My 2.5TL with stock (15") wheels needed new tires. I had Goodyears but this time I got some rather reasonably priced Kumhos ECTSA HP4 stock size P205-60/R15. Turns out that after replacing tires the speedometer and odometer both indicate some problems. On a 600 mile journey the odometer now reads 614 positively I am going a bit slower than 70 mph when my speedometer reads 70mph because people kept passing me . Ofcourse this is not the correct speed test but wondering if anyone ever noticed such issues?

I am thinking that these new tires are probably about 3 or 5 mm smaller in diameter but can this happen for tires of same size as the previous set?

 

Sometimes yes. Depends on your PSI as well.

 

I have the same problem too. I actually had to drive close to 75 mph in order to keep up with traffic. Also, when I tried to match my trip odometer with the mile posts on the highway, it reaches the mile about 0.07 miles too soon.

 

You could try tires that are 205/65 R15's

Thats what is on the 3.2's. Slightly larger overal diameter.

 

smaller diameter=more revolutions needed to get a faster speed... ken is right on the stock size for the 3.2...

 

ken's right. i have 205/60 r15's and i get a bit of error especially on the hwy. BTW, do 205/60's ride slightly harsher than 65's because of the shorter sidewall, or is the difference unpercievable - the reason I ask is that I've never had my TL on 65's - the 60's it has now are the tire it came with when we bought it.

 

i THINK that usually with a smaller sidewall the car will take bumps much harder... it makes sense cause there is less cushion and bounce play... think about it when u have bigger rims and a smaller tire... when u hit that pothole it hurts... but my stock 15 will eat potholes all day...

 

The problem with that is that mine IS a 3.2TL.

 

Depends on the brand of tire too. Depending on the tread pattern, it can be off by a bit.

 

This is exactly why I posted this thread in the Tires forum. From that, you would easily be able to tell that the "60" in your tire size makes your RD smaller: that makes your speedo read faster and your odometer read high.

 

You won't really feel a difference between a 60 and a 65, thy are both so tall anyways, they're both very soft.