I just recently ordered new aftermarket wheels for my '02 Carrera. But to my horror i just learned that they are way much heavier than the "standard" 18th inch the car comes with. What are the penalties of heavier wheels in terms of performace and handling? Is it noticeable?

A friend said that the car will not absorb the bumps and potholes as smooth as before.

Any feedback from past experiences??

Many thanks,
Ed (from DR)

 

The penalty is an increase in rotating mass and unsprung weight. This will cause the following;

- Slower acceleration and longer braking distances (it will take more energy to accelerate and decelerate a heavier wheel)
- Reduction in handling over areas where the pavement is not smooth (your suspension will have to work harder to control the extra mass and keep the tires in contact with the road)
- Reduction in ride quality (again your suspension is working harder to control the extra mass)

All of the above WILL occur.....

However the real question is "will you notice"

I doubt you will notice unless the difference is very large (i.e. 10 to 15 lbs or more/per wheel - the 996 is a powerful car). For example if your car was say .1 second slower in the quarter mile could you feel that??? I doubt it. If your wife rides with you in the car, do you notice a performance reduction (due to her weight)?? Probably not.

Now if you put 4 people in the car and load up the front trunk you will notice a difference, but if the weight change is slight you will probably never notice. (note: unsprung weight increases are more detrimental than sprung weight increases)

Here are a few links

http://www.racerchicks.com/qa/motor_weight.html

I know it's a chick site but the explaination is good!

http://www.hardracing.com/Rims/WheelWeightInfo.htm

http://www.wam.umd.edu/~greghess/sizematters.pdf

http://www.nerocam.com/SCC_TAPnew.asp

http://grmotorsports.com/news/012005...ls-for-you.php

http://www.tirerack.com/wheels/tech/...jsp?techid=108

http://www.turbomagazine.com/tech/0106tur_wheels/

http://forum.miata.net/cgi-bin/ultim...c;f=3;t=007412

http://forum.miata.net/ubb/ultimateb...=010655#000000

http://www.mini2.com/forum/showthrea...730#post279748

The first post in the link above is good

http://www.mini2.com/forum/showthrea...threadid=14738

Keep in mind that unsprung weight and rotational inertia, is more important than sprung weight. (i.e 1 pound rotational or unsprung weight is equal to more than 1 pound of static weight). Also someone once told me that another general rule of thumb is that every 100 lbs of static weight gain or loss is roughly equivalent to a 5 hp gain or loss.

Hope this helps!

 

Thanks for all that great info. I went to a 19" wheel and tire and my rear wheel weight actually went down by 5 lbs. I think this was mostly due to the tire being lighter since the stock wheel weighs 25lbs I believe and so did my 3piece forged unit.

It was weird because I was figuring the lighter weight would make a slight difference but it was actually noticable. The car pulls harder with the new wheels. The front wheel/tire whas slightly heavier though, because the wheel was 1/2 inch wider than stock. So not only unsprung weight matters but also if it's the wheel putting the power to the groud effects it more than the rolling wheels.

Tires can easily vary 5+ lbs in the same size so take that into effect next time you purchase tires.

The good news is you'll still have the stock wheels.

What wheels did you go with?

 

Keep in mind that the wheel weight by itself is not the only issue. You also need to consider where the weight is on the wheel/tire. In other words say you have two wheel tire packages....

Package #1 19" 45 lbs wheel/tire combined weight.

Package #2 17" 45 lbs wheel/tire combined weight.

In the case above package #1 will probably turn in better and feel a little more crisp due to the shorter sidewall. However the ride will be much worse.

Package #2 will probably accelerate and brake better (because it's smaller wheel will concentrate the weight toward the inside of the wheel). It will also ride better because of the taller sidewall

IMHO the "bling" factor in larger diameter wheels is getting a little ridiculous. I am not convinced that there is any real handling gain or benefit in having a performance wheel over 18".

I think that Porsche offering 19" wheels on the 987 and 997 has far more to do with consumer demand than handling improvement. (This is my opinion and you are free to disagree)

 

I ordered the Turbo Look (993) wheels, (i have never liked the stock 18th); and although they look good, they are heavy. At least 15-20lbs heavier each!!! I think i'm going to have to sell these new arrivals!!!

Ed (from DR)

 

You are correct....the Turbo Looks are very heavy (also very strong).

You probably will not feel a difference. I had these wheels on my Boxster before I switched them out for lighter wheels. I can barely feel a difference in the Boxster (which has much less power) so I doubt you will notice a difference in the 996.

If you like the look, but want a lighter wheel the actual turbo wheels look the same but have hollow spokes. This makes them much lighter and more resistant to pressure fluctuations (due to greater air volume).