I don't know if it's just me but I purchased a pair of Kumho tires the other day and it seems as though I have lost acceleration. I love the tires but the rpm's don't even seem to stay up the way it used to and it seems like the the engine takes longer to accelerate. Has this happen to anyone else? Maybe it's just me.

 

Must be the stickier tires. You just feel like the car is bogging. Except now it has more grip.

That's just my guess.

 

could be the stickier tires, the el42's probably spun out alot so the rpm's might appear to rev quicker. stickier tires should give you better performance tho.

 

The question that needs to be asked is: are your new tires the same diameter as the OEM's?? A width change can also influence drag to a small degree etc.

 

Yes the same excact diameter. The excact tire is the Kumho ASX 235/45WR17.

And yes I did notice the the EL 42's did spin more. Maybe the EL's are a little lighter also.

 

If the EL42s completed more turns per mile than the Kumhos then they are most definitely NOT the "exact diameter". This is not possible. If you went to a tire with a larger diameter, you accomplished the same thing as had you installed higher gears in your transaxle (final drive gears). This will reduce your car's torque multiplication, thereby negatively affecting acceleration.

 

So I assume the same size tire dosen't mean the same size diameter. How do I find out? I'm really not understanding.

 

To sufall96;

Your assumption is correct. I should have also mentioned, though I see someone else did, that weight will play a factor as well.

As for finding out, you need to do some research. While tirerack.com is an excellent source, I also go to the tire company's website to get their sizes.

Now just using tirerack.com and your Kumho's, you say you bought the stock replacement size of 235/45WR17. Tirerack shows them to have a diameter of 25.4 inches. Had you gone with the 245/40WR17's you would have had a diameter of 24.7 inches. That's nearly 3/4's of an inch which is a big difference and would most definitely improved your acceleration and felt throttle response, plus put more rubber on the pavement. However, your car would show a faster speed than you would actually be traveling and miles would rack up more quickly (there are always trade offs in anything).

Don't beat yourself up with this.

 

Thanks!

 

These are the two different tires on the car.
The first one being the Kumho.