I see a lot of comments about going for smaller wheels for better handling because of unsprung weight, and I'm a little puzzled.

Let's say we are going for a 205 tread width. One option is 17x7 wheels and 205/45-17 tires. Another would be 16x7 wheels and 205/50-16 tires.

17x7 wheels can be had with a 15-16 lb. weight, and 16x7 seem to be available at around 12-14 lbs. So, at best we are looking at 3 lbs difference in wheels.

Then we add tires. Aren't the 205/50-16 going to be heavier than the 205/45-17? I haven't found tire weights at the Tire Rack, but it seems that since we are going for the same overall O.D. on the tire, there is going to be more rubber in the sidwalls of the 16s.

So, it would seem that one would end up with a savings of one or two lbs.

Wouldn't the shorter sidewall be more important to handling that the small difference in weight?

 

OK, in general you want lower weight in-
Tires, brakes, rims, studs and nuts or bolts. Anything that is on or attached to that wheel. Multiply the effect by four and consider it takes energy to move that mass whether to increase or decrease it when in a moving or standing state. Weight isn't crucial going at a constant velocity/speed, it's when you change velocity that energy is required.

The further the weight is to the outer edge of the wheel the more it can make a difference albeit small. So loosing weight at the brakes or bolts is not as important as in the tire especially a lower profile tire like 30 or 35 series.

You don't always have that much of a choice on tire weight because alot has to do with the construction of the tire by the manufacturer. Often we opt for a heavier (relatively) performance tire because it offers better handling even though weight is more.

A good example is Goodyear eagle F1 GS-D3 (Max performance summer tire) handles much better than General Exclaim UHP (Ultra High Performance Summer tire) but it's weight is alot more. If you were to mount those two tires on the same wheel on the same car you'd say that the GS-D3 offers much more performance, is more fun to drive, and you don't really notice that much effect of the heavier tires while the Exclaim offers a much smoother and quiet ride and is well mannered but doesn't offer as crisp handling in wet or dry.

For 215/45-17 size
F1 GS-D3 22 lbs
Exclaim UHP 18 lbs

For 205/50-16
F1 GS-D3 22 lbs
Exclaim UHP 19 lbs

Want lower weight but still good handling then
In 215/40-16 the F1 GS-D3 is 19 lbs but tire diameter is smaller at 22.8" (good for lowering gearing- not really needed for R56).
In 205/45-16 ($64) the Exclaim UHP is 17 lbs with tire diameter 23.6". It won't be as sticky as the GS-D3 but the lower profile will offer a bit better turn in response. You'd still get some comfort (not as harsh ride) due to tire construction and tread design. Exclaim tends to be well priced.

So depending on your exact tire size selected and which tires you are looking at the weights are pretty close and not that big a factor. You can always choose a different size and that can affect the overall tire weight as well as the price. Those sizes that are more performance oriented will cost more.

Now lets look at some concrete examples even though you already have Centerline RPM 17x7 rims.

From Tirerack.com
Enkei Racing Series RPF1
16x7 $228 each 13.5 lbs
17x7 $237 each 15 lbs
1.5 pounds isn't that much but considering that the wheels are already quite light, 1.5 of 15 lbs is 10% reduction in weight with no loss in strength.
If the wheels were heavier like 19 lbs vs 17.5 then 1.5 of 19 lbs is only 7.8%.

O.Z. Hydra
16x7 $189 each 22.4 lbs
17x7 $219 each 23 lbs
This design does not really favor the smaller wheel- take your pick

The difference for 15x7 rims and 18x7 rims is much much larger. 16 vs 17" is not that big so consider the big picture and pick wheels with tires as a combo keeping everything in mind. As I mentioned in other threads sometimes it makes sense when starting fresh to pick a tire first, see what sizes it can fit the MINI then pick the wheel size that fits and see if you can find a design that works in that wheel size. Most people pick a wheel first and compromise on tires since there would be only a few choices for tire size.

Notice too that 16" rims allow for various sidewall sizes from 40 to 55 series while 17" rims do not- just have 40 and 45 series. Large rims leave less choice for tire sizes due to the limits of the MINI wheel wells. 15" rims allow for many choices that are better suited for both performance (225/45-15) or street comfort (185/65-15). Not to mention lower prices and light weight.

At the extremes, 15" wheels can offer better handling and performance with light weight, more choices and lower prices than 18" wheels which are much heavier, costlier, and force you to use 35 or 40 series tires in limited sizes and limited tire classes. While handling is good, ride comfort is reduced- it's still OK depending on which suspension you have. To reduce weight in a larger wheel size will add to the cost. Smaller wheels tend to be light without trying. 14" rims are often about 10 pounds each but won't fit over the MINI brake calipers.

Bottomline-
Check out the weights and just keep in mind that it's a factor and be wary of anything that makes weight more if you care about handling and quickness. If you drive the speed limit and just do street driving then you can do anything you want that looks nice to you. Picking tires that are larger/wider than stock tire diameter often increases tire weight so sizes like 205/55-16 or 225/50-16 are often heavier.

 

Tire weights are listed on the top page of each individual tire listing on the top left of the page under "specs". Lots of good info on that particular page.

As an example of compromises, my summer wheel/tire package will be 18 enkei wheels w/ the general uhp. Less than 1/2 the cost of a 17" package, 2+ more lbs than the 17s, less performance than the Goodyears, but more comfort. Overall weight will resemble stock(16"), maybe a pound less. An experiment for me as I love the DS-G3(3 sets in the last 2 yrs and my wife wouldn't let me have her set). This is a street setup. If I was racing, it would be another whole set of compromises as alluded to by minihune above.

An added circumstance is that my MCS is only a street car. I have race cars, so I don't feel the need for ultimate performance to the detriment of adequate(slippery term) comfort.

 

Thanks for the info.

I'm surprised that the 205/50-16 Michelin Pilot Exalto PE2 tires are the same weight as the 205/45-17. I would have expected the 16 to be heavier because of the extra side wall. Perhaps the slightly smaller O.D. makes up for it.

So, does the sidewall height not have much to do with handling performance?

 

Many things affect handling performance- Dry vs Wet and on different road surfaces.

Sidewall height is only one factor.

Rubber compound(s)
Tread design
Tire construction- sidewall and tread belts, overall design, speed rating
Overall tire width and height
and
your car's weight balance, suspension, alignment, etc.

In general for the same tire comparing sidewalls. Lower sidewalls like 40 or 45 series will handle better (more responsive turn in) than 55 or 60 series sidewalls. When comparing one tire to another tire especially in a different class, then it isn't so easy to generalize. But lower sidewalls are stiffer and can result in a harsher ride on anything but smooth roads.

 

The acceleration aspect of a lighter wheel can be dramatic, too:

http://www.sportcompactcarweb.com/fe...ram/index.html

This Sentra dropped 13 pounds per wheel, and knocked off .3 seconds and gained 1.5 mph in the 1/4 mile. 0-60 also dropped by 1/2 second. The rest of the article is a rather entertaining, if a bit extreme, look at weight reduction and it's effect on straightline performance.

I'm going from the 17" S Lites and 205/45/17 Euphoria RunFlats (25 lb + 22 lb = 47 lb) to a set of 16" Rota Slipstream and 205/50/16 tire (13.5 lb + 20 lb = 33.5 lb) for a reduction of 13.5 lbs per wheel. I had considered a 205/45/16 General Exclaim at 17 lbs, but would prefer to stick closer to a stock diameter for ride comfort and better gas mileage. I expect similar results as if I had done a 15% pulley, but without fear of any warranty issues. And of course there are the braking and handling improvements as well.