First passes of the year... added DR's, lowered 60's: same ET & lost 1 mph - Ford Mustang Forums : Mustang Forum
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post #1 of 3 Old 03-30-2003, 01:55 AM Thread Starter
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Unhappy First passes of the year... added DR's, lowered 60's: same ET & lost 1 mph

Last night was opening day at our local 1/8 mile track. The only thing I changed since the last day of last season was that I added Nitto DR's. I knocked off a tad from my 60's, but my ET w/ the DR's was the same as it was last year on street tires... and with a 1 mph lower trap speed.

Have I lost some power somewhere, or is the late-March air really that different from mid-October air?
The DR's are the ONLY thing I changed... heck I haven't even changed my oil yet! LOL

I am KINDA pleased with my 60's. My best ever on street tires were a couple of 1.99's, averaging 2.03-2.05's most of the time. With the Nittos I got a couple 1.93's, with a couple 1.97's & 1.99's still trying to figure out the DR's. But SOMEWHERE I've lost power. My ET's are the same, but a good tenth slower than I expected with the DR's, and my 1 mph loss on every pass shows that.

Here's my timeslip comparison:
(10/02 on Kumho street tires; 3/03 on Nitto DR's)

60': 2.03/1.96
330: 5.82/5.78
1/8: 8.92/8.95
mph: 79.62/78.13

Now I did get a best mph of 78.58 last night, but this was the pass that netted my best ET. I've also obviously pulled better 60's on street tires than the 2.03, but this was the pass that netted my best ET as well.

I know if I can find that 1 mph on the top end, my ET will be down where I think it should be with the better 60's... I just dunno where it is??
I think there is something to the difference in October & late-March air, but a WHOLE mph???

Black 1987 Mustang LX 5.0
Silver 2000 Lightning

Last edited by DMassey; 03-30-2003 at 01:58 AM.
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post #2 of 3 Old 03-30-2003, 12:57 PM
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I lost a mph or 2 when I switched from street tires to BFG DRs, I assumed it was because of the extra hieght and rolling resistance of the tire. I don't understand why your ET didn't drop though. Maybe you should go check out and see how different the weather was since last time.

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post #3 of 3 Old 03-31-2003, 07:06 AM
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Weather conditions can vary a lot, even at the same temperature. What was the barometric pressure and humidity? Could have been low pressure and high humidity vs. last fall.
This can change your MPH a lot. Also, a head wind vs. a tail wind can be 2 MPH. One trip to the track is not enough to draw a conclusion.

I keep a log with the barometer and density altitude if I can get it from another racer or from the airport.

If your 60' has improved don't worry - the ET and MPH will come with it.

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