My car is is different?

[E equals MC2]

2003 Mazda 6i 4cyl.

I had fun keeping track of random crap since this was my first brand new car. I remember this car with 8000~ mileage would hit about 88-90 MPH at exactly 3000 RPM at the highest (5th gear).

My car currently has 55,000 miles now. The RPM has to hit about 3200-3000 RPM just to reach 85 MPH, not even 88-90.

What's the deal?

 

[Ronstang]

Auto or stick? If auto your lockup converter may be bad of it could be as simply as worn tires.

Edit....I see you say in fifth gear so you must have a manual transmission. It could be a combination of worn tires and maybe a bad clutch.

 

[E equals MC2]

Originally posted by: Ronstang
Auto or stick? If auto your lockup converter may be bad of it could be as simply as worn tires.

Stick. Oh yea, I also changed their HORRENDOUS and downright DANGEROUS factory Michellin Energy MVX tires to BFG Goodrich T/A traction.

Maybe that could it. Is that bad?

 

[chuckywang]

No surprise there. Your clutch won't stay brand new after 55,000 miles. It might be slipping a tiny amount.

 

[Ronstang]

If you changed tires and the diameter is not exactly the same, also considering tire growth at speed, it will definitely affect you cruising RPMs and also you speedometer and odometer.

 

[Heisenberg]

Originally posted by: E equals MC2

Originally posted by: Ronstang
Auto or stick? If auto your lockup converter may be bad of it could be as simply as worn tires.

Stick. Oh yea, I also changed their HORRENDOUS and downright DANGEROUS factory Michellin Energy MVX tires to BFG Goodrich T/A traction.

Maybe that could it. Is that bad?

Did you change the tire size or are they the stock size?

 

[SVT Cobra]

Change Tire size?

Also readjust your clutch, pull it up with your hands until it clicks. Just a complete guess.

 

[Minjin]

No, tires won't affect the speedo's relation to the tach. Most speedos have a gear in the transmission or rear diff. It has no way of knowing if you have moster tires or skateboard wheels. All it sees is rotations per unit time and from knowing what the tire size should be, you get a speed display. So for a given rpm and gear, the tach and speedo's relation won't change (assuming that nothing is broken or going bad)...

 

[OS]

Originally posted by: E equals MC2

Originally posted by: Ronstang
Auto or stick? If auto your lockup converter may be bad of it could be as simply as worn tires.

Stick. Oh yea, I also changed their HORRENDOUS and downright DANGEROUS factory Michellin Energy MVX tires to BFG Goodrich T/A traction.

Maybe that could it. Is that bad?

those tires do suck but they aren't as bad as you describe.