wolverine

I just installed my 19" BBS RS-GT's with Goodyear Eagle F1-GS D3's on my 545i. I figured I would break even in terms of weight since the BBS wheels were very light. I weighed the wheel/tire combos on a balance (physicians type) scale. I repeated the measurements several times, and made sure the scale was zeroed out. I estimate I'm accurate to within 1/4 lb. I just weighed the OEM wheel/tire combo's for the 545i, and I was stunned by the difference. The results were:

BBS wheels/tires

Right and left front wheel/tire 19x8.5 245/35 46 1/4 lbs, 46 1/4 lbs
Right and left rear wheel/tire 19x9.5 275/30 49 3/4 lbs, 50 lbs

OEM wheels/tires

Right and left front wheel/tire 18x8.0 245/40 60 1/4 lbs, 60 1/4 lbs
Right and left rear wheel/tire 18x9.0 275/35 64 1/4 lbs, 64 1/2 lbs

This is a 56 lb difference in unsprung weight! Part of this difference is the wheels - cast OEM vs forged BBS, but I think a good part is the runflats. Anyone know if there is a significant weight penalty because of the tires?

6spdMan

56 lbs is a huge difference. Any difference in how the car rides and feels under normal driving conditions?
How is the UUC shifter working? Is the shifter a lot shorter than stock? Did you keep the stock shift knob?

Hartge530

What? 56lbs? you have to be joking

I got my 124's with Bridgestone S-03 Pole Positions (my oem wheels were 17'). I hope that the Bridgestones make up the difference in weight for the increase from 17's to 18's.....hmmm.....

wslam

This may very well ans a thread/question i posted a few weeks ago. I noticed significant improved fuel consumption by going after-mkt wheels as they were lighter. see if you see the difference in fuel consumption.

wolverine

I haven't driven the car yet, it's still at the dealer getting prepped. I'll post pics and a review probably this weekend.

I've done some research on intertial/unsprung weight and the 14 lbs per wheel should make a significant difference in performance including ride, braking, and accelleration. Depending on which formula or dragstrip results you look at, the reduction in inertial/unspung weight should give you 1-3 tenths in the quarter mile, and with the max performance tires, braking should be significantly improved. I'll report on the ride - I did drive the car in Germany. It should be as good or better than stock.
I don't have gas mileage to compare, but I'll be changing out the wheels/tires for winter tires on the OEM wheel around December so I'll compare then.

Marvel

The engines power rating is reduced dramatically as it's applied to the pavement due to so many factors. One of the factors is the size and the weight of the wheel itself. It takes less power to spin a smaller diameter and lighter wheel than a bigger diameter and heavier wheel. Thus, with the lighter wheel you don't burn much more gasoline to spin it compared to your heavier OEM wheel.

mrbelk

My drag-strip racing friends say that a 1lb reduction in unsprung weight is roughly equivalent to a 4lb reduction in sprung weight, so it's almost like you shaved ~200lbs off the car.

-MrB

530E60NL

Wow interesting!!!

The only thing I don't understand is BMW making al the effort by using aluminium where they can on this car (very expensive) while they could have had the same effect with less heavy wheels. Sometimes I do not understand the ideas car companies have.

mrbelk

The aluminum structure is probably there as much for the weight distribution as it is for total weight savings. Also, forged wheels are generally very expensive, even in quantity. I just read this the other day; that BBS is one of BMW's wheel suppliers. So the OEM wheels are nothing to sneeze at from a construction standpoint. I would also think that the soft forged aftermarket wheels are much more subject to damage from irregular road surfaces, etc.

Don't forget that the E60's suspension bits are all aluminum, which is also unsprung weight, so they certainly didn't ignore that aspect of it.

I'd be real curious as to the weight of the tires and how much difference the runflat/nonrunflat was.

-MrB

JBOO

The runflats on my Cooper were very heavy. I noticed a big difference in performance when changing to aftermarket tires. It was like a shot of HP!They were also much grippier and made the handling even that much better.