I just got a set of 15 inch R82 wheels which came with ContiTouring tires. I got them because I wanted the rims to mount snow tires on, but since I've had them, I'm starting to think about ditching my R85s with Goodyear runflats in favor of a 16" non-runflats (to reduce harshness). So here's my question: Should I really care about unsprung weight?

My car is a stock '04 MCS with winter, sport and performance packages. I'm not an auto-crosser and I'm not looking to drive on the edge of what the car is capable of doing. I enjoy some spirited motoring, but mostly I use my car to get to and from work, 50 miles each way. Half of my commute is in two-lane country roads, and the other half is in DC traffic. I can sort of visualize the effect of a heavier wheel from that old high-school experiment where you spun a wheel and sat on a stool using the wheel a gyro to spin you around.

I've seen people list tire/wheel combinations that are 1/3 to 1/2 of OE runflats. Will such a decrease in unsprung weight translate into meaningful decreases in stopping distance, brake wear, or improve turning characteristics for me?

 

gnhovis,

The short answer to your question is yes, it always helps to have lighter wheels. The compromise in your situation is that you are going from 17x7" rims to 15x5.5" rims and the more narrow rims don't allow for the best width performance tires.

If you keep the R82 (weighs 15 pounds each rim) and contis in 175/65-15 the tires will be good for commuting but not up to the task for performance driving. The tires weigh 14 pounds each so if you just put them on your have a wheel which is 29 pounds instead of 48 pounds of your stock S-lyte. So is that 19 pounds weight loss for each wheel noticable- certainly. Just try it out.

You can accelerate faster, brake faster, have a smoother ride due to not having the runflats. Handling in turns will be determined more by your suspension and tires than the weight of the wheels.

So in your case what might be a good combination?
Try the stock R82 and drive the contis so you know what it is like. If you need more performance (the tires will be squealing around the turns everytime) then consider changing the tires to a wider and lower side profile option. 195/55-15, 195/50-15 or even 205/50-15 are possible.

At edgeracing.com in 205/50-15 (load rating 89) there are-
http://edgeracing.com/tires/2055015/
The Toyo Proxes 4 treadwear 300 VR rated, in that size is $68 each but the wide tire would need to be shoehorned onto the narrow rim by a performance tire shop (figure about $20 for mounting and balancing each tire). It will fit no matter how bad it might look.
Or in 195/50-15 (load rating 86, a little lower than stock) the same tire would be $58 each
http://edgeracing.com/tire/886/

The Proxes 4 is a relatively new Toyo tire that is reasonably priced, offers good street performance and comfort and is good wearing and quiet. Not for autocross use and is isn't as safe as nonrunflats for punctures.

The Proxes 4 is also available in 205/45-17 (load rating 88) for the stock S-lyte rims.
But it costs quite a bit more.

Tirerack.com has lots of options in all tire sizes so take a look if you are considering tires. Too many to mention.

One downside to the 195/50 and 205/50 tire sizes in 15" is they are all smaller diameter than your stock 17" wheels so speedometer will be off but that smaller wheel will help with a slight gearing advantage for quickness.

 

when i was researching for new tires for my mcs, i would basically check some of the setups here on nam, check tirerack.com for some brands and pricing, and call alex@tirerack for some final advice. then i ordered from him, as i found out he had the lowest prices i could find, even with s&h.

or you could just phone him first to save a few steps. i p/u my set of 16" white asa lw5 with 205/50 yokohama es100's already mounted and balanced for ~ $1100 with s&h to hawaii. far less harsh riding vs. my oem 17" s-lites with runflats, even with h-sport springs on.

first mod, i'd do is swap wheels and tires. although alot of $$$, it changes your ride characteristics and looks. not to say the stock wheels don't look sharp, but the performance and comfort is somewhat less than ideal.

the final word from alex that swayed my decision to splurge on wheels/tires is that, i believe this is what he said, one pound of weight lost at the wheels equals four pounds of weight above. so the way i look at it is, 40# of weight in wheels/tires is the same weight of an additional passenger.

 

These tire sizes will be outside the recommended ±3% variation when compared to stock 205/45-17:

4.9% for 205/50-15
6.5% for 195/50-15

Even compared to stock 175/65-15:

3.7% for 205/50-15
5.3% for 195/50-15

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

While the above tire sizes will be beneficial for autocross, 195/55-15, 205/55-15, 195/60-15 or 185/65-15 are much more appropriate for street use.

Source: http://www.mini2.com/forum/faq.php?f...hoosing_wheels

 

imho, unless you do spirited driving most of the time with your car,
you don't need lightweight wheels....rather spend your money on dressup
wheels.

There is a very significant difference in performance when you reduce
more than 10lbs per corner though! Especially braking. (SSR's vs R90).

 

Remember how weight works in the wheels. When you have the car rolling at constant velocity you will not notice the difference in the wheels and the heavy weight is not a problem unless you brake hard or accelerate hard. If you do these actions gently and smoothly then the difference you will feel is smaller but if you push hard going or stopping then it will be a big difference.

So ask yourself how you drive and you will know what to expect. When I drive like a grandma I do feel a little different than when I am on the autocross course pushing for every 1000th of a second.

 

minihuni- I was basing my comment on the above... :smile: I personally
do not like heavy wheels because I am on the mini (I mean ON the mini!!)
when im driving her around usually. thus why Im on my SSR's instead of
R90's.