liquid_helix136

So lately ive been looking into doing the lighter rotational mass path.

This would include:
smaller wheels (i have 18's) which will be lighter (probably rpf1s)

and also was taking a peek at lighter rotors, a couple pounds off each rotor would be great!

However, I dont know much about aftermarket rotors and had searched to not really find anything I was looking for.

If anyone was able to point me in the direction of some lighter rotors that will still hold up fine to normal street use, I'd be greatly appreciative.

What would be awesome is a list of rotors with prices/weight savings/durability, but that may be asking a little too much

Also any thoughts/comments about my plan is always welcome

Thanks

mikegarrison

Rotors are not a good place to try and save weight. Even if you discount braking capability, you are going to have to spend a LOT of money for very little savings.

And mass has a lot to do with total heat absorption capacity, which has a lot to do with brake performance. So lightening the rotors will almost certainly reduce braking capability. It's true that you can give up some braking capability is you restrict yourself to "normal street use", because the brakes are overdesigned for that.

iam7head

whatever mike said

There are oem sized two piece rotor out there, it's aluminum hat/center with replaceable rotor surface/ring

you need to do more research on thermal capacity on different material before making that decision.

there's lighter tires out there too if you want to go that extreme

cenix

i was thinking the same thing about the previous two posts. the most lightening you could do on a rotor is probably getting the 2-piece rotor with aluminum hat.

other unsprung weight: lightweight calipers, forged/lightweight wheels.

JSWhaler

This is what you're looking for
Rotors

Neutered Sputniks

I have the Racing Brake 2-piece rotors According to Science of Speed (who I ordered them through), they've saved maybe 1lb each...

If you need new rotors anyway (I did), then it's not a bad way to save 1-2lbs of unsprung weight... If you don't need new rotors, then it's probably not really worth it.

Moving from 18's to 17's won't necessarily save weight (and it won't really even necessarily shift where that weight is either) Most 17's and 18's have a 1lb difference in weight with the same width wheels...conversely, most 18" tires weigh 1lb less than the same width/height 17" tire - so that 1lb shifts from the wheel to the tire sidewall - all in approx that same 1/2" radius. The biggest argument against 18's is due to the butt dyno...and we all know how accurate that is... 18's will generally ride rougher than 17's given less sidewall to help absorb the shock when going over bumps.

Dropping to 16's can shave a few lbs...but keep in mind that you'll be limited in tire widths.


Edited: Now, switching from relatively heavy 18's to relatively light 17's is a different story - but just switching from 18's to 17's doesn't necessarily drop unsprung weight/mass. When you shop for your wheels, make sure you add tire weight into the equation

h1gh0ct4n3

calipers aren't rotational mass but you shouldn't skimp on any braking...
there is all kind's of ways to make your car go faster and turn better but your brakes are the only thing to slow you down and pretty sure its to keep you from dying.

ans2k

i think brakes are not a very good place to talk about unsprung weight. rims is a good start but like someone mention you have to add tires into that. what about i light weight drive shaft?

liquid_helix136

Well my whole reasoning on this was of hearing all that 1lb of rotational mass = equivalant to 7lbs of unsprung mass

After reading around (mostly on some bimmer forums) and a bunch of engineers were talking about this, this isnt true, so my ingenious plan of losing about 200lbs worth of unsprung weight was flawed, and I'd rather keep my sweet looks of my 18s and my properly working rotors

I think they figured the rule of thumb to be somewhere along the lines of 1lb or rotational mass = 1.5lbs of unsprung mass.. so as its still a decent place to look for losing weight, its not as remarkable as I once thought, thanks anyways guys

/thread

urBan_dK

It seems to me that there are two ways of looking at this type of weight reduction. The first is the "unsprung" factor, which plays into suspension response speed to imperfections in the road. Less weight = better contact with road = better traction. Then there is the "inertia" factor. Reducing the moment of inertia of the wheel assembly is also a good thing, but it is best to lose that mass as far away from the center of rotation as possible.

All that is to say, it doesn't matter where the mass is on the wheel for pure "unsprung weight" but for the "inertial weight" (made up term) it does matter. Lose the weight in the tire, then the wheel, then finally the brake assembly.