?
 

well thank you all for all the info. I am hoping to be putting 16's or better 15's on the FIT soon so stay tuned for new pics