Effect of Tire/Wheel Weight on 1/4 Mile Times

[jhs914]

(edit-Cross post from LX General Forum)

I know this has been discussed many times before and the recent GIFO result was a consensus that the effect on the Hemi cars was minimal (based on dyno results). I ran across a Car Craft magazine article online where they conducted a 1/4 mile drag test using different tire/wheel combinations. The car was an early 70's big block Chevelle. The results were not dramatic, but were measurable.

This a summary. The listed wheel weights are combined for two tire/wheels per axle.....

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

If you consider that the GIFO dyno results show no difference in HP based on increased rotational weight of the drive wheels and this test shows over a tenth of second and one MPH in the 1/4, you would have to conclude that the difference in 1/4 mile times is more attributable to the 82 lb. weight reduction in the total car weight. My assumption is that if you had lightened the car by 82 lbs. anywhere else the results would have been similar. The article starts off with a reference to the common assumption that for every 100 lb. weight reduction you gain a tenth in the 1/4. In this case it was 82 lbs.

The complete article is here...... http://carcraft.com/projectbuild/116_9905_wheel/

[boggart]

I would agree. It's been longstanding common knowledge that 100lb = 1/10th in the quarter. Good test.

[srt8_hmi]

15's all the way around for it is!! (was this thread dead?)

[Todd TCE]

Great....now I have to make a brake kit for 15" front wheels too??? You guys are killin' me.

[gameover]

Todd, this test was on a 70s Chevelle. Great info!

[jhs914]

Talk about a resurrected thread! I posted that so long ago I had completely forgotten about it. Of course at my age my wife has to remind me where I am when I wake up every morning.