Do lighter wheels make a difference?
 

Hello all, I have an 2013 r56 cooper base. I will be replacing the tires soon but I was wondering if it is worth getting a lighter set of wheels before I mount my new tires on the stock mini 17x7 conical wheels which I believe are 21-22 lbs each. If I were to get another 17x7 that is 14-18 lbs does a couple of pounds make a difference in performance? If anyone has wheels to recommend please do share!

The factory wheels can be upwards of 24 lbs and yes shedding 10 lbs per wheel will help performance but most light weight wheels are not that cheap. If you can justify the cost, go for it.

unsprung mass - figure about 1lbs of unsprung is kind of like taking 10lbs out of the car. Yes they make a difference in straight and lateral acceleration and stopping. Do it.

Simple answer, yes.

Ok so ill take that as a yes, haha. Do you guys have any suggestions for 4x100 wheels I have seen some reasonably priced ones from O.Z. and Advanti etc. But I don't want the wheel to crack if I drive down some rough roads.

Zach -

Funny, yes, yes, yes...NO ONE mentions the details (or WHY !)..!
As has been mentioned, yes, in all cases, but on one has told you WHY..! That is IF...you are interested.

Accelerating in a straight line, (initial acceleration) - The heavier the wheel/tire combination is that you have, the more horse power is "wasted" in getting the wheel/tire into motion from a standstill. With lighter wheels/tires (combination) that horse power can be used to get the "car" (as a whole) moving.
Also, this same horse power is wasted in NOT being there to get the tires/wheels "rotating" as could be done with...lighter parts.

Accelerating (stopping) to zero (yes, accelerating to a stop IS the correct word..!) - Basically...see the above notes. The tires have to work at stopping BOTH...the weight of the entire car, AND the rotating mass of the tires/wheels. That's "two" jobs the tires have (initiated by the brakes). So again, the lighter wheel/tire combination, the more "work" can be transferred to bring the whole car to a stop, or slowed.

In up and down motion, (bumps/dips in the road) - Similar to the above answers, the heavier the wheel/tire combination is, the harder the shock absorber and spring have to work to keep the tire(s) planted on the ground. As you might expect, a tire that's off the ground, or bouncing...isn't in control of...anything, or able to do anything good..!.

In turns - While turning the wheels/tires (front) takes effort from all parts in the steering, from your hands, all the way to the lug studs/bolts and tires. While this is VERY minimal loss, see the above note. Heavier parts, make everything else work harder than should be required.

Mike

NOTE - Heavy brake rotors and calipers, are ALSO 'unsprung' weight. Heavier parts, again, make the springs and shocks work harder in keeping the tires firmly planted on the ground...where they need to be. This is a critical give and take that has to be weighed when buying suspension parts.

Mike, thank you very much, yes very informative this is just what I was looking for!

More like 1.5 for wheels and 1.75 for tires per 1 pound taken off in terms of
straight acceleration and stopping if you do the physics.
any reduction in weight of moving suspension parts helps with roadhandling
as the springs and shocks have a better time keeping the tire planted to the road.

So is there an ap or some formulas that can put all this into minutes or mphs?

+1

100%, going from 17" to 15" on the track was huge.