I went to Silver Dollar Raceway last night, and met up with some GTO owners.

My wife took video of the passes, but they didn't come out great.

The temp dropped into the 50's late, and the track prep was so so. Not good enough for a great 60', but not horrible.

That said, my best for the night was as follows.

R/T .230 (Worst of the night, most were .0XX)
60' 1.895 (Second best of the night, still a bit slippery)
330 5.514
1/8 8.517
MPH 82.39
1000 11.096
1/4 13.273
MPH 103.85 (Trap is lower with the DR's, due to a slightly smaller diameter)

I wish M/T made DR's that would fit the stock rims. I would be in the high 12's already! I'll get there on a day where track prep is very good, or the conditions are a little better.

I'll post some videos later.

 

13.27 seconds is impressive. Good show.

 

Nice run

 

Nice, I have to get some DR's now

 

Nice job-good driving...

 

slightly smaller diameter does not reduce mph

your mph was slower due to the weather conditions and or air pressure

good run!

 

Thats it Warren? I'm disappointed.

Nice run!

 

It does lower your trap speed due to gearing.

The M/T's were 26.0 when they were brand new, and have worn down to about 25.7. My Firestone WO's were 26.3 brand new, and are now about 26.2.

If you correct for tire diamater, even that little amount makes a noticable difference.

I would have trapped close to 106 with the street tires on.

http://www.moddedmustangs.com/perfor...culators/#tire

 

You're right, I must run a 12.9!!!!!

 

Did you get a ECU reflash of any kind? How did the GTOs do?

 

stock ecu.

One was a new 6 speed with 1,800 miles on it, and he had never run at the strip before. He worked his way down to a 13.9@104.xx best for the night. Judging from his 2.3 60', he could get down to the low to mid 13's with a great launch.

The other was an 05 with LPE AI, IAT relocate, Ported Intake Manifold, JBA catless mids, SLP UD pulley and Nitto 555R's. He had some good launches, and ran a 13.1@106.9 best.

 

Nice times Warren.

 

I'm confused. A shorter diameter will result in a shorter overall gearing. The only way shorter gearing is going to hurt is to possibly force you into a gear sooner than before, or cause you to spin more off the line. If you're not shifting to 5th, then the shorter tires are actually helping your trap.

 

Smaller diameter tires will make for shorter gearing, and a lower trap, not higher.

You may benefit a little on the bottom end, but you will lose trap speed on the top end.

Use the calculator link above too see how much of a difference it makes.

 

That's not entirely true because I have a lot of Mustang friends that swapped out on the long 3.27 gears in the their 96-98 Cobras for 4.10-4.33s and they actually gained 1-2mph. Gearing and trap speed is due to so many factors. It's true that you can over gear a car and sometimes gearing will suck out a little MPH.

If your tires were only .5-.6" shorter, then I can't see how that would suck out any trap speed. The gearing change is minimal. I lost 1.5mph doing from 26.2" tires do 23.5" BFG DRs. That's nearly 3". It took my car's gearing from a 3.31 to a 3.55.

I think your change in trap speed was just a reflection on the that particular track or the mood of you car.

 

But when you lost trap, it was a function of the *time consuming* shift to 4th in the automatic, correct?

The only two possible reasons that shorter gearing can hurt is traction, or causing a fremature shift into a taller gear.

 

I have run both wheels and tires at the same tracks, and always lost trap speed, even with the same 60'. The difference was 1-1.5 mph on average, back when both sets had most of their tread. The MT's have worn down a lot more now.

I stick with the smaller MT's now for better traction all the time.

 

Now, I can definitely see you posting smaller traps because of traction.

I can't launch for crap - that's documented. In my sedan, 2.2's are common. 2.1's aren't exactly rare, and I've been known to do 2.3's and even 2.4's. I've noticed that if I hook a low 2.1, my trap may be down by as much as 1mph versus a high 2.2.

Last december when I pulled my 13 second passes, I was running 101s and 102s with 2.1 sixties. One one of those runs, I spun at the line for a 2.3, and ended up with a 103 trap. I've never had a 103 trap since(but should the next trip out).

synopsis - I suggest your observations on lower trap are due to increased traction.

EDIT - apparently I don't know what I'm talking about - and reading comprehension owns me. I didn't notice the part where you said you had the same 60'.

 

I was comparing traps with the same 60'. I can get better 60's with the MT's, but I can also run 1.9's with the Firestone WO's. Doing that, my car trapped higher with the same 60', and honestly, it didn't change much when I ran 1.8's with the MT DR's, but I can run 1.8-1.9 consistently with those. That's why I have been sticking with them.

I ran just barely over 105 several times in a row at the same track with the WO's, and only 103.5-104 with the MT's.

 

I always ran same if not slightly higher traps with shorter gearing. 25.7" gearing is slightly shorter than stock, and doesnt cause you to shift into 5th down the 1/4, so technically it should be helping your acceleration and traps down the 1/4...if shorter gearing would cause you to go into 5th, then it would def drop your trap.