TESTED: Wheel weights (yikes!)

[treynor]

In prep for my runs at Sacramento Dragstrip next Saturday, I finally spooned on my Purner slicks & skinnies this afternoon. I took the opportunity to weigh each of the wheel/tire combos going off and on the car, and the results were interesting:

Stock 2001 front, 18" aluminum 1-piece wheel with 275/35 Michelin Pilot sport: 56 lbs
Stock 2001 rear, 18" aluminum 1-piece wheel with 335/30 Michelin Pilot sport: 65 lbs

Purner front drag set, 16" aluminum 3-piece wheel with 5.00" bias ply: 31 lbs
Purner rear drag set, 16" aluminum 3-piece wheel with 26x11.5" M/T ET street: 42 lbs

Stock wheels & tires: 242 lbs (!)
Purner wheels & tires: 146 lbs
Weight savings: 96 lbs of unsprung rotating mass.

 

[HogWhisperer]

100 lbs. = 1/10 in ET ....

Good luck and be sure and let us know how you do!

 

[dtittle]

Now that you lost a hundred pounds, can you imagine losing even more weight?

My front rotors are larger and weigh 8 lbs LESS THAN STOCK...EACH!!!

My rear rotors weigh almost 5 lbs LESS...EACH!!!

That's 26 lbs of unsprung, rotational weight removed with better braking to boot.

Dang that's cool.

Regards,

 

[GTS Dean]

So Ben,

Are you going to keep doing your dyno testing using the OEM wheel/tire combination so that you have a consistent baseline?

 

[9 seconds]

I just talked to John Purner this morning. He said that most of the weight savings comes from the tires. Stock radials have steel in them. His bias don't.

Also, Tom Welch told me in the past to dyno with stock radials for higher numbers. The soft sidewalls give a little more driveline loss. I don't have data, just his word.

Keep up the great posts, Ben. I've never seen anyone document their upgrades like you did.

 

[treynor]

For the moment, yes. If I end up swapping wheels I'll do one before/after run with old/new wheels to quantify the difference between the two.

Seems like one ought to be able to save ~5lbs/wheel with some good aftermarket rims. It would be very expensive, however...

 

[SoCal Rebell]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Paul Bilberry 99 ACR:
100 lbs. = 1/10 in ET ....

Good luck and be sure and let us know how you do!



<HR></BLOCKQUOTE>

I have to go on a diet, then maybe I'll touch the 11s.

BEN, thanks for the ride on Saturday. Your car is ungodly fast, I can't wait to see your 1/4 mile #s.

 

[JonB]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Paul Bilberry 99 ACR:
100 lbs. = 1/10 in ET ....
<HR></BLOCKQUOTE>

Actually, 100 lbs of DEAD weight is rule-of-thumb for 1/10th in the quarter. With rotating mass, the gain factor is much higher....I believe 3X!

 

[treynor]

The actual advantage depends on the rotation inertia of the old & new wheels/tires. In the case of the Purner setup, since much of the weight savings apparently comes from the tires, the gain may well be 2-3x. If you are simply talking about swapping wheels, and keeping tires constant, the multiplier is more like 1.4 - 1.5x, as the wheel's weight is closer to the hub and thus has a lower polar moment of inertia.

 

[treynor]

A bit more data -- per Tire Rack, the tire weights are:
MPS 335/30-18: 32.7 lbs, so the stock rear wheel is 32.3 lbs;
MPS 275/35-18: 27.6 lbs, so the stock rear wheel is 28.4 lbs

By way of comparison, the BBS LM wheels listed on Tire Rack are 29 lbs (rear) and 25 lbs (front), for a total weight savings of about 14 lbs for a mere $3700...
-----
SoCal, glad to hear you enjoyed the ride. I did warn you it'd be bad for your wallet

You should feel what it's like when the rear tires can hook up!