Light vs. Heavy wheels

Car crafters have been hearing the same rehashed speed secret for years: For every 100 pounds you remove, your car will run a tenth quicker in the quarter-mile. But is this adage really true? In past testing we've had mixed results--sometimes a 100-pound drop in static weight (such as a steel versus a fiberglass hood) will make the car go two-tenths quicker, while other times it doesn't seem to make a difference at all.

However, racers claim that more important than reducing overall weight is the benefit from reducing rotating weight (like wheels and tires) or reciprocating weight (like rods and pistons). Furthermore, wheels and tires are unsprung weight, which is supposed to make an even greater difference in vehicle performance than sprung weight. As a result, we've heard that swapping on a set of lighter-weight wheels and tires not only improves acceleration but reduces stopping distances.

We were more interested in dragstrip acceleration, so we tested traditional rally wheels from Wheel Vintiques (which makes reproduction rallies in numerous sizes) against lightweight Center Line wheels on our 502-powered Mean Street

Chevelle. For consistency, we used the same size/type rear tires (Mickey Thompson E.T. Street 26x10.5-15) mounted on 15x8-inch steel and aluminum rims. Up front we tested both 15x7- and 15x4-inch rims in steel and aluminum with the same diameter tires (to not affect rollout). Did the lightweight goods really make a difference? Check out the results box. A huge thanks to L.A.-based Flip's Tires which, as always, did all our mounting and balancing muy pronto.

All wheels, tires, tubes, and accessories were weighed using a postal-grade digital scale. Weights may vary slightly due to manufacturing tolerances, tooling changes, or scale accuracy--you get the point.

First up for testing was the heaviest combo: 15x8 rally wheels out back and 15x7-inchers and BFG radials up front. Four back-to-back dragstrip runs were made and then we swapped on the lighter 15x4-inch front rally wheels and made four more passes.

Then came the swap to lighter Center Line Convo Pro 15x8-inch aluminum wheels with the same Mickey Thompson rear tires as used with the rally wheel test. Up front were 15x7-inch Convos wearing BFGoodrich T/A radials. After four dragstrip runs, it was time to move on to even lighter front rolling stock.

We were pulling out all the tricks in an attempt to shed unwanted weight from our porky, near-4,000-pound '70 Chevelle. As a final test, we bolted on a lightweight set of Center Line 15x4-inch wheels encased in featherweight Mickey Thompson E.T. Front drag tires, hoping that the reduced weight and decreased rolling resistance from the skinny tires would help our e.t.'s. For all tests the engine's coolant temp was at 170 degrees, and the torque converter was stalled to 2,000 rpm during each launch.

From start to finish, we shaved 82 pounds, which reduced our e.t.'s by 0.111 second and upped our speed by 1.12 mph. That's not as big a difference as we were hoping for. For die-hard racers this lightweight combo may sound tasty, but many gearheads still prefer the classic--albeit slightly slower--rally wheel look. You make the call.

Test Configurations
Test 1
(2) 15x7 rally with BFG P215/60R15 = 95.56 lbs.
(2) 15x8 rally with M/T 26x10.5-15 = 93.70 lbs.
Total weight = 189.26 lbs
e.t. and mph = 12.137@111.99

Test 2
(2) 15x4 rally with M/T 26x7.5-15 = 70.86 lbs.
(2) 15x8 rally with M/T 26x10.5-15 = 93.70 lbs.
Total weight = 164.56 lbs.
e.t. and mph = 12.107@112.52

Test 3
(2) 15x7 Center Line with BFG P215/60R15 = 70.46 lbs.
(2) 15x8 Center Line with M/T 26x10.5-15 = 64.10 lbs.
(4) Center Line center caps = 0.96 lb.
Total weight = 135.52 lbs.
e.t. and mph = 12.103@112.10

Test 4
(2) 15x4 Center Line with M/T 26x4.5-15 = 42.12 lbs.
(2) 15x8 Center Line with M/T 26x10.5-15 = 64.1 lbs.
(4) Center Line center caps = 0.96 lb.
Total weight = 107.18 lbs.
e.t. and mph = 12.026@113.11

Total weight reduction = 82.08 lbs.
Total performance gain = -0.111 sec, +1.12 mph